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A FEASIBILITY STUDY OF THE PRODUCTION OF
ETHANOL FROM SUGAR CANE
Department of Chemical Engineering
University of Queensland
Report by: F.H.C. Kelly, A.M.T.C. M.Sc.(Melb). D.Sc.(Tas) F.R.A.C.I.,F.S.N.I.e.,M.I.E.(Aust) Chartered Chemist (Australia), Chartered Engineer (Australia)
Head of Department: D.J. Nicklin
Supporting Body: Queensland Department of Commercial and Industrial Development
ACKNOWLEDGMENT
We gratefully acknowledge the continuing support of the Queensland Department of Commercial and Industrial Development for this work.
November , 1977
Gardens Point A22335040B A feasibility study of the production of ethanol from sugar cane
i
PREFACE
For a period now spanning more than ten years, the Queensland
Department of Commercial and Industrial Development has sponsored research
and feasibility studies within the Department of Chemical Engineering of
the University of Queensland. A series of reports has been produced,
each concerned with some aspect of Queensland's Development.
The work has been carried under my broad supervision, generally
by research officers. Earlier workers who have produced reports in this
series include Mr. J.G. Job, Dr. P.J. McKeough and Dr. F.K. Mak.
When we accepted the present assignment to write a report on the
feasibility of producing ethanol from sugar cane, we had expected to
follow much the same procedure used in the past. However, at about
this time, Dr. F.H.C. Kelly visited the Department, and the possibility
of a somewhat different approach became clear.
Dr. Kelly is a man with very broad experience in the sugar industry -
experience in Queensland and overseas and in many aspects of the sugar
industry, which would be difficult to match. I invited him to work on
the project for the Department, and the report is attached.
I believe this will be a very useful starting point for consideration
of a massive expansion of the Queensland sugar industry to produce ethanol.
Others may prefer to fit alternative numbers to the various relationships
outlined or even to modify some of the relationships. If we have
provided a useful base from which to consider the alternatives, and if we
have caused others to think about better alternatives, I believe we will
have achieved our goal.
D.J. Nicklin 9.11.77
ii SUMMARY
1. A comprehensive study has been made of factors related to the production of
ethanol from sugar cane and problems related to its use in internal
combustion engines. All ethanol costs are "ex-distillery" estimates.
2. Cost estimates calculated for 25 sets of conditions range from 27 to 8c/l,
summarised in Table A and illustrated graphically in figure 4 with 12
relevant parameters.
3. Preliminary experiments with juice are deemed necessary at estimated R.6D.
cost of $100,000.
4. Highest costs are for distilleries associated with the present Queensland
sugar industry.
5. It is considered unwise to tamper in any way with the structure of the
present sugar industry for the purpose of obtaining low cost ethanol.
6. Full advantage should be taken of experience in growing sugar cane, control
of pests and diseases and of extracting juice.
7. If the sugar industry should wish to divert cane to ethanol production in the
event of failure of the export market this should be considered only as a
short term palliative.
8. Sugar cane grown in new areas specifically for ethanol would appear to have
good prospects for lower cost development if_ a new social and economic
structure suited to its own needs can be developed.
9. The social changes would include 7 days/week of operation for 39 weeks/year
for which 12 month employment conditions could be negotiated to cover
agricultural as well as processing areas. A suitable agreement with unions
would be a necessary preliminary determination.
10. An Industrial Alcohol Energy Authority should be established to oversee the
development and operation of the new industry with representation from
government and unions as well as producer and consumer groups.
11. Economic changes would include full mechanization of all agricultural
activities with programmed maintenance and 24 hr/day - 7 day/week operation.
This is not compatible with small farm units and the cost advantages of 1600
ha properties or 35,000 ha estates have been examined.
iii
12. Absolute costs are very difficult to estimate but the relativity of costs
is believed to be satisfactorily indicative. Cost evaluations have been
broken down to 12 main units and numerous sub-units providing a stability
to the cost structure. Thus for the lowest costing route at 8C/1 the
capital cost of the processing plant represents the highest cost component
at 26%. A 50% error in this figure would alter the overall cost by 1c/1.
13. Association with the present sugar industry could enable about 400 Ml/annum
to be produced at around 25.5C/1 with one distillery in each of the four
districts and using also all of the molasses produced from all of the mills.
Any increase beyond this could only result in a higher price for ethanol
produced within the structure of the present sugar industry.
14. Recent experiments in Brazil have indicated that ethanol can develop 18%
more power per litre than petrol but 15 to 20% more volume is used. A
compression ratio of 10:1 is needed to achieve these results. The Fiat
motor company in Brazil is prepared to make appropriate engine changes.
15. Logistic constrictions on the rate of development of a new industry in
Australia would mean initially blends with petrol in areas close to
production progressively extending through Australia. A 7 to 10% limit
is advised in high humidity areas (e.g. Queensland tropical wet season) but
up to 15% would probably be safe in low humidity areas.
16. Australia's present consumption of petrol of around 14Gl/year would require
seven Queensland sugar industry (QSI) units to supply the whole amount as
ethanol if only juice from stalk cane is processed.
17. If cellulose from fibre is hydrolyzed and fermented with 50% recovery and
whole cane (including tops and leaves) is processed only 4QSI units would
be needed.
18. A great deal of information is known about cellulose hydrolysis but not
with respect to sugar cane fibre. A research and development
investment of $2m specifically directed towards this objective is commended.
19. District area units of 35,000 ha or 0.1 QSI units are commended for new
area development, subject to qualifications relevant to item 15 table A.
iv
20. Capital costs for each new area are estimated to total approximately
$350m or $3,500m/QSI unit.
Carrying present knowledge of cellulose hydrolysis to a viable stage for
$2m could make the difference between a capital investment of $23,500m
or $13,500 m i.e. $10,000m. A R. & D. investment of $20m could well
be justified.
21. The average productivity in Te sugar/ha - season of the present QSI is
the best in the world, but Te cane/ha - season are only about 40% of
local well demonstrated achievable figures. Evolutionary improvement
is at the rate of 1.1 to 1.6% per year.
22. If actual average productivity could be increased to 80% of achievable
limit by wider application of already well known agricultural practices
this would double unit area ethanol production and reduce the number of
QSI units required to 2 or 3.5 depending on whether cellulose is
processed or not.
23. An establishment R.S D. investment of $llm is considered necessary
for such an achievement to be realised.
2*+. Since larger water supplies for irrigation would be required as well
as larger or more numerous processing plants the total capital investment
per QSI unit would be nearer $4,500m. The outcome of the $llm. R.£D.
investment would determine the real need or otherwise of capital
expenditure of $13,500m or $8,700m - again an investment that would
be well justified if it cost 10 times as much.
25. An establishment R.SD. investment of $3m is commended for developing
the requirements for optimum agricultural operations other than those
specifically relating to area productivity. This would have only
marginal influence on capital expenditure but would relate to a
difference in the price of ethanol of 5-8C/1 or $7-11,200m per year.
The initial gross benefit would be very much less but the manner in
which a new area development may be initiated will have long term
price influences.
V
26. The possibility of growing cassava as a fallow rotation crop has been
examined. It would seem to have little influence on the estimated
cost of ethanol but would increase area productivity by about 10(±3)%.
27. If cellulose hydrolysis is practised it may be done either with or
without using coal as fuel. The estimated productivity and cost
differences are marginal but more capital is required for the ethanol
plant if coal is not burned. The pro-rate capital investment for the
coal plant and transport is probably about half of that required at the
ethanol plant.
28. If coal is used total consumption would be up to 4.3MTe per 14G1 of
ethanol or 3256 litres of ethanol per tonne of coal. On the other hand
the use of this tonne of coal has enabled only 1333 1 of extra ethanol
to be produced which is still favourable when compared to 300 1 of
petrol possible from the same tonne of coal by hydrogenation.
Producing ethanol from sugar cane by the routes described may represent
a net gain of energy varying between 10% and 64% according to the
constrictions applied.
29. The energy input for full mechanization of farming procedures is
estimated at about 1% of ethanol output.
30. Up to 90% of fertilizer requirements are expected to come from recycled
evaporated distillery slops. When coal is burned about 74% of the
heat from this source is needed for slops evaporation if looked on as a
marginal effort. A very costly fertilizer - but convenient. On
the other hand when processing from stalk cane juice the fuel required
is readily available from surplus bagasse and two disposals are
satisfactorily handled.
31. A R. & D. investment to study the thermal balance of the distillery could
conceivably reduce coal consumption by up to 50% and make the non-coal
route more attractive. The possibility of recycling slops to the
hydrolysis heap needs investigation. An investment of $lm could
ultimately be worth $100m/year but much less initially and not critically
important until perhaps 1990.
vi
32. A levy of at least 1% and preferably 2% of the value of the product
is commended for R. & D. as a continuing investment.
33. A system of indexed amortization has been suggested to enable
development capital to be serviced at currently realistic rates
of interest.
34. Employment prospects are envisaged at 10,000 to 20,000 persons/14Gl -
year directly concerned in field and factory, generating supporting
employment 3 times this number. A similar number is envisaged as being
employed during development stages. Each district would have a
community of 6000 located in 3 sub-communities - one of 3000 and two
of 1500. These numbers relate to 1600ha property or 35,000ha estate
development. For 50ha farms an overall community of a million people
is indicated and believed to be too large a proportion of the nation's
manpower resources for a single product investment.
35. The possibility of applying space-age technology through remote control
has been examined and seems feasible with known technology. Complete
control could be effected from the Brisbane area reducing the need
for remote living to 1500 persons per district for maintenance and
operator-assisted duties.
TABLE A - SUMMARY
ITEM
1.
1 2'
[ 3.
4.
5.
6.
Dual production with raw sugar, from stalk cane plus molasses from surrounding district mills. Restricted to one unit per district. Table VI
Sole product from stalk cane at an existing mill plus molasses from district. Restricted to one unit per district. Table IX
Mew area developed, Stalk juice. Social change to 7 day-week, 39 week season3 annual employment on farm as well as factory. 50ha farms. Table XVIII.
As for 3 - 1600 ha properties. Table XVIII
As for 3 - 35,000 ha estates Table XVIII
As for 3 - whole cane processing including cellulose - 50 ha farms Table XIX
LAND1
AREA QSI UNITS
no extra
no extra
6.7
7.2
7.6
3.6
ESTIM. COST EtOH
27±2 4
28 ± 2 5
24
15.5
14.5
15.6
GROSS CAPITAL INVEST. A$m.
23,500
25,250
26,500
1 13,000
R. S D.
o.i2
As
2.5
3.0
3,5
0.22
3.0
R.&D. BENEFIT
(a) to process juice (b) thermal balance
for 1.
concept dev.3 save 3C/1. = $420m/year..
extra capital $1750m. cf.3, save 8.5cyi = $1200m/year
extra capital $3000m. cf.3, save 9.5c/l = $1330m/year
cellulose hydrolysis. concept dev. save capital $10,500m. cf.3 ! & 8.4c/1 = $1176m/year
t
7.
8.
9.
10.
11
12
13.
As for 6 - 1600 ha properties.
Table XIX
As for 6 - 35,000 ha estates
Table XIX
As for 3 - plus cassava fallow crop.
50 ha farms. Table XXI
As for 9 - 1600 ha properties
Table XXI
As for 9 - 35,000 ha estates
Table XXI
As for 6 - plus cassava fallow crop,
50ha farms. Table XXII
As for 12 - 1600 ha properties
Table XXII
3.9
4.1
5.4
5.8
6.0
3.2
3.4
11.1
10.6
22
15.2
14.1
15.8
11.6
13,500
14,250
19,000
203300
21,000
12,000
13,000
0,2
3.5
0.2
4.0
3.0
4.0
4.5
0.2
3.5
0.2
4.0
cellulose hydrolysis. concept
dev. extra capital $500m cf.6.
save 4.54/1 = $630m/year
cellulose hydrolysis,
concept dev. extra capital
$1250m.cf.6. save 54/1 -
$700m/year
concept dev. save capital
$4500m cf. 3. and 24/1 = $280m/
year
concept dev. extra capital
$1300m,cf.9. save 6.84/1 =
$950m/year
concept dev, extra capital
$2000m.cf.9. save 7.9c/1 =
$1100m/year
cellulose hydrolysis
concept dev. save capital
$1000m.of.6.extra 0.2c/1 =
$28m/year
cellulose hydrolysis
concept dev. extra capital
$500m.cf.7.extra 0.54/1 =
$70m/year
14.
15.
16.
17.
18.
19.
As for 12 - 35,000 ha estates
Table XXII
As for 6 - but with agricultural
productivity doubled. 50 ha farms
Table XXIII
As for 15 - 1600 ha properties
Social advantages over 17.
Save capital of $15,400m, cf. 3,
Save 15.6*/1 = $2180m/year cf.3.
Table XXIII
As for 15 - 35,000 ha estates
Table XXIII
As for 12 - but with portion of bagasse
as fuel and no coal. 50 ha farms.
Table XXIV,
As for 18 - 1600 ha properties
Table XXIV
3.6
1.8
1.9
2.0
3.7
3.9
11.1
11.5
8.4
8.0
12.4
9.6
13500
8100
8700
9000
14000
14700
0.2
4.5
! 0.2
11.0
! 0.2 [ 11.0
0.2
12.0
0.3
5.0
0.3
5.5
cellulose hydrolysis,
concept development.
save capital $750m. cf.8.extra
.5c/l - $70m/year
cellulose hydrolysis, concept
development, save capital
$4900 m. of.6. save 4.1c/1 =
$570m/year
cellulose hydrolysis, concept
development, save capital
$4800 in. cf.7. save 2.7£/l =
: $378m/year
cellulose hydrolysis-
concept development,
save capital $5250m, of.8, save
2.6C/1 = $360m/year
cellulose hydrolysis.
concept development.
extra capital $2000m, cf.12.
save 3.4C/1 = $476m/year I
cellulose hydrolysis,
concept development,
extra capital $1700m. cf. 13.
save 2.0C/1 = $280m/year
*
20.
21.
As for 17 but with space-age technology with remote control. Table XXV.
ESTIMATED MINIMUM PRICE ACHIEVABLE FOR ethanol FROM SUGARCANE
2.0 7.5
7
9200 As for 17 plus 5.0 space-age technology development -
extra capital = $200m,cf.17. save 0.5C/1 = $70m/year. save remote location of 90,000 persons
1. To produce 14Gl/year of ethanol.
2. Essential for development of entire concept. Initial investment only.
3. 30% of all concept development costs to process studies, 60% to agricultural studies.
4. Total production achievable at this price range = 200Ml/year
5. Total production achievable at this price range = 400Ml/year,
xi
FLOW SHEETS AND GRAPHS
FIGURE
1 Simplified flow sheet for dual production of sugar
and ethanol
2 Simplified flow sheet for producing ethanol from juice
of sugar cane
3 Simplified flow sheet for whole cane processing with cellulose
hydrolysis
4 Relationship between estimated price of ethanol as
related to the size of the farm unit.
Total steam 603
Figure Is Simplified flow sheet for dual production of sugar and ethanol.
CONTENTS Page
i ii
Preface Summary Flow Sheets and Graph xi
Introduction 1 Alternative fuels and their sources 6 The fermentation process 15 Agricultural considerations 19 Sugar cane for ethanol production 23 Technology studies 32 Basic fundamental information 38 Dual purpose factory 39 Effect of varying proportion of products 55 Locality for dual product operation 55 Dual product plant with molasses supplement 59 Single purpose ethanol-sugar cane plant 64 The precision of pricing procedures 76 The price of sugar and the price of oil 78 Ethanol from sugar cane in a new growing area 88 Location of a new sugar cane/ethanol complex 90 Seasonal considerations 92 Sunshine requirements for growing sugar cane 95 Water requirements for growing sugar cane 99 Fertilizer needs in sugar cane culture 105 Unit operations in sugar cane agriculture 110 Size of a sugar cane farm 112 New land development 117 Capital repayment alternatives 119 Methods of calculation for Table XIV 122 Estimated cost of mechanical component of farm unit operations 125 Irrigation application 128 Harvesting of sugar cane 129 Fuel Costs 134 Transportation of sugar cane 135 Factory equipment 138 Computer control factors 142 Farm equipment maintenance 143 Management of agricultural operations 144 Agricultural extension services 147 Productivity development on existing farm areas 150 The cellulose component of sugar cane 154 Cassava as a fallow crop 162 Effect of farm productivity on cost of ethanol 169 Coal as energy supplement 173 Carbon dioxide production 175 Fusel oil production 177 Denaturing of ethanol 178 Ethanol storage 181 The environmental impact of a large scale sugar cane/
ethanol industry 182 Ethanol and the internal combustion engine 185 Application of ethanol as a motor fuel 188 Development options 196 Predicting the future 198 Overall employment and income prospects 204 Application of space-age technology 208 Energy balance 213 Estimates of future Queensland and Australian requirements 216 Related relevant literature 218
TABLES Page
A Summary of estimated costs of ethanol production vii I Net Thermal Values of Selected Fuels 11 II Dual product plant without additional molasses - raw 53
material costs III Dual product plant without additional molasses - total 54
costs IV Queensland mill size and land productivity criteria 60 V Dual product plant with additional molasses. Raw
material costs 62 VI Dual product plant with total estimated costs of ethanol 63 VII Single product plant to produce ethanol without additional
molasses 67 VIII Single product plant to produce ethanol plus additional
molasses (raw material costs) 68 IX Single Product Plant with total estimated costs of ethanol
production 69 X Summary of estimated costs of ethanol production -
primary options 70 XI Total ethanol potential for an 817,000 Te cane complex 71 XII Effect of doubling the size of a sugar mill on ethanol cost 75 XIII Estimate of photosynthetic efficiency of sugar cane in
Queensland 97 XIV Tabulated indexed capital repayment rates 123-: XV Effect of size of field on cost of tractor usage 126 XVI Cost estimates for cane grown on large properties or
estates 129 XVII Estimated costs of road transport for sugar cane 137 XVIII Estimated cost of processing sugar cane stalk juice
for ethanol 14-1 XIX Estimated cost of ethanol from whole cane including
cellulose hydrolysis 161 XX Cost estimates for growing cassava for ethanol 166 XXI Estimated cost of producing ethanol from sugar cane stalk
juice and cassava 167 XXII Estimated cost of producing ethanol from whole sugar cane
plus cassava 168 XXIII Estimated costs of producing ethanol from whole cane
but with 80% achievable productivity. Coal as fuel. 171 XXIV As for XXIII but no coal as fuel 176
1
INTRODUCTION
Producing alcohol by the fermentation of plant sugars is probably
one of man's oldest technologies but until the development of distillation
as a means of concentration its use was restricted to such applications
as were suited to the relatively low concentrations it was possible to
achieve in this way.
Although) a distillation technique was described as early as Aristotle
in the 4th century B.C. it was not until the beginning of the 19th
century that its application to alcohol concentration became significant.
By the end of that century it had been developed to such a degree that
the fermentation and distillation of potatoes in Germany supplied
substantial quantities of alcohol for industrial purposes.
The word alcohol is of generic significance when used in organic
chemistry but in the current context the only alcohol with which we will
be closely concerned is ethanol (C.H OH) although some reference to other
alcohols will be made at appropriate stages.
Ethanol is the major product of alcoholic fermentations but small
quantities of amyl alcohols (d- and/or iso-) as well as some butyl and
propyl may also be produced and are generally referred to as fusel oil.
The amount varies between about 0.1 and 0.7% and may also include trace
amounts of fatty acids, esters, furfural and other substances.
Ethanol is the most important of the many products which can be
produced by fermentation for industrial purposes. The basic raw material
for this is the sugar glucose but this in turn is usually derived from the
breakdown of a higher molecular weight entity such as sucrose, starch or
cellulose. The relative importance of these as raw material will be
2
considered. There are a number of reasons for giving primary
consideration to sugar cane which will be given later. Suffice
it for the time being to say that there is already a well established
sugar cane growing community in Australia and the agro-technology is
well understood. Sugar cane is known to be one of the best plants for
efficiently utilizing sunshine in the synthesis of carbohydrate and it
grows well under a wide range of soil and climatic conditions with
appropriate cultural techniques. In fact Australia leads the world in
the annual rate of production of sugar in cane per unit of area under
cultivation.
Ever since the internal combustion engine was invented, the
possibility of using ethanol as a fuel or partial fuel has been considered
and very detailed study went into the subject during the latter part of
the 19th and earlier part of the 20th century. The net conclusions have
been that it can be used successfully under a wide range of conditions
without significant modification being required for the engine as marketed
during the 1970's. There have been periods when certain countries have
made quite significant use of ethanol for internal combustion engines and this
includes Australia during the 1930's and 1940's. Special circumstances
have had their influence and these will be discussed later. Brazil
currently is an important user and is developing this capability rapidly.
Ethanol is a fuel which can be continuously regenerated as long as
there is sufficient land available for cultivation.
For some years the Halthusian predictions of population growth
outstripping available food supplies and apparently abundant mineral supplies
of liquid fuels militated against serious consideration being given to wide
scale growth of plant materials for industrial energy. These are no
3
longer the spectre painted in the 1950's. Population growth now
appears to be most closely related to the economic advantages or
disadvantages of a large family. As long as there are economic
advantages, as in a labour intensive agricultural economy, population
growth is for all practical purposes, uncontrollable. With the
development of machine intensive cultivation techniques, the
disadvantages of a large family unit become apparent and slowly the
rate of population growth slows to controllable figures. The supply of
food is also related very strongly to the efficiency of harvesting and
storage techniques as well as to distribution facilities. The net
result is that with the exception of local conditions of drought or
flood the world in fact does have a surplus of food and there are good
reasons for believing that the situation will continue for the
forseeable future.
Ho person likes radical changes in their way of life, and a sudden
change from a petrol based liquid fuel economy to an entirely ethanol
based economy would be fraught with many problems. Fortunately this
should not be necessary in Australia and it could be introduced
progressively to replace imported petroleum fuel as it blends very well
with petrol in proportions which would be adequate to effect this change
with minimum of frustration and provide an extensive and well needed
development of employment in Australia involving a wide range of skills.
Ehhanol is a lesser fire hazard than petrol in storage and transport
situations. On the other hand it does have its own specific problems
such as unsocial results in human consumption and its miscibility with
water. There are ways and means of dealing . with these problems and
they will be discussed.
The environmental impact of large scale development would be expected
to be most prominent in two areas. Firstly the substantial extension of
cultivated land and new housing development, possibly but not necessarily
at the expense of forest land. Secondly there would be the problems of
waste disposal from the fermentation process. The installations would
need to incorporate equipment and procedures to cope with this. On the
other hand ethanol can effectively displace alkyl-lead additives commonly
employed for increasing the anti-knock rating of petrol and which pollute
the atmosphere by their presence in exhaust gases. Internal combustion
engines operate at lower temperatures and run more quietly when ethanol
is used as a petrol additive. As a complete replacement for petrol
there are more problems including a significantly lower thermal value,
but when used in minor additive proportions there is no noticeable
increase in volumetric consumption, nor are changes required in the
tuning of the engine of significance.
These matters will each be considered in detail at an appropriate
stage.
When considering alternative energy sources it is thought to be
impracticable to attempt to displace all currently used types of mineral
based energy with a single type of energy derived in one way from a solar
source. This study will confine itself to problems involved in the
progressive development of liquid fuel derived from nature's solar cell-
chlorophyll through the intermediate natural synthesis and storage of
carbohydrate in sugar cane.
Reasons for the selection will be elaborated during the course of
this study.
Two questions of major concern become significant - (1) can ethanol
be produced at a satisfactory price and in substantial volume and (2)
can ethanol be used effectively as a major liquid fuel? The two
5
questions revolve around each other and both must be answered effectively,
but it is largely a matter of choice as to which is discussed in detail
first. In this study the choice has been made firstly to study production
and secondly consumption, but always being cognisant of interactions and
side effects.
6
ALTERNATIVE FUELS AND THEIR SOURCES
The internal combustion (I.C.) engine has become such a widely used
device in present day living that it is almost inconceivable to imagine
alternatives achieving more than marginal significance. These engines
have been developed to employ fuels in either the gas or liquid phase,
endeavours to employ powdered solid phase fuels or mixtures of solid and
liquid phases have not been successful due mainly to problems concerned
with the exhausting of ash constituents of solid fuels.
Only a very small proportion of I.C. engines employ gaseous fuels.
Whilst they do enjoy many advantages including a continuing supply of
fuel in the event of a development of a hydrogen based energy economy,
the major disadvantage is the difficulty experienced in developing
satisfactory storage techniques especially for small mobile units such
as the motor car. From time to time there have been developments in
the use of producer gas units including their attachment to mobile
vehicles. It is not proposed to consider these more than marginally
in the present study.
For our purposes we will consider the development of the I.C. engine
along two main lines to which we will apply simply the terms ::diesel::
and "petrol1 engines and in this context, the terms will be used
essentially to define the method of ignition - the diesel engine relying
on pressure ignition and the petrol engine relying on spark ignition.
There is an interaction of these two mechanisms as the compression ratio
of internal combustion engines is increased and the implications of this
will be shown to be important. The development of the diesel engine
was dependent very largely upon the successful development of fuel
injection to specific cylinders under pressure. On the other hand, the
carburettor system of the petrol engine has become progressively more
complex and there has been a marginal but growing encroachment of direct
6
ALTERNATIVE FUELS AND THEIR SOURCES
The internal combustion (I.C.) engine has become such a widely used
device in present day living that it is almost inconceivable to imagine
alternatives achieving more than marginal significance. These engines
have been developed to employ fuels in either the gas or liquid phase,
endeavours to employ powdered solid phase fuels or mixtures of solid and
liquid phases have not been successful due mainly to problems concerned
with the exhausting of ash constituents of solid fuels.
Only a very small proportion of I.C. engines employ gaseous fuels.
Whilst they do enjoy many advantages including a continuing supply of
fuel in the event of a development of a hydrogen based energy economy,
the major disadvantage is the difficulty experienced in developing
satisfactory storage techniques especially for small mobile units such
as the motor car. From time to time there have been developments in
the use of producer gas units including their attachment to mobile
vehicles. It is not proposed to consider these more than marginally
in the present study.
For our purposes we will consider the development of the I.C. engine
along two main lines to which we will apply simply the terms T;diesel::
and !ipetrol: engines and in this context, the terms will be used
essentially to define the method of ignition - the diesel engine relying
on pressure ignition and the petrol engine relying on spark ignition.
There is an interaction of these two mechanisms as the compression ratio
of internal combustion engines is increased and the implications of this
will be shown to be important. The development of the diesel engine
was dependent very largely upon the successful development of fuel
injection to specific cylinders under pressure. On the other hand, the
carburettor system of the petrol engine has become progressively more
complex and there has been a marginal but growing encroachment of direct
7
fuel injection into the petrol engine field.
The diesel engine is designed essentially to operate on low
volatility liquid fuels whereas the petrol engine and high volatility
fuels are largely designed for each other. In the competitive area
of society as distinct from controlled economics there is usually a
substantial cost advantage in using low volatility liquid fuel. This
has been largely accentuated by the tax structure which has been
developed with progressively increasing intensity on volatile liquid
fuels.
For the present considerations it is necessary to eliminate as far
as possible the incidence of tax on fuels for a true comparison of their
relative usefulness as energy sources, but at the same time, recognise
that taxation in some form or another is inevitable.
Ethanol can effectively displace either diesel or petrol type fuels,
but initially it will be considered as a partial substitute for petrol
type fuels with cognisance being taken of the likely results of
progressively increasing the proportion in petrol type fuels as well as
of progressive displacement of diesel fuels as well as petrol.
For ethanol to become a commodity generally available to the public
it becomes of major importance for its use to be restricted to that of a
motor fuel or related industrial applications and not be readily converted
to human consumption. There are two reasons for the latter requirement,
one involves the unsocial side effects, the other relates to the loss of
revenue imposed more heavily on alcoholic drinks of all types than on
motor fuels. The measures taken to effect desired control in this area
are known as denaturing of alcohol. While this will be discussed in
some detail later, it is well to point out at this stage that the
selection of a suitable denaturant is one of the most important and at
8
the same time one of the most difficult of the problems which relate
to the production and widespread use of ethanol as a liquid fuel.
Whilst primary consideration is given to ethanol as a liquid fuel
it is recognised that numerous other alternatives have been proposed
from time to time, as either a partial or complete substitute for use
in either petrol or diesel engines.
Hydrogen is the simplest possible substitute when considered from
the point of view of chemical structure. It is a gas at atmospheric
conditions of temperature and pressure and is difficult to liquify
requiring high pressures for appropriate compression. Some attention
has been given in global planning to the prospect of developing a fuel
economy entirely based on hydrogen, which in turn can be a product of solar
energy. The most commonly studied route being the generation of
electricity with solar cells and the employment of this electricity
to decompose water into its elements - hydrogen and oxygen.
There are still so many problems related to the economic development
of electricity in this sequence that a fuel economy based entirely on
solar-hydrogen is believed to be still many years ahead. Also hydrogen
is of very low specific gravity and this reduces it to the status of a
second grade gaseous fuel.
Vlhen considering relative thermal values of fuels employed in internal
combustion engines the net value is of more significance than the gross
value since the latter includes the latent heat of condensation contained
in the water vapour of the products of combustion and condensation does
not take place in these fuel cycles.
9
Hydrogen gas is rated at 10.8 MJ/m3 at S.T.P. compared with 35.7
for methane. On a weight basis however, this would represent
120 kJ/g as compared with 43.7 for petrol.
Methane (CR4) as the most important constituent of natural gas or
produced by anaerobic fermentation is also difficult to liquefy and
currently of no real practical significance as a possible alternative
to petrol.
Methanol (CH3OH) is one of the most important products of high-
pressure organic syntheses used today, reacting carbon monoxide with
hydrogen produced as synthesis gas by the reforming of natural gas.
As natural gas is currently available in relative abundance in Australia,
the possibility of converting it to methanol as a liquid fuel supply must
be given significant credence.
Methanol can be used as a fuel for I.C. engines but it is not a
particularly good fuel having a nett thermal value (N.T.V.) of 20kJ/g
or 48% of that of petrol with ethanol at 27 or 63% of the value of petrol
on a V/V basis. Methanol is more volatile than ethanol which should
favour easier starting but the lower latent heat of vapourization is less
advantageous from the point of view of thermal efficiency.
Methanol has been important in the marketing of non-potable ethanol
by virtue of its usefulness as a denaturant. The classical denaturing
fluid has been "wood spirit" or "wood naptha" which used to be a product
of the distillation of wood. It is not a chemically pure material but
is considered to be about the nearest approach to a perfect denaturant
for ordinary purposes.
There may well be merit in blending up to 10% of methanol with
ethanol to be used for motor spirit but this will be discussed in
more detail later.
Diethyl ether [(C2H5)20] can be produced in a relatively straight
forward manner from ethanol by dehydration with sulphuric acid. It is
not a particularly strong competitor for ethanol as a straight motor
spirit although it does have a thermal value about 14% higher on V/V basis.
It is too volatile - boiling point 34.6 - to be useful alone, but when
blended with ethanol it is beneficial in improving starting characteristics.
Up to 40% has been used in Natal (S.A.) blended with 60% ethanol and known
as "Natalite". When converting ethanol to ether there is a loss of
37.5% on a volume basis offset by an associated gain of 20% in thermal
value.
Acetone (CH3.C0.CH3) is intermediate between ether and ethanol
in terms of volatility (B.P.56.5°) and with a N.T.V. of 28.5 kJ/g or 23
MJ/litre is 69% of petrol (V/V).
Ethanol by way of comparison has a B.P. of 78.5 and a N.T.V. of
26.8 kJ/g or 21 MJ/litre.
Although acetone can be produced by chemical synthesis it is also
a product of fermentation using Clostridium genus bacteria.
Unfortunately, acetone is normally produced in association with butanol
by this process, a typical product being 60% butanol, 30% acetone and
10% ethanol. The butanol is of little value as a motor spirit because
of its low volatility (B.P. 117.7).
The net thermal values for a range of gaseous and liquid fuels are
listed in Table I. Whilst the N.T.V. of a fuel is by no means the only
criterion for selection it is an important one in -the screening
10
procedure. Three gases are included in the table - hydrogen, methane
and acetylene. A major problem in each case is that of liquefaction
for the purpose of compressing it into a reasonable volume. It can
be seen that hydrogen even when liquified by compression has a very low
volumetric thermal value and combining this with the heavy weight of
cylinders required for storage it becomes a quite uneconomical fuel for
most I.C. engines.
Acetylene cannot be used in the simple compressed form owing to its
unfavourable explosive characteristics but may be compressed into a
solution of acetone. However, this is not an important possibility in
the current context and will receive no further consideration.
TABLE I - NET THERMAL VALUE OF SELECTED FUELS
Whilst the N.T.V. is a useful primary criterion for evaluating a
fuel for an I.C. engine it is by no means the only one and this will be
discussed in more detail with respect to ethanol at a later stage in
this report.
11
12
The history of ethanol production has seen several important
changes related to developments which have taken place in technology.
It was in the latter part of the 19th century that ethanol first
became available on a large enough scale to justify classifying it as an
important industrial chemical. This industry was based on carbohydrate
fermentation but the product invariably contained 5% of water because
of the ethanol - water binary constant boiling point mixture which could
not be economically separated by then known techniques of distillation.
For special purposes anhydrous ethanol could be made by preferential
reaction with a dehydrating agent such as lime or anhydrous calcium
sulphate but was very expensive.
During the first two decades of the twentieth century various
modifications of this technique were developed (although the first
patent for the use of CaO goes back to 1842) and incorporated in the
distillation technique to be removed with the water either at the bottom
or at the top of the column depending upon the relative volatility of the
additive as compared with ethanol.
Initially dehydration was very costly and only carried out for
special laboratory requirements. It was economically unthinkable even
to contemplate the possibility of anhydrous ethanol becoming an important
industrial commodity.
A radical change developed with the ultimate development of the
technique of introducing a third component to the distillation column
which would form a ternary C.B.M. (ethanol-water-benzene) and which
would separate into two liquid phases on condensation allowing a continuous
recirculation of the additive. This was perfected to the stage at which
the cost of anhydrous ethanol was very little higher than the 95% aqueous
azeotrope.
13
Another development in the production of anhydrous ethanol has been
for a process to handle directly a fermentation mash at 6% ethanol making
use of an extractive distillation technique.
The development of these techniques had, however, only a marginal
influence on the employment of ethanol as a motor fuel since 95% aqueous
ethanol can be used quite readily as a mild blend with petrol with no
significant influence from the water. It can also be used directly or
as a methanol-denatured spirit, in fact as much as 50% of water can be
tolerated in a spark ignition I.C. engine provided a more volatile fuel
is employed for starting. The water does of course reduce the thermal
value of the fuel pro rata.
During the 1940's the production of ethanol as a petrochemical began
to become important with a progressive phasing out of the fermentation
product and synthetic ethanol dominated the ethanol market until the
recent substantial use in the price of crude oil.
Synthetic ethanol may be produced either from acetylene originating
from calcium carbide or from ethylene available from processing crude
oil. The acetylene route only enjoyed a relatively short period of
serious interest once the price of natural gas and crude oil fell with
the extensive discovery and development of resources since the second
world war. The conversion of ethylene into ethanol is a relatively
straightforward chemical procedure involving for example firstly
sulphonation with strong sulphuric acid
followed by hydrolysis and reconcentration of the liberated sulphuric
acid. Alternatively, a more straightforward vapour phase hydration
may be effected in the presence of phosphoric acid at a temperature of
300 and pressure of 70 kilopascals.
14
Certain countries have continued to provide incentives for the
production of fermentation ethanol to encourage home industry and
reduce dependence on overseas energy supplies although generally the
latter effect has been largely marginal.
Since the rapid rise of the international price of crude oil there
has been a resurgence of interest in raw materials suited to fermentation
procedures. Future market situations will be influenced by relative
costs of raw materials, costs involved in processing techniques and the
development of technology related to the use of ethanol or its
competitors. The combination of these factors makes forecasting
hazardous. Venturing into forecasting will be deferred until later
until a more detailed study has been made of factors involved in the
production and use of fermentation ethanol.
15
THE FERMENTATION PROCESS
Ethanol produced by fermentation originates mainly from the
monosaccharide glucose (or dextrose) although its close relative
fructose (or levulose) ferments with equal facility. Mannose is also
a natural sugar which is fermentable but is not of industrial
significance. Galactose which is met with among the hydrolysis
products of many plant tissues is only fermented with difficulty.
Neither glucose nor fructose are sufficiently prominent in nature to be
important in themselves as raw materials but are produced from the
hydrolysis of more abundant carbohydrates.
On the other hand nature builds up complex carbohydrates from carbon
dioxide and water with the aid of sunlight with glucose and fructose
appearing fairly early in the synthesis chain. Whilst much attention
has been given to the development of plants of elementary or single cell
structure the stage has not been reached where these might be given
serious consideration as viable sources of raw material in competition
with more complex plant products.
There are three materials made by nature and which are currently of
significant importance as raw materials for fermentation industries.
These are cellulose, starch and sucrose. Both cellulose and starch
are hydrolyzable to glucose whereas the hydrolysis product of sucrose is
a 50-50 mixture of glucose and fructose. None of these three materials
is directly fermentable itself and nature has not developed a useful
storage system for glucose or fructose.
Cellulose functions essentially as part of the fibrous structure of
plants as a polymer of glucose units and similar in chemical composition -
(C6H10O5)n.
16
Associated with cellulose in the fibres of plants are significant
amounts of pentosans which are polymers of pentose sugars (C5H10O5)n and
of lignin which is of slightly variable composition and of very complex
and variable chemical structure. There are also smaller quantities of
specialised substances such as resins which are developed in specific
types of plants.
The only material in this complex group of cellular substances
which is reasonably amenable to fermentation is the cellulose which must
first be hydrolysed to glucose. This seldom constitutes more than 50%
of the fibrous components of plants and not unusually as low as 40%.
Pentosans can be hydrolysed to pentose sugars and these are amenable
to a small amount of fermentation but except under special circumstances
they are more of an impediment than a benefit to the use of cellulosic
plant materials for the production of ethenol by fermentation.
The lignin component is even more untractable from the fermentation
point of view and a waste product difficult to handle from the point of
view of a polluting effluent.
Starch is a food for both plant and animal and is stored in the plant
in a seed or tuber and to a lesser extent it often occurs in stalks and
leaves but usually en route to the storehouse. Hydrolysis of starch is
much more easily effected than of cellulose producing a readily fermentable
glocose solution. Whereas cellulose is usually hydrolysed with the aid of
mineral acid and high temperature - commonly with high pressure steam,
starch may be hydrolysed with very much milder conditions and at higher
reaction rates.
17
The plant enzyme - diastase is preferred when the fermentation
product is to be a potable alcohol. Diastase is an amylase enzyme
which hydrolyses starch to a mixture of glucose and maltose, the
latter being a disaccharide having the same empirical formula as sucrose -
C12H22O11 and like sucrose is non fermentable itself. It must therefore
be further hydrolysed to two molecules of glucose which is then fermented.
The diastase is usually prepared from a grain of which barley is
reported to be the best although sorghum grain is also a useful source
in tropical countries. The diastase is developed during germination of
the grain in a process known as malting.
Alternatively, amylase may be produced by using certain moulds of
the Aspergillus or Mucor genera.
Starch as it exists in nature is in the form of small grains which
usually need rupturing before they can be attacked by amylase. This is
done thermally to produce a gelatinised material.
Many different methods have been developed for the ultimate preparation
of the carbohydrate to a form fermentable by yeast, which is the organic
catalyst employed for the conversion of the glucose to ethanol.
If we start with sucrose as the raw material the hydrolysis step is
rather less complex than is the case with either cellulose or starch
since we start with a disaccharide. Yeast of the variety Saccharomyces
cerevisiae is commonly preferred for the fermentation step. Since this
contains the enzyme Invertase which is capable of catalysing the
hydrolysis of sucrose the yeast is sufficient to effect the double function.
However it is often an economic advantage to employ some acid and heat to
accelerate the hydrolysis.
18
Whilst sucrose occurs in many plant juices it is most strongly
concentrated in the sugar cane or sugar beet.
Alcohol has for many years been produced either in potable form or
for industrial purposes from the molasses resulting from production of
cane or beet sugar. In the case of beet molasses there may be a
significant amount of the trisaccharide-raffinose. Upon hydrolysis
this yields glucose and the disaccharide melebiose which further
hydrolyses to glucose and galactose.
Normally galactose is a difficult sugar to ferment but it may be
effected with a bottom fermenting yeast whereas glucose and fructose
are satisfactorily fermented with either a top or bottom yeast.
Molasses is commonly a relatively low-priced commodity as there is
only limited scope for alternative uses such as fertilizer or animal
food. However the amount available is limited by the amount of
associated crystal sugar which is produced and local fermentation for
industrial purposes is seldom economically viable from the point of view
of actual size of equipment. Transport of molasses adds to the cost
if a central distillery is operated and the time came during the 1950's
when even molasses could not compete with crude oil as a raw material
for industrial ethanol.
Since the steepening of the price of crude oil in the 1970's there has
been a re-awakening of interest in supplies of molasses, especially by
the Japanese.
19
AGRICULTURAL CONSIDERATIONS
Many agricultural materials have been used at one time or another
as a raw material for industrial ethanol production by fermentation
and others have been studied.
In the latter half of the 19th century and the early part of the 20th
century, Germany encouraged the production of industrial ethanol from
potatoes (4/5ths) and grain (l/5th). The industry was not originally
established to find a cheap substitute for petrol, but was one of the
consequences of a policy primarily directed towards the extension and
improvement of agriculture. Progressively the quantity of production
increased until an overproduction situation developed around the turn of
the century. However, the industry suffered heavily as a result of the
1914-18 war and never recovered in the face of developing competition from
sulphite pulp, wood and carbide in spite of substantial preliminary
subsidies.
Although conditions are very different today there are many lessons
which could well be learned from a detailed study of Germany's experience.
The growth of the industry was undoubtedly closely related to the
agricultural methods and dietetic habits of the people. In 1913 there
were some 6000 distilleries producing 300 Ml of ethanol which represented
80% of Germany's total ethanol production at the time. However, it is
apparent that such success as was achieved was due not so much to an
economically costed product as to the effect of State subsidies. The
differential nature of some of these subsidies and taxes also had a
significant influence on technology including the development of strong
mash fermentation. With an average yield of 16 tonnes per hectare a yield
of 1.4 kl was considered a good figure for potato culture.
20
Of other tuberous crops Jerusalem artichoke, sweet potato and yam
could be expected to provide yields of the same order of magnitude.
Cassava however could probably more than double this yield to
something of the order of 3.5 kl/ha. The starch content of cassava
tubers is much higher than potato and are the source of the tapioca
of commerce. Its cultivation is more restricted to tropical locations
as it is sensitive to cold. The soil soon becomes exhausted after
successive cropping and rotation. Crops of maize, sorghum or legumes are
not uncommonly grown.
Unfortunately cassava cultivation has not responded particularly well
to mechanisation. The tubers are long and spreading and can only be
ploughed out with difficulty, it being necessary to dig them out or pull
them by hand. Modern developments have been to breed better rooted
varieties able to be harvested mechanically and these together with
improved cultivation techniques have been able to double potential yields
of the above-mentioned value to figures over 7 kl/ha.
The yam (Dioscorea) and the sweet potato (Ipomona batotus) are two
other tuberous crops which store starch and can be heavy yielding in
tropical climatic conditions. They grow best in sandy soils and also
present problems for mechanisation.
Many statistics have been recorded for the yield of agricultural
products and many of these can be misleading unless there is appropriate
qualification. For example, we may compare average yields on a world
basis but find that the best country yields are at least twice as much as
the average and the best area within the best country may yield twice as
much as the average for that particular country or more than four times
the world average.
21
Another qualification required is the time taken to grow the
crop. In most countries sugar cane is an annual crop with a growth
cycle averaging about 9 months. Hawaii which records by far the best
yield may harvest annually, but the growing cycle extends to 2 years.
Some other areas have a similarly long growing cycle with suitable
local reasons for maintaining production.
Similarly in the sugar beet situation although it is an annual crop,
the related sugar mangold can crop more heavily in weight/hectare
but with a lower concentration of sugar and is commonly a biennial crop.
Trees which are frequently considered as a source of cellulose for
fermentation take a number of years to grow. Alfalfa on the other
hand can be harvested every few weeks for a useful portion of the year.
Certain species of palm trees are sources for the production of a
low quality sugar in village communities throughout areas from India
to Indo-China. When calculated in terms of sugar yield per hectare per
annum they compare quite favourably with sugar cane grown in those
countries. However, sugar cane in those countries is relatively low
yielding and there are substantial harvesting problems with the palms.
In sugar palms, sap must be extracted from the florescent zone which
is 6 to 15 metres above the ground. On the cultivation side the palm
goes on yielding suitable juice for perhaps 50 years with little
cultivation, fertilizing or irrigation and ground level cropping or
grazing may be carried on over the same area. The palm does, however,
take about 7 years before it reaches maturity levels of production.
The cultivation of alfalfa to yield both protein and carbohydrate
has been suggested with annual yields of up to 63 tonnes of carbohydrate
per hectare suggested as achievable, but the value of an associated 25 tonnes
of vegetable Drotein would in itself be a quite significant factor in costing.
22
It is of some importance to know the nature of the carbohydrate
in the plant. If we assume an ethanol recovery in production of
88% of that theoretically obtainable from the carbohydrate, then a
yield could be expected of 600 1/tonne for sucrose whereas starch or
cellulose would yield 634 and glucose or fructose 570.
Whilst the hydrolysis of sucrose can be expected to be stoichiometric,
the efficiency of cellulose hydrolysis is usually very low and often as
low as 50% or even 35% with recalcitrant types. A high degree of
saccharification can be achieved with starch and a yield of 634 1/tonne
is not unusual. This represents a 5.6% benefit over sucrose and 11%
over glucose or fructose.
Cellulose hydrolysis and fermentation processes of a commercially
viable character have been particularly difficult to achieve and there
is still a great deal of investigation going on in this field both in
Australia and overseas.
SUGAR CAME FOR ETHANOL PRODUCTION
After reviewing a wide range of possible plant sources of
carbohydrate suitable for ethanol production it is evident that the
sugar cane is high on the list. Poor sugar cane may not compare
particularly well with very good alfalfa, cassava or sugar beets,
however, Australia stands well to the top of the list in world sugar
cane productivity with Hawaii ahead and Ethiopia also reporting very
good yields. The latter are no doubt related more to climatic
benefits than cultural expertise.
Furthermore, the sugar cane is recognised as being one of the most
efficient users of sunshine in the plant kingdom. Not only does the
sugar cane produce substantial quantities of sugar which it conveniently
stores in the stalk, but the fibre in the stalk is additional
carbohydrate of a similar magnitude to the sucrose. The fibre could be
a source of cellulose for fermentation, but it has significant value as
a fuel and this will also be examined in detail in this analysis. Sugar
beet, cassava and cereal grains provide nothing in the way of
associated fuel and the cost of this commodity required in the ethanol
production must be added.
Sugar cane juice also contains the hexoses glucose and fructose
(known collectively in the trade as "reducing sugars") which are useful
sources of ethanol but not of crystal sugar. The relative amount of
the hexoses varies according to the season and the quality of the cane.
Sugar cane which is poor in terms of sucrose for any reason may contain
twice as much hexose as better quality cane. This serves as a
beneficial balancing influence if the sugar cane is thought of in terms
of a source of ethanol.
23
24
Sugar beet juices do not have any significant residual
unsynthesized hexose sugars, all soluble carbohydrate being in the form
of sucrose unless some deterioration has taken place.
Perhaps the next question to consider is the useful yield which
might be expected from an Australian crop of sugar. The pricing system
in the Australian sugar industry has been designed to give financial
encouragement to those farmers whose cane is able to produce the highest
proportion of crystal sugar. The farmer also recognises the economic
advantages of heavy yields of the cane itself per unit area. These
two desiderata are not necessarily compatible, in fact increases in
tonnage of cane often results in lower yields per tonne.
The net result of these two influences is that in Australia over the
long term the tonnage of cane per hectare has shown an average annual
increase of 1.1% and tonnes of sugar per hectare a corresponding growth
rate of 1.58% on a compound interest basis. Throughout the 75 years
over which these figures have been taken, the question has continually
been asked as to whether continued improvement could be expected.
There have always been fluctuations from year to year and it would be
invidious to select any particular year as being representative, and if
a ten year period were taken and averaged, the average for the next ten
year period would be more predictable and could be expected to be higher
by 11 1/2% for tonnage of cane and by 17% on tonnage of sugar.
Furthermore, there is substantial variation from district to district
throughout the cane growing areas of Queensland. There is sugar cane
grown in northern N.S.W. but as the sugar produced in those areas
represents less than 4% of the total Australian production consideration
of ethanol production prospects will be restricted to Queensland although
some reference will be made at a later stage to possible areas for
development in other parts of Australia.
25
There are further difficulties with statistics. Sugar production
is referred to in terms of 94 Net Titre (N.T.) in Australia. This is
a quality criterion of local concern, designed to estimate the actual
amount of refined sugar crystal which can be produced from raw sugar of a
certain quality and involves corrections for the ash and hexose content
of the raw sugar.
Furthermore sugar contents are referred to in terms of "pol"
which is an abbreviation for polarization and refers to the technique
universally employed for analysis. It is well known that this does not
reflect the true sucrose content but is a sufficiently close approximation
for most purposes to allow full advantage to be taken of the rapidity of
the method. We can get an indication of the order of precision of the
pol value if we have an analysis of the final molasses from the same
factory at the same time in terms of both pol and sucrose. If we take
as an example a sample of 100 tons of crystal sugar having the following
analysis which is typical of Australian conditions:
Pol = 98.37 per cent
Reducing sugar = 0.37
Ash = 0.38
Moisture = 0.43
The N.T. value then equals Pol - R.S. - (5xAsh) = 96.10
Tonnes of 94 N.T. sugar = tonnes actual sugar x actual N.T. = 102.23. 94
Experience indicates that the actual sucrose content would probably
be closer to 98.52 than to the pol value of 90.37. Thus if the figure
for tonnes of 94 N.T. sugar be reduced by 3.8% a better representation of
the weight sucrose in crystal raw sugar would be obtained. Actually a
discount of 4% is commonly applied which very closely represents the weight
of pol.
26
In actual fact there is no such substance as polr. The term is
an abbreviation for the word "polarization which refers to the technique
commonly employed for analysing sugar house products. It is obtained by
observing the sugar solution with a beam of light which has been optically
polarised. The sugar in the solution proportionately affects the degree
of polarization and the instrument is appropriately calibrated.
Unfortunately sucrose is not the only substance in a cane sugar juice
or raw sugar solution which affects the polarised light in this way.
The two main non-sucrose substances in sugar cane products which act in
this way are the hexose sugars glucose and fructose. The fact that they
have an influence opposing each other and which largely compensates has
enabled the convenience of the method to be extensively applied in the
sugar industry. Under conditions of poor technology, it does not matter
very much but the better the standard of technology the more significant
is the difference between the sucrose and pol values. To perform a true
sucrose analysis is difficult, complex and tedious with the consequence
that experimental analytical error can be of the same magnitude or even
greater than the real difference.
However, it is considered to be valid to take into account the
differences between pol and sucrose for the purpose of the current exercise
and to apply the correction in accordance with the best experience.
Statistics recorded in Queensland literature for yields of sugar per
hectare are in terms of 94 N.T. quality and require appropriate correction.
This however represents only the sugar recovered as crystal. From the
point of view of ethanol production, we are more concerned with the total
sugar content of the juices in the cane since both glucose and fructose
can be fermented to ethanol. Unfortunately these are even more difficult
27
to estimate because sugar cane in Australia is evaluated in terms of
C.C.S. which letters stand for "Commercial Cane Sugar". The C C S . is
calculated from a formula designed to estimate the actual amount of
"94 N.T." sugar which can be produced from a particular tonne of cane. The C C S . is calculated as follows:
C.C.S. = Pol in Cane - 1/2 Impurities in Cane
Since Impurities in Cane = Brix in Cane - Pol in Cane
then C.C.S. = 3/2 Pol in Cane - 1/2 Brix in Cane
Like Pol the term Brix does not refer to any substance in particular.
It also refers to the result of a convenient analytical technique and
approximates the total solids dissolved in the juice or syrup. The
measurement involves a determination of the density of the liquid usually
using a type of hydrometer especially calibrated for sugar solutions.
In high purity juices and syrups the readings are usually sufficiently
accurate for most purposes but in low purity juices and molasses there is
a progressive deviation from the true figure as the proportion of non-
sucrose increases. Brix may also be measured by means of a refractometer
the values for which are intermediate between the true total dissolved
solids and the hydrometric value. The measurement of Brix is not
particularly critical at this stage as far as the ethanol proposal is
concerned.
The C.C.S. formula was designed also to evaluate the Pol and Brix
content of the cane itself from the analysis of the juice expressed by the
first roller of the milling tandem. Whilst the technique has distinct
advantages from the point of view of speed and simplicity it does have
limitations from the point of view of precision. Present day techniques
prefer to sample the cane rather than the juice and to perform a direct
analysis on the sample of cane. The added complexities have very largely
been minimised by the development of better technology for sampling, sample
preparation and sample analysis.
28
In the example which has been quoted the C.C.S. for the corresponding
cane was 13.11 and the density of cane growth was 84.6 tonnes of cane per
hectare. The pol in cane was recorded as 14.41%. If this be corrected to
a sucrose value it would probably have been 14.83 or 2.9% higher than pol.
It is estimated from the analysis of juice resulting from the cane that
the hexose concentration would have been about 3% of the pol or 0.43% on
cane. For the purpose of estimating ethanol production it is convenient
to convert this to "equivalent sucrose" or 0.41%. Some other workers in
this field prefer to convert to "equivalent glucose".
Thus the fermentable sugars "as sucrose" in the cane would be 15.24%
and the production per hectare 12.9 tonnes.
If productivity and quality of cane continue to improve at the rate
of 1.58% per annum then for the 11 year period 1980/90 a mean value of 15.2
tons per hectare would be indicated as compared with the mean of the 11 year
period 1963/73. Predictions for specific years have a lower precision
(St.D. ~ 7.5%) than predictions for a decade (St.D. - 2.5%) owing to variable
seasonal influences. There is some levelling out of these influences by
virtue of the north/south relationship of the Queensland sugar belt in
that a bad season in one area seldom extends through all the other sugar
growing areas and vice versa.
There is a substantial difference between the highest and the lowest
yielding areas with the Burdekin as high as 18.7 tons of 94 N.T. per hectare
in 1973 as compared with 8.84 for the Mackay and Proserpine areas in the
same year.
Traditionally ethanol production in the cane sugar industry has been
very largely restricted to the use of molasses as a raw material. There
is no technical reason however, restricting production from the juice itself.
29
This has been widely practised in the beet sugar industry especially
in France and Scandinavian countries. If we look at Queensland sugar cane
with 12.9 tonnes/ha of fermentable sucrose equivalent (13.6 as fermentable
glucose equivalent) as an ethanol source then the availability should be
reduced by about 4.5% to compensate for loss during the mill extraction
operation. This would indicate a yield of the order of 7.39 kl/ha on
1973 average figures or 8.71 for 1980/90. (These figures are equivalent
to 660 or 777 imp. gallons per acre for comparison with figures in pre-
metric period reports).
Queensland sugar cane stalks also yield about 11.6 tonnes/ha of
fibre which if added to 12.9 or 15.2 would give figures of 24.5 or 26.8 as
total carbohydrate yield or perhaps a "round figure" of 25 to 26 tonnes/ha.
Fibre is a mixture of many substances insoluble in hot water and sugar
cane fibre has the following approximate composition.
Cellulose 53
Pentosans Xylan 19
(Cane Gums) Araban 4
Lignin bodies 19
Waxes 3
Ash 2
There are variations within each group, and the chemical specification
of a group is itself open to some discussion. However, these are not
of sufficient significance to prevent a discussion of the properties of
the fibre using the above distributions as a basis.
30 The fibre appears in the sugar cane factory as "bagasse" which
is the residual material from the milling tandem after juice has been
extracted. The bagasse contains moisture and residual sugars having
the following approximate average composition:
Bagasse: fibre 50
sugars 2.2
moisture 47.8
Traditionally it is used as a fuel to generate the steam required
for the operation of the factory. It is part of sugar factory technological
design and control to arrange matters of steam consumption and electrical
and mechanical power requirements as well as steam generator efficiency so
as to be able just to consume the bagasse supply. Operating a tandem of
mills plus a distillery means rather different problems of steam
consumption than for the same tandem of mills to operate with the
conventional concentration and crystallization operations.
The employment of bagasse as a fuel has made very difficult any attempts
to place on it a monetary value. As a fuel the above mentioned bagasse
would have a net thermal value of 8175 kJ/kg which is about half that of
wood, a third to a quarter the value of coal and one fifth of that of
fuel oil.
All cellulosic materials contain only about 50% of their dry weight
as cellulose and are not significantly different from the composition of
sugar cane fibre sometimes with resins and fats replacing the waxes.
The cellulose is practically the only constituent of the fibrous material
which can be converted to carbohydrate which in turn can be fermented to
ethanol and even this is difficult with yields not unusually as low as
250 1/tonne representing a recovery of only 30% on theoretical.
31
The pentosans hydrolyse to pentose sugars which are not fermentable
by yeast and lignin is also not a raw material for ethanol production.
Attempts have been made to utilise bagasse as a source of ethanol
by hydrolysing it with 1.8 to 2.5 of sulphuric acid for 50 minutes at a
pressure of 700 to 800 k Pa but results so far have not been encouraging
although this situation may change and will be discussed later. For
the time being there would seem to be merit in maximising the energy
value of bagasse as a fuel and more detailed consideration will be given
to fermentation possibilities at a later stage.
The pentosan xylan can be converted to furfural with moderate
simplicity and is probably worth costing for limited development, but
would utilize only 19% of the dry matter of the bagasse.
32
TECHNOLOGY STUDIES
The idea of producing ethanol from sugar cane in Queensland is by no
means new. In 1918 the Advisory Council of Science and Industry (Australia)
in Bulletin No. 6 (which was reprinted with an appendix as Bulletin No. 12
in 1921) drew attention to a range of possibilities but no action seems to
have eventuated.
The C.S.R. Co. has produced industrial ethanol from molasses at
Sarina (Qld.) from cane factory molasses and at Pyrmont (N.S.W. ) from sugar
refinery molasses. The 1977 Australian price of bulk ethanol is 27.3¢/1
in Sydney.
During World War II a definite proposition was considered for the
production of ethanol from sugar cane juice at a time when export of raw
sugar was substantially restricted. For a number of reasons it did not
get beyond the proposition stage. At the same time ethanol from molasses
was being blended with petrol and retailed as a normal motor fuel. Also
there was much activity in the construction of distilleries in the Victorian
and M.S.W. wheat areas with the object of usefully using a surplus of wheat
anticipated as the result of wartime shipping problems. The first of these
to be completed operated for only a very short time. This as well as those
in lesser stages of completion were soon abandoned as by that time the
wheat was given higher priority use as a food.
The international oil companies never seem to have been favourably
disposed towards ethanol as a supplementary motor fuel and whilst becoming
almost the only producers of industrial ethanol have restricted it to the
status of an intermediate in the production of other chemicals.
33
This may be seen as very largely related to the pricing policy of
the oil companies with ethanol being invariably priced higher than
refined petrol, although pricing of petroleum products or petroleum
based materials is so extraordinarily complex that it is impossible to
be able to make a real comparison on the basis of specific costs. In a
multi-product industry, real costs are not the only factors involved in
pricing policies.
The present resurgence in interest for agro-ethanol has resulted from
anticipated shortages in available mineral oil supplies and related price
escalations.
Industrial ethanol and potable ethanol have for many years been produced
from sugar cane molasses and about 40% of the Queensland molasses production
is diverted for use in this way in Australia and a similar amount exported
of which an unknown proportion is converted to industrial ethanol.
Molasses production in Queensland amounts to about 216 kg/tonne sugar or
28.7 kg/tonne of cane. As the molasses contains about 54% of total
fermentable sugars (as hexoses) this is equivalent in ethanol to only about
8.8 1/tonne cane.
In other countries the sugar cane juice contains less sucrose and a
higher proportion of hexoses and non-sugars. As a result the molasses
production may be 2 to 3 times as high per tonne of cane with consequently
higher ethanol production potential.
One effect of this is that it was not really economical in Queensland
to establish a distillery for the molasses from only one sugar factory.
The only distillery which has been established in Queensland to process
molasses for industrial ethanol has drawn its supplies from a number of
factories using mostly rail transport. The distillery is currently
located at Sarina and is now rated at a capacity of 50 Ml/per annum.
34
The actual amount of molasses required to produce this quantity of ethanol
will vary somewhat according to the amount of fermentable sugars it
contains.
Total sugars in final molasses when converted to glucose amount to
approximately 53% in the Central-Burdekin areas, which on an ethanol
recovery of 88% of stoichiometric would mean 3001/tonne. At this recovery
it would require 1679000 tonnes of molasses.. In the 1975 season the
molasses produced in the central district - Mackay area alone was 177,632
tonnes with an additional 88,654 tonnes in the Burdekin district from which
some supplies are also drawn.
There are two distilleries in Queensland licensed for the production of
potable ethanol which differs in its pricing structure from industrial
ethanol.
If central distilleries for industrial ethanol from molasses were
located in the Northern, Burdekin and Bundaberg areas and used 90% of the
molasses available they would have outputs of the order of 30, 26 and 20M1
(with allowance for current usage for potable ethanol production.
Thus something of the order of 100 Ml might be obtainable from all the
available molasses in Queensland. In actual volume it would be equivalent
to about 2 1/2 days of Australia's total petrol consumption or 5 weeks of
consumption of a 7% blend.
At current prices of Australian crude oil ( A$2.2/bbl) ethanol would be
far from being a commercially viable alternative. However, Australia
has been importing oil to the extent of about one third of her total
requirements and this proportion is expected to more than double within ten
years. Figures concerning this industry get out of date so quickly that
it is difficult to orient thinking correctly at any particular time.
35
Also it is difficult to determine the amount of petrol which is
produced from a barrel of crude oil as it varies according to the quality
of the crude and the economics of the oil refineries. According to the
Australian Institute of Petroleum the petrol produced in Australia
represents about 40% of the crude oil. It is likely that a higher
proportion is produced from Australian crude as it is rated as a lighter
type of material than Middle East oil with a higher proportion of low
boiling point fractions.
The annual consumption of petrol as such in Australia is around
14 Gigalitres. It is customary to regard ethanol as being of less thermal
value than petrol and to compare the two in terms of net thermal value
which are in the ratio of 3:2 (petrol:ethanol). There is however, doubt
about the validity of this as there are compensating factors. This will
be discussed in more detail later in this report and for the time being,
volumes will be considered as equivalent.
For a Queensland sugar industry production of 20 million tonnes of cane
capable of yielding 92 1 of ethanol per tonne of cane this would require
7.6 Q.S.I.'s (one Q.S.I. equals one Queensland Sugar Industry at 20 million
tonnes of cane or 3 million tonnes of sugar). One Q.S.I. equals 1-84 Gl
of ethanol.
It would require 2.5 Q.S.I.'s to replace petrol from the present
proportion of crude oil, or possibly less if the proportion of petrol from
Australian crude oil is higher.
Factors relating to this implication will be discussed later but
for the present two postulated situations will be examined in some detail,
as well as some related possibilities which become evident.
36
(a) A sugar cane factory in which the crystal raw sugar production
is reduced to 50% of normal capacity whilst juice not required
for this as well as molasses produced after raw sugar crystallization
is processed for ethanol production.
(b) An entirely new sugar growing area is established together with a
factory for processing juice extracted from the cane for ethanol.
There are several intermediate possibilities such as doubling the
capacity of the juice extraction plant, increasing the size of the steam
and electricity generation facility and attaching fermentation and
distillation facilities to handle juice from the increased cane supply.
This would also require all the provisions involved in doubling the cane
production, harvesting and transport facilities.
Alternatively, if raw sugar production is to be curtailed, then the
whole of the evaporation and crystallizing plant would become redundant,
as well as the sugar handling and transport facilities. There would also
be strong objections to changes in the status quo which is a factor common
in any comparable situation.
Before discussing any of the possible arrangements in detail, it is
necessary to establish certain basic parameters.
When contemplating the establishment of a new industry, one should
expect to be able to commence with only the best of technology known
at the time and plans for the proposal are prepared. Invariably there are
developments in progress all the time but it becomes necessary at some stage
in the proposal to "freeze" developments and produce operating equipment.
This does not prejudice future improvements which can be expected to be
made operational as economic and other factors indicate.
37
For a number of years developments in the ethanol fermentation field
have been proceeding at very leisurely pace because of the heavy dominance
of synthesis ethanol. Since the current energy crisis has developed
the fermentation for ethanol has received very much attention and it is
inevitable that important "freezing" decisions will become necessary.
In such a situation there will be endeavours to sell outdated
technology at a discounted price. This can appear to have many economic
advantages in the short term but for disadvantages to become progressively
more prominent. Decision makers will also have to evaluate the relative
merits of tested techniques with those which have not proceeded beyond the
laboratory stage no matter how hopeful prospects may be.
The same applies to raw material supply - cane breeding, growing,
harvesting and transport.
It is most unlikely that an ethanol processing facility could be
established to operate effectively before the 1980 sugar season even on a
limited scale of dual operation. Nothing earlier than 1983 might be
contemplated for entirely new area development.
Because the sugar cane growing industry is well established in Australia
and all the mechanisms for progressive development appear to be operating
satisfactorily, it should be safe to use anticipated 1985 field productivity
figures as a basis for estimating the average type of situation which might
be expected for the first 5 years of meaningful operation. This will be
done for the purpose of this report and appropriate modifying factors may be
applied if so desired.
38
BASIC FUNDAMENTAL INFORMATION
Productivity of cane = 90.0 tonnes/ha. average 1980/1990.
(actual projected figure = 90.49 ± 1.81)
Yield of sugar = 13.92 tonnes of 94 N.T. sugar /ha (±0.1)
C.C.S. = 15.3
Comparable to Central District average 1970 - 15.24 C.C.S. 16.51 pol % cane
or Burdekin 1969 - 15.56 C C S . 16.72 pol % cane
Sugar in cane as equivalent sucrose = 17.0% cane
" " " " " " " glucose = 17.9% cane
Productivity as equivalent glucose = 16.2 tonnes/ha
Stoichiometric ethanol potential = 6481/tonne glucose = 9.72 kl/ha
Juice extraction = 95.5% nett = 84%
Fermentation/distillation efficiency 88%
Nett ethanol production potential = 0.8 kl/ha or 97.4 1/t.c.
The price of cane is qualitatively related to the price of sugar:
Price of cane = Price of Sugar x .009 (CCS.-4) + 0.382
Price of sugar = $170/tonne 94 N.T.
Equivalent price of cane = $17.67 tonne
Molasses = 2.75% cane - 53% of total sugars as glucose.
Part of the stability of the present sugar industry in Queensland must
be related to the fact that no new complete sugar production plant has been
erected in Australia since the Tully Mill which produced its first sugar in
1925. In fact several of the smaller plants have been closed down including
the sugar beet factory at Maffra in Victoria. Most of the other plants in
Queensland were erected towards the end of last century or early in the
current one, although many changes have been made and present standards of
equipment are generally good by any standards.
39
DUAL PURPOSE FACTORY
To produce ethanol does not require that crystal sugar must first be
made, but a split of the juice stream is all that is required. Superficially
this is the simplest way in which to distribute raw material for both
crystal raw sugar and ethanol production in the same complex. In fact,
some rationalization would optimize processing. The juice extracted
at the mills falls progressively in purity from stage to stage along the
tandem.
In the absence of information upon which to make a real decision it
would seem to be favourable to prefer higher purity juice for crystal
sugar production and route lower quality juice to ethanol manufacture.
At the present time we do not have any information on the hydrolysis and
fermentation characteristics of sugar cane juice as distinct from molasses.
There is a very much lower concentration of non sugars in juice than in
molasses and it would seem that fermenting the juice should be a slightly
less difficult undertaking. Until more basic information becomes
available, we may not be justified in taking any possible quantitative
advantages into account but a qualitative allocation of juices would seem
to be in order.
For the purpose of these calculations it will be proposed to
crystallize 50% of the normal factory output of raw sugar. For an
average Queensland sugar mill the full assigned production would be
93,000 tonnes of 94 N.T. sugar. Since preference could well be given to
a larger mill for a primary installation a capacity of 120,000 tonnes of
crystal sugar will be considered, reduced to 60,000 tonnes for 50%
production. The total cane, however, will be the equivalent of 125,000
tonnes of 94 N.T. sugar or 817,000 tonnes of cane. The juice from the
balance of the cane will be required for crystal sugar production with a
residual molasses of 1720 tonnes containing 53% of sugars or 910 tonnes of
40
glucose equivalent. The juice from the balance of the cane would contain
73121 tonnes of glucose equivalent, making a total of 74031 tonnes.
Total production of ethanol = 42.2 Ml or 103 1/tonne of cane allocated
to ethanol (see later calculations for details to give 43.6 Ml).
The cost of ethanol in terms of raw material would be 17.11¢/1 (later
reduced to 16.74¢/1 - see details for reasons).
In actual fact it would probably be best to use only the first mill
juice and if necessary portion of the second mill for crystal sugar
production and only boil A massecuites. The first mill extracts about
73% of the sugar in the cane, but since the per cent of sugar recovered
in an A massecuite is of the order of 63% this would require about 76%
of the total sugar in the syrup. There would be a loss of perhaps 0.5% of
sugar in mud during clarification. Hence the first mill juice would be
barely sufficient except under better than average conditions of operation.
The juices from the later mills progressively become more dilute as the
result of the water added for lixiviation as an aid to the milling process.
This would be compensated by the addition of the concentrated A molasses
(probably about 75% total dissolved solids).
Further economies could be effected by operating with a continuous
sugar boiling pan of which there are indications overseas that these are
more satisfactory than the corresponding units developed for C massecuites.
There are also rather better prospects for steam economy but that is of
marginal value unless fibre can be hydrolysed, in which case it would be
of substantial value.
To estimate a cost for processing the sugar juice to ethanol is
difficult.
41
A distillery operating on cane juice associated with raw sugar
production experiences both advantages and disadvantages from this
arrangement.
Advantages include a "free" supply of steam and electric power
generated from burning the fibre from the cane as bagasse. There are
also benefits accruing from a common management and service facilities
such as roads.
On the other hand it may well be restricted to operate only at times
when the raw sugar side is operating. At the worst this means for only
about 70% of a 32 week crushing season or 157 operating days - 43% of a
year. This would correspondingly increase the capital charges.
Arrangements could be made to store the molasses and process this
in the slack season, or even to concentrate juice and store (such syrup
is being successfully stored in the sugar beet industry in U.S.A. under
quite high summer ambient temperature conditions). In these circumstances
coal would be required to generate steam when bagasse is not available.
Unfortunately bagasse does not store at all well unless it is baled and
baling costs money. There are also the costs of storing the baled
bagasse in a shed and then of recovering the bagasse for firing.
Very careful costing is necessary before these complex issues can be
resolved and there is probably no single best answer" depending upon
local circumstances.
Information regarding real costs for both capital and operating charges
is both difficult to obtain and such as is available from different sources
is very conflicting. A great deal of secrecy prevails concerning these
matters both in Australia and overseas.
42
As examples of these conflicts may be cited, firstly capital cost
items.
An attached fermentation/distillery plant should not require additional
steam or power generation facilities as already indicated.
A plant to produce ethanol at 42.2 Ml within 70% operational time of
a 32 week season would be rated as having 100 Ml/annum installed capacity.
One Australian estimate for a plant of this capacity and attached to
a sugar factory is $40m. At the other extreme are figures from U.S.A.,
Germany or Japan closer to $4m.
It is well known that Australian costs for capital equipment are high
compared with overseas costs but not to this extent. Perhaps a factor 1.3 or
even 1.5 should be more realistic than a factor of 10.
Steam consumptior figures seem to be reasonably consistent with a
figure of 2 kg steam/1 of rectified ethanol being obtained with modern plant
in the distillation and rectification stages. Sterilization of juice and
miscellaneous needs would add another 1 kg and the dehydrating distillation
a further 1.5 kg making a total of 4.5 kg steam/1 of absolute ethanol.
The figure of 2 kg for the production of rectified spirits is based on
the processing of molasses diluted to a concentration of 10% of sugars.
Juice would have a concentration of 17% of sugars or 24% after mixing with
the A molasses.
Research on fermentation has aimed at processing higher concentration
solutions and since the purity of the juice - A molasses mixture with respect
to total sugars would be close to 84% compared to about 66% for final
molasses there may be good prospects of operating at higher concentrations
43
with the purer materials. For the juice - A molasses mixtures, if fully
effective hydrolysis and fermentation can be achieved, this would be
equivalent to 15 to 15.5% of alcohol (w/w) in the product mash or 19% v/v.
These concentrations are probably approaching the limit and a practical
limit of 15% v/v would be more realistic - actually values up to 14% have
been claimed for fermented molasses beers and molasses diluted to sugar
concentrations as high as 18% are reported to be successfully treated in
fermenters.
There are undoubtedly further steam economics which could be effected
in the fermentation/distillation procedures but it would require more
specific experimentation with sugar cane juice itself before these could
be estimated. Fermentation of so-called high-test molasses would be with
a raw material somewhere between final molasses and the juice - A molasses
mixture envisaged here. Whilst there is experience with high-test molasses
overseas this has not been a raw material in Queensland distillery experience,
high-test molasses has always been too valuable for crystallizing sugar.
Labour requirements indicated from reported experience seems to be about
400 1/man-hr but this varies according to the size of the distillery and the
degree of automation and a halving of this cost would not be too difficult
to envisage.
Undoubtedly there are differences in techniques and problems of suitable
selection of equipment and processes are compounded for a 1979+ installation
because of the long time which has elapsed since competitive quotations have
been common in the field of fermentation ethanol. It is difficult also to
know just what charge to make for the use of sugar mill equipment and
management, obviously this cannot all be charged against the 50% usage of
its facilities for sugar production. Here again much secrecy prevails
concerning real operating costs although there are some yardsticks such as
examining financial information provided for shareholders and applying
44
appropriate factors. The monies received from the sale of raw sugar
are debited with the costs of selling and the balance distributed between
the farmer and miller. The proportion which the farmer gets varies with
both C C S . and price of sugar. As a general statement distributions
are recognised as being aprroximately two-thirds for the farmer and one
third for the miller. At C.C.S. values above a certain figure the farmer
gets more than this proportion and when the price of sugar is above a
certain figure he gets less than this proportion. The following
calculations closely approximate the turning points in this relationship. It can be seen therefore just how difficult it is to translate income
from processing for raw sugar to income for processing for ethanol.
At the 15.3 C.C.S. average figure chosen for this exercise, if the
miller operated at 100 coefficient of work (he might well operate up to
102 in this C.C.S. range) then he would receive 32% of the sugar price
and the farmer 68%. He would have to process his ethanol at 7.78¢/1.
Calculated thus:
Cost of 100 tonnes of cane @ 15.3 C C S . and sugar @ $170/tonne 94 N.T.=$1776
Money which would have been received if 15.3 tonnes of sugar had been
produced = 15.3 x 170 = $2601
Miller's share = 2601 - 1776 = $825
45
Value of sugar actually produced = 7.6 x 170 = $1292
Miller's share = 1292 x 825 = $409.80
2601
Income the miller would expect to receive for processing to ethanol=
825 - 409.80 = $415.20
Ethanol expected to be produced from 100 tonnes of cane under these
conditions = 5340 1.
Pro-rata money required = 7.78¢/l ethanol.
We are also now in a better position to cost the farmer's
contributions.
Total money the farmer receives = $1776
Money paid to farmer for the 7.6 tonnes of sugar produced: this would
have come from 7.6 x 100 = 49.67 tonnes of cane 15.3
49.76 x 17.76 = $882.20
Value of cane used for ethanol production = 1776 - 882.20 = $893.80
Pro-rata ethanol cost = 16.74¢/1 (see previous figure of 17.11)
Total cost of ethanol = 24.52 ¢/1.
The costs of chemicals for fermentation are difficult to assess because
of the differences between juice and final molasses. It is necessary to
determine whether the juice for ethanol should be put through the classical
sugar juice purification stages or merely heated for sterilization. The
general appearance of clarified juice would be much better, but the lime
used for neutralizing the natural acidity of the juice would have to be
paid for as well as the cost of sedimentation and mud filtration.
Clarified juice at a pH around 7 would have little natural hydrolysing power
for the sucrose where a pH of 5.5 for raw juice would be quite useful in
this respect especially if temperatures are taken to 100 for sterilizing.
Much of the protein in the raw juice would be coagulated by this
treatment but there would seem to be no point in separating this, rather
46
allow it to go forward to the fermentation stage. The juice would need
to be cooled to a primary fermentation temperature around 27°. This is
most easily effected by flash cooling but a vacuum higher than normally
achieved in a sugar factory would be needed viz. 29 inches rather than
26.5 or an absolute pressure of 3.5 kPa instead of 12. Flash cooling
to 50 supplemented by refrigeration cooling would appear to be a
desirable combination to give positive temperature control.
A pure culture yeast should be selected on its ethanol producing
capacity rather than one which might be more suited to also producing
the associated flavours desirable in the manufacture of potable spirits.
Yeast at the rate of l0kg/kl would seem to be the order of magnitude
required if the yeast is separated from the mash by means of centrifugal
separators and recycled as in the Helle process. This is done before
distillation and the separated yeast re-introduced into fresh "mash".
With this process it has been found possible to re-use the yeast
continuously for periods as long as a sugar season and with yields of
91-92% of ethanol.
Three stages of distillation are employed - the first two being with
double effect conservation of energy and 95% ethanol-water is produced as
a constant boiling point mixture. This is dehydrated by azeotropic
distillation to produce absolute echanol.
The total protein in the juice is likely to be about 0.5% on raw
juice solids or about 200 g N/kl of raw juice. The amount of N required
for fermentation is somewhat less than this figure but the extent to which
the yeast might be able to avail itself has yet to be determined. Raw
juice should contain about 500 g of P2O5 /kl which should be adequate for
the yeast. Other mineral constituents of raw juice would include about
47
1300g/kl of K2O, 300g/kl of CaO and 400g/kl of MgO. Each of these
should be adequate for the requirements of the fermentation process.
The actual concentrations and proportions of the various mineral
constituents vary according to the composition of the soil and the
nature of the fertilizer programme in the cane field.
The slops or residue from the still would contain 18.5 to 20 kg of
solids at a concentration of 6.3% and disposal as effluent is undesirable
from the environmental point of view. It might be used as irrigation
water as the soluble substances are mainly good plant nutrients. This
would not be entirely without cost and some storage would be needed
because irrigation usage would not necessarily coincide with process
production. Furthermore it would then be necessary to acquire some of
the water required at the mills for lixiviation.
Alternatively the slops could be used partly as maceration fluid for
the lixiviation process. Recycling of weak alkaline juices for this
purpose has never been a satisfactory exercise in sugar mill operation
because excessive slippage tends to develop under these circumstances.
The slops however would tend to be acidic and may be suitable for recycling.
Recycling of slops solids as fertilizer is simplified if they are
concentrated to about 50% total solids. For this purpose a multiple
effect evaporator would be required and a quadruple unit would be adequate
from the point of view of steam economy. If the concentration of solids
in slops were to be doubled by recycling for lixiviation this would have
little effect of significance on the overall steam balance but the size of
the unit could be reduced to less than half.
A possible flow sheet is outlined in Figure 1, together with a balance
of materials and steam requirements.
48
A fibre content of 14.4% on cane is assumed for these calculations.
The estimated total steam requirement for the dual process is 748 kg/tonne
cane if quintuple effect evaporation combined with steam bleeding from the
second effect for juice heating is employed for the concentration of juice
and a quadruple effect with pre-heating from the first effect is used for
slops concentration.
If the steam is generated with an efficiency of 82% on N.Th.V. of
bagasse the potential supply would be 876 kg/tonne cane. An efficiency
of this magnitude is quite common for bagasse fired units when it is
needed, in fact such equipment was installed and successfully operated in
Queensland as far back as 1938. In the present day situation fibre values
of cane are significantly higher as a result of variety changes and much
lower steam generation efficiencies are adequate.
For full crystal sugar production the factory would require not more
than about 550 kg of steam/tonne cane in which case the steam would need to
be generated at an efficiency of only 51%. The efficiency would need to
be increased to 70% to operate the distillery and its accessories. In
modern boiler installations there is a certain built-in flexibility to
enable higher efficiencies to be operated for seasonal periods when fibre
in cane is low and incineration conditions when fibre values are high.
Whether the available flexibility is sufficient to cope with an increase
to 70% would depend upon the particular installation concerned. There
would in fact need to be sufficient flexibility to go up to the 82% if
the fibre were to fall as low as 12.3. This is possible for the early
weeks of a season and the probability would have to be estimated from a
study of local data. Values as low as 13.3, however, would probably have
to be allowed for with an equivalent efficiency of 76%.
49
The efficiency of steam generation is related to the amount of heat
recovered from gases leaving the furnace which may be used to pre-heat
the air used for combustion and/or feed water.
Whilst flexibility in steam generator efficiency is important
it is also necessary to look at steam generator capacity. This would
need to be increased by 36% on average figures. However, normal sugar
factory steam generators are required to be able to take overloads of up
to 25% to cope with the variable demand imposed by batch operated sugar
boiling pans.
An inspection of steam generator capacity data for Queensland mills
processing 800,000 tonnes of cane in a season appear generally to have
installations rated at about 180 tonnes steam/hr to compare with an
average demand envisaged at 160. This would allow a 13% surplus which
should be sufficient to cope with the sugar boiling pans operated at
half capacity.
The fermenters and distillery would need cooling water, but it is
considered that this would be available from the requirement displaced
by closing down 50% of raw sugar production.
It is not possible to assess the total electric power requirements
until more specific information is available concerning the actual
fermenter mash concentration. The quantity of mash to be treated
would be between 1500 and 30001/min depending upon concentration which
can be operated in the fermenter. Throughputs of this order would need
200 to 400 kw to sustain continuous operation of a centrifugal separator.
Since sugar factories of this capacity usually have about 8Mw of
electrical generating capacity this should be sufficient for the fermenter
centrifuge requirements when operated on a dual product basis.
50
In assessing costs it is necessary to take into account the
loss of income experienced by the miller from the sale of molasses which
would amount to some 22,500 tonnes for cane of the quality treated.
To offset this would be the value of concentrated slops as fertilizer.
The quantity of such product would be 15,000 tonnes of dry solids.
The average price of chemical fertilizer is of the order of $100/tonne
so that a value of perhaps $50/tonne of dry solids might not be an
unreasonable valuation. It will be assumed for the purpose of this
exercise that the value of slops fertilizer compensates for the loss of
molasses.
Furthermore no credit has been transferred to ethanol production
which would result from the simplifications made possible in the production
of raw sugar whereby only A massecuites are boiled and which are more
easily treated in the centrifugals than the normally succeeding B and C
massecuites. Mo large crystallizers are required for C massecuite
exhaustion.
These benefits are difficult to quantify and are marginal but never
theless real.
Cost estimates for the acual production of ethanol in dual product
operations would need to be closely related to the general pattern of the
sugar industry.
The distillery would require labour for its own operation, the raw
sugar section would also require labour but in smaller numbers for a 50%
production rate, but not a pro-rata reduction.
The cost of transporting cane to the mill is part of the miller's
cost structure and the distillery would be expected to pay for 50% of
51
this cost, also 50% of the costs of milling and of operating the steam
generating plant.
The labour required to operate the distillery itself would depend
upon the degree of automation incorporated in the process. For a
distillery of the size associated with this project a figure of 800 1 of
ethanol/man-hr is the one which will be used here. This would appear to
compare reasonably with a figure of 400 1/man-hr quoted for some
distilleries overseas with throughput rates of the order of one quarter
of that envisaged here.
Although the distillery under discussion would be expected to produce
44 Ml of ethanol in a season of 150 days it would be rated at closer to
100 Ml if operated continuously on a yearly basis. This is twice the
rated capacity of the present molasses based distillery at Sarina which
is described in the 1977 Australian Sugar Year Book as being "large by
world standards".
At 800 1/man-hr a labour force of 15 men per shift would be required.
On the raw sugar side there might be 8 men per shift reduced to 6, half of
whose costs should be carried by the ethanol plant.
Half of the capital charges of the sugar plant should also be borne
by the ethanol. It is very difficult to assess a figure for this since
no new sugar mills have been built in Queensland for over 50 years
although many items of equipment may be relatively recent installations.
Perhaps an idea of the "book value" may be obtained from observing that a
sugar mill of about half of the size being considered here changed hands
in 1976 for around $4m. which would indicate a figure of the order of $6m
for one twice the size. Two sugar mills of about the size being
considered here also changed hands in 1975, but were included in a package
deal which tended to mask the actual values put on the sugar mills themselves.
52
However a figure of perhaps $8m. each may not be very far out as they
were rather more efficiently equipped than the smaller $4m. unit.
Undoubtedly all three figures are well below replacement costs, but
would be within range of the cost strictly to be taken into account for
assessing the ethanol plant liability.
Since it is easier to assess the capital charges at an overall
figure for the entire sugar milling and factory complex the service charge
for transport of cane relates only to the cost of labour and consumables
such as fuel for the locomotives.
The cost picture now emerging is ummarized in Table II. Since the
quality of cane varies from one district to another an indication of the
order of magnitude of this effect is given as well as for the "average"
conditions
It is evident therefore that the cost of producing ethanol in a dual
product arrangement with a 50-50 split in the manner indicated would result
in the ethanol processing costs exceeding the cost of the equivalent raw
sugar production by about 45% if the miller is to be recouped for his effort
in terms satisfactorily in line with current sugar industry arrangements.
The increase necessary in the price of ethanol is 3.88¢/1.
53
TABLE II
Dual Product Plant to produce ethanol not using molasses from other mills
in the district. Processing costs only
54
In Table III is set out the effect of different quality of cane normal
to the four districts. The differences have been proportioned relative to
average C.C.S. ratios for each district taken over the years 1971/75 to the
average C.C.S. for Queensland during the same period and the equivalent
C.C.S. calculated relative to the base average figure of 15.3 which we
have so far been using. The corresponding price of cane has been
calculated relative to a raw sugar price of $170/Te 9*+ N.T.
The corresponding raw material cost has been evaluated in terms of
¢/l of ethanol. The appropriate processing cost has been transferred from
Table II and added to the raw material cost to give an indication of the
total estimated cost of ethanol produced under the conditions specified.
These figures do not include the cost of transport to the nearest port.
TABLE III
Dual Product Plant to produce ethanol not using molasses from other mills in the district. Raw Material plus Processing Costs
55
EFFECT OF VARYING THE PROPORTION OF PRODUCTS
It is of some interest to study the effect of varying the ratio of
raw sugar to ethanol without changing the total quantity of cane
processed in a season. If we use the same criteria as before, viz:-
to obtain the same overall return of money as would be obtained from a
corresponding production of raw sugar.
For an arrangement of 75 sugar-25 ethanol the total quantity of
ethanol produced would be only of the order of 24 Ml and there would be
difficulty in meeting capital cost requirements unless significant economies
could be effected in this direction.
The 50-50 arrangement would seem to be close to optimum conditions
for dual purpose operation.
LOCALITY FOR DUAL PRODUCT OPERATION
Two alternative situations are considered in this arrangement.
(1) No increase in cane cultivation but ethanol production would take
up problems associated with a falling export market for raw sugar.
(2) The export market for raw sugar does not fall but sugar cane
growing is extended in existing areas to provide cane for
ethanol production.
It is evident that a simultaneous development of an ethanol industry
at all of the 30 existing raw sugar factories would not be a particularly
practical proposition. Even given the capability for such an achievement
the novelty of the development would suggest the wisdom of an element of
caution as it would appear inevitable that in the present state of knowledge
the second installation would be technologically better than the first and
56
it would be some time before reasonable equilibrium had been reached
in design details.
Therefore if there is to be an initial selection of certain factories
for preferential development the criteria for selection should first be
identified. The following criteria are listed in the event of the
choice being the first of the two alternatives just listed.
(1) Magnitude of current scale of sugar production - it is only in
this way that any advantages associated with large scale
production of ethanol could be secured. There is no difficulty
in identifying factories meeting this criterion, simply by
reference to the list of assigned sugar production in statistical
records or "mill sugar peaks" as it is known in the industry.
Also see Table IV set out in this report.
(2) Efficiency of operation. This criterion is more difficult to
identify. Firstly there are at least two measures of efficiency -
(a) yield of sugar as crystal relative to sugar in the cane and
(b) labour cost involved in production. Other efficiency
criteria might include (c) management and (d) cost of materials
such as lime and added fuel. Most of this information is of a
confidential character.
Information related to operating efficiency is exchanged between
factories through the co-ordinating services of the Bureau of Sugar
Experiment Stations but it is still confidential within the group.
Financial information is even more confidentially covered and only an
intelligent guess is possible from such company balance sheets as may
be published or from such other stistics such as employment records
which might: be ferreted out of government files if access is possible.
57
(3) Locality with respect to a port should be given some weight as a
pipeline of several kilometers could be a viable proposition whereas
50 km or more would pose a significant capital expense and transport by
rail would be expensive. Transportation cost has not been included in
the ethanol price whereas it is in the sugar production cost. Using
these criteria it would be possible to give a ranking to a mill for
which three grades might be recognised in each group. However, if
two mills with rankings 3-3-1 and 2-2-3 were to be compared the fact
that each had a similar total ranking value would not necessarily mean that
the cost of ethanol would be similar in each case. An increase in the
number of ranking steps for each criterion could well improve selection
but a detailed study of information is justified for such an important
decision.
Other criteria might also be deemed to be important depending upon
many local circumstances. Some previous experience in the production
of fermentation ethanol could have short term advantages but the technical
expertise of the Queensland sugar industry is such that the opinion is
submitted that it would not be long before this advantage was overtaken.
Developments along this line could see four or five of the best
ranking factories producing upwards of 250 Ml of ethanol each season
by 1981 or 1982, of which about 10% could be used locally in blended
fuels and the balance would be about enough to provide for most of
Queensland's petrol needs in terms of a 10% blend.
It would deprive the Australian sugar industry of about 12 1/2% of its
annual sugar production.
58
In the event of it being decided to expand sugar cane growing,
additional criteria for preferred area selection would need to be
identified such as:-
(4) Productivity of existing assigned land area.
(5) Additional available land of suitable character and suitably located
with respect to the mill.
(6) Ability to increase productivity on existing land by such means as
increasing irrigation.
It would be invidious in this report to identify specific mills in
relation to the first three criteria and the sugar industry itself has well
researched the criteria in relation to its programmes of expansion which
have been taking place during the period of progressive development of
overseas markets.
The report of the Commonwealth/State Burdekin Project Committee
titled "Resources and Potential of the Burdekin River Basin" (June 1977) gives
a very good detailed survey of the possibilities for both expansion of area
and increase in productivity. Although specific to the Burdekin area it
also contains valuable discussion relevant to other aspects of the sugar
industry. The estimate of an anticipated annual growth rate for the
industry of 2.5 per cent may need revision with respect to the export market,
but prophets in this field have for many years been almost invariably
distinguished by error. Otherwise the writer would generally support the
findings of the report, being well acquainted with the area and its
potentialities and having been a member of an unofficial local committee
studying the same subject in about 1940.
59
In Table IV is listed the total gross areas of land assigned for
the growing of sugar cane associated with each of the 30 sugar mills in
Queensland and the corresponding annual sugar production allotment or
"mill peak as it is known in the industry. The figures are as listed
in The Australian Sugar Year Book, Strand Publishing Co., Brisbane, 1977
and refer to the year 1976.
If one were to take the simple ratio of mill sugar peak to gross
assigned area of land, a first order indication would be obtained of the
expected efficiency of land usage in the various mill districts and afford
a quantifying number for the fourth criterion for locality selection.
There is a certain realism in such figures by virtue of the annual
adjustments which are made after the submission of lengthy arguments
essentially related to the real life situations at the time.
DUAL PRODUCT PLANT WITH MOLASSES SUPPLEMENT
In the short term it should be possible to utilize the potential
capacity of the distillery to process final molasses from other mills in
the district. The benefits of this would become progressively less if
other distilleries were to be installed within the same district.
Before this could be done it would be necessary to examine
carefully present commitments for the sale of molasses. About half of the
molasses is disposed of overseas and cognisance would need to be taken of
possible long term contracts. The overseas price is also uncertain and if
demand exceeds supply this is likely to rise, but international molasses
prices are just as difficult to predict as international sugar prices and
in fact there is a certain inter-relationship.
It would also be necessary to negotiate local arrangements in
Queensland and rationalize transport so that for example molasses produced
in the central district goes to a central district distillery and molasses
60
TABLE IV
QUEENSLAND MILL SIZE AND LAND PRODUCTIVITY CRITERIA
61
produced in the Burdekin district goes to a Burdekin district distillery.
All this would seem merely to be common sense, but we are considering
the prospects of a changed situation.
For the purpose of this consideration it will be assumed that the
desired molasses supply arrangements are accomplished and that there is a
sugar mill suitably located in each of the four Queensland sugar growing
districts. The basic data already used may not strictly apply in each of
the four areas but are considered to be sufficiently representative to
use for the next stage of calculations and appropriate adjustments may be
made if desired.
Two possibilities for processing present themselves - one is to store
all of the final molasses from other factories and process this during the
slack season using coal as a fuel for steam generation and thus reduce
capital costs on distillery and steam generation plant. This would also
have social benefits in providing longer employment prospects for distillery
employees. The other is to build a larger distillery, devise techniques
for maximum steam economy throughout and supplement with coal if extra fuel
is needed, and process all of the extra molasses during the sugar
production period. In the first year there would be the problem of all
mills within the area not commencing or finishing on the same date but
this could be overcome by storage of a balancing stock of molasses carried
over the slack season.
The former of these two options will be accepted for estimating costs
here, recognising that there may also be other options and various mixtures
of options are possible. A much more exhaustive and detailed study would
be required before final decisions could be taken with confidence.
The cost situation for selected options is summarized in Tables V and
VI.
62
TABLE V
Dual Product Plant to produce ethanol - also using additional molasses
from other mills in the district. Raw Material Costs
63
TABLE VI
Dual Product Plant to produce ethanol - also using additional molasses
from other mills in the district. Total estimated costs of ethanol.
SINGLE PURPOSE ETHANOL - SUGAR CANE PLANT
There are several possibilities for the location of a single purpose
plant operated only for the production of ethanol from sugar cane juice.
(1) Conversion of an existing raw sugar factory.
(2) Erection of a new complex within the ambit of the existing raw
sugar industry.
(3) Erection of a new complex completely separated from the existing
raw sugar industry.
Looking at the factors involved in converting an existing raw sugar
factory for the processing of the whole of the juice from sugar cane to
ethanol production, the cane preparation and milling tandem would remain
unchanged.
A flow sheet of the main operations and processes involved is shown
in Figure 2 together with an elementary analysis of materials balance and
steam requirements. A more detailed study of the flow sheet could well
reduce the steam requirements but at this stage, a more simplified picture
is considered to be sufficient for the present purpose.
If slops from the stills were to be recycled to the field as irrigation
then the amount of steam required to produce anhydrous ethanol would be
much the same as for the production of raw sugar. If however, the slops
are to be concentrated to a 50% water content and this is done by quintuple
effect evaporation then this would increase steam consumption from about
550 kg/tonne cane to 750. This is well within the capability of the
bagasse supply for a fibre of 14.4% in cane and would require a steam
generator efficiency of 70% on N.Th.V, or alternatively could cope with a
65
drop in fibre content of cane to 12.5 if efficiency were to be pushed to the
achievable limit of 82.
The total rate of steam generation would need to be about 185 tonnes/hr
which is sufficiently close to the rated figures of steam generators
installed in sugar mills processing 817,000 tonnes of cane in a season
(actually 181-183).
Cooling water required for the fermenters and for the distillery
as well as for the condenser of the slops evaporator would be expected
to be available from the normal cooling water system of the raw sugar
factory.
The mechanical power requirements of a raw sugar factory complex is
concentrated in driving the rollers of the mill tandem and this would
be the same for the distillery. Electric power consumption in a raw
sugar factory is probably higher than for a distillery. In the former
there are heavy demands for the operation of centrifugals and these are
particularly strong generators of surges. In the latter there would be
some significant power required for the centrifugal yeast separators
but these would operate on a continuous cycle and without power surges.
The electric power production capacity of the raw sugar plant should be
adequate for the total needs of an ethanol plant.
Total ethanol production from 817 kTe of cane would be expected
at 79.5 Ml (without additional molasses processing).
A larger ethanol plant would be required than for a 50-50 dual
product plant and the two costs are taken as being related by the
exponent 0.6 which is a commonly accepted value for relating the relative
cost of plants of different sizes thus:-
67
TABLE VII
Single Product Plant to produce ethanol without additional molasses
68
TABLE VIII
Single Product Plant to produce ethanol also using additional molasses
from other mills in district. Raw Material Costs.
69
TABLE IX
Single Product Plant to produce ethanol also using additional molasses.
Total estimated costs of ethanol.
Thus to summarize the cost estimating situation so far a tabulation
has been set out in Table X indicating the estimates for each selected
option for each of the four present sugar cane growing districts in
Queensland. A weighted average cost for Queensland is given, weighted on
the basis of ethanol production rather than for the average 817,000 Te cane
complex. This average would, however, only be meaningful if each of the
four districts was equipped for ethanol production and would likewise lose
meaning if any one district was equipped with two plants.
70
TABLE X
Summary of Estimated Costs of Ethanol Production - Primary Options
Total ethanol potential for an 817,000 Te cane complex - Megalitres of ethanol per annum
The lowest cost situation would appear to be in the central district
for one only dual product arrangement and with the final molasses from all
the mills in the district also being processed in the same plant. This
cost is estimated at 21.5C/1 for an annual production of 96 Ml. Any
increase in production of ethanol within the district would appear to result
in a rise in this cost due mainly to loss of further income from raw sugar
production. The reality of such a situation would have to be faced according
73
All of the dual product options reveal a lower cost for ethanol than
the corresponding single product option because the whole of the molasses
produced within the complex is processed for ethanol. This and related
benefits of dual product operation more than offset the scale benefits for
a larger distillery for single product operation. There would no doubt
be a point at which larger scale operation would reverse this trend if
the capacity were to be increased.
The dominance of the cost of raw material is, however, always evident.
There are opportunities for either increasing or decreasing the price
of the product such as incurring a higher capital expenditure than
anticipated or finding that portion or all of the contingency provision
is not required.
Rises in wages over the next 10 years would have more effect on the
capital cost of new equipment than on the operating cost of a process.
There is abundant evidence of this in the history of the sugar industry
over the past 40 years when operating costs in field as well as in factory
have been very largely contained by more efficient operation, better
management or an increase in automation.
The capital charges for this exercise have been calculated to return
20% on outstanding capital during a 20 year period of equal amortized
payments. The actual annual payments represent 20.54% of the capital
invested.
Maintenance costs have been assessed as 7.5% of the total capital
cost for the annual requirements. This is generally considered to be a
generous allowance for a plant of this character.
74
It is at this point that we could look at the effect of increasing
the growing area for sugar cane associated with a particular mill district,
and how this would effect the cost of ethanol. There are of course two
possibilities - (a) to double production in all areas and (b) to double
production only in the areas producing ethanol. In either situation, the
full benefits of scaling up would not accrue to the ethanol production
since it would have to contribute towards capital costs of increasing the
capacity of the cane transport system, the milling tandem, the steam
generators and the electricity generators as well as paying the fee for
the labour involved in performing these functions. On the other hand,
it would not have to compensate the miller for lost profits or redundancy
of plant since the quantity of sugar produced would remain unaltered.
In Table XII are set out the costs for such a venture but only "average"
conditions have been assessed, the inter-regional effects would be much the
same as before on a proportional basis. The only situation corsidered
for the calculations in this table is the one for which expansion takes
place only for ethanol production and the total production of raw sugar
remains unchanged.
A further capital cost disadvantage which this type of expansion
would experience would be that the new sugar milling and related equipment
would be at a very much higher pro-rata cost than the "book value" of the
currently operating equipment used in the previous calculations.
TABLE XII
Effect of Doubling the Size of a Sugar Mill on Ethanol Cost
sugar on the world market which is notoriously unpredictable. Ten per
cent variation in this component would be reflected by a 6% variation in
the price of the resulting ethanol since the price of sugar cane is
directly related to the price of sugar. The price of cane grown for the
production of domestically consumed ethanol could be stabilised in much
the same way as it is for domestic crystal sugar consumption but whether
at the same level or not is a matter which would also involve political
components in any decision.
The capital influenced component of the distillery itself is a
much lesser proportion at 12%. It would require an error of 50% to have
the same influence on the price of ethanol as a 10% variation in the
price of sugar.
Due to recognised difficulties in estimating capital costs for new
equipment in the current Australian economic environment. Estimates of
capital costs could increase by 50% , or quotations could vary by as much
as ± 50%. Variations of this order of magnitude would affect the price
of the ethanol ex-bowser by perhaps 3 to 4% or 1.0 (±0.2) /1.
The total labour component involved in transporting and processing
the cane is a relatively minor proportion of the total cost at around
10%. It is likely that the labour assessment for operating the distillery
itself may be on the high side, on the other hand there could be lengthy
discussion from representatives of the sugar industry concerning the
assessment of costs attributed to normal sugar industry operations. A
net charge of 25% in labour costs could only affect the bowser price by
about 0.6C/1.
This is not to be confused with any overall unexpected increase in
wages which would have an influence permeating the whole cost structure,
but should not be more than 12.5(±2.5)% or an ex-bowser effect of 3.75
(±0.75)£/l, of which perhaps 30% would be absorbed into the inertia
This is still a higher figure than anything experienced prior to 1973.
There have been endeavours to reach international agreement on the
production and price of sugar but with no marked success. During 1977
conferences have been convened under United Nations auspices to try and
reach something in the way of an agreement under current conditions but
decision making has been deferred.
One of the big problems in the recent round of discussions has been
the effect of development of the sugar beet industry in Europe. In the
eighteenth century Europe was under seige by the British fleet and was
desperately short of sugar normally imported from the West Indies. Under
those conditions the sugar beet was first farmed as an alternative source
of sucrose. In 1977 Western Europe had a surplus of 3 million tonnes of
sugar with which to barter at the conference table after feeding her own
population of nearly 500 million people at the rate of over 37 kg per head
per annum as compared with a world average figure of 20 - little more than
half of that of Europe. Belgium has currently been the country with
highest productivity for sugar beet yielding 9.2 tonnes of sugar per hectare
as compared with a little over 11 for sugar cane in Australia but requiring
5.7 tonnes of beets to produce a tonne of sugar compared to 7 tonnes of
cane in Australia. On a world basis, sugar cane growers can only average
5 tonnes of sugar per hectare and require nearly 11 tonnes of cane to
produce a tonne of sugar. Hence the role of Europe as an importer of sugar
has gradually been reversed at least as far as the continental countries
have been concerned. Britain with her colonial sugar interests and long
term contracts with Australia is slowly being forced to accept continental
European beet sugar as part of the price of membership of the E.E.C.
The U.S.S.R. has been a substantial importer of sugar and in recent
years has accepted the very large export surplus produced by Cuba. This
supplements a sugar beet crop of over 8 million tonnes which if farm and
81
reduce to some extent the rate of fall of the world sugar price and
enable perhaps 3/4 million tonnes still to be satisfactorily exported.
In this context an examination will be made of the situation which
would develop in the event of individual sugar factories in Queensland
having only 50% of its cane used to produce raw crystal sugar and the
balance diverted to ethanol production.
The argument just elaborated depends also on the price of oil
maintaining an upward trend of 8% per annum. At present, the cost of
petrol to the Australian consumer is heavily modified by the low price
of Australian crudes. This is unlikely to last as current prices
strongly militate against the discovery and development of new fields.
However, the chief argument in the present thesis is the displacement of
imported crude oil which is not only more highly priced but represents
the export of Australian currency outside her traditional or newly
developed trading areas.
The precision of the predicted 8% per annum rise in OPEC crude oil
prices is also difficult to estimate but is probably more predictable than
the corresponding world sugar price.
The price of oil itself is not the only factor in this area of
discussion. The real subject is the price of petrol which in itself is
complex. There must be some relationship to the basic price of crude
oil but this relationship is by no means simple or obvious, in fact it
is variable but its variability seems to have been the component least
subject to concern on the part of economic analysis although strongly
suspect by the ordinary consumer.
In Australia we have been free of complexities arising from aromatic
based crude oils as Middle East crudes are essentially aliphatic in
character as are also Indonesian and indigenous crudes. The latter do,
however, differ from M.E. crudes in having a lower sulphur content and
a higher proportion of lower boiling point components. We do have
aromatic components in Australian retail petrol in the form of
alkylbenzenes (mostly toluene), petrol marketed in the Sydney area for
example is known to have contained as much as 35 mole per cent of
alkylbenzenes in recent years, and Borneo crude oils contain aromatic
components. Alkylation of benzene is practised in the production of
petrol, benzene being a product of the pyrolysis of coal.
The basic liquid fuel of particular concern, at least in the
forseeable future (50 years?) is M.F. crude oil and the possibilities
of the progressive displacement of its petrol product by ethanol.
This proposal poses a threat as far as interest in Australia is
concerned, to substantial vested interests in that industry.
Superficially the threat may not appear to be serious but a lesson might
well be learned from the reactions of such interests in the 1930's to
the relatively minor production of ethanol from Queensland molasses. The
interests affected at that time were mainly marginal and local rather than
fundamental and international, nevertheless the reactions were strong and
clear. Ethanol was clearly not wanted by the oil interests as a
component of retail petrol.
A major lesson to be learned appears to be to get the oil interests
on-side with ethanol production from sugar cane by financial and technical
participation. The technical participation being essentially in
distribution and consumption. The vested interests of manufacturers of
motor car engines impinge also on the area of consumption and their
participation and co-operation would be of equal value to the venture.
The term vested interest is not used here in any derogatory sense.
The full economic implications of having a viable operating industry are
recognised and the effects of change can be widespread in any community.
Before attempting to examine the price structure of petrol it is well to
understand what is meant by petrol or gasoline, as it is known in the U.S.A.
and its dependent areas. Petrol is a comprehensive mixture, not only of
hydro-carbons, but also of additives designed in one way or another to
improve the performance of the basic blend.
Petrol is officially rated in terms of its octane number in relation
to its behaviour in an ignition engine with specific reference to the
knocking characteristic. In fact it probably is more closely related to
heptane than to octane, which is in fact often used as a standard fuel.
For example n-octane has a boiling point of 126°C whereas data from
one major oil company indicates that the boiling point range is more like
37-185° with 50% boiling below 112°. The b.p. of n-heptane is 98.4°
and ethanol 78.5 . It now seems to be common practice for petrol
companies to employ a similar basic blend of hydrocarbons and each has their
own special additives. The following is a list of recognised additives
which may or may not be representative of any particular brand of petrol:-
The total comes to just on 1% of the weight of the basic petrol.
These additives are more costly (w/w) than the hydrocarbon base and
would probably add 10% to its cost including the costs of measuring
and mixing. Whilst the retail price differential between standard
and "super" grades is closer to 6% this reflects very largely the cost
of the anti-knock additive which is generally tetra-ethyl or tetra-methyl
lead compounds. The lead compounds also require the presence of ethylene
dibromide to inhibit the deposition of lead oxide on the engine valves.
This compound is vital to the use of lead anti-knock compounds and the
availability of bromine for its manufacture has at times been critical.
Alkyl benzenes also have useful anti-knock properties when used in
high compression engines all of which makes the processes of blending and
selection of additives highly specialized undertakings.
We also know that one litre of Australian petrol requires 2.5 litres
of crude oil for its production. Since the proportion of light fractions
in Australian crude oils is higher than for M.E. products it is possible
that it takes 3 litres of crude oil imported from those regions to make one
litre of petrol for the Australian market. Mo doubt this picture over
simplifies the overall situation since the progressive development of fuel
for aircraft jet engines has an influence on the proportioning of products
by oil refineries. The tune which they play is a melody of many notes and
is highly orchestrated.
The actual costs of production of petrol are extraordinarily
difficult to assess because it is not a simple calculation.
As is the case when pricing sugar, the capital cost component of the
retail price is not assessed on present day replacement costs of oil
refineries but on a " book value" related more to the original installation
cost. Unlike raw sugar factories there have not been corresponding
86
88
ETHANOL FROM SUGAR CAME IN A NEW GROWING AREA
The present Queensland sugar industry has grown steadily since it
became organized at the time of federation. This growth has been
associated with a marked degree of stability but has involved the
development of certain practices which could be considered as restrictive
in a competitive environment. Many factors have also enabled the price
of sugar to be kept at low encugh levels to permit these to continue
relatively unchallenged and in certain cases relatively unknown to the
public at large. The conscience of the industry has considered this
reasonable in exchange for a stable supply of sugar to the community of
high quality at an acceptable price and with financial stability within
the industry itself.
Two of such practices are the self-imposed restriction on weekly
operation of raw sugar factories themselves. These are operated for
only 5 of the 7 days each week largely in agreement to union pressure to
mitigate the unfavourable social effects of a short operating season. In
overseas countries it has been common practice to operate for a period of
about 21 days and then to close for the minimum time required for cleaning
and maintenance - commonly less than 24 hours. Australian process
industry is by no means inexperienced in continuous operation (e.g. the
metallurgical industries) and many appropriate working contracts have
been developed over the years.
It is common practice in these situations to operate on a 4-group
basis for the three shifts employing a roster system whereby each person
works on an average of 42 hours per week but at the rate of 8 hours per
day.
The fact that overseas (South-East Asian for example) sugar factories
may operate on the basis of a 12-hour/man/day operation for 84 hours per
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week may on first sight be abhorrent in the eyes of Australian workers.
On closer examination it does not differ very greatly from Australian
workers desirous of adding highly lucrative rates of pay for overtime,
as most of the workers in the overseas situation are employed on a
seasonal contract basis with an equal willingness to work long hours
for extia money.
During the 1976 season the industry worked for only 61.6% of the
gross available time which provides much food for thought.
On the agricultural side the mechanical harvesters have reached a
quite sophisticated stage of development enabling the cost of cutting in
1977 to be kept below the cost in 1937. But machines which complete the
harvest of their daily quota within a period of 4 to 5 hours and are then
idle for the remaining period of the 24 hours as well as at weekends could
be said to be working for only about 13% of their available time.
Operation of these harvesters is currently restricted by law to the hours
of daylight, a poor comparison with the grain harvesters in the U.S.A.
for example.
These are just two reasons why the development of an ethanol/sugar
cane industry should be closely examined in terms of what could be achieved
if every endeavour were made to achieve maximum productivity at all stages 3
but at the same time retaining cognisance of the social needs of the
worker. These will be examined in detail later but first a look will be
taken at more superficial aspects of what would be involved in establishing
such an industry on a worthwhile scale in entirely new localities in
Queensland.
90
LOCATION OF A NEW SUGAR CANE/ETHANOL COMPLEX
There are two aspects to this proposition - (1) location of an
area suitable for growing sugar cane in the quantities envisaged and
(2) the location of the factory site within the area selected.
The need for neighbouring port facilities is a desirable feature
but not necessarily critical. For example the best sugar cane growing
area in Queensland is in the Burdekin district with an average distance
of 80 km from the port facilities in Townsville. Transport of ethanol
to a port is less of a problem than the transport of sugar.
Pipeline transport can be a viable alternative to rail or road
tankers over short distances - perhaps up to 10 km but some careful
costing is needed to establish the relative economic merits of the three
systems for each particular case, for which a knowledge of the quantity
to be handled is equally as important as a knowledge of the distance.
Ethanol is a more valuable commodity than raw sugar - weight/weight
at $310/Te corresponding to $170/Te for raw sugar from similarly priced
cane.
The factory does need to be located close to a supply of water
sufficient for its process cooling requirements, and also to be in reasona!
proximity to a town to provide the residential community for its employees
In entirely new area development it may be necessary to also develop the
town as has been the case with the various new mining ventures in recent
years.
The primary requirements for new area selection are suitable soil
and climatic conditions. Sugar cane will in fact grow in practically anj
type of soil. It does object to saline conditions and does not
91
particularly like heavy alkaline clays although there are ways and means
for dealing with the latter.
From the climatic point of view a rainfall of at least 1.5m during
the growing period is needed either as natural precipitation or as
irrigation or a suitable combination. More water at the right time and
in the right manner is beneficial but this will be discussed later in a
cost-benefit study of irrigation development.
Temperatures within the range 27-33° during the growing period are
favourable. The terrain is desirably flat, well drained and suitably
protected from floods.
The main growing season is between the vernal and autumnal
equinoxes during which time about 75 to 80% of the total growth usually
takes place.
When growing cane for crystal sugar production it is desired to
develop as much sucrose as possible within the stalk of the cane and to
harvest as much of the crop as possible during the period when this is a
maximum.
It is recognised that maximum sucrose content of the cane occurs
in about September-October but it would be uneconomical to restrict the
season to these two months hence it it spread more or less equally about
these tvro months and various types of adjustments made in growing conditions
and breeding to obtain marginal improvements during the early and latter
parts of the season.
It is also recognised that for the best sucrose development, certain
climatic criteria need to be realized during say August-October, bright
sunshine and cool nights but not frosts, preferably not below 10-15 .
92
In some countries where these conditions do not prevail, it has been
found that a temporary lowering of the water table at this time is
beneficial for sucrose development.
When it comes to growing sugar cane for ethanol production, these
criteria are of much less importance. The change in total sugar content
of the cane is less than the change in sucrose content and any of the
hexose sugars in sugar cane are suitable for making ethanol.
SEASONAL CONSIDERATIONS
In Queensland the growing of sugar cane is looked on as a crop
to be harvested annually between about mid-June and mid-December dictated
largely by the period of maximum maturity as measured in terms of
crystallizable sugar and the size of the crop relative to the capacity of
the mill. Larger crops in relation to the capacity of the mill are
handled by lengthening the season and in 1975 the season lasted from
26th May 1975 to 10th January 1976 or 229 days. If we look specifically
at the northern district which is the most likely to be affected by wet
weather during this period the season lasted from 17th June 1975 to
8th January 1976 or 205 days.
On an average the northern district could expect rain to fall on
61 days (30% of total) and to lose about 14% of crushing time for this
reason. If the season were to be extended to operate from 1st April to
31st December and it be assumed that wet days in April are twice as
effective in causing lost time at the mill as those normally experienced
then the total lost time could be expected to increase to 17%. This is
considered to be an acceptable figure for the benefits of an extended
season in the ethanol industry.
There would undoubtedly be a period during which the fermentable
sugar potential of the cane is at its peak, but this is believed likely
to be less prominent than the peak for crystallizable sugar.
The social benefits of a longer season are significant in that a
9 month or 275 day season would enable a large proportion of the work
force to be employed on a continuing basis if we allow one month for
vacation and two months for work on maintenance. The added job security
should make it possible to obtain better contracts with appropriate
unions. In return the operatives would be expected to work during week
ends and public holidays and to minimize industrial unrest.
The wet season normally commences in early January and ends in early
April, and these two dates would largely determine the effective
operational period available.
The following time allocation emerges:-
Crushing season 275 days gross
Maintenance 59 ::
Annual holidays 31 ,:
Wet weather allowance 17%
Scheduled maintenance 2%
Non-scheduled maintenance 4%
Operational time 77% = 212 days
Under these conditions a crop of 2MTe could be processed operating
at 400 Te/hr or 9,600 Te/day (nominal).
Average current operating conditions would indicate a crop total of
1.22MTe being processed at the same hourly rate.
94
The longer season and fuller working times would indicate an
ability to process an additional 64% of cane. A close study of wage
structures and present overtime and slack season employment would need
to be carried out in order to establish patterns of labour cost which
might be expected. Also the effects on available fermentable sugars
in cane that would be experienced would require careful assessment.
The effects of a longer harvesting period would also be reflected
in the employment opportunities in the field. There would be direct
effects on the period of employment for those concerned with cane
harvesting and transport. The cultivation of ratoon crops would also be
spread out but there would probably be little effect on planting or
irrigation schedules. There would need to be better organization of
maintenance schedules for mechanical equipment employed in these operations.
The thermal losses incurred as the result of interruptions in
operation are quite significant and equipment of the type used in
distilleries may be more seriously affected than corresponding equipment
used in raw sugar manufacture. In the raw sugar industry in Queensland,
as long as there is bagasse to burn, the unfavourable thermal affects
of the week-end closure of the plant is not taken very seriously. In
fact surplus bagasse has been an embarrassment over the past 15 years and
it has not been difficult to adopt a prodigal attitude towards thermal
conservation proposals. The situation with an ethanol distillery is
not expected to be quite so simple, at least the fine points of efficient
operation will be less clearly understood until appropriate experience is
gained in the industry.
95
SUNSHINE REQUIREMENTS FOR GROWING SUGAR CANE
BOth sunshine and rain are needed to grow sugar cane, the one will
not work effectively without the other. However, vre will look at each
in turn in order to obtain an estimate of the contribution which each
makes.
The sunshine is the source of energy for the photogenetic
chlorophyll cells contained in the leaves and which are responsible for
catalysing the combination of carbon dioxide and water in the first of a
series of steps which with the aid of enzymes go to produce the sugars and
other components of the plant. The first recognisable substance produced
by photosynthesis appears within a matter of seconds as 2-phosphoglyceric
acid, phosphates being required in the plant juices to help initiate the
process.
Experiments with sugar cane have indicated that maximum photosynthesis
occurs in the blue wave lengchs at *+80nm for most types with additional
absorption peaks at the red end of the spectrum between 620 and 640nm and
at 670nm.
Tropical skies have some limitations regarding sunshine due to cloud
cover and summer days which are relatively short compared with those
experienced in higher latitude temperate zones. There is some compensation
with longer winter days with less cloud cover, but 7 5 to 80% of the sugar
cane weight is developed between vernal and autumnal equinox.
Sugar cane grows very well in Queensland and exceptionally well in
the Burdekin district. Some years ago the Bureau of Sugar Experiment
Stations carried out experiments in the Bundaberg district aiming to
determine the maximum amount of cane which could be grown per hectare given
the very best conditions of water and fertilizer. A figure of 222 tonnes/
hectare of stalk cane was achieved in these experiments. The stalk is
96
about 32.5% of organic substances or 72 Te/ha. But the stalk is only
about 45% of the whole cane including the root system so that the total
effect of photosynthesis would be to produce 159Te/ha of organic
substances. In the Burdekin district even higher yields are not uncommon
experiences among the best farmers with stalk yields of 275Te/ha or total
yields approaching 200 tonnes of dry organic substances. These figures
may or may not be beatable but for the time being they might be accepted
as target figures and other achievements rated as a percentage of the
target figure.
Current average achievements in the Bundaberg district are nearer
86Te/ha or 39% of the achievable target. It is common experience for
the best farmers in an area to obtain 50 to 60% better values than the
average and for the best district in Queensland to be 50 to 60% better
than the average for Queensland.
In Table XIII are set out data endeavouring to estimate the
efficiency of the cane growing procedure. As well as the actual and
estimated production figures, calculations have also been made of the
most likely production of total organic material including the tops and
the leaves about 78% of which would be hexose carbohydrate, about 8.5% of
lignin and a similar proportion pentosans, the balance being protein, wax
and fats and other organic substances. This has involved a certain
measure of guesswork but the figures obtained are believed to be a useful
first approximation.
Furthermore estimates have been made of the integrated daily solar
radiation useful for photosynthesis. Actual values are known for Brisbane
-2 -1 to range between 14.6 and 32 MJ m d of total solar radiation. It is
also believed that only about 50% of this is useful for photosynthesis.
98
It appears therefore that the sugar cane can use around 8% of the
available useful solar energy for the photosynthesis of organic substances
over the period between the vernal and autumnal equinoxes when up to 80%
of total growth takes place. On the average in Queensland it actually
uses about 2.7% which is about three times as efficient as most members
of the plant kingdom.
The best man-made solar cells do not yet seem to have an efficiency
better than 10% and many are still around the 2% mark. Hence the sugar
cane does function well as a solar absorber if it is properly tended,
albeit within restricted wave length bands.
It has been reported that sugar cane along with certain other
tropical grasses possesses an additional enzyme system not found in
temperate type grasses or cereals and which provides it with the facility
to transfer solar energy into carbohydrate more efficiently.
Sugar cane belongs to the so-called C-4- group of plants which have
been observed to have a photOsynthetic capability exceeding that in the
so-called Calvin-cycle plants by a factor of 2 to 3.
Fundamental studies are being carried out in Puerto Rico aiming to
determine breeding characteristics of sugar cane with respect to its
photosensitivity. It has been reported that blue sensitivity is
consistently high from the oldest to the youngest species whereas the
older species show rather higher red sensitivity than the younger species
although there is a recurrence of red sensitivity in certain types of
modern hybrids. The natural photosynthesis employs only a small fraction
of the solar radiation spectrum and any means for extending the range of
use should be equally as acceptable as increasing absorption efficiency
at known existing ranges of wave length.
99
Almost all of the active chlorophyl containing cells are located
in the leaves of the top of the plant and are part of a complex of
chromophores in which chlorophyl a and b are recognised as well as
carotenoids in the absorbance spectra of sugar cane leaves. Carotenoids
are yellow pigments which occur with chlorophyll in the chloroplasts
within the leaf.
Heavy increases in productivity per unit area are frequently viewed
with some suspicion as the carbohydrate is not necessarily the currently
desired crystallizable sugar. It is felt that this should be of less
importance when growing for ethanol production than when crystal sugar is
to be the end product.
WATER REQUIREMENTS FOR GROWING SUGAR CANE
Perhaps the most important statement that could be made with respect
to the water1 requirements of sugar cane is that the soil should be well
drained and fields should be adequately protected from floods. The fact
that sugar cane seldom dies completely when it is inundated with flood
waters probably accounts for the fact that there are still flood prone
areas of sugar cane growing land in Queensland. Flood prevention is
costly and certain areas of flood prone land have been unfortunately selected,
although they probably do produce heavily in betvreen visitations of floods.
Water logged root systems are not in the best interests of healthy
plant development.
From simple observation it is evident that very often tractors and
cane harvesters are unable to operate, not because of a general wetness of
the soil but because of boggy patches in badly drained areas. The
correction of these drainage problems could well decrease the unavailable
time for using this equipment by as much as 30 to 40%. This in turn has
100
a beneficial effect as far as the milling of the cane is concerned in
reducing the amount of time lost due to wet weather. The cost factor
related to time lost by the milling plant and factory is quite substantial
and any money spent in the field which is able to reduce this lost time
is of appreciable financial significance.
The possibility of using field equipment employing some aspect of
the hovercraft principle has been studied seriously by sugar industry
leaders in areas of high rainfall but up-to-date costs have been
considered too high. Tracked vehicles rather than rubber tyred units
have also been examined and at times are used in various parts of the
world.
The cost of an effective drainage system and preparing properly
drained fields should be part of the capital development cost and
maintenance part of the cost of soil preparation in the annual cycle of
cultivation.
If field drainage is not properly achieved in the initial
preparation of the field it is difficult to make satisfactory corrections
during the course of field usage. Because it is customary in Australia
(and reputedly economically the most suited) to grow two ratoon crops
following a plant crop and allow a fallow season it is possible to work
on any particular section of land only once every four years for the
purpose of correcting drainage problems.
When considering the amount of water required for growing sugar
cane the question arises - how do we assess it? General experience seems
to indicate that for growing under natural rainfall conditions a
precipitation of 1.5 to 1.6m is needed of which around 80% should fall
between the two equinoxes and not too much during the latter part of the
harvesting season in October/November, or say 70% between early December
and early April.
101
There have been experiments carried out in various countries aimed at
determining the optimum amount of v/ater and the optimum time of application
and for devising techniques of measurement to enable the application of
supplementary water in the form of irrigation to be applied under more
scientific control, with varying degrees of success.
There is a rule-of-thumb criterion often quoted in the industry that
"it takes a ton of water to make a pound of sugar". If we examine this in
terms of a 90Te/ha of cane at 15.3% sugar and a water supply of 1.6m we see
that this means 0.86 kg sugar/kl water. If it referred to crystallizable
sugar it would be closer to 0.77 kg/kl or 1.7 lb. sugar/ton water. The
rule-of-thumb is actually rather close to the 1 lb/ton ratio in other sugar
cane growing countries where the production of sugar in the field is less
efficiently accomplished for reasons which are not perfectly clear.
However, if we use a figure of 0.86 kg sucrose/kl water as a first
approximation representation of conditions experienced in Queensland, we
can make some interesting observations consequent upon this.
The sugar cane itself is made up of approximately 69% water in the
liquid phase and a further quantity as water of chemical constitution in
the carbohydrates. A total accounting would place the water content
nearer 82 to 84%.
As we have already seen the stalk represents only about 4 5% of the
whole of the plant including the root system, a hectare of land producing
90Te of stalk would have grown 200Te of total cane holding up 166Te of
water in various forms. Thus 10.4 kg of water would be retained in the
plant for every kilolitre applied - an efficiency of usage by the plant
of about 1%.
We do know that the sugar cane grows with a very high rate of
respiration which is believed to contribute very largely to its favourable
growth characteristics. The water is absorbed by the growing cane through
the root system, travels up through the stalk to the leaves and then evaporate
from the surface of the leaves, most of which are at the top of the stalk.
A proportion of the water supplied to the plant disappears by percolation
through the soil and is lost in the drainage system. This is in fact a
very important part of the growing process as can be well established by
anyone attempting to grow a plant in an impervious pot without a drainage
hole.
There is also water evaporated from the surface from the soil. The
proportion which is lost from the system in this way is at a maximum during
the early growing stages and gradually becomes less as the canopy of leaves
covers the field.
It is necessary to avoid water-logging on the one hand and dessication
on the other. If 85% of the water applied, passes through the plant in
the process of respiration and plant synthesis this would indicate 84% to be
dissipated in the atmosphere to increase the humidity in the immediate
vicinity of the plant and gradually disperse into the atmosphere by turbulent
and natural convection.
We might say that sugar cane is not very efficient as a plant in its
use of water but this is the penalty which seems necessary for a high rate
of growth, i.e. for a high degree of photosynthetic efficiency.
Studies of the efficiency of application of water to sugar cane tend
to the view that there may well be a lesser proportion of water actually
passing through the plant. Whilst it is difficult to define application
efficiency, figures for furrow application have been quoted of the order of
40% with up to 70% for spray application. Drip irrigation either on the
103
surface or below the surface is even more economical in water usage which
would tend to indicate that perhaps not more than 10 times as much water
actually passes through the plant as is retained in plant synthesis.
The questions then become - how much water can be usefully applied
to grow sugar cane, how much does it cost and how much sugar does it
produce?
The value of water is probably not linear with respect to total
carbohydrate produced but as a simplification if we consider it being so we
can look at the cost benefit of an irrigation supplement.
Estimates have been given for the costs and capacities for several
dam installations on the Burdekin River in the 1977 Burdekin River Basin
report. It is difficult to know just how to charge the capital cost
against water supplied3 especially if there is to be associated hydro-electric
power generation. An amortization at a 5% interest rate over a period of
75 years requires an annual payment of 5.13% on capital cost which is used
as the basis for this calculation.
Taking the average estimate for four such dams with a storage capacity
of 1500 Gl and an annual supply of 400 Gl, the cost is of the order of
$50m to deliver water at 0.64-C/kl. This may be compared with a small
irrigation project developed at Eton in the Central district in 1973 for a
capital cost of $10.15m and providing a supply of around 30G1. The equivalent
value of the water would be 1.74c/kl. The annual operating cost for
delivering the water to the farm in this latter case works out at 0.33c/kl.
Low initial cost of water especially associated with a high price for
sugar tends to favour furrow techniques which themselves have the lowest
capital cost of alternative application systems. High initial cost of water
tends to favour spray irrigation and very high costs to favour underground
permeation techniques.
104
The amount of water which a man can handle with furrow irrigation
has been reported as around 300 1/sec (approximately 10 cu.secs.). With
an agricultural labour cost at $5/man-hr. This would be equivalent to
2.16c/kl.
We could then look at a cost figure around 3c/kl from dam to root.
In conditions comparable to those experienced in the Burdekin district
where experience indicates that the yields of cane are at the rate of
about 100 Te/ha for 1 m of effective water supplied. With useful
natural rainfall of 0.5 m crops averaging 130 Te cane/ha would require
1.6m as irrigation at 50% effectiveness of application or $3.69/Te cane.
With spray irrigation this might be reduced to $2.50 if the
effectiveness is increased to 70% and perhaps around $2 with highly effective
drip type of application.
If the credit for the irrigation be on a pro-rata basis and the cane
be valued at $10/tonne it would show a cost-benefit for irrigation in
excess of 100%.
105
FERTILIZER NEEDS IN SUGAR CANE CULTURE
There are three chemical nutrients of main importance in growing
sugar cane which are the elements nitrogen (N), phosphorus (P) and
potassium (K).
In a continuing system a balance must be maintained between nutrients
removed at harvest and those added during the growing cycle. When considering
the development of a new area whether from forest or grassland in which nature
has been recycling on a continuing basis there is usually a good supply of
available nutrient. In modest cropping plants use about 10% of the
available nutrient supply and with heavy cropping this rapidly becomes
depleted. Sugar cane cropping creates a heavy drain on soil nutrients for
three main reasons:-
(a) leaching of the soil by rainfall or irrigation
(b) soil erosion physically transferring soil from the field to
neighbouring watercourses
(c) the transfer of cane from field to factory
The effect of the first two is minimised by good cultural practices.
The effect of the third can be estimated from a knowledge of the general
composition of sugar cane especially of the millable stalk. For every
100 tonnes of millable stalk there are about 80 tonnes of green leaf and
tops. With mechanical harvesting as currently practised the latter are
comminuted and redistributed at random over the field. For a crop of 90
tonnes/ha of millable stalk some 55 kg of N will be removed or O.Skg/Te
cane; 36kg of P2°5 or 0.4 kg/Te cane and 72 kg of K20 or 0.8kg/Te cane.
The tops and trash contain rather more at 126. 55 and 300kg/ha respectively.
It can be seen that the return of the nutrients in the tops and trash plays
an important part in the economic management of the soil.
106
The total nutrient removed in the chemical form mentioned above
is 1.8 kg/Te cane but in the form of fertilizer for renewal it would
amount to about 3.6 to 4- kg. In actual fact the total fertilizer usage
is closer to 10 kg/Te cane, which represents not only replenishment of
stalk removal losses but a significant excess. Overall use of N is
2 kg/Te cane.
When new ground is brought into production there may not be just the
right kinds of nutrients present in the right amounts and some adjustments
become necessary until an equilibrium is reached between fertilizer removed
and fertilizer added.
The crude average cost of fertilizer is around 13 c/kg or $1.30/Te
cane, which includes a Commonwealth Government bounty on N and P fertilizers.
In the Burdekin area with heavy cropping the recommendations are for
135 kgN/ha for a plant crop to supplement the fallow cover crop contribution
and 210 kg N/ha for the ratoon crops. There seems to be little or no need
for P and K to be added once the level has been adjusted in new land
development, for example in the new land of the Barratta area initial amounts
of 45 kg P and 135 kg K/ha seem to be needed but progressively reduced.
Legume fallow crops are capable of retaining up to 220 kgN/ha which
should be sufficient to provide the requirements of the plant crop.
Whilst there are several waste products from a raw sugar factory which
can usefully be recycled to the farm there would really only be two from
an ethanol distillery. These are the distillery slops and the ashes from
the bagasse furnaces.
107
The ash resulting from the combustion of the bagasse contains minor
amounts of P2°5 and k2o but is rich in silica (65-70%) usually in a form
which can be readily absorbed by the plant to provide its needs in what
is essentially a minor but nevertheless, important element for plant
nutrition.
The amount of ash was at one time about 2% of the dry matter of bagasse
or about 3 kg/Te cane, but with the advent of mechanical harvesting this
can go up to as much as 8 or 12 due to dirt which is picked up in the
harvesting operation. For the ash to be useful as a plant nutrient it needs
to be friable in character and not fused. This is now generally the case
with present day furnaces in which burning is done in suspension. With the
older type hearth furnaces, there was a tendency for varying portions of the
ash to fuse to a glass in which form it is virtually useless as a fertilizer.
With quantities as much as 8 to 12 kg/Te cane being removed from the fields
there would seem to be merit in returning a larger proportion than currently
is the case as this represents significant depletion over a period of yeai&.
The effluent from a sugar cane/ethanol plant should be more easily recycled
than the corresponding effluent from a molasses/ethanol plant since bagasse
is available as a fuel for evaporation to enable it to be concentrated to a
more convenient form for recycling. Also it is more convenient than a sugar
cane/raw sugar plant in that the corresponding effluent in this case is molasses
which is extraordinarily difficult to distribute on the fields at a low enough
rate per hectare. Furthermore 50% of the molasses consists of sugars which
do have value as animal food or as a substrate for fermentation but no value
as a fertilizer.
If the distillery slops are concentrated to a form in which they are
recycled to the ratoon crops which forms only two thirds of the sugar crop.
Statistics indicate that actually about 72% of the area harvested is in the
form of ratoon cane and 27% plant cane with about 1% of standover. It is
estimated that about 80% of the plant nutrients removed from the field in
108
the stalk would be in the distillery slops and should provide adequate
replenishment for 72% of the cultivated area.
Although a number of European distilleries operating on sugar
beets or potatoes have for many years evaporated and recycled distillery
slops for fertilizer, some preliminary experimental work would appear to be
desirable starting with sugar cane juice in order to obtain some information
about the physical properties of the effluent as well as its chemical
composition.
Since the area from the second ratoon crop becomes the fallow land for
the next season and the area from which the plant crop was removed becomes
the first ratoon for the next season. In fact in a M- yearly rotation cycle
the gross area must be subdivided into 4 equal areas if the cycle is to be
correctly maintained. However, some cane must be sacrificed to provide
plant material for the next season's plant crop. This is usually taken from
a stand of plant cane - hence the smaller proportion of plant cane supplied to
the mill.
As already indicated legume cover crops can supply as much N for the
plant crop as 2-2.5 kg/Te cane. The total nitrogen content of leaves and
tops from a tonne of stalk cane is about 0.9 kg/Te stalk but if a fire is put
through the field before harvesting as is the current practice then perhaps
20 to 30% of this would be lost. Rain and non-symbiotic fixation sources
can add as much as 0.4 kg/Te cane but between 0.05 and 1 kg can be lost by
leaching.
If water is supplied by furrow or drip irrigation instead of by spray
or by rain then the aerial nitrogen component is proportionately reduced
and any over-irrigation will increase the loss by leaching.
109
It would seem to be quite practicable for the cycle to become self
sufficient with respect to IT requirements and 80% of its P and K with
the additional 20% being available in the bagasse ash which might be able
to be mixed with the slops.
There would be a cost component to the transport of slops concentrate
back to the fields and its distribution. With slops solids at about
2 kg/Te cane a cost of 8£/Te cane would be $*+0/Te slops solids and this is
probably the kind of figure that should be postulated until such time as
more specific information is available on the chemical composition and
physical properties of the concentrated slops.
UNIT OPERATIONS IN SUGAR CANE AGRICULTURE
The type of work which has to be carried out on the farm for the
production of sugar cane may be studies from the point of view of unit
operations. The idea of unit process studied has been implied in
discussions on the effects of sunshine, rain and fertilizers in which
chemical reactions are involved with materials and energy balances playing
important roles in quantitative studies.
The sugar cane farm is in fact the real factory where the sucrose
and other carbohydrates are made together with all of the associated
chemical entities. The sugar mill and factory merely employ the unit
operations of extraction, concentration and crystallization with some unit
process as well as operations studied in purification. There are in fact,
few chemical processes during these stages and of relative simplicity
compared to the highly complex chemistry of plant physiology.
The unit operations identified in relation to producing sugar cane
1. Ground preparation (a) Primary
(b) Secondary
(c) Tert iary
2. Planting (a) cutting of plant material
(b) preparation of plant material
(c) planting
3. Water requirements (a) drainage
(b) irr igat ion
4. Fertilizing
111
5. Chemical treatments
6. Harvesting
7. Transport of Cane (a) from field
(b) to factory
8. Ratoon preparation
9. Equipment maintenance
10. Sundry
The opinion is expressed that each of these unit operations would
yield to the same type of scientific study as has successfully been
applied to the factory in such areas as time and motion study, equipment
maintenance schedules and the amount of mechanical energy which can
effectively be put at the disposal of an operator as well as the
efficient use of this energy.
The twentieth century has seen the progressive mechanisation
of all types of operations in farming for crops or animal husbandry.
One factor which has become particularly pertinent in these studies has
been the size of the property and added to this have been the importance
of efficient farm management and the devising of effective and efficient
maintenance schedules for the equipment employed. The pattern for the
size of farms for growing sugar cane in Queensland was set at the time of
federation at the beginning of the century and not much more than
marginal changes have been made since that time to keep in step with the
very substantial degree of mechanisation which has taken place.
Before examining mechanization in general and the various unit operations
in particular we will consider the farm area factor in the context of a
newly developed ethanol industry.
112 SIZE OF A SUGAR CANE FARM
In order to achieve, for raw sugar, an orderly marketing programme
the policy was established for allowing sugar cane to be grown only on
land assigned for the purpose. This also facilitated the identification
and control of diseases in the crops, a factor which has been of very
substantial importance in maintaining a viable sugar industry in this
country. There have been many discussions on the relative merits of
controlling the area of land a farmer may work or the amount of potential
sugar he may produce. Both aspects have had to be considered and a high
measure of success has been achieved. Many important lessons are to be
learned from the experiences of the sugar industry in maintaining stability
at all levels of operation. One very valuable result of controlling
the area of land has been to encourage increases in productivity, which
combined with the quality oriented cane payment system has done much to
develop the very high standards achieved in these matters in Queensland.
As at 30th June 1976, a total of 325,000 hectares of land were
assigned as the gross area permitted for the growing of sugar cane and
subdivided into about 7300 units. The precise number of units was not
published in the 1977 Australian Sugar Year Book but numbers were
previously published and variations from year to year are only marginal.
There is some multiple ownership but very little. The average unit is
therefore 44.5 ha,
At the time of rationalization of the industry at the turn of the
century - concurrent with federation - the policy was adopted to
discourage large plantation type holdings and encourage as many persons
as possible to become farmers provided a viable unit size can be
maintained. This policy has been maintained and there are today only
the estates of the CSR Co. at Kalamia and of the Bundaberg Sugar Co.
having a combined total of the order of 5000 ha which has only a second
decimal influence on the average assignment unit.
113
It may be pointed out that political observers in other states have
not been particularly impressed with the degree of protection received
during the first half of the century by fewer than 10,000 farmers along
the coast of tropical Queensland. Larger numbers would only have meant
smaller and less viable unit assignments requiring even more protection to
keep the coastal strip inhabited.
The average unit size of the assignment is as much as one man can
work on his own. That this is so has been checked by personal observation
and discussion. It is necessary to employ two persons for planting cane
as this requires the operation of a cane planter unable to be operated
together with the tractor by one man. His harvesting is done by
contract.
The unit assignment would produce around 2900Te cane and be paid
$20/Te to provide a gross income of $58,000. Included in this are some
costs of which we already have an indication, e.g. $1/Te cane for average
watering costs, $1 for fertilizer and we will see later that it costs
around $1 to harvest and deliver to the mill transport system. Sundry
employment of labour may amount to another $1. This would leave $46,400
to pay for his capital costs, maintenance of equipment, chemicals and his
own family support.
A sugar cane farmer enjoys a relatively stable life style and
bankruptcies are unusual. No one should wish to tamper with the existing
structure for sugar production.
Ethanol costing from sugar cane on the other hand would be highly
competitive with alternative energy supplies on the one hand and with
sugar for food consumption on the other and if to be embarked upon on a
worthwhile scale new concepts of sugar cane culture will need to be studied
seriously.
114
Increase in the size of farms has proceeded in parallel with
mechanization in other agricultural areas especially in the U.S.A. where
the wheat industry is now perhaps the most advanced in this type of
production enabling costs to remain competitive in spite of the escalation
of wages. The cane sugar industry outside of Australia is not a
particularly good one to study from the point of view of mechanization
in agriculture because of its operations very largely being associated
with low labour cost countries. The sugar beet industry, on the other
hand, has developed a very sophisticated degree of mechanization in
England and certain other areas of Western Europe as well as in the U.S.A.
and Canada, where the human hand does little more than drive a tractor from
seed time to harvest.
Although sophisticated mechanization may not be common in sugar cane
growing overseas there are many examples of very large estate operations.
One example may be quoted describing an overseas situation just to
give a picture of what is involved in establishing operations on an estate
which is considered large in terms of growing sugar cane. This refers to
a factory and related estate to provide cane during the season at a nominal
rate of 18,000 Te/day. This is probably the largest sugar cane factory
at present operating in any country in the world, and is located in
Argentina, although there has been one of similar size projected for the
Sudan. The establishment in Argentina involves a plantation of 30,000ha
to produce an annual crop of 2.5m Te cane. The sugar factory itself
produces 275,000Te sugar (70% refined, 30% raw) and has a plant for
processing surplus bagasse to cellulose and paper pulp with annual
production of 34,O0OTe as well as an ethanol distillery of 32 Ml annual
capacity. There is a staff of 300 professionals and technicians with
6000 employees and 7000 temporary labourers employed for the annual
harvesting. The services for operating the complex include main
irrigation canals of 250 km and more than 1000 km of irrigation ditches.
115
There are the workshops and warehouses, a powerhouse with a 50 Mw capacity,
a 250 km industrial railroad, a 500 km road network, 500 tractors, 160 cars,
1 jet, administration offices and laboratories, 3 computer units, 2 small
towns, 1 hospital, primary and technical schools, social centres and so on.
The industrial administrative and service buildings occupy an area of
16.5 ha. Such an installation is a massive undertaking requiring
substantial expertise for its efficient running.
The cane growing area associated with a particular factory is of
necessity related to the processing capacity of the factory which by
convention is rated in terms of tonnes of cane milled per day of 23 hours
of operating time - 4.17% lost time is implied. Current installations
world-wide vary from about 6,000 to 18,000 Te c.d. Because of the lower
yielding canes in other countries the corresponding sugar production is
proportionately lower.
The logistics simply of harvesting and transporting cane at the rate
of 18,000 Te/day are of a magnitude still well beyond Australian experience
although not necessarily beyond Australian capability.
The mill which is at present the largest in Queensland comparison,
would be nominally rated at 8500 Te c.d., operates two tandems of mills
in parallel. There have been installations of 6500 to 9000 Te c.d. in
recent years in Thailand and Malaysia as well as in South American and
African countries. A spate of building new mills coincided with the
rise of sugar prices which broke towards the end of 1974.
A mill designed for a nominal capacity of 10,000 Te c.d. or 435 Te
c.hr. will be considered here as a basis for study as to what would be
involved for new factory development for ethanol production. The
operational period previously indicated of 212 days would be reduced to
200 days if the above average rate of operation is achieved. This would
refer to a crop of 2 MTe for which a gross growing area of 30tO00 ha would be
The view is expressed that it would be uneconomical to split this
up into 600 unit areas each operated by an owner farmer, but that a
minimum unit area of 500 ha would be more suited to an owner farmer.
For these studies a 1600 ha property is used as a unit size as it
divides usefully into 4 x 400 ha sub-units and 22 such properties
constitute 35,200 ha which is a suitable area unit or estate.
An important problem arising for individual ownership of a large farm
is the capital cost. The more successful farmers could conceivably
grow by a factor of 10 in a free enterprise competitive economy with the
other 9 being financially unable to keep in business. Large company
ownership would however look to not less than 5000 ha and more likely to
the 35,000 ha estate.
A new industry of this character would not be a haven for bankrupt
farmers from other rural areas nor an emotional answer to pools of
unemployment. The minimum skill would be that of a tractor driver, cane
planter or irrigator.
Large estate scale of operation does not necessarily mean higher
productivities per unit area unless some new feature is introduced. In
fact it has been general experience in most agricultural vegetative
industries that unit productivity falls off with increase in scale of
operation. The reasons for this are that personal concern is lowered
and mistakes are more costly. In the sugar cane industry, productivity
of 90 Te cane/ha for a 50 ha unit could be expected to fall to around
80 Te/ha for a 30,000 ha unit and the growing area really required would
be closer to 34,000 ha.
The following general relationship between productivity and unit
area of growing has been found useful in the writer's experience with
respect to sugar cane growing:-
117
Area 0.0184 Prod - ( old.) x Prod a new Area old
new
If there are changes in cultural techniques, additional appropriate
factors must be applied.
Ten units of 35,000 ha would be equivalent to one present Queensland
sugar industry (QSI unit) and 3 QSI units would be 30 area units for the
same number of sugar mills as there are operating in Queensland at the
present day, with 185 Ml of ethanol to be expected from each growing area
to replace 40% of Australia's current petrol consumption - a million hectare
development.
Better guidelines for estimating the relative merits of 500, 5000 or
35000 ha unit management areas will emerge as some cost factors are
generated for land development and cultivation.
The cost of a farm in new country represents the cost of land
acquisition plus the cost of preparation. Economics should develop with
larger scale of operations but a 35,000 ha unit would appear to be a
convenient one for these considerations.
NEW LAND DEVELOPMENTS
The cost of developing new land will depend heavily on the type of
land selected. Forest land may provide very good soil for cultivation
but it is expensive to develop. In other countries a great deal of
forest land has been cleared for sugar cane cultivation but paid for from
the value of the timber removed usually with a profit margin to spare.
The view is submitted that in Queensland further extensive development
be considered in savannah country, although there are still limited areas
118
in Cardwell and Cooktown districts which might provide 35,000 or 70,000
ha each, but for million hectare development it would be worthwhile
looking at the Gulf country. Admittedly;, the southern end of this area
is of low natural rainfall (0.5-0.75m) and is subject to flooding on an
annual basis. Irrigation would become essential but there are many rivers
although suitable gorges may be few. Along the western side of the Gulf
of Carpentaria the annual rainfall progressively increases to reach a peak
of 1.7m at Cape York, but at some places north of the 1.3m isohyte bauxite
soils are encountered which are generally considered of low fertility, but
some day they may grow sugar cane well.
It is not proposed here to consider specific land development in more
detail but to use a set of figures which are believed to have some
relevance and adjustments may be made as and when desired to suit selected
sets of conditions.
Million hectare developments mean developing Queensland and to convert
$20/ha-yr country to $1000/ha-yr cropping represents a responsible
recognition of the value of land in a world of expanding population.
The costs of land development for cultivation of this value status
represents a permanent improvement for the country and amortization under
conditions comparable with those for dams and irrigation works such as
75 years @ 5% or 5.13% p.a. which could well involve a leasehold arrangement
with the operator.
Infra-structure involves roads, electricity and telephone supplies,
new town and community facilities, sewage and potable water servicing and
reticulation, situations comparable in many respects with those experienced
for developments in new mining undertakings. Whereas mines are a wasting
asset no matter how long their life may be, agricultural land is always a
developing asset.
A gross 35,000 ha area development is expected to cost something of
the order of $250 m for the land, the component items recognised being:-
Item $ x 10~6
Land development 35 ($1000/ha)
300 km roads 15 ($50,000/km)
Drainage and flood mitigation 100
Town services 20
Irrigation dam and channels 60 (2m = 525Gl/yr)
Unidentified costs 20
Total estimated development ^ costs
Although much of the town services costs could be recouped as rates
and service fees from residents as could the cost of housing which might
run to $20m.
CAPITAL REPAYMENT ALTERNATIVES
It is evident that highly mechanised farming is a capital intensive
undertaking and that the ultimate cost of ethanol will be sensitive to
error or variations in the capital cost of developing the land even more
than the capital cost of the processing equipment.
The interest rate of 5% related to monies required for area development
and infrastructure is probably unrealistic in the 1977 context of interest
rates unless special government financial provision is extended. A more
realistic interest rate would be 11% for government sponsored borrowing or
20% if private development is expected.
A repayment term of 75 years may not be unrealistic for permanent type
land and infrastructure development but a 25 year life is probably as long as
120
should be expected for the processing plant and a 5 year life for agricultural
machinery.
The high interest rates of 1977 make the financing of new developments
of this character very difficult to undertake if uniform rates of
amortization are employed.
It is suggested that thought be given to indexing the capital and
interest repayments under conditions comparable to those existing with
wages and the price of the product.
An element of risk lies in predicting future escalation in wages
and prices but we can achieve some modifying of this risk if we view such
changes over a long period of time. For example over a period of 4-0 years
(1936/76) the retail price of sugar and petrol have each increased by an
average of about 3-1/ 4% per annum whereas the basic or minimum wage has
increased by nearer 7% with increases in the prices of eggs and bread
averaging something like 61/2%.
We are on more shaky ground if we attempt to predict the occurrence
of calamities such as war, earthquakes, major floods or major droughts
but we can use figures predicting the probability of such happenings.
One way in which indexation of capital repayments could be
implemented is set out here by way of an example and a set of figures is
given in Table XIV. In this table are listed several options, viz.
repayment periods of 20, 40 or 75 years associated with interest rates
of 5, 11 or 20% on outstanding capital. Four levels of indexation of
repayments are listed at 0 (i.e. equal annual repayments), 3, 5 or 7%.
Indexation of capital repayments could allow up to 10 years for the
establishment of operations under favourable conditions. The object of
the exercise is to endeavour to maintain the ratio of capital repayments
121
to price of product at a constant value. This is unlikely to be achieved
every year in say 75 but there should be a long term evening out. Petrol
which is retailed at 16C/1 in 1977 could well be expected to be $1.48 in the
year 2052 (3% p.a. increase) were there no special circumstances of supply
shortages to accelerate this happening to as early as the year 2010 (0 7%
p.a. increase), or may be even earlier. An intermediate indexation rate
of 5% would be very helpful and provide a margin for hope that the rate of
price increase could be kept down to this figure. By the year 2010 the
industry should be well able to afford to pay the higher rate of capital
repayment.
With the method of indexation calculated here the total amount of
money repaid in interest is kept at the same figure for the same amount of
capital irrespective of the degree of indexation which might be adopted.
The full capital debt is also assumed to be repaid in the same period of
time and this sum is included in the periodical payments. A column,
however, is given to indicate the amount of interest, only, which would be
repaid over the period indicated.
Several other figures are listed b y way of interest viz. the payments
which would be expected at the end of the first, third and sixth years, when
half way through the payment period and the payment which would be required
in the last year.
The manner in which the figures for Table XIV have been calculated
are set out and include a formula for calculating the payment which would be
expected for any selected year of interest.
Other methods of repayments of capital and assessment of interest
are possible and may be used as desired.
122
METHODS OF CALCULATION FOR TABLE XIV
Let C = capital debt ($100 for Table XIV)
R = repayment in equal amounts for equal time intervals
i = interest rate (uniform throughout period)
n = number of time intervals - years
r = rate of indexation
x = a particular year selected for inspection of repayment rate
TABLE XIV
TABULATED INDEXED CAPITAL REPAYMENT RATES
Annual payments per $100 of capital investment - combined repayment of principal and interest.
Repayment 1 Index - %
0
3
Interest Rate - % \
20
11
5
20
11
5
Total payments in specific years
1st year
20.54 20.01 20.00
12.56 11.17 11.00
8.02 5.83 5.13
15.29 10.62 3.85
9.34 5.92 3.03
5.97 j 3.09
1.41
3rd year j
20.54 20.01 20.00
12.56 11.17 11.00
8,02 5.83 5.13
16.71 11.60 6.02
10.22 6.48 3.31
i 6.53 3.38 1.55
6th year
20.54 20.01 20.00
12.56 11.17 11.00
8.02 5.83 5.13
18.25 12.68 6.57
11.17 7.08 3.62
7.13 3.69 1,69
median year
20.54 20.01 20.00
12.56 11.17 11.00
8.02 5.83 5.13
20.54 19.18 16.67
12.57 10.70 9.17
8.02 5.58 4.27
Completion Situation
last payment
20.54 20.01 20.00
12.56 11.17 11.00
8.02 5.83 5.13
27.60 34.63 50.50
16.38 19.33 27.79
10.78 10.08 12.96
number of years
20 40 75
20 40 75
20 40 75
20 40 75
20 40 75
20 40 75
Total Interest Paid
311 701
1400
151 347 725
60.50 133 285
311 701
| 1400
151 347 725
60.50 ;
133 285
Repayment
Index - %
5
7
Interest
Rate - %
20
11
5
20
11
5
Total payments in specific years
1st year
12.42
6.63
1.98
7.59
3.70
1.09
4.85
1.93
0.50
10.02
4.01
0.66
6.13
2.20
0.36
3.92
1.17
0.17
3rd year
14.37
7.68
2.30
8.79
4.28
1.26
5.62
2,24
0.59
12.27
4.91
0.81
7.50
2.74
0.45
4.79
1.43
0.20
6th year
16.64
8.88
2.66
10.17
4.96
1.46
6,50
2.58
0.68
15.02
6.01
1.00
9.19
3.36
0.55
5.87
1.75
0.26
median
year
20.23
17.59
12.36
12.37
9.82
6.79
7.91
5.12
3.17
19.71
15.52
8,36
12.05
8.67
4.60
7.70
4.52
2.14
Completion Situation
last
payment
32,96
46.65
76.99
20.15
26.04
42.36
12.87
13.59
19.75
38.77
60.05
105.66
23.71
33.52
58.13
15.16
17.48
27.11
number of
years
20
40
75
20
40
75
20
40
75
20
40
75
20
40
75
20
40
75
Total Interest Paid
311
701
1400
151
347
725
60.50
133
285
311
701
1400
151
347
725
1 60.50
| 133
285
125
ESTIMATED COST OF MECHANICAL COMPONENT OF FARM UNIT OPERATIONS
Mechanization is only part of the farming involvement. Selecting
the timing of the operation is equally important. As it is assumed that
2m of irrigation is available the moisture content of the soil can be
suitably conditioned before ploughing. This can both reduce the number
of times the operation is needed and also improve the quality of the result.
The good farmer in an area well endowed by nature as far as rain fall is
concerned will get the shower of rain he needs somewhere around the right
time and will plough when the soil is just in the right condition. But
nature is not always co-operative and irrigation is one of man's answers
to nature's vagaries.
Whilst the major step in mechanization was to change from horses to
tractors there are still further economies to be achieved by increasing the
power of tractors to operate with wider implements and at higher speeds.
Economics of increasing the speed of ploughing, for example, may
be estimated from the following relationship:-
high speed High power = (low power) (low speed }
(there are variations of the exponent related to the nature of the soil
but they are in the second decimal place).
There is also some relationship between the quality of the ploughed
field, the type of plough and the actual speed, but this is not a specialist
dissertation in agricultural engineering.
We can, however, see that as a first approximation, if we double
the speed the power required increases by only 25%. On the other hand if
we double the width of operation of the plough, we could expect to double
the power required to pull it.
126
On a 50 ha farm the area to be prepared per crop of sugar cane
averages 12.5ha and there may be three different fields for each crop or
an average of 4.17 ha per field. The full advantages of increasing
mechanization cannot be realized on fields of 4 ha because of the high
frequency of turning requirements. Thus for an equipment assembly
designed to cover a 4 ha field at 1 ha/hr, the same equipment could cover
a 400 ha field at speeds nearer 5 ha/hr or 7 ha/hr for fields of 4000 ha.
The effects of substantial variations in the size of field on the
cost of a unit operation/Te cane are summarized in Table XV charging tractor
time at $12.50/hr including driver and fuel, and also adjusting for lower
productivity from larger farms.
TABLE XV
EFFECT OF SIZE OF FIELD ON COST OF TRACTOR USAGE
Size of farm -ha
45
1600
16000
Size of field -ha
4
400
4000
Product ivity Te cane/ha
90.0
84.1
80.6
Cost of tractor usage C/Te cane J
13.9
3.0
2.2
It can be seen that the economic advantages of increasing field
size beyond 400 ha or tractor speed beyond i0 km/hr provide progressively
decreasing returns per tonne of cane. Gross earnings may increase with
further increases in scale of operation but will have only a marginal effect
on the ultimate price of ethanol.
Much more detailed studies would be needed to establish more
precisely the optimum scale of farming operations, but for the purpose of
127
this exercise the following data are used for costing purposes - as a
first approximation:
Optimum size of farm = 1600 ha
Productivity to be expected = 100,000 tonnes cane
(i.e. 83.3 Te/ha under crop)
Cost of tractor = $50,000
Cost of driver = $7/hr
Also for the purpose of this exercise it is estimated that ten
tractor-drawn unit operations are required per annum - i.e.does not include
irrigation. This equates to $1.39/Te cane for present average sized farms,
30c/Te for a 1600 ha property and 22c/Te for a 16,000 ha estate.
Increasing scale of operations also allows better use to be made
of mechanical equipment.
For example with a 45 ha farm the tractor would be required for
only 450 hrs/yr or around 5% of total available time. In fact the farmer
probably would not own a tractor powerful enough to operate at 1 ha/hr
but would be satisfied with 0.5 ha/hr. He also has a very lax schedule
of maintenance as compared with that operated under stricter discipline
for the non-mobile machinery in the sugar mill.
For the 1600 ha property tractor usage would be required for 3200
hrs/yr or 37% of total available time. If we allow for usage to be
restricted to the 9 months associated with the harvest period this becomes
49% of usable time or an average of 12 hrs/day. A property of this size
could economically use a tractor of this capability but would require
disciplined schedules of maintenance and operation. The tractor could be
amortized over 5 years at 20% p.a. to cost $5.22 per working hour and with
maintenance costs equated to the resale value at the end of the 5 year
period.
128
Whilst there are undoubtedly differences in the actual costs of specific
tractor-drawn unit operations for example planting is probably more costly
than fertilizing, the figures listed in Table XV will be used for average
considerations.
The costs of property development are assessed at $8000, 7500 and 7,100/ha
including the supply of water up to 200 kl/ha-yr. The total development cost
of $250m is amortized at 11% over 75 years and indexed at 5% p.a., the actual
calculation being based on the 6th year of indexed amortization, i.e. the
median year of the first 11 years of operation.
IRRIGATION APPLICATION
The real cost of applying irrigation is difficult to determine in
Queensland as the farmer is able to do this himself if he works a farm of the
average size viz. "45 ha. Some information from Hawaii for applications of
2.5m per year by furrow irrigation has indicated labour requirements of the
order of 50 man-hrs/ha-yr for this amount of water. For a Queensland
situation presently applying 0.3m this would require only 200 man-hrs of
work for the average farm for the cane crop itself with perhaps an additional
10-15% for the fallow area.
This has been used as the basis for calculating the estimated cost of
application for a 50 ha farm and scaled to the two larger properties.
It is evident that whilst the cost of applying irrigation is high for the
50 ha farm at 23% of the total cost it is not a dominant cost. There may be
some incentive for the farmer to reduce the amount of time spent on irrigating
but the situation would not be particularly pressing. There would be no
real incentive for him to incur too much in the way of capital expenditure
for spray or trickle irrigation.
TABLE VXZ
COST ESTIMATES FOR CANE GROWN ON LARGE PROPERTIES OR ESTATES (Stalk juice ethanol production)
On the other hand there would be substantial incentive for the 1600 ha
property owner or the c5,000 ha estate manager to seek to minimize these
costs which he could well do by an order of 35 to 50%. Whilst this
incentive may appear to be greatest in the first eleven year of operation
it is a labour intensive undertaking, and the cost could be expected to rise
progressively with time paralleling the property development cost.
HARVESTING OF SUGAR CANE
This has now become the most sophisticated of the unit operations
employed in the production of sugar cane. Whilst it may not yet have
reached the peak of its development in terms of mechanical equipment, any
new areas being established can benefit from the experiences of the Queensland
130
industry through the past 10 to 15 years, although mechanical harvesting
has been practised in restricted areas as far back as 1940 and had been
introduced in Hawaii during the previous decade.
There are now several types of harvester being used in Queensland and
practically 100% of cane is harvested mechanically in the form of chopped
billets. It is customary to put a fire through the field before harvesting
but studies are currently in progress to determine the economics of green
cane harvesting.
One of the more popular of the harvesters is the unit produced by the
Ilassey Ferguson Co. and known as the MF102 costing in 1977 around $56,000.
It is suitable for purchase by a small group of farmers with a total crop
of about 20,000 tonnes - 7.4 :!average:; farmers.
Only one man is required for operation and he has 130 h.p. under his
control. This does, however, represent a substantial under-utilization of
the unit which could cut up to 1500 or 1600 tonnes per day but is seldom
used to average more than 200 to 300.
A rate-controlling factor as far as the hourly rate is concerned is often
the rate at which the containers are taken from and returned to the machine.
One of the legacies of the *+3 ha farm unit is that a farmer is allocated
a periodical quota so that his canemay be milled progressively through the
season. The average farmer would have a crop of 2800 tonnes of cane
which would represent only 100 Te/week during the season. It is obviously
very uneconomical to allocate a machine to this task which is capable of
cutting out the whole weekly quota in the matter of about 2 hours.
This no doubt accounts very largely for the fact that there are some
1500 machines owned by growers in Queensland for a total crop of 18 to 20 MTe,
131
representing only 450 Te/roachine/veek. This is easy for the machine, and
provided the capitalization can bo carried at $1.67/Te cane (5 years @ 15%)
it is easy for the farmer.
The contract cutting price for the driver is currently around 33<?/Te
giving a total cost of $2/Te cane.
The writer has done a brief time and motion study of this unit and an
associated cost-benefit analys.is. In the event of new regional development
unrestricted by the situation of the present sugar industry - which
understandably has invested heavily in bringing mechanical harvesting to it;-
present stage - another.? stage is envisaged whereby the real advantages or rhv.
Queensland can harvesters may be realised.
In a new development a farmer owning a 50 ha farm unit would be little
better off except perhaps for the fact that the maturity period in terms of .
crystals izable sugar in cane may not be so critical for ethanol production,
in which case a cut once every 4 weeks in a 40 week season could be acceptable
At 338 tonnes of cane this would enable the machine to be used for a full
8-hr operational period on tho farm and moved before the next day's harvest.
This would increase the seasonal capacity of tho harvester to 95,000 Te/cane
to reduce the capitalization. The cost of a unit of '45 Te cane/hr capacity
is estimated at $83,000 by 1985. The amortized cost of the machine, at
20% for 5 years would be 26.1c/Te cane to which must be added maintenance
at 10% p.a. of capital cost or 8.7£/Te cane to give a total equipment
cost of 34.8c/Te cane.
If the driver be costed on an hourly rate cf £7/hr the actual cutting-
cost would be 15.6*/Te cane. This is doubled to allow for the cost ci"
transfer from one field to another and for cleaning cf the machine and
minor maintenance.
132
Thus total harvesting cost is estimated at 57.3c/Te cane.
Even this arrangement does not take advantage of the full cutting
capacity of the machine by operating at night. It is normal practice
in the U.S.A. to operate wheat harvesters under floodlight conditions.
Their operation is normally on contract rates and they may work 12-16
hours a day during the relatively short harvest season.
It is envisaged that cane harvesters could be operated for 168 hours
a week just as the factory machinery will be expected to do, and allowing
for a scheduled lost time of 2% plus non-scheduled lost time of 6%. The
drivers would work on a 4-shift roster system for which a rate of $8/hr is
estimated as comparable to that of a shift worker in the factory. The
cutting programme would involve two quotas per 24 hrs of 15 hrs, 2 hrs lost
time and 3½ hrs per transfer, or a total of 4.732 Te cane/week and 190,000
Te cane for the season.
The capital and maintenance costs then become 11.7*/Te cane. There
would be 4 men responsible for driving duties which if paid at an hourly
rate of $8 for 42 hours per week and 40 weeks would represent a total cost
of $13,440/driver, or 27.6c/Te cane.
Total capital and labour cost of harvesting = 39.32c/Te cane. It is
suggested that there would be social advantages in employing these men on
a continuing basis with 12 months of employment of which one month would
be regarded as holiday and two months for work on slack season maintenance
of farm equipment. A lower hourly rate of pay should be negotiable for
these conditions.
If all cane production is to be carried out on 50 ha farms there would
be 875 farm units to require 12 harvester units. It would probably prove
to be a wisely economised maintenance support to have two additional units.
133
The farmer is also responsible for the cost of transfer of cane from
the harvester to the pick-up point for the mill transport system. The
actual cost of this part of the exercise is difficult to estimate at this
point but a figure of 40C/Te cane is considered to be the right order of
magnitude.
Transferring our study to the 1600 ha property or 35,000 ha estate
introduces comparable problems in that a double row harvester would become
justified and this is the largest size currently manufactured. Furthermore
it is unlikely that a 3-row harvester would be workable. It is also
unlikely that the operating speed would be increased because of the physical
problems of manual control. Thus a cutting rate of 90 Te/hr is accepted
as the limit with present known technology.
The twice daily transfer of the machine should be reducible. For the
1600 ha property we will assume 4 x 400 ha units which are cut, as before,
once every 4 weeks and to be cut out in 40 weeks. Each cutting quota would
now be 3333Te or 37 hours of cutting time. Allowing a 5 hr transfer time
this would enable a machine to cut 4 quotas/week or 533,280 Te/season less
8% lost time or 490,000 Te/season.
A total of 4.5 machines would be sufficient to cut the crop, but 5 would
be necessary with 2 small machines as stand-by units. The 1985 cost of a
double-row harvester is estimated at $126,000. The capital costing for the
machine, including maintenance at 10% p.a. would be 11.5c/Te cane. Labour
costing on a four shift roster system at $8/hr would be at 12.3c/Te cane,
requiring 20 men to operate the five machines at a seasonal cost of
$13,440/driver.
The cost of transferring cane to a pick-up point will be discussed in
more detail under the general heading of transport costs and will be shown
134
to be around 33.5c/Te cane unless special arrangements are made for
direct pick-up by mill or contract "canetainers".
The use of larger bins or canetainers also enables a higher average
cutting rate to be attained as there is leas time lost in changing bins.
For operation of a single estate of 35,000 ha the total number of
double-row harvesters required could be reduced to «+ by optimising quota
sizes and transfer times to a minimum.
The costs would be 9.56c/Te cane for capital and maintenance charges
plus 10.24c/Te cane labour costs or a total of 19.8c/Te cane.
With operation on an estate basis the full cost of transport of cane
from the harvester to the mill can be considered as a single cost and
itemised with processing costs.
FUEL COSTS
The cost of fuel for mechanical harvesters is necessary to take into
account for which the following assessments have been made:-
(1) Single-row harvester plus tractor = 30 1/hr of diesel fuel @ 15C/1.
Total effective time = cutting time + 25% = 12.5C/Te cane.
(2) Double-row harvester plus tractor = 55 1/hr. Total effective
time = cutting time + 12½% - 10.3c/Te cane.
(3) Double-row harvester @ 40 1/hr. Total effective time = cutting
time + 6-l/4% = 7.1c/Te cane.
135
TRANSPORTATION OF SUGAR CANE
(a) From field
It is customary for the harvester to fill containers with chopped
cane and for these to be transported from the harvester to a loading
point for a tramline transport system or to a corresponding loading point
for road waggons. Sometimes the farmer may do the full transport
operation himself or by road contract as far as the mill itself.
The size of the containers varies from about 3 to 6 tonnes. The
latter size are generally more economical although requiring heavier
lifting and handling equipment. Increase in container capacity and
horsepower for transportation should be able to minimise costs at what
can be a bottleneck in handling procedures.
3 The packing density of chopped cane stalks is only about 300 kg/m
which is the figure commonly used for estimating the sizes of containers.
A single-row harvester operating at 45 Te/hr will fill a 3 Te
container in 4 minutes - frequently less. Two men, each with a tractor
and trailer with mechanical coupling/uncoupling can keep a harvester
operating and transfer containers up to about 600 m. It might be
difficult for one man to be able to keep up this rate with 6 Te
containers.
With a tractor and trailer at half the cost of the harvester this
would represent a cost of 33.5c/Te cane including driver, using the same
bases for calculation as for the harvester and driver. An exchange of
driver duties becomes desirable because of the intense concentration
required in driving the harvester.
136
The double-row harvester would require two men driving tractors to
service the machine with six tonne containers. The cost would still be
33.5c/Te cane.
For larger equipment to operate from the field special design would be
required by increasing the number of wheels or using track or semi-track
units in order to be able to operate under moderately wet conditions.
Irrigation drains and headlands can be troublesome and these also
need to be designed into the system.
(b) From field to factory:
The most common method in Queensland for transporting sugar cane from
the field to the factory is by mill-owned tramway systems which handle
over 80% of the crop, only about 13% being transported by road. It is
obvious that there must be many advantages for the tramway system for such
a high proportion of cane to be transported in this way.
When coming to a new area one is faced with the high cost of laying
tracks and the observation must be made that a road system is also required
for normal servicing of the area. If cane is to be transported by road
the standard of the roads would need to be increased and there would be
additional maintenance required. In certain overseas situations "road
trains" are used especially in estate operated areas.
The length of a cane transportation system to service a district
with 35,000 ha of gross assigned area for growing will be heavily dependent
on the distribution of the assignments and a figure of 300 km has been
arbitrarily assessed for a road system.
Careful costing is necessary to determine the most economic system from
the cost-benefit point of view.
table xvii
Estimated Costs of Road Transport for Sugar Cane
138
For the current purpose a road transport system is considered and
appropriate costs are estimated. These are itemised in Table XVII.
Three options have been considered based on a 20 Te "Canetainer"
semi-trailer arrangement operating on a 7 day/week schedule. These units
have been built with fast operating devices for minimising turn-around
times and 20 round trips of 30 km are claimed per 24 hours to transport
M-00 Te cane.
The possibility of using one or two 20 Te trailer units is considered
here, the one trailer unit being possibly suited to the 1600 ha properties
and the two trailer unit to a 35,000 ha estate. In the latter case the
responsibility for the roads would be entirely with the management of the
processing complex.
In the ethanol processing systems under consideration it is proposed
that distillery slops be concentrated to 50% solids and returned to the
fields as fertilizer. There would seem to be economic advantages in
rationalizing the two transport exercises. The amount of fertilizer to be
recycled is estimated at 50(±10) kg/Te cane or one tonne to be returned to
the field for every 20 tonnes of cane transported to the factory.
FACTORY EQUIPMENT
A sugar-cane/ethanol factory would require a cane preparation and
crushing unit comparable to that employed for the extraction of juice for
raw sugar manufacture.
The size of the plant is rated at 10,000 Te c.d. which would require
an 81% operational time to process a crop of 2.2MTe cane. Although two
crushing tandems are employed at the largest mill in Queensland for a nominal
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rating of about 8500 Te c.d., experience with new larger capacity units in
other countries indicates that a new single tandem unit could be designed
to handle 10,000 Te c.d.
Experience shows that every design engineer has his own especially
favoured combination of units and settings of mill openings or
preparatory devices.
The preference indicated here would be for a 3 roller crusher unit
followed by a shredder and a tandem of G x 3 roller mill units, the
roller sizes being 1065 x 2134 ram (42 x 84"). Placing the crusher unit
ahead of the shredder would be the reverse of conventional Queensland
practice but is commended on the grounds of reduction in power required
for the shredding process. There is not very much point in expending
power on shredding juice which can readily be extracted by a crusher.
Furthermore with cane already having been cut into short lengths in
chopper harvesters, it should be possible to operate with only one heavy
set of top knives before the crusher.
In the writer's experience further economics in mill tandem operations
are possible with plate type of compression feeders instead of twin roller
compression units commonly in use in Queensland.
An average extraction of 95.5% has been used for estimating yields
but it is considered that with a tandem of the type described an
extraction approaching 96.5% is not unattainable. Each 1% of extraction
would be equivalent to approximately 2 Ml of ethanol in 2.2 MTe of cane.
The flow sheet would otherwise be similar to that suggested for
conversion of an existing raw sugar factory to an ethanol distillery but
with such modifications as would be more appropriate for the production
of ethanol.
A simplified flow sheet for such an arrangement is given in Figure
2 together with an elementary material balance.
In Table XVIII are set out estimates for the cost of processing the
sugar cane for the production of ethanol under three conditions of cane
growing. The high productivity of 50 ha farm units would require a
larger processing plant if served by the same gross area. On the other
hand the lower unit cost of cane grovm on 1600 ha properties or on a
35,000 ha estate effect significant reductions in the total price of
ethanol ex-distillery.
The production rates of the distillery at 200Ml/season would be small
in terms of petroleum refineries being equivalent to processing only
8,600 bbl of crude oil a day but the product is indefinitely renewable as
long as sunshine and rain continue.
It can be seen from the figures in Table XVIII that the estimated
cost of ethanol could be reduced to as low as 1H.5C/1 (1985) if the cane
is grown under optimum conditions on a 35,000 ha estate or 15.5c if grown
on 1600 ha properties.
Unlike the situation for small farm production the price of cane
becomes slightly less than the factory processing cost instead of
approximately twice as much.
The influence of the capital cost component becomes more significant
in the case of low priced raw material - as is the case when molasses at
$25/Te is processed alone for ethanol, the fermentable sugar in the cane is
in fact only $34/Te compared to $47/Te for the fermentable sugar in molasses.
For the lowest costing ethanol the capital cost component is 54% of
the processing cost and 25% of the growing cost at the sixth year.
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TABLE XVIII
Estimated cost of processing sugar cane s ta lk juice for ethanol
If amortization of cap i t a l cost is indexed at 5% it makes less than 0 .1c /1 difference in the s ix th year .
142
These figures do not include the capital component of farm and transport
machinery. If all capital components are included they represent around
55% of the ex-distillery cost estimate. Thus one would call it neither
a labour intensive nor a capital intensive industry. Escalation of
labour costs at the rate of 7% p.a. combined with the built-in 5%
escalation in land development amortization would result in an annual
cost increase of around 3.8%.
The relative merits of the social benefits of 1600 ha properties and
the cost benefits of a 35,000 ha estate in terms of around 1<:/1 of ethanol
fall more in the realm of a political decision.
COMPUTER CONTROL FACTORS
The use of computers is expected to play a very important part in
the control of operations and decision making procedures. In costing,
this is part of both capital and operating costs and at this stage no
serious attempt has been made to optimise the requirements, more detailed
study being necessary as well as narrower guidelines for specific development,
The present Queensland sugar industry is developing computer assistance
for farmers with special respect to block productivity results. In the
context of 45 ha farm units this makes a great deal of sense. It is
likewise important for large property sizes. But in the latter case the
importance of scheduling equipment usage and maintenance become equally as
important and the benefits of computer-assisted decision making would be
necessary to achieve the type of results envisaged in this report.
Scheduling of cane harvesting and transportation need not be so
complicated with large properties but because of the high capacity equipment
involved effective management control becomes financially very
significant.
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Within the processing plant itself every advantage should be taken
of the opportunities for sophisticated instrumentation, unit automation
and over-riding computer decision-making when designing equipment.
FARM EQUIPMENT MAINTENANCE
A high degree of farm mechanization brings with it the need for a
higher standard of maintenance of equipment. There are various ways in
which these are handled - by the farmer himself, by contract at some
central site or by itinerant maintenance tradesmen.
The farmer does need to have his own workshop and facilities for
essential maintenance and requires to be competent himself in a variety
of technical skills or to employ a person who is able and willing to do
this.
Costing of these operations should ideally be distributed among the
individual items of equipment in order better to assess their cost-benefit
contributions to the farm. The extent to which this is done will depend
largely on the attitude and application of the farmer as well as his
ability to handle the bookwork involved. This is an area in which estate
management has substantial potential advantages although they may not
always be realised in practice as competently as the system warrants.
There is also important decision making related to planned maintenance
or anticipatory maintenance based on equipment behaviour observations as
well as replacement decisions. Skill in management as well as technical
procedures becomes increasingly important.
The farmer needs to keep certain stocks of spare parts but there are
limits to this in which he is aided by district representatives for
equipment as well as by improved means of transport and communications
such as better telephone services and C.B. radio.
In an estate situation associated with a factory greater economy
and reliability in maintenance may be sought centralizing maintenance
services at the factory site probably in association with transport
maintenance, but with effective patrol services and C.B. radio area
communication.
MANAGEMENT OF AGRICULTURAL OPERATIONS
This is undoubtedly, the most costly component of sugar cane farming
for 50 ha area units, but there is little significant incentive to
convert to larger units in the context of the present industry. The
policy of single person or family units was enunciated at the time of
rationalization of the industry concurrent with federation, and still has
many social advantages for its maintenance with appropriate built-in
preservation structures. Concurrent strategic and political benefits
confirm this way of life. Possible effects on the retail price of sugar
may be grudgingly accepted by the community at large in return for
stability of price, and currently a satisfactory price situation in
relation to world markets. The acceptance is less so during periods when
the domestic price is significantly higher than world market situations
but the built-in inertia of the system has maintained its economic
constraints and controls.
A new industry such as ethanol will have a different social
impingement and the community is less likely to accept too much artificial
structuring of the domestic price in the light of current known technology -
new sources of technological expertise impinge on the problem, and have
more significant effects.
Whilst a good manager may operate at anything up to 25 or 30% below
average costs simply by good management the same good manager could equally
as efficiently manage a farm ten or a hundred times as large as his own.
Thus an estate is able to pay well to retain the most competent expertise at
only a fraction of the cost per tonne of cane as is possible for the
individual farmer. Cn the other hand an estate which is poorly managed
experiences financial crises of much greater magnitude than those of an
individual farmer.
Intermediate between the single estate and the 50 ha farm unit a unit
of 1600 ha has been examined and calculations indicate that the relatively
small increase in costs may well be compensated by the social benefits of
the intermediate unit.
Whilst the price of cane itself may be 17% higher from a 1600 ha
property than from an estate this is usefully offset by the higher
productivity to be expected from the smaller unit. The overall cost-
enefit of the estate is reduced to only 7% after processing of the cane
to ethanol. It is, however, still only two thirds of the price of the
50 ha unit operations.
For a single new area development 700 x 50 ha farmers would be needed
whereas only 22 at 1600 ha or one manager for a single estate. The
probability of being able to recruit the 22 managers with the required
expertise to operate 1600 ha properties would be rather better than the
prospects of recruiting 700 farmers with the expertise to manage 50 ha
highly mechanized units with the necessary efficiency.
Mechanization means providing operatives with mechanical power to
extend their manual abilities. In a sugar cane factory where units are
stationary and running for 24 hours in a day, albeit only for 5 days in a
week, an individual operative has under his control something between
146
150 and 200 h.p., individuals may have as much as two to three thousand
and to operate for 95% of the available time.
The best which may be said of his counterparts on the farm would be
for the harvester driver who has power units under his control of the order
of 130 to 180 h.p. but seldom operating effectively for more than 50% of
available time of an individual operator - even the time spent in turning
at the ends of a row is in effect an inoperative use of the time available
to the machine and driver, in other words long rows are better in a
mechanized farming economy.
The over-all situation on a farm is difficult to assess but it could
well be that net more than 15 to 20 h.p. is used by the farm operator on a
continuous basis - or maybe even less. Machinery locked up in a shed or
mechanically inoperative is an expensive luxury, it only earns its keep
while it is working.
Effective management also involves careful and accurate costing and
the advantages of computerized assistance in this area has already been
pointed out.
The farm manager needs an accountant competent in his field and the
accountant needs to understand the computer system in order to provide
the manager with the best of advice for making decisions.
For a single new area development 70 accountants could well be
required to service the needs of 700 farmers. A 1600 ha manager could
afford to employ one on a full time basis in which case 22 would be required.
On the other hand the estate would probably employ a staff of accountants
and clerks of varying degrees of expertise. Either of these groups would
more readily be available from the employment pool than the 70 required for
servicing small farm operators.
147
The transport of sugar cane is usually effected in Queensland with
an economy more comparable to that of the factory than of the farm.
Perhaps it is no coincidence that the operation and cost of the basic
transport system is the responsibility of the factory.
In other countries where there is an individual farmer economy the whole
of the transport system is more commonly in the hands of independent
contractors or of the farmers themselves. It has been conspicuous in
these situations that the economy of operation has been more of the standard
of general agricultural operations than of those of the factory.
Queensland also has a built-in price incentive which provides
financial benefits to the farmer who gets his cane to the factory in the
shortest possible time with minimum deterioration. This somewhat complex
incentive system also gives financial benefit to the factory for good fresh
cane. In overseas situations where corresponding benefits have been
successfully introduced associated improvements in quality of cane and
efficiency of transportation have materialized.
AGRICULTURAL EXTENSION SERVICES
It may well be said that an individual farm economy can only develop
efficiently with a high quality, efficient and effective extension service.
This is already operating well in the Queensland sugar industry but did not
reach its present stage overnight. The service has been progressively
developing, as has also the relationship with the farmer.
One area in which this has been of paramount importance has been that
of the control of diseases in the sugar cane and to a lesser extent to pest
control. Whilst services in the area of agronomy have made the differences
between a poor industry and a good industry, the services in the field of
disease control have meant the difference between a healthv industrv and
probably no cane sugar industry at all - at least as far as Queensland is
concerned.
The relevance of this to prospective development in a new area cannot
be too strongly emphasized. When a new area is developed in this way the
basic ecology is interfered with to such a degree that pests and bacteria
which were previously benign suddenly flare into a condition of very high
activity the specific nature and extent of which is difficult to predict.
The development of new varieties of sugar cane is also an important
function of centralised services. New varieties are continually needed
not only to improve productivity but also to resist disease. Even to
maintain productivity requires the continual development of new varieties.
The commercial growing of sugar cane involves plant propogation from
segments of the stalk of a previous generation followed by successive
regeneration of the root system. This is the only practicable means of
operation. To grow a crop from sowing seed each year would be quite
impracticable. However, employing the clone propogation technique
means that the genetic age of a particular stalk is the sum of the ages of
all of the previous generations since its ancestor was initially developed
from a seed. After about 10 years of self propogation, it becomes
economical to introduce a new variety, which requires primary propogation
from a seed.
The breeding of sugar cane for new varieties initially involves the
controlled fertilization of flowers followed by collection and germination
of the seed. This and successive stages in the procedure for development
of a new variety are highly skilled, professionally controlled exercises,
to which should also be added the very high degree of professional skill
involved in selecting the desired parentage for fertilization.
Development of a new area for sugar cane growing should take
maximum advantage of the skills and organization already developed in
149
Queensland. Undoubtedly local representation of a professional standard
would be required but desirably related to the base organization.
Appropriate funding would be needed for the new industry. There is some
government financial assistance to the agricultural research and
development programmes for the existing sugar cane industry in Queensland
but only on a marginal basis. For significant new area development a
primary injection of government finance would be needed to set the new
area on its way but to be progressively financed by levies on new
production with a corresponding reduction in the scale of government
assistance.
The suggestion is submitted that worthwhile addition to the pool of
expertise in this field, as would be required by new area development,
might profitably be obtained by a policy of selective migration from
overseas where corresponding skills have been developed. Freer- inter
communication between Australia and neighbouring countries could be of
benefit to both parties in this area of operation.
Whereas there is a wealth of expertise available in Australia on
growing sugar cane and processing for raw sugar the expertise in ethanol
production is relatively restricted.
A new source of appropriate technical expertise would need to be
created concerned not only with production of ethanol but also with its
applications as a liquid fuel.
150
PRODUCTIVITY DEVELOPMENT ON EXISTING FARM AREAS
It has already been indicated that average rate of increase of
productivity over the past 75 years has been at the average rate of
1.58% p.a. in terms of Te sugar/ha. In terms of the present gross
assigned area of the sugar industry in Queensland this is equivalent
to adding another 5135 ha or 43,500 tonnes of sugar each year which is
nearly half a new sugar mill of average peak assessment.
Maintaining a growth of this magnitude requires a significant total
effort but a relatively small individual effort when distributed among
7000 growers.
The two chief factors which can be adjusted to maximise yields are to
provide all the water the cane needs, when it needs it and to provide
adequate fertilizer. Much effort has been expended in determining the
optimum needs in each of these requirements. Water supplies of irrigation
have been progressively developed and fields have been improved from the
point of view of drainage. There seems to be good reason to believe that
the 1.58% p.a. increase in productivity can continue to be maintained
for many years to come if developments of water supplies and field
drainage continue.
To these must also be added the contribution from the continual
breeding of new varieties and persistent efforts to combat disease and
pests.
Other areas of study in the general growth characteristics of sugar
cane have included the use of hormone growth stimulants or flowering
controllers.
151
The importance of the carbon dioxide/oxygen cycle to the growth of
the plant has been noted. The supply of carbon dioxide from the atmosphere
is always adequate for the plant synthesis processes. The behaviour
of sugar cane contrasts somewhat with that of sugar beet from this point
of view. Sugar beet has been found to respond favourably to higher
concentrations of C0 2, or putting it another way - sugar beet is strongly
C02 sensitive whereas sugar cane is not.
Sugar cane has been observed to show a strong response in photoperiodism
in that it is often in full flower during the harvesting season which
generally coincides with the period of lengthening of daylight hours.
When flowering occurs the plant itself stops growing although there may be
an increase in sucrose content. Each of these is important in the sugar
industry (undesirable and desirable respectively), but the latter would
be much less important in the ethanol industry. The sucrose pre
cursors are hexose sugars which themselves are fermentable without the
need for hydrolysis.
On the other hand when the cane stops growing the tonnage per hectare
has reached its peak for the season and this is unfortunate in either
industry.
It is known that the flowering of sugar cane is related to the
length of the day - sugar cane is a ''short day" plant which means that
flowering initiates when the length of day reaches a certain value during
the time between the longest and shortest day of the year and is in full
bloom shortly after the shortest day.
Three main approaches to this problem have been made. One is by
breeding - it is well known that some varieties of sugar cane flower
much more prolifically than others. In fact in some countries
152
no flowering occurs at all, e.g. Pakistan and the breeding station is
located in some other part of the country where flowering does occur.
Photoperiodism is probably more noticeable as the latitude increases
but there are complexing factors.
Hormone spraying has been used to inhibit flowering but has been
found too costly and not as reliable as desired.
Simple extension of daylight time has also been tried - sometimes
successfully, at other times without success. It has been demonstrated
that the sugar cane plant (as with other short day plants) is responsive
to irradiation at night with artificial light. The light intensity does
not need to be strong, actually something only marginally stronger than
the light of the full moon is sufficient to confuse the responses of the
plant. If an effective intensiry were to be as low as that of the full
moon, then nature herself would be in confusion. Also it is found that
only a short period of artificial illumination is sufficient to effect
the desired confusion of the plant, perhaps as little as two to five
minutes.
What does seem to have had less attention is the precise time in
the growing cycle when the artificial radiation should be applied. It
is obviously no use to apply the treatment once the flower has begun to
develop, but how to determine the right time and how the farmer might be
able to identify this to his own advantage are questions to which there
do not yet seem to be adequate answers.
The type of equipment which night be employed is envisaged as being
comparable to that used to illuminate a sports arena at night. A tower
could be suitably placed to command a large area of sugar canefields and
capable of rotation by 360° so that full advantage could be taken of the
installation.
153
The return which might be expected by way of increased yield
would probably be something of the order of 10% ± 5 depending also upon
a variety of related factors. However, a return of this order of
agnitude would appear to justify the cost of treatment if the right
technique can be defined.
The sugar cane is a hardy plant from many points of view. It has
needed to be in order to survive and still to grow wild in many countries.
Recovery after drought or flood does take place, the sucrose development
may not be at its best under these conditions and it may prefer to develop
new shoots to grow into stalks. Like other living things the plant does
have its preferences.
It luxuriates in sunshine but does not like to get its canopy
of leaves sunburnt. For this it needs an ample supply of water to
maintain a high rate of respiration, the final phase change which the
respiring water experiences as it leaves in vapour form to humidify the
surrounding atmosphere involves a substantial consumption of heat by way
of the latent head of vapourization. On the other hand it does not
like to have wet feet and grows better if looked after in this respect.
Also it does not like cold feet and objects to frosts. Its favourite
temperature conditions for optimum growth are between about 27 and 37 .
At lower temperatures its growth rate slows and becomes very slow below
20°. When its own temperature gets into the mid thirties it starts to
experience problems of heat exhaustion and when the surrounding shade
temperature gets to 4-0 it can be in real trouble unless the water supply
is maintained.
The sugar cane may be a hardy plant but it responds remarkably well
to the tender loving care appropriate to its needs, the response being by
way of prolific growth and more effective and efficient use of the
sunshine in which it thrives.
THE CELLULOSE COMPONENT OF SUGAR CANE
Sucrose and the hexose sugars are by no means the only
carbohydrates within the sugar cane. There is also a high proportion
of cellulose in the fibre and it is potentially fermentable to ethanol.
The proportion of cellulose in the fibre is not known precisely but is
believed to be around 53% of the dry weight of fibre. The number of
tests from which this information has been obtained is relatively few
and more comprehensive studies are needed for firm conclusions.
Cellulose has the empirical formula (C6H205) and is a polymer
of glucose to which it hydrolyses and which in turn is fermentable to give
the stoichiometric relationship of 720 1 of ethanol per tonne of cellulose.
Unfortunately both the hydrolysis and fermentation steps are
difficult and it has required an input of research and development to
increase the overall production of ethanol to 50% of the stoichiometric
value.
If these figures are applied to sugar cane fibre it would indicate
a potential availability of ethanol of 190 1/tonne fibre. For a fibre
content of stalk cane of 13.8%, it would enable a further 26 1 of ethanol/
Te cane to be obtained from this source. However, we do know that every
tonne of stalk is associated with about 690 kg of tops, leaves and trash.
Unfortunately we do not know exactly how much, nor what the fibre content
of these components may be, nor how much is lost during the burning
operation which precedes harvesting. More of these data are necessary before
firm estimating is possible but tentatively we could consider the prospect
of harvesting the whole cane with 500 kg of tops and leaves of the same
fibre content as the stalk. The tops and leaves also contain sugars,
albeit much more hexose than sucrose but no doubt fermentable. The
concentration of sugars in the tops and leaves would be less and this we
155
might assess as 10% in terms of hexose sugars. Thus in the tops and
leaves, we could expect to have 36.5 kg of cellulose and 50 kg of hexose
sugars from which 42 1 of ethanol would be expected (13.2 + 28.7).
The possibility of fermenting hydrolysed cellulose and of processing
tops as well as stalk adds a new dimension to the use of sugar cane as an
energy source. We will first of all consider the possibility of reducing
extraction requirements to the use of only the crusher and first mill and
assume that the shredder between the crusher and first mill is useful.
An extraction of 70% of the available juice could be expected with this
arrangement and the first mill bagasse be used directly for cellulose
and residual sucrose hydrolysis.
Yield from 1000 kg stalk cane: - juice - 96.3 litres ethanol
fibre - 26.3
500 kg tops - juice - 28.7
fibre - 13.2
164.5
164.5 1 ethanol/Te stalk cane.
A great deal of detailed study of cellulose hydrolysis and
fermentation is currently proceeding in a number of laboratories in
different parts of the world including Australia.
The cellulose is difficult to attack with micro-organisms because of
its close association with lignin and pentosans present in approximately
equal proportions. In sugar cane, they each represent about 19% of dry
fibre weight. The pentosans hydrolyse to pentose sugars without a great
deal of difficulty but these are virtually non-fermentable to ethanol by
any known commercially viable technique.
156
Most workers first endeavour to break the fibre complex either by
mild sodium hydroxide or sulphite treatment probably with the aid of
heat in the form of high pressure steam. This is equivalent to a mild
type of pulping treatment.
In the present context the author does not view this approach at all
favourably owing to the deleterious effect this would have on the fructose
which is 50% of the hydrolysis products of sucrose and is very labile in a
hot alkaline or acid environment.
The U.S. Army Natick laboratories have been extensively concerned
with the problem of cellulose degradation since 1971 when they were
confronted with the mounting waste disposal problem on U.S. army bases.
A mutant of the fungus Trichoderma viride was found to be able to produce
an especially useful form of the enzyme Cellulase which was capable of
breaking down crystalline and generally insoluble cellulose. This fungus
had earlier been observed on a rotting cotton cartridge belt being used in
the jungles of New Guinea, whereas other forms of cellulase had previously
been obtained from Aspergillus niger. This group of workers was able to
derive mutants from the original Trichoderma strain, which were able to
produce two to four times as much cellulase as the wild type and considered
to be capable of still further improvement. The yield of glucose so
obtained was reported to be 50%, and more highly fermentable than the
glucose type hydrolysates obtained from other strains of cellulase.
A major problem with cellulose hydrolysis is kinetic and rates are
generally very slow. If a slow rate is acceptable then it is considered
that a 50% over-all recovery of ethanol (combined hydrolysis and
fermentation steps) should now be achievable. To increase this to 75%
will require more study and it is thought that such an achievement may
well represent an economic ceiling or possibly even something in between
at around 64%.
157
It has generally been considered that such slow rates would result
in uneconomic sizes for suitable processing equipment, hence the attempts
to speed up biodegradation of cellulose by applying a mild preliminary
softening treatment to the fibre. The view is expressed here that in the
case of sugar cane fibre the economic advantages of being able to leave up
to 30% of sucrose bearing juice still in contact with the fibre make it
worthwhile exploring possibilities for low temperature slow speed
biodegradation. The suggestion is therefore put forward that some adaptation
of the Ritter system of bagasse storage could adequately meet the
requirements of this situation at modest cost for a slow degradation rate.
The Ritter system has been developed essentially to store bagasse in bulk and
keep the bagasse pile wet with a biological liquor - in this case to
prevent deterioration of the fibrous material. The earliest experiments
with the system commenced as far back as 1930 and the first industrial
operation was established in 1956 in South Africa. The bagasse is first
conveyed from the sugar mill to an elevated channel where it is mixed with
a biological liquor to form a 4% suspension and flushed to a large slab of
concrete which is used as storage area. The concrete floor is traversed
in one direction by a number of parallel draining channels allowing the
liquor to be recirculated by a pump.
The bagasse at first forms a large pyramid and by directing the
flow of bagasse the pile can be adjusted with ease, the sides inclined at
an angle of 45°. The storage pile can reach as high as 25 m in which
case a mechanical flushing device is used to lift the bagasse towards the
top of the pile.
The bagasse on the storage area absorbs approximately 50% of the
biological liquid used; this amount has to be replaced by chlorine-free
filtered fresh water, together with fresh biological culture at the rate
of 0.25% of the circulating liquor.
158
The bagasse is mechanically reclaimed from the pile and then
flumed via the transverse channels to a central tank for subsequent
processing.
The particular biological fluid employed in this process is a
carefully developed strain of Lactobacillus selected for the purpose of
preserving the fibre but there would seem to be no technical reason why
this should not be replaced with a suitable biological medium developed
to carefully destroy the cellulose component and then process the
resulting liquid phase for subsequent fermentation. It might be suggested
that carrying out this reaction in the open air leaves the pile too
susceptible to undesirable infection, however this is still a problem with
the Lactobacillus liquor to which much attention is successfully devoted
to maintain the desired strain of this biopreserver. The leaching of ore
bodies with biological fluids is another area in which an operation of
this type is carried out.
With this process as much as 140,000 tonnes of dry fibre equivalent
are stored in an area of 4.5 ha which would represent the fibre from
675,000 tonnes of stalk cane together with the fibre from the tops and
would represent a residence time of 70 days which should be adequate for
effective and satisfactory degradation of the cellulose.
The use of bagasse fibre for cellulose hydrolysis would deprive
the distillery of its natural fuel. Some relief could be obtained by
recovering the undegraded lignin and cellulose (25% assumed to be recoverable
for fuel) first drying it by passing through two sets of roller mills and then
firing it as fuel.
The writer has observed the Ritter storage and preservation system
in operation and was well impressed with the high degree of mechanization
possible throughout the handling stages. Although the object was
essentially to preserve the bagasse it was evident from the brown colour
159
of the heap that at least some lignification had taken place which is just
what is needed if cellulose is removed by biodegradation.
For the time being it has been envisaged that the bagasse transferred
from the first mill to the hydrolysis heap is not thermally sterilized
in the same way as the juice but is appropriately treated either chemically
or biochemically to ensure that the desired route of biodegradation is
followed as closely as possible. Some closer study on the economic limit
to which juice is extracted will need to be done when these details are
worked out.
It is assumed that the pentosans break down in some way, they can be
a source of furfural and this could be investigated later, but for the time
being this possibility is ignored. The theoretical yield per tonne of
stalk cane, processing the tops also, would be about 23 kg/Te stalk cane so
that a 50% yield of this chemical would indicate a potential recovery of
23,000 Te furfural from 2MTe cane. If only stalk is processed, this would
be reduced to 15,000 Te.
The lignin is assumed to be left in the heap after biodegradation and
to amount to 45 kg/Te whole cane. This should be in a convenient form to
return to the factory to two sets of 3-roller mills through which it is
passed for drying in preparation for use as fuel.
Lignin has a very complex chemical structure and leaves paper pulp
plants in large quantities as an effluent difficult to dispose of and not very-
useful except for making vanillin, and the market for vanillin can be quickly
saturated. The chemical composition actually varies slightly and it is
probably not a single compound. An average empirical formula is C 4 9 H5 2 ° 1 4
and having a lower proportion of oxygen it has a better fuel value than the
pentosans or cellulose. The N.Th.V. of lignin is estimated at 24,000 kj/kg
compared to 18,100 for dry bagasse.
160
If the lignin is dried to 48% moisture at the rollers the fuel
value (nett) would be 14,350 kJ/kg or 74% more than bagasse of the same
moisture content. It would be worth about 0.25C/1 of ethanol for its
fuel value in terms of the coal it could displace.
Instead of using heaps of bagasse on a concrete floor, concrete
towers in the form of silos could be constructed and operated as tower
type continuous countercurrent cellulose hydrolyzers in a specialised
ensilage type of operation. There are in fact, various possible types and
arrangements of equipment but detailed designs must await more specific
information on cellulose biodegradation kinetics and yields. Countercurrent
diffusers designed for the sugar cane or beet industry operate at rates of
7 to 10,000 Te/day and adaptation should not be difficult.
There is sufficient information available, however, to enable a
first approximation to be made in estimating the order of magnitude of the
cost of ethanol which could be produced in this way.
The estimated magnitude of the components of the cost are itemised
in Table XIX indicating around 11C/1 for large management areas of cane
growing and 16c/1 for 50 ha unit farms. If a yield of 64% can be achieved
in the cellulose hydrolysis and fermentation instead of 50% this could
enable a further cost reduction of the order of 1C/1 to be effected.
A simplified flow sheet with materials and energy distributions
is set out in Figure 3.
TABLE XIX
E s t i m a t e d c o s t o f e t h a n o l from whole cane i n c l u d i n g c e l l u l o s e h y d r o l y s i s
C o s t s a r e p e r t o n n e o f s t a l k cane and p e r l i t r e o f e t h a n o l
CASSAVA AS A FALLOW CROP
Cassava probably ranks second to sugar cane as a natural
photosynthesizer with starch being stored in tubers. It is a very common
crop in many tropical countries - known as manioc in South America. When
grown under conditions of traditional culture yields are relatively low and
the root system is so complex that it would be very difficult to design a
suitable mechanical harvesting unit. However, it is reported that it has
been possible to breed a variety with a root system sufficiently simple and
compact to enable mechanical harvesting to be carried out without difficulty.
Demonstration yields have been as high as 13.5 Te/ha of starch
but it is felt that this should be viewed in somewhat the same light as
the 222 Te/ha of cane in the demonstration crop at Bundaberg and that
average yields under good conditions are likely to be nearer 7 or 8Te/ha
of starch. This may be compared with the Queensland average sugar cane
crop yield of 11.5 Te/ha of glucose equivalent to compare with 32 Te/ha
under demonstration conditions or 19 Te/ha which has been obtained as a
seasonal average yield in the Burdekin.
Cassava cropping has also been found to deplete the soil heavily,
requiring continual replenishment of plant nutrients in order to maintain
soil fertility and a continuation of satisfactory area productivity. On
the other hand it probably does not require as much water as sugar cane
and it stores well enough in the ground to enable the harvest to be spread
over a reasonable period.
It is suggested here that cassava might be considered as a more
profitable fallow crop than the usual legume. It is not an uncommon
practice to grow a root crop in rotation with a cereal and this is one of
the successful sequences for sugar beet growing. In fact it is essential
to interspace a surface crop between crops of sugar beet to maintain
productivity. An attempt to grow successive sugar beet crops in the same
area of ground in Canada for example, proved unsuccessful, due to the
development of an uncontrollable infestation of nematodes. Cassava
is also known to benefit from the interspersing of another crop.
It is unlikely that a cassava crop could be grown to be harvested
between the two sugar seasons since this would be the wet season and a
period when it is most unlikely that root vegetables would thrive or store
very satisfactory quantities of starch. Nevertheless, it may still
be a profitable venture.
The programming of planting and harvesting of both sugar cane and
cassava would need to be carried out carefully in order to get the best
results from both crops and some time and study will be required before
this can be fully assessed.
Assuming that this can be done satisfactorily, the concentrated
slops equivalent to the cassava growing area would be expected to be
recycled and to maintain 85% of the K and P requirements and 35% of the N
requirements. It would be necessary to replenish the balance for the
next crop of plant cane.
The ethanol cost and production estimates are summarized in Table
XX for cultivation and Tables XXI and XXII for processing and total costs
when processing either stalk cane juice without cellulose hydrolysis or
whole cane including cellulose hydrolysis.
There are quite serious difficulties in estimating the costs of
cassava cultivation, harvesting and transportation. Also the benefits
or otherwise of increasing the scale of farming operations. The writer
is at present of the opinion that the cost benefits of large scale farming
operations are likely to be proportionately less for cassava than for sugar
cane. How long this is likely to remain to be the case will depend very
largely on the technology which is devised for harvesting cassava as well
as on the success of breeding in producing a root system that will lend
itself to effective mechanical harvesting of a type that can take full
advantage of large scale farming. The sugar beet industry was very
successful in developing seeds and plants to suit mechanization but the
R. S D. cost was high and the time-span 15 to 20 years.
It can be seen by comparing the costs when processing juice only
from stalk cane in Tables XVIII and XXI that growing a cassava fallow crop
may result in a very marginal decrease in cost for the large properties or
estates(2%) and a slightly better (8%) decrease for 50 ha farms.
From Tables XIX and XXII it can be seen that when processing
cellulose as well as juice from whole cane there may be a marginal increase
in cost of 5% for large properties and estate growing but only a very
marginal increase for 50 ha farm units at around 1%.
Productivity, however, will be increased in all cases varying from
25% in the case of processing only juice from stalk cane to 14% in the case
of processing both cellulose and juice in whole cane.
Although district development costs are initially only a minor
proportion of final ethanol costs due to the nature of the accounting,
these costs are high in unit terms and the proportion will escalate.
Therefore the increase in productivity derivable from growing cassava as a
fallow crop is considered sufficient to justify the practice in spite of
additional fertilizer being required.
The costing given in Table XX relating to the estimated costs for
growing cassava as a fallow crop with sugar cane must on no account be taken
as an indication of growing cassava as a crop in its own right. No property
A * > „ ^ ~™«„,4- ™oi-s have been charged against cassava as a fallow crop as these
165
have already been charged against the cane. Also the cultivation
requirements of preparing ground and planting cassava instead of legumes
following a second ratoon crop of sugar cane are rather different from
the cultural requirements for cassava as a crop in its own right.
The view is expressed nere that in order to develop its maximum
potential in continuing productivity, that cassava will need a rotation
crop, just as sugar cane benefits from the legume fallow crop. It appears
therefore that sugar cane as an associated crop with cassava would be just
as beneficial to the cassava as the cassava would be to the sugar cane.
The time could be envisaged with increasing development of cassava
agricultural technology that it might become economical only to grow one
ratoon of sugar cane and double the production from cassava, but this is
an exercise in relative economics very much for the future.
On the other hand every endeavour has been made here to be
consistent in the application of constraints in the case of both sugar cane
and cassava growing technology.
166
Table XX
Cost Estimates for growing Cassava for Etftianol
(as follow crop for sugar cane cultivation)
167
Table XXI
Estimated Cost of Producing Ethanol from Sugar Cane Stalk Juice and Cassava
Table XXII
Estimated Cost of Producing Ethanol From Whole Sugar Cane and Cassava
EFFECT OF FARM PRODUCTIVITY ON COST OF ETHANOL
Whilst we have examined the effects of several technical and social
innovations on the estimated cost of ethanol we have not seriously
examined the influence of changes in the productivity of farm units. It
has been pointed out that the average productivity of farms in Queensland
is only around 40% of demonstrated capability and that the rate of growth
in productivity is only 1.1% p.a. in terms of Te cane/ha or 1.58% p.a. in
terms of Te sugar/ha. The relatively low growth rate is commonly viewed as
providing a useful bonus, the real value of which is only noticed over a
10 or 15 year period.
However, we have set out to take advantage of whatever useful
innovations in technology are available and sufficiently proven. To be
consistent we should at least examine the effects which could be expected
from applying this reasoning to farm productivity. The production
capability figures used here were demonstrated over 40 years ago and the
only change which might have taken place in the meantime would be to raise
the ceiling. The essential requirements for achieving these yields are
well known and not unrealistic, they have been demonstrated time and again
by the best farmers.
Selecting 10 men who could achieve similar success on an estate
and given $2m each per season to manage the estate would be sufficient to
provide the operation of 350,000 ha of cane and half of Australia's current
motor car fuel requirements.
In Table XXIII the effects of such an innovation on the estimated
cost of producing ethanol have been summarized.
The productivity figures for the three selected area units have
been doubled to represent an 80% capability achievement for 50 ha farm units
or 71% for the 35,000 ha estate, relative to a ceiling of 225 Te cane/ha.
If the new area proved to be as productive as the Burdekin delta district
such an achievement percentage would be some 10% less.
If productivity figures of this magnitude are allowed to develop
simply by the effluxion of time it would take 70 years to achieve, and yet
we do know today, basically what is needed for their achievement - water and
fertilizer in the right amounts at the right time, the right composition of
the fertilizer, good drainage and effective control of diseases and pests.
In the calculations for Table XXIII it has been assumed that one
factory unit could service a 35,000 ha area when productivity of this order
is achieved. This would require a crushing unit nominally of 20,000 Te
cane/day which cuts across our earlier premise of the limiting effects of
logistic problems.
As we are idealising to a certain extent with respect to farm
productivity we will allow such to extend. to logistics capability being
achieved for a rating of this scale.
Looking at specific items in Table XXIII the allocated cost of
property development has not been changed (in terms of costs/1 ethanol)
because 40% of this component is made up of providing water storage required
for growth.
If area productivity is to be doubled, it is conceivable that
irrigation water needs would be doubled. Whilst it could legitimately be
claimed that a scaling index could be used such that costs would increase by
52% if the scale is doubled, no advantage has been taken of this factor.
Cultivation costs per unit of production should be effectively halved
but only a 67% change has been scheduled. Fertilizer costs per unit of
171
Tab le XXIII
E s t i m a t e d c o s t o f e t h a n o l from whole cane i n c l u d i n g c e l l u l o s e h y d r o l y s i s f o r
80% a g r i c u l t u r a l p r o d u c t i v i t y . C o s t s a r e c p e r l i t r e o f e t h a n o l .
production are expected to be virtually unchanged whereas the cost of
chemicals could be nearly halved. A combined change of 80% has been
scheduled. A similar adjustment has been made for harvesting costs.
The cost of applying irrigation and of management in relation to the
unit of production have been adjusted at 67%.
In overall terms the cost of production of the raw material has
been reduced by an average of 23%. The effect on processing cost is
essentially one of scaling and could equally as well have been achieved
by servicing a larger producing area (except for transportation costs).
The savings in processing costs are thus further increased by 24%.
The overall average reduction in cost is 25%.
Growing cassava as a fallow crop is likely to add slightly to the
cost of product until such time as growing, harvesting and transportation
technology is brought up to demonstration levels of achievement. The
addition to total production would be only 7% which conceivably could be
increased to 10% by improved productivity of the cassava crop.
At these figures the possible benefits of growing cassava as a
fallow crop become debatable and a prolonged period of experimental develop
and careful costing is indicated as being desirable before a general policy
decision can be made on sound economic grounds.
Thus if we are looking for a base level figure for the cost of
ethanol ex-distillery to which all other cost figures might be referred in
terms of achievement capability this figure would seem to be 7c/1 ex
distillery in 1985.
In Figure 4, the various estimates for the cost of producing
ethanol have been set out in graphical form to illustrate the basic
distillery. The secondary effects of nine other parameters are also
included and interpolations can be made as desired. These additional
parameters are (1) social change (2) cellulose hydrolysis (3) cassava
growing as a fallow crop (4) disaster effects (5) seasonal fluctuations (6)
high productivity development on the farm (7) dual operation with an
existing sugar mill (8) stalk cane/whole cane processing and (9) the step
effects of new developments in technology.
COAL AS ENERGY SUPPLEMENT
Once cellulose in fibre is successfully hydrolyzed it becomes
necessary to employ an alternative source of fuel. Coal appears to be a
suitable fuel for this purpose in Queensland and it has been estimated
that 310 kg of coal would be needed per kilolitre of ethanol produced
by this route. Or looking at it another way, 1 tonne of coal enables
3.23 kl of ethanol to be produced. It would, however, be more correct
to say that 1 Te coal enables an extra 1.33kl of ethanol to be produced.
The alternative route for producing motor spirit by hydrogen tion
of coal would enable about 0.3 kl of motor spirit to be obtained from coal
of corresponding thermal value. The ratio in terms of equivalent usable
motor fuel would be 4.4:1 for an engine with a compression ratio of 10 or
3.0:1 on the basis of relative net thermal values.
To produce 14 Gl of ethanol per annum by the cellulose hydrolysis
route would require an annual supply of 4.3 MTe of coal.
The energy input for full mechanization of the farming procedures and
transport of cane is estimated to amount to approximately 1% of the net
thermal value of the ethanol or 1 1 of diesel fuel per tonne of cane. The
farmer probably also uses as much as this in his private car.
The energy input as fertilizer is largely recycled concentrated
distillery slops for which coal is required to effect the evaporation.
Since this is an additional process to the basic operations of
distillation the whole of these costs should be debited to the coal-cost
component and this accounts for 74% of this cost.
It would appear to be worth studying the recycling of stripping
column slops to the hydrolysis heap instead of condensate to the evaporator
in order to allow the solids concentration to build up and hence economise
in evaporation requirements.
The estimated steam usage is based on quintuple effect evaporation.
The economics of additional effects may need study or possibly cascade
evaporators of the type used in water desalination plants.
Concentration of slops as such is probably not a particularly good
way of making fertilizer in terms of fuel economy but when the combined
costs of chemical fertilizers plus the operation of an effluent treatment
plant for the slops are taken together the net benefit of slops evaporation
and recycling as fertilizer becomes a more realistic economic benefit.
The use of coal could be avoided by employing a full tandem of
mills to extract as much juice as possible and then burn sufficient of the
bagasse plus residual lignin at maximum efficiency, to produce the steam
necessary to process the juice plus the remainder of the bagasse to ethanol.
A balance of materials indicates that this can be achieved for whole cane
processing by diverting 32% of the bagasse to the furnace of the steam
generator. The overall return in terms of ethanol/Te cane is reduced by
only 1½% because of the more favourable processing route for the juice
sugars and the normally low recovery (50% on cellulose) from the fibre
processing.
In view of the value of obtaining a good extraction of juice, the
size of the milling plant has been returned to 10,000 Te cane/day and 6 sets
of mills employed with a 94% overall extraction. The estimated capital
cost of the extra mills and auxiliaries has been added as well as scaling
up of the slops evaporator required to process the extra water needed for
maceration.
The estimated costs under this arrangement are summarized in Table
XXIV where it can be seen that the cost estimate rises by 0.93<: for 50 ha
farm production and by 1.55C/1 for the 1600 ha properties.
The use of coal enables costs to be reduced mainly by making possible
a slightly more simple route which in turn makes it worthwhile scaling up to
20,000 Te cane/day - when juice extraction is not a controlling criterion.
It may be pointed out that milling whole cane is a more difficult operation
than milling stalk cane hence the proposed introduction of 6 mills to the
tandem (total of 7 + shredder + crusher) and a more conservative extraction
figure of 94% instead of the currently achieved 95.5% when milling only
stalk cane.
CARBON DIOXIDE PRODUCTION
No mention has as yet been made of the carbon dioxide produced
during fermentation. This would be substantial - 770 kg C02/kl ethanol.
The simplest thing to do is to vent it to atmosphere after stripping
it of ethanol vapour.
It could have some commercial value in the form of "dry ice" as a
refrigerant but the local market for this would be rather limited and it
might not be able to bear the cost of transport to a site where it would be
of more value.
Table XXIV
Estimated Cost of ethanol from whole cane including ce l lu lose
hydrolysis for 80% a g r i c u l t u r a l p roduc t iv i ty . Costs are C/l e thanol
using por t ion of bagasse for fuel and mil l ing to 94% ex t r ac t i on .
177
As a chemical it could have some value in converting ammonia to urea
but it is unlikely that it could stand the cost of transport to a fertilizer
plant making this conversion, and to compete with other sources of the gas.
The economics of using the carbon dioxide would have to be determined
for each individual situation.
When processing 2 million tonnes of stalk cane a season there would
be over 100,000 tonnes of carbon dioxide generated in the fermentation step
and correspondingly more if fibre from leaves and tops is also processed for
ethanol. Carbonating of irrigation water could have interesting
fundamental effects on productivity
FUSEL OIL PRODUCTION
Fusel oil is a mixture of alcohols of higher molecular weight than
ethanol and are chiefly composed of propyl, butyl and amyl alcohols and
possibly also some esters. The amount is variable between about 3 and 11
litres per kl of ethanol. If the production is 5 1 fusel oil/kl ethanol
then the total amount of fusel oil resulting from the processing of
2 m tonnes of stalk cane would be about 830 kl.
The fusel oil separates during the distillation operation and
requires only storing and putting into containers such as drums. It is
likely that there would be a satisfactory market for this for the manufacture
of solvents and other petro-chemicals, and at a price of the order of 10 times
that of ethanol or say $2/1 net. At this price it would represent a credit
of 1 c/1 ethanol.
Ho account of any fusel oil contribution has been included in the
general costing.
DENATURING OF ETHANOL
Ethanol if intended for industrial use must be denatured or
rendered unfit for drinking. There are various additives which may be used
for this purpose depending upon the ultimate use for the ethanol.
It is perhaps well first to list the main conditions which a
denaturant is required to fulfill:-
1. It must be soluble in ethanol and petrol and in mixtures of these
two substances.
2. It should impart a taste and smell sufficiently disagreeable to
prevent ethanol being drunk even after dilution, sweetening or
flavouring.
3. It should not be capable of being eliminated easily by filtration,
distillation, precipitation or by any other operation which might
be readily applied.
4. It should be capable of detection with ease and certainty even
when present only in minute quantities.
5. It should be stable on keeping and should be unaffected by
contact with metals. Conversely it should not corrode metals,
nor should the products of combustion be corrosive or of
offensive smell.
6. It should not be actively poisonous.
7. It should not add materially to the basic price of the ethanol.
8. It should be obtainable in sufficient quantity, and not be liable
to great fluctuations in supply or price.
There is in fact no single substance which completely fulfills
all eight requirements.
Two possibilities appear to be worthy of primary consideration, viz.
methanol and petrol or perhaps both.
If the ethanol distillery is suitably close to a petrol blending
depot then direct blending with petrol for use within the distribution area
of the depot would account for a proportion of the ethanol. The balance
could be transported "in bond" to a major blending depot.
To transport large quantities of ethanol (such as by sea or road
tanker) "in bond" would be a difficult exercise but should not be
insuperable. It might well, however, be politically and/or socially
unacceptable.
Simply to add 5% of petrol at source would be a moderate safeguard
and could make "in bond"i transport less hazardous from the human consumption
point of view.
Methanol is not as good a denaturant as wood spirit which is the
classical denaturant and is crude 77% methanol obtained by the distillation
of wood, but now that wood distillation is no longer practised and methanol
is readily manufactured from natural gas there is really no longer any
choice.
The addition of 5% of chemical methanol would be about as effective
as a similar quantity of petrol but would only have half of the fuel value
of the petrol. In the small quantity used this may not be of significance.
The net cost of either the petrol or methanol would be the cost of
transport to and from the distillery plus overhead charges. This should not
add more than a fraction of a cent to the cost of a litre of ethanol.
Petrol is a denaturant but not a good one as it can too easily be
removed to make the ethanol potable. All that is required is to dilute 1
mixture with water when most of the petrol will separate to leave an aque<
ethanol containing only about 1% of petrol which can be readily removed
by a simple distillation.
A trace of a strongly and offensively smelling additive could
improve the value of either petrol or methanol as a denaturant or simply be
sufficiently effective in its own right. Pyridine is one such compound
which can be used in this way.
There are however, two quite effective compounds, either of which
could probably be prepared at the distillery itself without too much
difficulty. These are the products of bone or vulcanized tyre distillation.
Redistilled bone oil contains useful amounts not only of pyridine,
but also of pyrrole the combination of which can be very objectionable in
concentrations as low as 0.125%. The second distillation significantly
improves the value of the bone oil as a denaturant. Furthermore, this
denaturant cannot be removed from ethanol by any process commercially
feasible.
Heating old motor car tyres made of vulcanized rubber (the sulphur
used in the vulcanizing is important to this process) liberates very obnoxious
products when distilled over the temperature range from ambient conditions up
to 300°. This has been known in the trade as "Caoutchoucine" and is
required in concentrations of about 0.5%. Some pyridine added to this makes
it doubly effective.
It may well be found cheaper to purchase technical grades of pyridine,
pyrrole and-a suitably obnoxious compound containing sulphur as trade chemicals
and transport them as such to the distillery.
Concentrations of 0.125% would require 1.25 kl per Ml of ethanol.
A dyestuff should also be added to characterise the appearance of
the ethanol until such time as it is blended with petrol. The straight
ethanol could readily be identified and any subsequent dilution with water
would be conspicuous.
The ethanol industry would have to stand the cost of control by excise
officers for which a levy of 0.1c/1 would be required.
ETHANOL STORAGE
In view of the seasonal nature of the ethanol production appropriate
storage facilities would be needed to carry over the non-productive period.
Normally this would be about 22 weeks in a year but reduction to 13 weeks is
envisaged for new area development.
The main markets initially would be the coastal cities and towns
of central Queensland thereby reversing the cost structure of petrol
distribution. This would fulfill the spirit of the legislation introduced
in the late 1920's for the use of ethanol from molasses fermentation when
the high cost disadvantages cf petrol in north Queensland were restricting
economic development.
If distribution is initially restricted to blending then it would
soon become necessary to service Brisbane and Sydney. Production of 200 111
would be absorbed by 20% of Australia's total petrol consumption in a 7%
blend.
Only elementary port facilities would be required - sufficient to be
able to fill liquid tankers. A loading of 25 Ml would be for a small tanker
by today's standards and the reflective costs of operating a tanker of this
size for 7 trips or for providing additional storage capacity to enable
larger tankers to make fewer trips would need to be carefully evaluated.
181
A dyestuff should also be added to characterise the appearance of
the ethanol until such time as it is blended with petrol. The straight
ethanol could readily be identified and any subsequent dilution with water
would be conspicuous.
The ethanol industry would have to stand the cost of control by excise
officers for which a levy of 0.1c/l would be required.
ETHANOL STORAGE
In view of the seasonal nature of the ethanol production appropriate
storage facilities would be needed to carry over the non-productive period.
Normally this would be about 22 weeks in a year but reduction to 13 weeks is
envisaged for new area development.
The main markets initially would be the coastal cities and towns
of central Queensland thereby reversing the cost structure of patrol
distribution. This would fulfill the spirit of the legislation introduced
in the late 1920's for the use of ethanol from molasses fermentation when
the high cost disadvantages cf petrol in north Queensland were restricting
economic development.
If distribution is initially restricted to blending then it would
soon become necessary to service Brisbane end Sydney. Production of 200 111
would be absorbed by 20% of Australia's total petrol consumption in a 7%
blend.
Only elementary port facilities would be required - sufficient to be
able to fill liquid tankers. A loading of 25 Ml would be for a small tanker
by today's standards and the relative costs of operating a tanker of this
size for 7 trips or for providing additional storage capacity to enable
larger tankers to make fewer trips would need to be carefully evaluated.
182
It is worth mentioning here that ethanol storage is less of a fire
hazard than corresponding storage of petrol and ethanol fires can be more
readily extinguished because of its miscibility with water. Nevertheless
appropriate fire precautions are essential.
THE ENVIRONMENTAL IMPACT OF A LARGE SCALE SUGAR CANE-ETHANOL INDUSTRY
New agricultural development on a large scale has a significant
influence on the environment in any circumstances.
Destruction of rain forest country deprives the fauna of its
habitat and they will virtually be destroyed with the forest. Land
recovered by clearing tropical rain forest is normally very rich in plant
nutrients and has a correspondingly good texture. Insect pests may well
remain and some find the sugar cane to be a favourable host.
Grassland cleared for cultivation is likely to have a lesser effect
on native fauna especially if it has not previously been a high rainfall
area.
Development of irrigation on the other hand is more likely to
attract fauna and stimulate flora as well as providing enhanced attractions
for birdlife. Sugar cane is unlikely to experience deleterious effects
from these developments.
Almost invariably, however, new problems arise when new areas are
developed and it is difficult to anticipate the precise nature of these
problems.
For example a new area developed in Malaysia after clearing
tropical rain forest grew sugar cane very successfully for a few months
but was so badly damaged by a top borer infestation that further development
183
had to be delayed for a matter of years. The infestation did not respond
to insecticidal sprays and the developer was unwilling to pay the price of
biological control.
There are other examples which could be cited from the sugar industry
and such could be multiplied by examples from other types of crops.
However, there is a very substantial pool of experience in the
existing Queensland sugar industry and maximum use should be made of this
experience in the event of substantial development.
Sugar cane to replace grassland on even a vast scale can be very
pleasing to the eye and present a rich green canopy over a big proportion of
the land throughout the year.
The development of irrigation facilities - large storage dams and
channels have the problems normal to developments of this character and of
which there are many examples in Australia and a broad base of experience
is available to anticipate problems in this area.
The establishment of the factory introduces additional environmental
problems from the point of view of effluent waste disposal.
Gaseous effluents consist of flue gases from the furnaces of the
steam generators and carbon dioxide from the fermenters. The flue gases
need to be cleaned of suspended solids - fly ash - by the installation of
appropriate collectors in the system. These have now been well designed
for bagasse furnaces which had been particularly bad distributors of fly ash.
Should coal be the preferred fuel then fly-ash collection presents no new
problems and appropriate equipment is available. Sulphur dioxide is not
present in flue gases from bagasse combustion and is not a problem with flue
gases from Queensland coals.
184 The carbon dioxide from the fermenters needs to be stripped of
ethanol vapour and possibly odoriferous substances which are best removed
with the ethanol vapour. This does not present serious difficulties.
Liquid effluent consists of slops from the stripping column and
has an undesirable impact on the environment if discharged into streams
or on vacant land. It can be used, under control, for irrigation of sugar
cane or pastures. On the other hand the soluble solids are useful plant
nutrients and it is proposed in this report that they should be
concentrated by multiple effect evaporation and distributed at a
concentration of about 50 to 60% solids for use as fertilizer for growing
the sugar cane, especially the ratoon crops.
There will also be some liquid washings from floors and process
vessels. These should be collected and added to the slops for
concentration and disposal. If they contain useful amounts of fermentable
carbohydrate they could be used elsewhere in the system.
Additionally there will be water from the condensers. This
should be recirculated through cooling towers, any surplus being suitable
for irrigation.
There would be no solid effluent comparable to the filter muds from
raw sugar factories but there may be some protein rich solids from
separators. This could be used for fertilizer and recycled to the fields.
The ashes from the furnaces of the steam generators have a small
value as either fertilizer or as clean filling for reclaiming otherwise
waste land.
185
ETHANOL AND THE INTERNAL COMBUSTION ENGINE
Ever since the invention of the internal combustion engine there
have been experiments on a range of fuels which could be used and ethanol
was early on the list. A vast quantity of experimental information was
generated in laboratories up to V7orld War II and again in more recent
years as interest in ethanol as a potential fuel has been regenerated.
There have also been several large scale tests on a normal operating
scale including various ethanol-petrol mixtures in fleets of London buses.
Most of the results from these tests have been somewhat confusing.
There is no doubt that ethanol and ethanol-petrol or benzol mixtures
can be used quite well in standard internal combustion engines. It has
become clear that the real potential of ethanol could not be realized until
the development of the high compression engine.
Tests before VJorld War II suffered from the problem of low
compression engines and at that time the prospects that the motor industry
would of its own initiative progress towards high compression ratios was
not entirely anticipated.
There has been a substantial resurgence of experimental work in
Brazil in recent years and tests there now indicate that a compression ratio
of 10:1 is needed to get the best results from ethanol. With appropriate
engines operating on straight ethanol it has been found that 18% more power
can be delivered per litre than with petrol although this is effectively
cancelled by a 15 to 20% increase in the volumetric rate of consumption.
It has been found that because an ethanol engine can be tuned to
run much leaner than a petrol burning engine the fuel is more completely
burned giving ethanol a slight practical advantage in kilometer/litre
186
results and significantly lowers the amount of pollutants emitted.
Deductions of as much as 50% for carbon monoxide and oxides of
nitrogen have been claimed. Furthermore, ethanol and ethanol-blended
petrol does not need tetra-ethyl lead additive to achieve satisfactory
octane ratings and hence lead pollution of the atmosphere is eliminated.
When straight ethanol is used in the present day conventional
motor car it is consumed faster but for blends up to 20% no engine
adjustments are required.
Chrysler-Brazil have demonstrated that existing Chrysler motors
could operate with up to 20% ethanol-petrol blend without retuning and
with the alcohol blend to pass the very stringent California pollution
specifications without special control equipment. FIAT-Brazil has
indicated that its model 1M-7 can be adapted to use 95% ethanol/water when
they receive Government guidance to proceed. Brazil has been placing more
emphasis on the widescale use of the 95% ethanol presumably because it
requires one less step for its production and the last step is rather
heavy on steam consumption, although it is estimated here that the overall
cost effect would be marginal.
In fact internal combustion engines will operate with ethanol/water
mixtures as dilute as 50-50, but with much reduced power. A larger fuel
tank and larger jets in the carburettor are perhaps two of the most obvious
adjustments needed to cope with this behaviour.
Dilute ethanol/water mixtures would also pose some starting problems
needing something in the way of a primary fuel heater for initiation.
It has been observed that engines run on ethanol operate at lower
temperatures and reduce the load on the radiator. The latent heat of
187
vapourization of ethanol is much higher than for petrol by a ratio of
2.5 to 1. One effect of this is for the vapour to be colder with a
tendency to enrich the mixture for which appropriate compensation is
needed.
The fact that ethanol may have only two thirds of the net thermal
value of petrol is by no means the whole story and compensation can be
effected to cope with this.
The combustion of ethanol requires only two thirds of the amount
of air which is required for petrol, hence the relative benefits achieved
with ethanol in engines with super-high compression ratios. If we were
to compare fuels on the basis of the total heat energy liberated by the
combustion of one litre of the correct explosive mixture we would find
very little difference between the values for hexane (3.91kJ), benzene (3.8*0
and ethanol (3.83).
This is approximately the case for all hydrocarbon fuels as well
as for alcohols but not for acetylene or hydrogen. The value for
acetylene is higher and that for hydrogen is lower.
Direct injection of fuel into cylinders of an internal combustion
engine has become more significant in recent years although still more
costly than a carburettor installation. It has been suggested that the
ethanol fuels will reach the peak of their performance with high compression
engines using fuel injection techniques. The main advantage of fuel
injection seems to be in the ability to distribute the petrol more
uniformly between cylinders with perhaps lesser benefits in other
characteristics of behaviour.
Recently experiments have been conducted in Brazil, to determine
the usefulness of ethanol as a diesel fuel. The temperature at which
188
ignition of air/ethanol mixtures takes place upon adiabatic compression
was known to be 100 higher than with corresponding air/petrol mixtures.
This would indicate the need for a higher compression ratio in the diesel
engine to effect the desired ignition. However, the experiments in
Brazil have indicated that satisfactory operation with conventional diesel
engines has been achieved with 50-50 mixtures of ethanol and diesel fuels.
Tests in Brazil with bedded turbine engines have indicated that
ethanol is a good turbine fuel.
APPLICATION OF ETHANOL AS A MOTOR FUEL
It is necessary to consider the various problems associated with
the mechanics of distribution as well as of consumption.
Mention has been made of the possibility of initial distribution
in blends up to 15 or even 30%. There has been previous experience in
Queensland with blends up to 15% but difficulties occurred at the upper
end of this concentration range especially during the wet season in North
Queensland. Separation into two phases was observed to develop in
storage tanks, motor car tanks and in the carburettor bowl. For mixtures
up to 7% this problem was not noticed.
The first stage would be to replace leaded petrols substituting
ethanol essentially as an anti-knock additive and give time for the
progressive development of the new industry. If leaded petrols constitute
60% of total petrol consumption then for a total annual usage of IM- Gl this
could accept up to 600M1 for a blend strength of 7%. For this, some
110,000 ha (gross) of sugar cane growing area would need to be developed,
equivalent in scale to approximately one third of the present Queensland
sugar industry.
189
The second stage is envisaged as blending the balance of
Australia's petrol to the 7% concentration stage to consume 1 Gl of ethanol
requiring 185,000 ha (gross) area developments.
The problem of two phase separation from 15% blends may not be
so serious in the cooler or drier parts of Australia, and perhaps half
of the total consumption could safely be blended to this strength. This
could use another 500 Ml requiring a further development of 90,000 ha
(gross).
These three stages would require a total of 285,000 ha or 11 units
of 35,000 ha producing 2.1 Gl of ethanol to displace 15% of total petrol
consumption, and slightly more than double the size of the present Queensland
sugar industry.
The fourth stage would be to market straight ethanol as a motor
car fuel from bowsers side-by-side with petrol bowsers. Many things would
need to be done before this could be carried out to the full satisfaction
of both customer and marketer.
First of all a reliable system would have to be devised to prevent
illegal dilution of the ethanol with water before sale to petrol station or
ultimate consumer.
Coloriumetric measurements of a dye might be made instantaneously
during metering if a suitable photo-cell arrangement were devised. Some
electrical property of ethanol-water mixtures might be found to be more
suitable. Even direct measurement of density using a gamma-ray technique
might be brought into an acceptable cost range by mass production
techniques.
Ethanol with up to 10% of water might well become acceptable as a
l:standard:: or lower grade of motor spirit although the 95% C.B.M. would be
190 more easily marketed it being less expensive to produce requiring one
less stage of distillation. The 95% ethanol should not introduce any
starting problems. If flash point temperature can be taken as an
indication of the starting characteristics of a motor fuel then 95%
ethanol/water should present no problems from this point of view with a
flash point temperature of 13.5° compared to 23 3° for petrol. Even
proof spirit (57.1% of ethanol v/v) ?ias a flash point temperature the
same as petrol at 23.3°. It should be noted that this is proof spirit
according to the British regulations. The U.S.A. has a different
reference point for proof spirit , viz. 500 v/v.
As has been pointed out acceptability of ethanol as a motor fuel
has had to await the development of high compression engines. The use
of aqueous ethanol would progressively reduce the load on the cooling circuit
and whereas an air cooled engine for a motor car is now a well accepted type,
a 50--50 aqueous ethanol might enable even water cooled engines to operate in
an air cooling situation. In other words make possible the marketing of a
low powered car with a very simple type and less expensive air-cooled
engine.
Whilst waiting for the development of the high compression engine
there have been many mixtures of ethanol and other types of liquid fuel which
have been used either experimentally or commercially.
Many of the tests carried out before the second world war •- and the
actual number was really very large - are not immediately clear as to whether
pure ethanol was used or the 95% CD.II. It is in fact most probably
the latter except for certain specially designed tests, because of the rather
higher cost of producing anhydrous ethanol before the modern ternary
distillation techniques were industrially developed.
191
Care must therefore be exercised in evaluation these results.
For example in tests run with benzol-alcohol mixtures, problems were
experienced with two phase separation at low temperatures. Better
experiences were recorded at higher temperatures under which condition
this particular mixture is more satisfactory than a corresponding petrol-
alcohol mixture. But a reversal takes place at lower temperatures -
London winter.
Thus at 0 solid benzene separates from a 50% mixture of benzene
plus 90% alcohol.
In ethanol-petrol mixtures the precise nature of the petrol has
quite an important influence on the properties of the mixture. Petrol
with a high proportion of aromatic hydrocarbons (up to 38%) is reported
to be more suitable for mixing with ethanol than petrols consisting
chiefly of paraffinic hydrocarbons.
A mixture of 50 parts ethanol (90%) with 25% of benzol and 25% of
paraffinic petrol was reported to have given satisfactory results in
Germany.
Studies of the properties of mixtures of this character would seem
to be warranted for going to a higher proportion of ethanol in commonly
marketed motor fuels.
Certain mixtures containing ethanol have found favour with racing
motorists. One preferred mixture contains 77% of the 95% C.B.M. mixed
with 22.5% of aromatic hydrocarbons. Another mixture containing 48%
combined with 29.5% of aromatic hydrocarbons, 15% of paraffins and 7.5%
of naphthenes is more of a commercial grade of fuel. Note should be made
that this particular racing mixture has a net thermal value of 30kJ/g
compared with 34 kJ/g for the commercial mixture and 43.7kJ/g for regular
192
It is obvious that the racing motorist using the ethanol/aromatic
hydrocarbon mixture has been looking for something valuable to him which
is not predicted simply by the net thermal value. Just what it is may not
be clear but is worth some study for the current situation.
Aromatics in motor fuel originate as such in the crudes although they
may be given a reforming treatment in the refinery. Motor fuel originating
from oil shale is also usually rich in aromatic components.
A aphthene based fuel which has some special interest in this
context is that known as tetralin - tetrahydronaphthalene ( c 1 0 H 1 2)- This is
a very good fuel for diesel engines but cannot be used for a motor fuel in
its undiluted form because of its high boiling point (206 ). It is however
considered to be very suitable when mixed with petrol, benzol or ethanol.
However, the concentration of tetralin should not exceed 25% or running
difficulties are experienced.
One suitable mixture is:-
Benzole - 50%
Tetralin - 25%
95% Ethanol/water - 25%
The final boiling point of a petrol should not exceed 185 whereas
tetralin at 206° is slightly higher than the figure specified for petrol.
Motor benzole in this context contains about 96% of aromatic hydrocarbons,
1.5% of paraffins and 2.5% of unsaturated hydrocarbons.
In warmer temperature zones naphthalene itself may be tolerated in
petrols in quite significant quantities, but is very much less soluble in
ethanol hence these mixtures should be avoided. Naphthalene is not
currently believed to be a common constituent of petrol in Australia,
193
although it was used privately in Queensland as an unrationed, if expensive,
additive during World War II, and presumably with satisfaction to the user
under the circumstances.
In Germany, a mixture known as "Reichskraftstoff" was used during
World War I and consisted of equal proportions of benzol, tetralin and 90%
thanol/water.
Diethyl ether is probably the next additive to be considered which
has been used with ethanol on a commercial scale. Although the ether has
only 20% higher thermal value than ethanol it is much more volatile and
should be able to improve the starting characteristics substantially. Whilst
its boiling point is only 34.6 ., which presents certain climatic problems
for its manufacture in Australia, the initial boiling point of ordinary
motor fuel is around 37°.
The fact that ethyl ether can be manufactured from ethanol by a
relatively simple technique makes it attractive in this context. This
simply involves dehydration either in the liquid phase using sulphuric
acid as the catalyst or in the vapour phase using alumina as a catalyst.
Another simple method developed for use in this particular context merely
bubbled ethanol vapour through a mixture of ethanol and sulphuric acid at
a temperature between 100 and 150 . The product was rectified and
mixed with ethanol to suit.
The separation of water from mixtures of ethanol and ether seems not
so likely to occur as with ethanol-benzene or ethanol petrol mixtures.
From a study of phase equilibrium data for the 3 component systems, it appears
that up to 30% of water may be mixed with the ethanol and still be completely
miscible with ethyl ether over the temperature range 0 to 25 .
Ethanol-ether mixtures were used in South Africa in the sugar belt
as early as 1918 under the trade name of "Natalite". These contained 60%
194
ethanol (95%) and 40% of ethyl ether. It seems that some corrosion
problems must have been experienced with the exhaust system as 1% of ammonia
had also been added to the fuel.
Very favourable reports of the use of this fuel were recorded with
consumption figures up to 86% of those obtained with petrol in the same
vehicle although the net thermal value of the mixture was only 68% of that
of the petrol (v/v).
Although the Natalite was reported to be free of detonation problems
in the low compression engines of those days this was by no means the case
with ether-petrol mixtures. The latter was confirmed by unofficial
experimenters in this field during World War II. There would seem to be
room for some study of the detonation behaviour of ethanol-ether mixtures
in the higher compression cars of the present day.
The theoretical yield of ether is only about 5 litres from 6 litres
of 95% ethanol so that the higher the proportion of ether the higher the
cost of the fuel.
During the latter part of World War II the Hawaiian sugar industry
considered the possibility of an ethanol-ether motor fuel but it does not
appear to have been proceeded with, not having got established before petrol
began to be available, in ever increasing supply.
A mixture of 5% ether with 65% of ethanol (95%) and 30% benzol was
subjected to bench tests by the London General Omnibus Co. in 1919 with
seemingly satisfactory results. In France a mixture containing 10% ether,
25% benzol and 65% ethanol (95%) was used at about the same time and known
as "E.H.A"
195
Since the end of the last century there have been suggestions
for using an ethanolic solution of acetylene as a motor fuel. Acetylene
is soluble in ethanol to the extent of six volumes at ordinary temperatures
(English) and pressures but will not stand high compression without pre-
ignition. Gases dissolved in liquids do not form a particularly stable
system and are partially given off in storage which would result in
undesirable conditions in the petrol tank of a motor car.
Acetone may be mixed with ethanol or ethanol-petrol mixtures but
there is not a great deal of information available on their use.
Acetone would normally be more expensive than either ether or
ethanol unless it is produced at a satisfactory cost by a fermentation
process. It can be an associated fermentation product with ethanol under
certain circumstances and increase the overall yield of volatile liquid
from the raw material. Here again more information is needed about such
processes to effect a reasonable costing.
A patent was taken out in the U.S.A. in 1919 for a mixture of ethanol,
acetone and cellulose nitrate. This could be an alternative way of achieving
use of the cellulose in bagasse as a motor fuel rather than carrying out a
difficult hydrolysis for fermentation. Perhaps cellulose acetate might
be less dangerous to handle and less difficult to make with the acetic
anhydride being derived from ethanol.
196
Development Options
In t h i s repor t i t i s merely intended to out l ine poss ib le
options which are ava i lab le for development, as considerations
add i t iona l to s t r i c t l y technical and economic factors need to be
taken i n t o account when making decis ions .
From the point of view of t ime-scale requirements it would
be expected tha t a more de ta i led f e a s i b i l i t y study would be required
before reaching a deci si on-making stage with respect to spec i f i c
implementation.
There are two important areas where more de ta i l ed information
is needed. These are (1) spec i f i c problems r e l a t ed to the fermentation
cha rac t e r i s t i c s of sugar cane ju ice to provide su f f i c i en t information
to design hydrolysis and fermentation vessels espec ia l ly such as could
be used for continuous operation and (2) spec i f i c problems r e l a t ed to
the hydrolysis and fermentation of sugar cane f i b r e .
The second group of problems is the more d i f f i c u l t and is
l ike ly to take longer, but the f i r s t group is bas i c to the whole
e n t e r p r i s e . The en te rpr i se could be launched with only the f i r s t
group of problems ef fec t ive ly solved and the fibre could qui te we l l
be used as fuel u n t i l such time as i t s problems are solved.
It could be well sa id tha t a complete solut ion to both or
e i t h e r problem would require i n f i n i t e t ime.
The raw sugar industry in Queensland is i t s e l f considered to
be highly developed from the technological point of view, but the
industry has been systemat ical ly and s c i e n t i f i c a l l y studying i t s
197
problems for nearly 50 years and is s t i l l spending at l e a s t $3,000,000
a year on research. Any suggestion tha t it has solved i t s problems
a f t e r 50 years of research would have a very cool recept ion .
The study of ju ice hydrolysis and fermentation are the more
urgent of the two major problem areas . There is a great deal of
information about processing re l a t ed mater ia ls but spec i f i c information
is needed about opera t ional cha rac t e r i s t i c s at the concentration range
of juices and as the non-sucrose so lu tes are r a the r less than for the
r e l a t e d molasses the ef fec ts of t h i s change a lso need to be known.
A properly organised programme aimed at th i s goal should be able
to generate su f f i c i en t information within a period of 12 months to
enable the design of procedures and equipment to be undertaken with the
necessary confidence.
VThilst a workable so lu t ion to the f ibre problem may not be qui te
so urgent i t w i l l probably take longer, but the value of the goal is
high - i t s so lu t ion could ul t imately double the production of e thanol
from a given area of cu l t i va t i on .
To design and bu i ld a factory from the date of decision is
est imated to take 2 years for a dual operation uni t and 3 years for
an e n t i r e l y new p l a n t . The development of a new p lan t in a new area
requires a lso the development of tha t area with the appropriate i n f r a
s t r u c t u r e . Land development requires not only c lear ing and l eve l l i ng
but a l so associated drainage and flood mitigation as wel l as water
s torage and i r r i g a t i o n r e t i c u l a t i o n f a c i l i t i e s . Simply surveying the
land and s e t t i n g it out for development w i l l take up to 12 months.
198 Plant ing and growing the crop must be done in a step-wise
fashion so t h a t the factory would be unlikely to como on-stream at
f u l l production capacity in i t s f i r s t season. In the f i r s t season i t
would be unlikely to exceed 45 to 50% of r a t ed capacity because of the
time required to grow the necessary p lan t ing mater ial in the f i r s t place
and then the main crop i t s e l f . The second season could be at 70 to 80%
of capacity with f u l l capacity operation being achieved in the t h i rd
season.
This s ign i f i can t ly affects cash-flow benef i t s for both the farm
and the factory and must be recognised. On the other hand progressive
development towards f u l l capacity enables a b e t t e r understanding to be
obtained of the opera t ional cha rac t e r i s t i c s not only of factory equipment
but a lso of the mechanical f i e l d equipment and of the t ranspor ta t ion
system.
By way of comparison with recent achievements - it took 6 years
to br ing the Ju l ius Dam at Mt. Isa in to commission from the time of the
preliminary repor t in 19 70 to 19 76. This was a $33 M. undertaking.
Pred ic t ing the Future
To look i n t o the c ry s t a l b a l l and pred ic t the future is fraught
with many d i f f i c u l t i e s not the l e a s t of which is the experience of
many pred ic tors in the f i e l d of economics whose pred ic t ions are very
often se l f -de fea t ing .
Before attempting a predic t ion i t is wel l to look back in to
the p a s t , and to get a b e t t e r perspect ive i t i s des i rable to look
back for more than one generat ion. For t h i s exercise a period of 40
years is used, being the working l i f e - t ime of the w r i t e r and changes
199
are within the time-span of memory as wel l as of experience.
Actually it does not make a great deal of difference if one goes
back 100 years or 400 years . Picking an indiv idual year is not
p a r t i c u l a r l y s a t i s f ac to ry as t h i s i s suscep t ib le to the e f fec t of
aberrant f luc tuat ions in the general t rend.
Be t te r bases for comparison are a five year average at the
beginning and end of a 50 year time-span. However 19 36/76 figures give
a useful guide to the ra te at which change has taken place in Aus t ra l ia
and periods of i n f l a t i o n , de f l a t ion , depression and re f l a t ion have been
by no means uncommon experiences whatever names have been coined, as
wel l as d i sas te r s both man-made and n a t u r a l .
The r e t a i l pr ice of sugar in Aust ra l ia has increased at the
average ra te of 3.2% p . a . and the r e t a i l p r ice of p e t r o l by p r a c t i c a l l y
the same amount depending on what figure is accepted as the r e t a i l pr ice
of p e t r o l in 19 76 or 19 77. The r e t a i l p r ice of eggs has increased by
6% and bread by about the same.
The London free market p r ice of sugar may be said to have
increased by around 8% although there have been numerous major and
minor i n s t a b i l i t i e s .
The average Austral ian wage has increased by 8% on gross
earnings although closer to 7% on ne t ea rn ings , whereas an executive
receiving a sa lary of $30,000 in 1976/77 would be in a bracket which
has experienced a gross r a t e of increase around 9% and net a l i t t l e
under 8%.
In attempting to p red i c t l ike ly costs over the period 19 81-19 89
with 1985 as the median yea r , the r e t a i l p r ice of sugar could be expected
200
to be around 35CAg and the pr ice of p e t r o l 22c/ l if we could expect
the base pr ice of crude o i l to be unaffected.
The average wage would be close to $350/week and the executive
sa la ry $60 ,000/annum.
What we cannot p red ic t are d i scon t inu i t i e s in the curve, but
we can make an est imate of the p r o b a b i l i t i e s of such happenings. For
example there is a 90% probabi l i ty tha t the r e t a i l p r ice of p e t r o l
w i l l r i s e at a f a s t e r r a t e than 3% which could well include a s teep
s tep superimposed on the an t ic ipa ted curvature.
The r e t a i l p r ice of sugar on the Australian domestic market
has t r a d i t i o n a l l y been wel l regulated and there is a high probabi l i ty
t h a t t h i s may continue.
On the o ther hand the London daily free market pr ice of
sugar has t r a d i t i o n a l l y been subject to s u b s t a n t i a l f luc tuat ions and
there is every reason to bel ieve tha t t h i s w i l l continue to be the case.
Looking spec i f i c a l l y at the subject of Austral ian sugar
product ion, i t is evident tha t product ivi ty and efficiency must have
improved at a f a s t e r r a t e than the increase of wages. For example
the cost of harvest ing is very l i t t l e d i f ferent in 1977 to t h a t which
was the cost in 19 37 - per tonne of cane. The cost of f e r t i l i s e r has
increased but the cost of appl icat ion has been held or even reduced
in ce r ta in s i t u a t i o n s . The cost of t ranspor t ing cane from f i e l d to
factory has probably increased at 5 to 6% p. a.
There has been l i t t l e done to the average s ize of the farm
in order to contain c o s t s , changes have been developmental and the
201
effec ts marginal. The average s i ze of the factory has increased and
marginal improvements have been made to processing but there have been
no fundamental changes. The ''undetermined loss" experienced in
processing has been minimised and much b e t t e r control of a l l operations
has been achieved as wel l as of thermal balances .
What of an ethanol production p lan t? It could be expected
t h a t many d i f f i c u l t i e s would be experienced with processing techniques
during the ear ly stages requ i r ing probably 3 to 5 seasons to ef fec t ively
el iminate tee th ing t r oub l e s .
There would seem to be b e t t e r prospects for containing costs in
the f i e ld than in the factory provided a new s t a r t can be made,
l i b e r a t e d from the self-imposed r e s t r i c t i o n s of the present sugar
indus t ry . This has been spec i f i ca l l y geared to sugar production and
wisely so .
It would be unwise to tamper with the s t ruc ture of the sugar
industry where it is e s s e n t i a l l y producing food for human consumption.
To produce an energy product in the form of l iquid fuel for i n t e r n a l
combustion engines means enter ing a f i e ld of operation with e n t i r e l y
d i f fe ren t c o n s t r a i n t s .
The Queensland sugar industry current ly spends something over
$3 M p. a. on organised research or 15c/Te cane and has had highly
t r a ined groups of s c i e n t i s t s studying i t s problems for j u s t on 50
years at a reasonably high degree of i n t ens i t y and to a l e s se r degree
for another 25 yea r s .
Much of the e f fo r t has gone i n to the breeding of sugar cane
and the control of diseases and pes ts and r i gh t ly so . The development
202
of the Australian cane harvester features prominently in local achievements
although there have also been developments in this area in other countries,
suited more to their particular needs.
Otherwise the industry has very largely acquired technology,
modified it to suit its needs and very often improved it under local
conditions. Any claims to lead the world sugar industry in technology
should be seen from the perspective of effective application rather than
fundamental developments.
An ethanol industry would be wise to take the fullest possible
advantage of the substantial Australian developments in cane breeding and
disease and pest control as well as cultural practices and go on to develop
fresh applications of mechanized technology under a new set of operating
conditions. It would need to establish its own expertise in these areas
and intercommunication between the two areas would be of substantial benefit
to each.
On the process side of ethanol production there are areas of
uncertainty for which the investment of funds for research and development
would be required at an early stage.
We do not know enough about the hydrolysis and fermentation
characteristics of sugar cane juice to be able to design the best type and
size of equipment for these processes. Some of the questions which are
pert inent are:-
(a) Can juice be efficiently fermented without dilution over and
above that used for maceration?
(b) Is it necessary to clarify juice before hydrolysis/fermentation?
(c) What are the physical properties and chemical composition of
concentrated slops?
(d) What is the best thermal cycle for the distillery?
The major area of uncertainty at present is in the chemistry and
technology of the use of the fibre. Burning the fibre efficiently is
very well understood in the sugar industry and the Queensland industry
is well to the fore in this respect. There is no reason why this
technology should not be transferred to the ethanol industry.
To convert the fibre efficiently to ethanol would be a more
valuable achievement. Currently it is estimated that 50% of the
theoretical conversion of the cellulose component of the fibre could be
converted to ethanol (26.5% of dry weight of fibre) with a 70% hydrolysis
efficiency and 72% fermentation efficiency. By dint of good research the
combination of these two steps might be increased to 60% within 5 years
but to raise it to 70% would take rather longer. Some entirely new
development would be needed to expect the overall conversion efficiency
to rise to 80 or 90%.
New processes, as with new technology, are unpredictable to a
large extent, but the probability for such a development within a time span
of 10 years might be estimated at 70% (or 2:1 in favour) if the incentive
is there by way of a viable industry.
A sugar cane/ethanol industry should be able to support its own
research and development once it has become viably operational but
stimulation will be needed in the preliminary stages. To set figures is
difficult but an initial investment of $3m is considered to be the order of
magnitude required to cover effectively questions to which answers are
needed for plant design to be undertaken with confidence. A further $10m
would be needed to acquire land for plant breeding facilities and establish
buildings, provide equipment and recruit staff for the basic research needed
to underpin the industry. This money could be amortized and recouped from
the industry when it is established. An operating levy of 30£/Te cane
is considered to be the type of levy needed to support a research and
development programme on a scale compatible with the standard of efficiency to
be expected.
204
OVERALL EMPLOYMENT AND INCOME PROSPECTS
The present Queensland sugar industry employs a total of about
35,000 persons made up of 7000 farmers, about 7500 employed in 30 sugar
mills and 20,500 other workers mostly employed by farmers either directly
or by contract for varying periods. Of a gross income of the order of
$750m perhaps two thirds would be distributed among the 35,000 persons or
an average of $14,286. If we index the personal component at 7% this would
be equivalent to $24,550 by 1985. If the industry is unable to expand
further it would be necessary to reduce the work force to 26,000. On
the other hand if expansion continues at the average world rate of increase
in consumption of 3.39% and price increases by 3.2% then the work force
could be maintained and in fact increased to 35,600.
The increase in sugar production would amount to 1.07MTe of which
O.401MTe would be expected from the normal rate of increase of productivity.
An additional 73,000 ha would need to be assigned which if done progressively
would represent an annual increase of 2.56%.
Achievement of any of these figures would only be remarkable in the
sense that they predicate no failure of the overseas export market but
maintenance of the growth rate that has been the average figure over the last
40 years.
In the event of failure of the overseas export market, ethanol
production could not become an economically viable alternative without a
reduction in the workforce or a reduction in the average income of employed
persons. Ethanol would need to achieve a monetary return at the rate of
34.3C/1. This is by no means impossible if a rate of increase of price of
M.E. crude oil is maintained at 8%. Also a marginal reduction in the work
force could be sustained by virtue of the likelihood that processing for
ethanol would require fewer persons than when processing the same tonne of
cane for raw sugar.
205
On the other hand comparisons with an ethanol industry operating
in a new area with properties larger than 1600 ha could be invidious.
If we now look at a corresponding picture in a projected ethanol
industry of one QSI unit the total number of factory employees would be
around 1500. For 50 ha farms there would be 7000 farmers and perhaps
16,500 other workers or a total of 25,000. Costing at $24,550/person
this would represent 29.5C/1 of ethanol - not very much below the figure
for the expanded present industry.
The actual cost estimated for production under these conditions
was 23.9C/1 (Table XVIII), implying a total work force of 13,500 or 10,500
to assist the farmers instead of 16,5003 or 1.5 additional employees per
farmer instead of 2.36. The reasons for this are largely related to the
social changes predicated for 7 day/week operation and 39 week season and
have been discussed earlier in some detail. A broad overall comparison
of this type with the present sugar industry is not strictly correct but
is left this way for the time being.
Looking at the 1600 ha properties for which a price of 15.45c/l
(Table XVIII) was calculated this would represent employment for 8140 persons
or 30 persons per property. It is considered that a work force of 16
persons per property would be a more realistic figure under the conditions
of management and mechanization envisaged - or a total work force of 5000
for factory and field. This would allow more money to be devoted to
servicing the extra capital needed to achieve the specified degree of
mechan ization.
The employment requirements for 35,000 ha estates producing ethanol
at 14.46/1 are not significantly different.
206
Looking at the other end of the spectrum for ethanol at 8.4c/l
and 1600 ha properties (Table XXIII) with 20 factories/QSI unit a total
of 10,000 could be employed for the same proportion of gross income for
employment as above (viz. 41% as compared to a figure of 67% assessed here
for present QSI disbursement). A work force of 32 per property would thus
be indicated whereas 25 might more realistically compare with the 16
mentioned above. The extra 9 persons are envisaged as needed to cope with
the higher field productivity specified for this exercise. The total work
force for factory and field would then be 8500.
The work force per unit factory district would thus be of the order
of 425 to 500. It is recognised that employment generates other employment
and a multiplying factor of 3 is not uncommon to quantify this effect.
Thus total employment in a new QSI with supporting services would be of the
order of 20,000 to 40,000 persons.
The total employment generated to provide 14 Gl of ethanol per
annum would be around 80,000 persons. This does not include the large work
force which would be needed for development representing probably another
20,000 persons plus support employment of 60,000. The actual number would
of course depend upon the rate of development which would be conditioned by
policy determinations, rate of availability of capital and logistic
requirements of the operation.
Some of this work force, especially from the support services would
no doubt remain to become more permanently settled in the industry.
Looking again at a single community of 2000 working persons this
would represent a total community needed to service the district, and
it is considered that it would be better for the community to live in three
settled areas - one of 3000 to service the factory and portion of the
property needs and the other two of 1500 persons each to be suitably located
to service the needs of the remainder of the properties. A similar
207
arrangement could operate for larger properties or even for a 35,000 ha
estate.
Should 50 ha estates be preferred direct employment would approach
90,000 per 14 Gl-year or 360,000 including multiplied personnel or
community totals around a million people. VJhilst there may be many
advantages associated with such numbers it would be in terms of a national
cost of 24C/1 for ethanol supplies which by the time this pervades the
general cost structure is believed to be less beneficial to the national
good. Also the query arises whether as a nation we could afford a work
force of this magnitude with a community forming 7% of our present population.
Although 7 day week and 24 hr/day operation has been specified
for maximising the use of mechanical equipment the total number of people
actually rostered for this type of work would probably not be more than
300 including the factory or 15% of the total work force employed in the
district. It would have an important social effect but not dominating.
The background to the commendation of 1600 ha properties with
community settlement and continuous operation of mechanized equipment lies
in the writer's experiences in numerous countries with an assortment of
cultural fulfillment varying from cane sugar factories of 1500 Te cane/day
employing 700 workers employed for 12 hrs/day and 7 days/week to beet sugar
factories of 5 times this rated capacity employing only 20 workers on 4
shift roster system. From farms as small as one hectare to estates of
10,000 or 20,000 ha. Also a number of years were spent in the Australian
metallurgical industry where 24 hr/day and 365 day/yr was indispensible.
The synthesis represents the selection of the best techniques
arranged to minimise costs and maximise human endeavour. A personal
preference is expressed for the 1600 ha properties as retaining a sufficient
measure of personal oversight and responsibility in contrast to less personal
concern commonly associated with the management of area-unit estates.
20S
APPLICATION OF SPACE AGE TECHNOLOGY
We have become progressively accustomed to the application of automatic
process control techniques to industrial equipment and in more recent years
to the development of over-riding computerized systems for co-ordinating
and directing the combined production procedures. Introducing space-age
technology refers essentially to the sophisticated development of remote
control. The requirements for effecting this on an industrial site do not
involve difficult communications links and even sugar cane complexes are
gradually evolving in this direction.
More innovative developments seem possible on the agricultural side
once a concept of large property operation is accepted or better still an
estate of the 35,000 ha unit size considered in this report.
For example driving a tractor in the operations of field preparation
represents a significant under-usage of the capabilities of the driver.
Except for the procedures involved in turning at the end of each row, the
remainder of the operation is very boring and demands little attention.
Remote control of moving objects has become familiar to many hobbyists
interested in model aeroplanes or boats and appropriate equipment is
available at most hobbyshops within a modest price-range. More sophisticated
activities of this type have become familiar to Australians in the Jindivik
or the Ikara defence developments. There seems to be no technical reason
why such types of control facilities should not be applied to tractors and
for remote control to be effected through video technology. With this type
of technology it should be feasible for one operator to be able to "drive"
ten tractors simultaneously from the comfort of a control room comparable to
that of a nuclear power station or airport control tower situation.
With development cf this character there appear to be no technical
reason why the control room should not be located in Brisbane or in any
other selected locality. Land line communication could accomplish
connection with the remoter area but greater flexibility should be achievable
through a national satellite system, the establishment of which is being
considered for 1985 or thereabouts.
The capital cost of establishing remote control facilities might well
reach $500 m a figure which would be offset by the fact of operators living
in an established community large enough to be viable in its own right. If
each operator located in the established community is able to relieve the
need for 5 operators in the remote area this could in turn relieve the
ethanol establishment cost of $350 (±50)m and the expenditure of $1000
(±150)m for supporting personnel. Thus remote communities of 1500 persons
would be envisaged rather than 6000.
Once procedures had been developed the possibilities of electronic
programming could be studied and progressively applied until perhaps one
operator could be responsible for the remote control of 50 tractor units.
The operation of planting would be difficult to conduct completely
by remote control but this could no doubt be developed with a progressively
diminishing degree of local assistance, again with the intention of reducing
the manual assistance component as automation is developed.
The application of irrigation is a significant component of the
growing cost and would require the development of maximum efficiency in
usage as well as in application. This also involves appropriate selection
of techniques. Instrumental methods of estimating water requirements by
agricultural land in specific places at specific times are available and
used in many places. Telemetering of information to provide computer
monitoring of the status of any selected area at any particular time is a
210
logical next step using already well established technology. Certain
areas of agriculture in the U.S.A. are in fact already using remote control
features for the application of irrigation in large area situations.
Experimental work is currently proceeding in the IJambour area with means
for automatic application control in relation to prevailing evaporation
rates and has reached a useful stage of development.
The harvester would also be difficult to operate by remote control
but by no means impossible. It has up to 15 control features incorporated
into its operation to each of which a suitable sensing device would need to
be adapted.
One important feature in the development of space-age technology has
been the marked improvement in the reliability of remote operating systems
and the ability to incorporate a wide range of adjustment facilities.
There would still need to be maintenance personnal located in the remote areas
and these would need to represent a range of skills from mechanical to
electrical as well as micro-electronics technology. The last-named field
is essentially a development of television maintenance procedures involving
the identification of troubles, their location and the replacement of
components. A very high degree of reliability in micro-electronics has
been progressively developing and more faults appear to surface from a newly
commissioned item than with equipment in which the initial problems have
been rectified.
A picture evolves in which a control centre might be established
adjacent to Brisbane - further centralization within the greater Brisbane
region itself would seem to be retrograde - from which the operations of
both farm and factory could be directed. A single building divided into
10 main control groups would suffice for each Q.S.I. unit.
Each district instead of requiring a community of 6000 could function
with a community of 1500 or possibly as low as 1000 as the generating factor
of the smaller community would have a smaller local component.
There would be nothing significant by way of new technology involved
in an establishment of the type just envisaged, it is the logical direction
of development for a new industry established to cater for the liquid
energy needs of the dawning 2ist century.
It would be desirable and justified on the grounds of sound economic
assessments and a lower price for ethanol. An endeavour has been made
to do this with respect to 35,000 ha estates and high productivity
conditions. Stepping from the estimated cost components set out in Table
XXIII a corresponding cost estimate has been itemised in Table XXV.
The overall result of this estimation indicates an ethanol price of
7.53c/l ex distillery with the application of space-age technology to
compare with 8.01C/1 without sophisticated remote control facilities.
This represents a reduction of only 6% in the ex-distillery price but for a
total production of 14 Gl would be equivalent to $67m/year.
As the estimated price of ethanol recedes the scope for further
reductions likewise diminishes although the possibility of reducing the
price to 7 or even 6c/l could be envisaged. Every extra cent is becoming
more and more difficult to cut, but 3 to 5C/1 may not be impossible.
212
TABLE XXV
ESTIMATED COST OF ETHAKOL AS FOR TABLE XXIII BUT WITH SPACE AGE TECHNOLOGY COSTS ARE c/l ETHANOL
213 ENERGY BALANCE
Information relevant to the energy requirement is incorporated in
Figures 1, 2 and 3 together with the materials balance and a simplified
flow sheet. In Figure 1 conditions have been set out for the dual
production of raw sugar crystal and ethanol in the same factory and the
energy factor of chief significance is that there should be adequate
bagasse to provide the steam required for both processes with a potential
surplus of 31.7% The ethanol route is shown requiring 6.44- kg steam per
litre of ethanol or m.5 MJ of latent heat in steam to produce 21.3 MJ
of N.Th.V. potential in the ethanol or a net gain of 32%. If the steam
is generated from bagasse it can be done with an efficiency of 82%
relative to N.Th.V., or if generated from coal or oil it may be done at
higher efficiencies. If we assumed a steam generator efficiency of 85%
this would represent an overall net thermal gain of 2 0%. Approximately
1% would also be used for mechanical equipment employed in producing and
transporting the cane. The mechanical component of milling which is
included in the production figure represents around M-% of the ethanol N.Th.V.
If ethanol is produced as the sole product from juice extracted from
the stalk of the sugar cane (Figure 2) then 7.3 kg steam are shown as being
required to produce a litre of ethanol. The main reason for the slightly
higher steam consumption resides in the use of molasses from the raw sugar
crystal production route which has been debited for its concentration.
The net gain in thermal energy is only 9% (with steam generation
at 85%) reducible to 8% after allowing for the energy of cane production.
In these processes the fuel has actually been produced by photosynthesis
with continuing capability and used at lower furnace efficiency as a
convenient means of disposing of the surplus. Generation of additional
electrical power would of course be an option open to development for the
potential surplus of fuel.
In the event of cellulose being hydrolyzed for fermentation to ethanol
a fuel supplement may or may not be needed. Figure 3 illustrates a route
in which all of the bagasse has been subjected to hydrolysis treatment and
coal is used as a fuel supplement.
The steam requirement for this route is indicated as 6.7 kg/1 of ethanol
equivalent to a net thermal gain of 29% reducible to 16% in terms of the
N.Th.V. of the fuel used to generate the steam. Alternatively we might look
at the thermal gain in terms of usage of non-renewable energy source in which
case it would represent a gain of 64-%.
It is believed that there is scope for reducing the thermal needs of
the process to a figure closer to 6 kg/1 in which case the net thermal gain
would be increased to 24% in terms of total fuel used.
The residues from the hydrolysis heap and recycled for fuel are shown
as lignin to represent 19'j of the dry fibre weight of the cane (some
Queensland data have shown as high as 23%) and 24% of the cellulose to
represent a recovery of 48% of the unhydrolyzed fraction. It has been
assumed that the pentosans have been hydrolysed.
An alternative to the evaporation of distillery slops would be to
pump to storage and reticulate for irrigation as and when required. Some
supplementation of fresh water would probably be needed for processing
unless effective recycling within the process can be accomplished. The
proportion of dilute slops to ethanol varies from 6.9 (Figure 1) to 8.2
(Figure 2) to 8.8 (Figure 3) kg/1.
The energy used for evaporating the slops varies from 39 to 25 kJ/kg
of dry slops solids - including correction for steam generation efficiency.
The energy required to transport the dilute slops to the fields would need
to be carefully costed in terms of the technique adopted but may well be of
a similar order of magnitude.
It had been considered that outgoing concentrated slops could be
returned by using the transport system bringing the cane to the factory for
returning it to the field. The outgoing concentrated slops would be only
about 5% of the weight of incoming cane hence the system would be quite
capable of handling this. On the other hand unconcentrated slops would
only be about the same weight as the cane coming to the factory. This
could no doubt be done but would be an untidy exercise. Furthermore
there is some doubt about the usability of fresh distillery slops for
irrigation, it may need aeration. As irrigation it would represent only
about a 25 mm application which is very marginal and could be accepted at
any time.
From the point of view of energy balance, it is considered legitimate
to relate the energy input only to the coal employed as supplementary fuel
since the lignin component of the cane is envisaged as being recycled for
steam generation and lignin can be photosynthesized on a continuing basis
and has no other known industrial use of significance than for combustion.
In this case the net thermal gain overall would be close to 64%.
If distillery slops are not recycled and commercial mineral fertilizers
are used, the energy component would be much less than that involved in
evaporating slops. The total usage of fertilizer in Queensland averages
10 kg/Te cane or between 60 and 100 g per litre of ethanol. Synthetic
nitrogenous fertilizer is particularly energy consuming for its production
but would be used at a rate of not more than 20 g/1 ethanol. A total energy
component of 1% would be the order of magnitude involved compared to nearer
30% for evaporating distillery slops or 3% for recycling dilute distillery
slops. All of the 3% and perhaps more would be required just to dispose of
distillery slops as acceptable process plant effluent.
An acceptable compromise might be to evaporate only half of the
contemplated amount of water. This would still leave sufficient to
recirculate and virtually halve the volume to be recycled, although it
would still be very dilute. An energy saving of the order of 15% could
be useful provided the cost of application was acceptable.
ESTIMATES OF FUTURE QUEENSLAND ADD AUSTRALIAN REQUIREMENTS
At present Queensland uses approximately 15% of total Australian petrol
consumption or around 2.1 Gl/year. Attempting to predict likely usage in
the year 2000 is fraught with numerous difficulties. The rate of growth is
likely to be small - possibly to average not more than 1% yearly. The
ownership of cars is already high at a little more than one for every 3
persons. If 30% of the petrol consumed is used by cars and station wagons
this would represent 2400 1 for each vehicle in a year or sufficient for
about 16,500 km of travelling being an average distance of 4 5 km/day.
If we combine the parameters pf population, ownership of vehicles
and their usage a figure of 4(±1)% annual rate of increase could be
envisaged. This would predict a consumption of 5(±1)G1 in the year 2000
or 2.4 (±0.5) "times the present consumption.
A consumption of this order would require between 2 50,000 and one
million hectares gross assignment of land depending upon which of the
productivity options is selected and achievement realised.
To predict the likely Australian requirements in the year 2000 is
correspondingly difficult but using similar factors to those employed above,
it could be expected to reach a total of 33(±5) Gl. This would require a
minimum gross assignment of land of 1.65 million hectares (16,500 km ) or
4.7 Q.S.I, units. A contribution from West Australia and Northern
Territory could be expected to have been developed by that date.
217
The view is expressed that the rate of increase of consumption of
I.C. engine liquid fuel will taper as alternatives become more highly
developed. The electric car may well be sufficiently developed by the
year 2000 to have a significant effect on the extent of use of I.C.
motivation. Commuter services may or may not have an effect of a similar
order of magnitude - past history in Australia tends to a less than
optimistic view. The relative costs of fuels will determine much of the
economics and higher standards of living will generally be prepared to pay
more for convenience of transport. Marginal increases in the price of
liquid fuels are considered unlikely to diminish the rate of increase in
consumption and radical improvements in commuter services are thought to be
needed to have any noticeable effect on private consumption. The only
country at present achieving this objective to a significant degree is China
where private ownership of vehicles is restricted by proclamation, a means
which would be considered socially unacceptable in the Australian community
even if economically desirable or necessary.
RELATED RELEVANT LITERATURE
1. Advisory Council of Science and Industry, Australia, Bull No. 6 (1913) and reprint with appendix, Bull No. 20 (1921)
2. Morner-Willlams, G.N.: Power Alcohol - its production and utilization. Hodder and Stoughton, London, 1922
3. Underkofler, Leland A. and Hickey, Richard J.: Industrial Fermentation" Chemical Pub. Co. Inc. New York, Vol. I 1954
4. G.H. Jenkins. "Introduction to Cane Sugar Technology" Elsevier, Amsterdam, 1966
5. Bureau of Sugar Experiment Stations, Queensland. Laboratory Manual for Queensland Sugar Mills 5th Ed. 1970
6. George P. Meade: "Cane Sugar Handbook" John Wiley and Sons Inc. New York. 9th Ed. 1964.
7. Hugot, Emll: "Handbook of Cane Sugar Engineering'1 Elsevier, Amsterdam 2nd Ed. (English) 1972
8. Spiers, E.M.: "Technical Data on Fuel" British National Committee World Power Conference
9. Perry, Robert H. and Chilton, Cecil H.: Chemical Engineers' Handbook" McGraw-Hill, Kogakusha. 5th Ed. 1973
10. Shreve, R. Norris: "Chemical Process Industries" McGraw-Hill, Kogakusha. 3rd Ed„ 1967
11. Groggins, P.H.: "Unit Processes in Organic Syntheses" McGraw-Hill, Kogakusha. 5th Ed. 1958
12. King, Norman J., Mungomery K..W. and Hughes, C.G.: '-Manual of Cane Growing'"' Elsevier, New York 1965
13. International Society of Sugar Cane Technologists System of Cane Sugar Factory Control. 3rd Ed. 1971
14. Paturau, J.n. "By-Products of the Cane Sugar Industry Elsevier, Amsterdam 1963
15. The Australian Sugar Yearbook Strand Publishing Co., Brisbane. An annual production since 1941
16. Kelly, F.H.C.: "The Ultimate Analysis of Bagasse" Bureau of Sugar Experiment Stations Queensland. Tech. Comra. No. 10 1937
17. Proceedings of the Queensland Society of Sugar Cane Technologists 1930 -
18. Proceedings of the International Society of Sugar Cane Technologists 1924 - especially useful are proceedings of XVth Congress, Durban, S.A. 1974
19. Bonner, James and Galston, Arthur W. : "Principles of Plant Physiology::"
W.H. Freeman & Co., San Francisco 1952
219
20. Peck., U.K. "Sol,tr Energy Utilization" Inst. Eng. Aust. Qld. Tech,. Papers XVIII, No. 1, Feb. 1977
21. Commonwealth and Queensland Year Books
22. Hatch M.D. and Stack C.R.; "Photosynthesis by sugar cane leaves" Bicchem. J. 1966, (101:103)
23. Richcigl, M. (Jn): "Man, Food and Nutrition5' C.R.C. Press Cleveland Ohio 197 3
24. Gartside, G., Regan, D.L. ar.d Neiss D.E.: Photosynthetic Production of Liquid Fuels from Plants Intern. Solar Energy Society Conf. Uni. N.S.W. 26th August 1977.
25. Associated Octel Co. Ltd. "A Review of Gasoline Quality: Australia and New Zealand" April/May, 1974: September 1974.
26. Brazil Secretaria de Tecnologia Industrial. :Etanol: Combustivel £
!lateria-Prima" (in Portugese) Mi.nisterio da Industria 6 do Comercio Dec. 1976.
27. Cellulose Conference Proceedings 1974 - Cellulose as a Chemical and Energy Resource" No. 5 3 Enzymatic Conversion of Cellulosic Material5- Mo. 6. Editor C.R. VTilke. Interscience. John Hiley New York, 197 5
28. Hanks, P.A.: Australian Institute of Petroleum., Queensland Branch Conference &th July 1977
29. Burdekin Project Committee (Commonwealth/State) "Resources and Fotentiai of the Burdekin River Basin Queensland" Aust. Govt. Publishing Servicej Canberra June 1977
30. Prince, R.G.H. 'Biological Energy Conversion1: Current Affairs Bulletin 1977, p.13
31. Dunning, J.w. and Lanthrop E.G.: "Industrial Fermentation'' Ind. Eng. Chem. 1943, 37, 24
32. Saddler, H.D.W., McCann D.J. and Pitman H.G.: ; A n Assessment for Crop Production for Energy in Australia 1 Australian Forestry 1976, 39_, (No. 1 ) , 5
33. McCann, D.J. and Saddler, H.D.VJ.: "Photobiological Conversion in Austral ia;; Search, 1975, 7, 17
34. McCann, D.J. Saddler H.D.W. and Prince, R.G.H. "The Efficient Processing of Photobiological Material" The Institution of Engineers, Australia Technical Conference 1976
35. "Alcohol a Brazilian Answer to the Energy Crisis" Research News. Science 1977, 1_95_, 564
36. Producer's Review (Australian Cane Growers' Official Journal) Strand Publishing Pty. Ltd. Brisbane, A monthly publication.
37. Power F a m i n g Magazine published by Pacific Publications (Aust.) Pty. Ltd. 29 Alberton Street, Sydney 1974 is vol. 83 in annual units. Useful from 1965 vol. 74.
