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Institut technologique FCBA : Forêt, Cellulose, Bois - construction, Ameublement
Conversion factorsA necessity for an accurate estimation
of wood consumption by industries
Alain THIVOLLE-CAZATTechnological Institute FCBA
10, avenue de St Mandé75012 Paris (France)
Workshop on National Wood Resource
Balances30th Marsh –1 st April 2008
Page : 2
Existing conversion factors
Conversion factors are necessary for estimation of wood inputted in industrial processes used for wood final products (sawn timber, pulp and panels, processed wood fuel).
Conversion factors yet exists but:• There is important variations from a country to
another• Variations inside countries and processes• Use of existing conversion factors leads to under
estimate industrial wood consumption Need of improvement of existing conversion factors by country and process, defined with verified data
2
Page : 3
Compilation of existing conversion factors
FAO 1979
EFSOS 2000
M.Fonseca (p.c.) 2005
EPF 2008
Finland (p.c.)
France (p.c.)
Sawnwood Softwood 1.32 -2.39 1.42 - 2.1 1.99 1.83 1.5 - 1.9 Hardwood 1.44 - 2.55 1.4 - 3.52 1.95 2.32 1.7 - 2.30 Veneer 1.2 - 3.1 1.59
Veneer/Ply
Plywood 1.63 - 2.94 1.5 - 3.1 2.02 1.8 – 1.9 Panels Particle board 1.1 - 2.2 1.2 - 1.8 1.32 1.53 1.2
OSB 1.7 2.07 1.5 Hardboard 1.98 - 3.01 2.16 MDF 1.73 1.86 1.9 Insulation board 0.63 - 0.91
1.5 - 3.3
0.66
Mechanical 2.4 - 3.27 2.16 - 2.9 2.68 2.72 – 3.18 2.4 Semi mechanical 2.04 -3.30 2.2 - 3.2 2.78
2.5 – 3.26 2.6
Sulfate 3.68 - 5.64 4.9 4.26 – 4.73 4.6 Sulfite 4.65 - 6.24
4.48 - 6.4 4.6
Page : 4
Conversion factor =
Round wood input (M3 u.b.)
Final product output
Round wood input u.b. = cubic meter under bark equivalent to round woodFinal product output = unit depends on product and process
outputproductFinalu.b.input woodRound
Typical flow of an industrial wood process
3
Page : 5
Round wood inputs Product outputs
Definitions
• At mill• In forest
• At road side
• On mill yard• At the entrance of the process
Where ?
• Volume
• Surface
• Air dry weight
• Absolute dry weight
• Volume over bark
• Volume under bark
• Fresh weight
• Air dry weight
How ?
• Final product
• By-products
• Round wood
• Chips
• Recovered wood
What ?
Page : 6
Final product : cubic metersquare metertonnes
Input wood : cubic meter over bark/under bark (saw log) green tonnes, air dry tonnes (pulp wood, chips, recovered wood)
Units
Construction of a conversion matrix for transformat ion of different wood measurements into others :
• Bark factor• Humidity• Dryness• Specific gravity
4
Page : 7
Conversions factors between units of measurements
Construction of a conversion matrix for transformation of different wood measurements into others :
• Bark factor• Humidity• Dryness• Specific gravity
Page : 8
Saw mill industry
5
Page : 9
Location of logs volume measurement
• Forest
• Road-side
• Mill yard
Forwarding
Road transport Losses risks
Losses risks due to :• logs forgotten in forest or at road side• slashing for cull elimination
Page : 10
Logs volume measurement
Log is assumed as a cylinder
Sm
all D
iam
.
Total Length
Mid. Diam.
Big
Dia
m.
Sm
all D
iam
.
Total Length
Mid. Diam.
Big
Dia
m.
Cylinder volume ≤ log volume
12diam)smalldiam(bigxlenght
Difference2−= length
6
Page : 11
Metric decrease on diameter = 2 cm/m
D=15 cmD=20 cm
D=25 cm
D=50 cm
D=35 cm
0%
2%
4%
6%
8%
10%
3 4 5 6 7 8 9 10
Log length (m)
Vol
ume
diffe
renc
e (%
)Metric decrease on diameter = 1 cm/m
D=50 cm
D=25 cm
D=20 cm
D=15 cm
0%
2%
4%
6%
8%
10%
3 4 5 6 7 8 9 10Log length (m)
Vol
ume
diffe
renc
e (%
)
Logs volume measurement
Difference increases with :• Log length• Difference between big and small diameter
Page : 12
Log volume measurement
Due to different specifications of the saw mill, the log volume measurement can lead to an under evaluation of volume.
Example of some French and German sawmills :
• Length is rounded to the 1m or 50cm inferior• Diameter is rounded to the 1cm or 2cm inferior
These rounding leads to an under estimation of 3 to 5 %of the real volume.
7
Page : 13
Recovery rate : Species variations
• Large variation of recovery rate due to quality degree asked to final product
• Bark factor varies between species
-40%
-20%
0%
20%
40%
60%
80%
100%
Oak Beech Spruce Maritime pine
Pro
duct
s an
d by
-pro
duct
s (%
)
Bark Final product Final Offcut Edgings
Slabs Log Offcut Saw dust
Page : 14
Log volume measurementBark volume
Log volume can be measured over or under bark.
A bark factor must be applied on log volume over bark.
Bark factor depends mainly on :• species• log size
DBH Diameter
13 %
5,5 %
9 %13 %
23 %
14,5 %
6 %
12 %14 %
23 %
19 %
10 %
15 %16 %
27 %
Oak
Beech
Norway spruceDouglas fir
Maritime pine
∅ > 40 cm∅ 25-35 cm∅ ≤ 20 cm
8
Page : 15
Volume measurement of sawn timber
• Rough sawn timber
• Dried sawn timber : shrinkage can induce 15 to 25 % of volume reduction
• Planning and surfacing : can induce 5 to 10 % of volume reduction
Page : 16
Pulp industry
Main problem : conversion of green tonnes in volume u.b.
9
Page : 17
Fibre/Particle Panel industry
Roundwood
By
products
Internal use
for energy
Green
Weight
Green
Weight
Chips
Air dry
Weight
Humidity
Specific
gravity
HumiditySpecific
gravity
Round
wood
equivallent
volume
u.b.
Bark factor
Fibre / particle
Pannel
Chips /
recovered
wood
Main problem : conversion of green tonnes in volume u.b.
Page : 18
Measurement realised• fresh weight of round wood over bark• fresh weight of chips• air dry weight of pulp
Needed values of inputted wood• Volume under bark
density woodfactorbarkxdrynessxweightfresh
Necessity of conversion factors for conversion of fresh weight measurement in volume u.b. ⇒
Pulp wood measurement
10
Page : 19
2.078
Volume over bark(m3 o.b.)
Volume under bark
(m3 u.b.)
Fresh Weightover bark
(ft o.b.)
Fresh Weightunder bark
(ft u.b.)
Dry Weightover bark (dt o.b.)
Dry Weightunder bark
(dt u.b.)
0.8801.136
0.750
2.17
1.333
0.460
0.890
2.470
1.124
0.405
0.361
2.774
0.481
0.8521.173
2.078
Volume over bark(m3 o.b.)
Volume under bark
(m3 u.b.)
Fresh Weightover bark
(ft o.b.)
Fresh Weightunder bark
(ft u.b.)
Dry Weightover bark (dt o.b.)
Dry Weightunder bark
(dt u.b.)
0.8801.136
0.750
2.17
1.333
0.460
0.890
2.470
1.124
0.405
0.361
2.774
0.481
0.8521.173
Matrix conversion factorMaritime pine example
Page : 20
Pulp wood measurement
• Dryness =
• Humidity =
• Bark factor =
• Seasonal variations
• Great variability inside a short log
• Species variations
weightGreenweightDry
weightDrycontent Water
o.b. Volumeu.b. Volume- o.b. Volume
11
Page : 21
Pulp wood measurementHumidity variation
50%
55%
60%
65%
70%
75%
80%
Jan
uary
Feb
ruary
Mar
sh
Apr
il
May
Jun
e
Jul
y
Augu
st
Sept
em
ber
Octo
ber
Nov
embe
r
Dece
mber
Measurment Month
Moi
stur
e co
nte
nt (
%)
Oak Beech
Seasonal variations of green tonne ⇒ necessity of association of humidity measure to weight measure
Page : 22
Pulp wood measurement
Difference of dryness between the point of sampling and the mean dryness of the short log.
Mean dryness is best estimated when sampling is made at about 50cm from the end of the log.
12
Page : 23
Pulp wood measurement
Number of samples by truck load for a given precision rate
12821481894 m
12514321282 m
15 %10 %5 %3 %2 %1 %Log length
Aberrant values probably due to insufficient number of samples
40
45
50
55
60
65
70
75
80
10/12/02 20/03/03 28/06/03 06/10/03 14/01/04 23/04/04 01/08/04 09/11/04 17/02/05
Sampling date
Dry
ness
Douglas Fir Norway Spruce
Page : 24
Proposition for conversion factor improvement
Accurate conversion factors must be calculated with accurate data :
We need :
• Data knowledge / Process knowledge
• Accurate volume measurement and conversion in volume u.b.
• Weight measure and accurate conversion in volume u.b.
• Work level : country and process
13
Page : 25
Data knowledge
• Inputted wood volume� Measurement procedure� Unit� Object � Procedure of calculation of equivalent round wood
under bark (measures used, bark factor, volume calculation formula)
• Output quantities of final product� Object� Characteristics� Unit
Page : 26
Volume measurementSawing / veneer industry
• Quantify the difference between volume measured u.b. and real volume u.b.
• Real bark factor at mill yard
• Verify that final product measurement is raw sawn timber
14
Page : 27
Weight measurementPulp / fibre and particle panel industry
• Matrix of conversion between green/rough tonne to round wood equivalent volume u.b. by species, country and type of wood
• Real bark factor at mill yard
• Specific gravity
• Mean annual humidity or monthly mean humidity
Page : 28
Panel industry(and processed wood fuel)
• Bark content in final products
All industries
• Loss analysis and estimation
• By products generation
• By products utilisation (energy, pulp and panel industry)