Bioethanol

Roselen, Wanxi, Eugenia

CONTENTSI. What is bioethanol?II. Bioethanol ProductionIII. FeedstocksIV. Fuel PropertiesV. ApplicationVI. AdvantagesVII.Disadvantages and ConcernsVIII.Ethanol ControversyIX. Comparison of Bioethanol and BiodieselX. Case study [Brazil]XI. Future development

What is bioethanol? Colourless and clear liquid Used to substitute petrol fuel for road

transport vehicles One of the widely used alternative

automotive fuel in the world (Brazil & U.S.A are the largest ethanol producers)

Much more environmentally friendly Lower toxicity level

Bioethanol Production• Wheat/Grains/Corn/Sugar-cane can be used

to produce ethanol. (Basically, any plants that composed largely of sugars)

• Main method : Sugar fermentation• 3 methods of hydrolysis :

(extraction of sugars out of bio-mass wastes)– concentrated acid hydrolysis– enzymatic hydrolysis – dilute acid hydrolysis

Bioethanol Production• (1) Concentrated Acid Hydrolysis

– ~77% of sulfuric acid is added to the dried biomass to a 10% moisture content.

– Acid to be added in the ratio of 1/25 acid :1 biomass under 50°C. 

– Dilute the acid to ~30% with water and reheat the mixture at100°C for an hour.

– Gel will be produced and pressed to discharge the acid sugar mixture.

– Separate the acid & sugar mixture by using a chromatographic column .

Bioethanol Production• (2) Enzymatic Hydrolysis (Not

popular)• (3) Dilute Acid Hydrolysis

– oldest, simplest yet efficient method– hydrolyse the bio-mass to sucrose – hemi-cellulose undergo hydrolysis with

the addition of 7% of sulfuric acid under the temperature 190°C.

– to generate the more resistant cellulose portion, 4% of sulfuric acid is added at the temperature of 215°C

Bioethanol Production• Wet milling process

– corn kernel is soaked in warm water – proteins broken down– starch present in the corn is released

(thus, softening the kernel for the milling process)

– microorganisms, fibre and starch products are produced.

– In the distillation process, ethanol is produced.

Bioethanol Production• Dry milling process

– Clean and break down the corn kernel into fine particles

– Sugar solution is produced when the powder mixture (corn germ/starch and fibre) is broken down into sucrose by dilute acid or enzymes.

– Yeast is added to ferment the cooled mixture into ethanol.

Bioethanol Production• Sugar fermentation

– Hydrolysis process breaks down the biomass cellulosic portion into sugar solutions which will then be fermented into ethanol.

– Yeast is added and heated to the solution.– Invertase acts as a catalyst and convert

the sucrose sugars into glucose and fructose. (both C6H12O6).

Bioethanol ProductionChemical reaction 1

The fructose and glucose sugars react with zymase to produce ethanol and carbon dioxide.

Chemical reaction 2

Fermentation process requires 3 days to complete and is carried out at a temperature of between 250°C and 300°C.

Bioethanol Production• Fractional Distillation Process

– After the sugar fermentation process, the ethanol still does contain a significant quantity of water which have to be removed.

– In the distillation process, both the water and ethanol mixture are boiled.

– Ethanol has a lower boiling point than water, therefore ethanol will be converted into the vapour state first condensed and separated from water.

Feedstocks• Sugar is required to produce ethanol by

fermentation. – Plant materials (grain, stems and leaves) are

composed mainly of sugars– almost any plants can serve as feedstock for ethanol

manufacture

• Choice of raw material depends on several factors – ease of processing of the various plants available– prevailing conditions of climate– landscape and soil composition– sugar content

Crops used in Bioethanol production

Brazil sugar cane

USA corn

Europe wheat and barley

Feedstocks• R&D activities on using lignocellulosic

(woody materials) as feedstock – Lignocellulosic biomass is more abundant and

less expensive than food crops– higher net energy balance– accrue up to 90% in greenhouse gas savings,

much higher than the first generation of biofuel – However, more difficult to convert to sugars due

to their relatively inaccessible molecular structure

Fuel Properties• Energy content

– Bioethanol has much lower energy content than gasoline

– about two-third of the energy content of gasoline on a volume base

Fuel Properties Gasoline Bioethanol Molecular weight [kg/kmol]

111 46

Density [kg/l] at 15 C⁰ 0.75 0.80-0.82

Oxygen content [wt-%]

34.8

Lower Calorific Value [MJ/kg] at 15ºC

41.3 26.4

Lower Calorific Value [MJ/l] at 15ºC

31 21.2

Octane number (RON)

97 109

Octane number (MON)

86 92

Cetane number 8 11Stoichiometric air/fuel ratio [kg air/kg fuel]

14.7 9.0

Boiling temperature [ºC]

30-190 78

Reid Vapour Pressure [kPa] at 15ºC

75 16.5

Fuel Properties• Octane number

– Octane number of ethanol is higher than petrol

– hence ethanol has better antiknock characteristics

– increases the fuel efficiency of the engine

– oxygen content of ethanol also leads to a higher efficiency, which results in a cleaner combustion process at relatively low temperatures

Fuel Properties Gasoline Bioethanol Molecular weight [kg/kmol]

111 46

Density [kg/l] at 15 C⁰ 0.75 0.80-0.82

Oxygen content [wt-%]

34.8

Lower Calorific Value [MJ/kg] at 15ºC

41.3 26.4

Lower Calorific Value [MJ/l] at 15ºC

31 21.2

Octane number (RON)

97 109

Octane number (MON)

86 92

Cetane number 8 11Stoichiometric air/fuel ratio [kg air/kg fuel]

14.7 9.0

Boiling temperature [ºC]

30-190 78

Reid Vapour Pressure [kPa] at 15ºC

75 16.5

Fuel Properties• Reid vapour pressure

(measure for the volatility of a fuel)– Very low for ethanol,

indicates a slow evaporation

– Adv: the concentration of evaporative emissions in the air remains relatively low, reduces the risk of explosions

– Disadv: low vapour pressure of ethanol -> Cold start difficulties

– engines using ethanol cannot be started at temp < 20ºC w/o aids

Fuel Properties Gasoline Bioethanol Molecular weight [kg/kmol]

111 46

Density [kg/l] at 15 C⁰ 0.75 0.80-0.82Oxygen content [wt-%]

34.8

Lower Calorific Value [MJ/kg] at 15ºC

41.3 26.4

Lower Calorific Value [MJ/l] at 15ºC

31 21.2

Octane number (RON)

97 109

Octane number (MON)

86 92

Cetane number 8 11Stoichiometric air/fuel ratio [kg air/kg fuel]

14.7 9.0

Boiling temperature [ºC]

30-190 78

Reid Vapour Pressure [kPa] at 15ºC

75 16.5

Application• transport fuel to replace gasoline• fuel for power generation by thermal combustion• fuel for fuel cells by thermochemical reaction• fuel in cogeneration systems• feedstock in the chemicals industry

Application• Blending of ethanol with a small proportion of a

volatile fuel such as gasoline -> more cost effective • Various mixture of bioethanol with gasoline or

diesel fuels– E5G to E26G (5-26% ethanol, 95-74% gasoline)– E85G (85% ethanol, 15% gasoline)– E15D (15% ethanol, 85% diesel)– E95D (95% ethanol, 5% water, with ignition improver)

Advantages• Exhaust gases of ethanol are much cleaner

– it burns more cleanly as a result of more complete combustion

• Greenhouse gases reduce– ethanol-blended fuels such as E85 (85% ethanol and

15% gasoline) reduce up to 37.1% of GHGs• Positive energy balance, depending on the type of

raw stock – output of energy during the production is more than

the input• Any plant can be use for production of bioethanol

– it only has to contain sugar and starch• Carbon neutral

– the CO2 released in the bioethanol production process is the same amount as the one the crops previously absorbed during photosynthesis

Advantages• Decrease in ozone formation

– The emissions produced by burning ethanol are less reactive with sunlight than those produced by burning gasoline, which results in a lower potential for forming ozone

• Renewable energy resource– result of conversion of the sun's energy into usable energy– Photosynthesis -> feedstocks grow -> processed into ethanol

• Energy security– esp. Countries that do not have access to crude oil resources– grow crops for energy use and gain some economic freedom

• Reduces the amount of high-octane additives• Fuel spills are more easily biodegraded or

diluted to non toxic concentrations

Disadvantages and Concerns• Biodiversity

– A large amount of arable land is required to grow crops, natural habitats would be destroyed

• Food vs. Fuel debate– due to the lucrative prices of bioethanol some

farmers may sacrifice food crops for biofuel production which will increase food prices around the world

• Carbon emissions (controversial) – During production of bioethanol, huge amount

of carbon dioxide is released– Emission of GHGs from production of bioethanol

is comparable to the emissions of internal-combustion engines

Disadvantages and Concerns• Not as efficient as petroleum

– energy content of the petrol is much higher than bioethanol

– its energy content is 70% of that of petrol• Engines made for working on Bioethanol

cannot be used for petrol or diesel– Due to high octane number of bioethanol, they can

be burned in the engines with much higher compression ratio

• Used of phosphorous and nitrogen in the production– negative effect on the environment

• Cold start difficulties– pure ethanol is difficult to vaporise

Disadvantages and Concerns• Transportation

– ethanol is hygroscopic, it absorbs water from the air and thus has high corrosion aggressiveness

– Can only be transported by auto transport or railroad

• Many older cars unequipped to handle even 10% ethanol

• Negatively affect electric fuel pumps by increasing internal wear and undesirable spark generation

Ethanol Controversy

Is it justifiable?..to use agriculture land to grow energy crops instead of food crops when there are so many starving people in the world. In the developed countries that is not a problem, but in the developing ones where we have a large number of people living below the poverty this may lead to a crisis.

Ethanol Controversy• Is burning biofuel more environmentally friendly

than burning oil?– Fact that producing biofuel is not a "green process“– requires tractors and fertilisers and land– With the increase in biofuel production, more forests will

be chopped down to make room for biofuel, ↑ CO2

• Better alternative suggested by scientists..– steer away from biofuel and focus on reforestation and

maximising the efficiency of fossil fuels instead

Comparison of Bioethanol and Biodiesel

Bioethanol Biodiesel Process Dry-mill method: yeast, sugars and

starch are fermented. From starch, it is fermented into sugar, afterwards it is fermented again into alcohol.

Transesterification: methyl esters and glycerin which are not good for engines, are left behind.

Environmental Benefit

Both reduce greenhouse gas emissions as biofuels are primarily derived from crops which absorb carbon dioxide.

Compatibility ethanol has to be blended with fossil fuel like gasoline, hence only compatible with selected gasoline powered automobiles.

Able to run in any diesel generated engines

Costs Cheaper More expensive Gallons per acre

420 gallons of ethanol can be generated per acre

60 gallons of biodiesel per acre soybeans cost of soybean oil would significantly increase if biodiesel production is increased as well.

Energy provides 93% more net energy per gallon

produces only 25% more net energy.

Greenhouse-gas Emissions (GHG)

12% less greenhouse gas emission than the production and combustion of regular diesel

41% less compared to conventional gasoline.

Case study [Brazil]• Brazil the first to produce the cheapest ethanol in

the world.• WHY BRAZIL?

– Favourable conditions– Tradition of culturing sugarcane– Sugarcane being the most efficient raw materials for

production of ethanol

Case study [Brazil]• The FACTS

– Brazil second biggest producer of ethanol in the world (20 billion litres)

– Fuel used in 45 % of Brazilian vehicles is ethanol

– Feedstocks: sugarcane bagasse and straw (rich in cellulose and turning entire sugarcane biomass to be used with no wastage)

– 1 tonne of bagasse produce 186 litres of ethanol

Case study [Brazil]In 1930s• Brazil’s ethanol industry started• Government directed sugarcane into ethanol production• Made addition of ethanol to gasoline compulsory

In 1973• International oil crisis doubled Brazil’s expenditure on oil imports• Government was forced to consider alternative sources of energy to

decrease its dependency and spending on fossil fuels.

In 1975• Increase ethanol production as a substitute for gasoline• Invested in increasing agricultural production• Modernising and expanding distilleries• Establish new production plants• Introduce subsidies to lower prices and reduce taxes for ethanol

producers

Case study [Brazil] Over 15 years, production of ethanol escalated from 0.6 billion litres in

1975 to 11 billion litres in 1990. Progress further with Bioethanol establishments:

1975 to 1978• One part of ethanol was added to four parts of gasoline.• Additional processing stage to remove water from the fuel

1979• Production streamlined to focus on hydrous ethanol• Ethanol which contains 5% water that could be used in cars fuelled

entirely by ethanol

Researchers in Aerospace Technology in Sao Paulo, developed alloys to protect the internal parts of gasoline-powered engines and fuel tanks from corrosion by ethanol. 1986 to 1989, 90% of all new vehicles sold in the domestic market were ethanol-fuelled.

Case study [Brazil]• PROBLEMS faced:

– Waste!!– VINASSE – a corrosive liquid byproduct of

ethanol distillation– Being dumped in rivers causing environmental

damage– Bagasse – leftover sugarcane fibre

Case study [Brazil]• SOLUTIONS:

– Vinasse was found to be a good fertiliser.– Transportation system was developed– Combination of trucks, pipes and ducts to carry Vinasse

from the distilleries to the fields– Bagasse was collected– Produce energy, building on existing methods of burning

the bagasse to power steam turbines for electricity generation

– Developed cauldrons under greater pressure– More energy could be produced allowing ethanol plants to

become more autonomous in terms of energy– CONTRIBUTIONS IS TO KEEP ETHANOL

PRODUCTION COSTS LOW

Case study [Brazil]• Social impacts

– Created jobs for locals (mainly in rural areas)– Brazilian sugarcane industry has a particularly

poor record in respecting worker’s rights– Expansion in sugar cane cultivation may

increase food prices. This would leave the poor with a harder survival.

– Although the ethanol industry has greatly increased the wealth of the sugar and alcohol sector’s industries, the poor have to be the one handling the negative impacts.

Future development• For bioethanol to become more sustainable to

replace petrol, production process has to be more efficient– Reducing cost of conversion– Increasing yields – Increase the diversity of crop used

• As microbes are use to convert glucose into sugar which is ferment in bioethanol– Microbiology and biotechnology will be helpful in the

genetic engineering

Thank You!