Bioethanol
Bioethanol in
the world
Bioethanol is probably the most
widely used alternative automotive fuel in the world, mainly
due to Brazil’s decision to produce fuel alcohol from sugar
cane, but also due to its use in North America as octane
enhancer of gasoline in small percentage. The world’s largest
ethanol producers are Brazil and the USA, which together
account for more than 65% of global ethanol production; the
figure for Europe is 13%. Fuel ethanol is produced in Brazil
mainly from sugar cane and in the USA from corn, accounting
for 11.9 and 7.6 million m3 respectively in 2001.
In Brazil, 60% of the produced
ethanol is sold in hydrated form (93 vol-% ethanol and 7 vol-%
water), which completely replaces petrol in vehicle engines.
The remaining 40% ethanol is applied in water-free form in a
mixture with petrol up to 24%.
Bioethanol
production in the EU
The European bioethanol
production amounted to 1,592 m litres in 2006. With 431 m
litres, Germany is the leading producer in Europe.
However Spain is a close second with 396 m litres. The
sector’s success in Spain can be explained by the fact that
Spain does not collect tax on ethanol. France was the third
largest European producer in 2006 with 293 m litres.
Spain and France transform part of their bioethanol production
into ETBE.
BIOETHANOL
Production in Europe |
(Million
litres) |
|
|
Country |
2004 |
2005 |
2006 |
Germany |
25 |
165 |
431 |
Spain |
254 |
303 |
396 |
France |
101 |
144 |
293 |
Poland |
48 |
64 |
161 |
Sweden |
71 |
153 |
140 |
Italy |
0 |
8 |
78 |
Hungary |
0 |
35 |
34 |
Lithuania |
0 |
8 |
18 |
Netherlands |
14 |
8 |
15 |
Czech Republic |
0 |
0 |
15 |
Latvia |
12 |
12 |
12 |
Finland |
3 |
13 |
0 |
Total |
528 |
913 |
1592 |
EBIO |
|
|
|
Feedstocks
Sugar is required to produce
ethanol by fermentation. Plant materials (grain, stems and
leaves) are composed mainly of sugars, so in principle almost
any plants can serve as feedstock for ethanol manufacture. In
practice, the choice of raw material depends on what grows
best under the prevailing conditions of climate, landscape and
soil composition, as well as on the sugar content and ease of
processing of the various plants available. The result is a
wide variety of ethanol feedstocks, and hence production
processes.
Worldwide, most bioethanol is
produced from sugar cane (Brazil), molasses and corn (USA),
but other starchy materials such as wheat, barley and rye are
also suitable. Crops that contain starch have to be converted
to sugars first. A feedstock of around 3 tons of grains is
needed for the production of 1 ton of ethanol. In Europe, the
main crops for the production of bio-ethanol are starch crops
(such as common wheat) and sugar beet. Sugar beet crops are
grown in most of the EU-25 countries, and yield substantially
more ethanol per hectare than wheat.
|
Common wheat |
Sugar
beet |
|
Litres/ha |
toe/ha |
Litres/ha |
toe/ha |
Austria |
1,792 |
0.92 |
6,677 |
3.42 |
Belgium |
2,847 |
1.46 |
6,970 |
3.57 |
Germany |
2,620 |
1.34 |
6,384 |
3.27 |
Denmark |
2,561 |
1.31 |
6,399 |
3.28 |
Greece |
916 |
0.47 |
4,926 |
2.52 |
Spain |
1,052 |
0.54 |
6,181 |
3.16 |
Finland |
1,057 |
0.54 |
3,440 |
1.76 |
France |
2,554 |
1.31 |
7,980 |
4.09 |
Ireland |
2,996 |
1.53 |
4,710 |
2.41 |
Italy |
1,637 |
0.84 |
4,346 |
2.23 |
The
Netherlands |
2,839 |
1.45 |
6,472 |
3.31 |
Portugal |
499 |
0.26 |
5,234 |
2.68 |
Sweden |
2,069 |
1.06 |
5,266 |
2.70 |
United
Kingdom |
2,686 |
1.38 |
6,355 |
3.25 |
Czech
Republic |
1,568 |
0.80 |
4,982 |
2.55 |
Estonia |
659 |
0.34 |
- |
- |
Hungary |
1,365 |
0.70 |
n.a. |
n.a. |
Lithuania |
1,050 |
0.54 |
2,964 |
1.52 |
Latvia |
908 |
0.46 |
3,036 |
1.55 |
Poland |
1,215 |
0.62 |
3,555 |
1.82 |
Slovenia |
1,330 |
0.68 |
4,040 |
2.07 |
Slovakia |
1,360 |
0.70 |
3,486 |
1.78 |
Potential bioethanol yields from common wheat and
sugar beet in some of the EU-25 member states
At present, R&D activities
in the field of bio-ethanol focus on using lignocellulosic or
woody materials as a feedstock (see dedicated
section). These include short rotation energy crops
(for example willow, popular, miscanthus and eucalyptus),
agricultural residues (e.g. straw and sugar cane bagasse),
forest residues, waste woods, and municipal solid wastes.
About 2 - 4 dry tons of woody or grassy material is required
for the production of 1 ton of ethanol. With a total sugar
content of 60–70% (40% glucose as cellulose and 25% xylose as
hemicellulose), wheat straw can produce around 230 kg of
ethanol per ton of dry material.
There are several reasons for
shifting to ethanol production from lignocellulosic biomass.
Lignocellulosic biomass is more abundant and less expensive
than food crops, especially when it concerns a waste stream
with very little or even negative economic value. Furthermore,
it has a higher net energy balance, which makes it more
attractive from an environmental point of view. Indeed,
ligno-cellusolic bioethanol has the potential to accrue up to
90% in greenhouse gas savings, well ahead of first generation
biofuels. However, these kinds of biomass are more
difficult to convert to sugars due to their relatively
inaccessible molecular structure.
Production process
The predominant technology for
converting biomass to ethanol is fermentation followed by
distillation. Fermentation is a bio-chemical conversion
process in which the biomass is decomposed using micro-
organisms (bacteria or enzymes). This technology can be used
for various types of biomass feedstocks.
Practically all ethanol
fermentation is still based on Baker’s yeast (Saccharomyces
cerevisiae), which requires simple (monomeric) sugars as raw
material. Conventional yeast fermentation produces 0.51 kg of
ethanol from 1 kg of any the C6 sugars glucose, mannose and
sucrose. However, not all feedstocks contain simple sugars.
Starch and lignocellulose are polymers, and an hydrolysis is
required to break the bonds between monomers and produce
simple C6 sugars for fermentation. To top
The first step in this conversion process comprises milling
or grinding of the grain so as to release its starch. Then
this material is diluted in water to adjust the amount of
sugar in the mash. This is necessary to maintain the yeast and
make the mash easier to stir and handle. Then this mixture is
cooked to dissolve all the water-soluble starches. The starch
is converted to sugars simultaneously. This can be done by
enzymes or acid hydrolysis. In the case of acid hydrolysis,
dilute mineral acid is added to the grain slurry prior to
cooking. The short carbohydrates resulting from these
processing steps can be fermented by micro-organisms. For
growing of the yeast needed for the fermentation process, the
solution must be slightly acid, namely a pH between 4.8 and
5.0. During fermentation, ethanol is produced, which is
diluted with water. This process also results in the formation
of CO2. Through a series of distillation and dehydration
steps, the ethanol concentration can be increased.
The conversion process of lignocellulosic biomass to
ethanol only differs from the process described above with
respect to the break down, or hydrolysis, of the raw material
to fermentable sugar. This hydrolysis process is more
difficult than the hydrolysis of starch. Lignocellulosic
biomass contains carbohydrate polymers called cellulose
(40-60% of dry weight) and hemicellulose (20-40% of dry
weight) that can be converted to sugars. Cellulose is composed
of glucose molecules bonded together in long chains that form
a crystalline structure. Hemicellulose consists of a mixture
of polymers made up from xylose, mannose, galactose, or
arabinose. It is much less stable than cellulose. Both
materials are not soluble in water. The remaining fraction, a
complex aromatic polymer called lignin (10-25% of dry weight)
cannot be fermented because it is resistant to biological
degradation. This material can be utilised for the production
of electricity and/or heat.
For fuel applications, the purity of the ethanol must be
almost 100%. This means that the water content must be much
lower compared to ethanol produced by current industrial
technology. For the dehydration of ethanol several
technologies are available, such as the use of molecular
sieves and membrane separation, which can still be improved.
The power and heat production from the non-fermentable
fraction of the biomass and the overall process integration
can also be developed further, which will lead to an increase
of the energetic efficiency and economic performance of the
process.
Fuel
properties Bioethanol has much lower energy
content than gasoline (about two-third of the energy content
of the latter on a volume base). This means that, for mobility
applications, for a given tank volume, the range of the
vehicle is reduced in the same proportion.
The octane number of ethanol is higher than that for
petrol; hence ethanol has better antiknock characteristics.
This better quality of the fuel can be exploited if the
compression ratio of the engine is adjusted accordingly. This
increases the fuel efficiency of the engine. The oxygen
content of ethanol also leads to a higher efficiency, which
results in a cleaner combustion process at relatively low
temperatures.
The Reid vapour pressure, a measure for the volatility of a
fuel, is very low for ethanol. This indicates a slow
evaporation, which has the advantage that the concentration of
evaporative emissions in the air remains relatively low. This
reduces the risk of explosions. However, the low vapour
pressure of ethanol, together with its single boiling point,
is disadvantageous with regard to engine start at low ambient
temperatures. Without aids, engines using ethanol cannot be
started at temperatures below 20ºC. Cold start difficulties
are the most important problem with regard to the application
of alcohols as automotive fuels.
Fuel properties of gasoline, bioethanol and ETBE
Fuel properties |
Gasoline |
Bioethanol |
ETBE |
Molecular weight
[kg/kmol] |
111 |
46 |
102 |
Density [kg/l] at
15ºC |
0.75 |
0.80-0.82 |
0.74 |
Oxygen content [wt-%] |
|
34.8 |
|
Lower Calorific Value [MJ/kg] at
15ºC |
41.3 |
26.4 |
36 |
Lower Calorific Value [MJ/l] at
15ºC |
31 |
21.2 |
26.7 |
Octane number (RON) |
97 |
109 |
118 |
Octane number (MON) |
86 |
92 |
105 |
Cetane number |
8 |
11 |
- |
Stoichiometric air/fuel ratio [kg
air/kg fuel] |
14.7 |
9.0 |
- |
Boiling temperature
[ºC] |
30-190 |
78 |
72 |
Reid Vapour Pressure [kPa] at
15ºC |
75 |
16.5 |
28 |
Applications Ethanol
can be used :
- as a transport fuel to replace gasoline
- as a fuel for power generation by thermal combustion
- as a fuel for fuel cells by thermochemical reaction
- as a fuel in cogeneration systems
- as a feedstock in the chemicals industry
Ethanol is best used in spark-ignition engines because of
its high octane rating. Due to its poor ignition quality (low
cetane number), it is less suitable for diesel engines.
It is generally impractical to use neat ethanol in
spark-ignition engines due to its low vapour pressure and high
latent heat of vaporisation which make cold start problematic.
The most cost-effective aid is the blending of ethanol with a
small proportion of a volatile fuel such as gasoline. Thus,
various mixture of bioethanol with gasoline or diesel fuels
have been used. The most well-known blends are (by volume):
- 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)
Bioethanol has been extensively tested in light duty
flexible fuel vehicles (FFV) as E85G. ETBE is also used in
blends of 10-15 % with gasoline to enhance its octane rating
and reduce emissions. Blends of gasoline with up to 22%
ethanol (E22G) can be used in spark ignition engines without
any material or operating problems. Blends of diesel with up
to 15% ethanol (E22D) do not introduce any technical engine
problem and require no ignition improver.
The introduction of E85 in Europe started in Sweden
around the year 2000. Only in the last 2 years has the
E85 infrastructure expanded to other countries in the EU such
as Germany, France and Ireland. The map below shows the
E85 infrastructure density in Europe as of April 2007.
Click
here to download the map To top
Economics Fermentation
of sugars to ethanol is a mature technology, which is applied
commercially on a large scale. There is a little chance of
technological improvements that may significantly reduce the
current production costs. These costs are largely determined
by biomass feedstock prices, which can account for 55 - 80% of
the final price of ethanol.
According to an ECN report, present production costs for
ethanol derived from sugar and starch crops are 20 €/GJ (corn,
USA–0.42 €/L, or 834 €/toe) and 15-25 €/GJ (sugar beet, North
West Europe). This is about 0.32-0.53 €/litre, or 625–1040
€/toe.
Another source (BTG, 2004) presents the following
bioethanol production costs analysis. Prices of 140 EUR/ton
for common wheat, and 26.2 EUR/tonne for sugar beet are
assumed. The co-product credit reduces the production costs of
ethanol. In case of ethanol from wheat, the co-product is
Dried Distillers Grains Soluble (DDGS), while the by-product
of beet sugar ethanol is sugar beet pulp. To top
Bioethanol production costs in the EU-25 + Bulgaria,
Romania
|
Wheat
based |
Beet
based |
|
€/L |
€/GJ |
€/toe |
€/L |
€/GJ |
€/toe |
Net feedstock cost |
|
|
|
|
|
|
- Feedstock |
0.40 |
18.9 |
790 |
0.26 |
12.3 |
513 |
- Co-product credit |
0.15 |
7.1 |
296 |
0.03 |
1.4 |
59 |
Subtotal feedstock cost
|
0.25 |
11.8 |
493 |
0.23 |
10.9 |
454 |
Conversion costs |
0.28 |
13.3 |
553 |
0.22 |
10.4 |
434 |
Blending costs (incl. adaptation of
gasoline) |
0.05 |
2.4 |
99 |
0.05 |
2.4 |
99 |
Distribution costs |
0.01 |
0.5 |
20 |
0.1 |
4.7 |
197 |
Total costs at petrol
station |
0.59 |
27,9 |
1165 |
0.6 |
28.4 |
1184 |
Source: BTG, 2004
Bioethanol production in the
EU The European bioethanol production amounted
to 309,500 tons in 2003. With 180,000 tons, Spain is the
leading producer in Europe. The sector’s success in Spain can
be explained by the fact that Spain does not collect tax on
ethanol. Sweden was the third largest European producer in
2003 with 52,300 tons. Spain and France transform part of
their bioethanol production into ETBE.
Evolution of the bioethanol production in the EU-15
Bioethanol production in the EU-15
|
2002 |
2003 |
|
Bioethanol |
ETBE |
Bioethanol |
ETBE |
Spain |
176,700 |
376,000 |
180,000 |
383,400 |
France
|
90,500 |
192,500 |
77,200 |
164,250 |
Sweden
|
50,000 |
0 |
52,300 |
0 |
Total
EU-15 |
317,200 |
568,500 |
309,500 |
547,650 |
Source: Eurobserver, 2004
R&D
Current research and
development activities mainly focus on the conversion of
lignocellulosics biomass. This technology is not available on
a commercial scale yet. Scaling up still proves difficult and
commercially unattractive. An important issue is the
development of cost-effective and environmentally sound
enzymes, pre-treatment and hydrolysis technologies. At
present the majority of utilities and energy groups talk a lot
about this 2nd generation as the future of biofuels,
preferring to wait several years for the technology to
arrive. EUBIA would like to see more development today
in higher yielding and lower input requiring 1st generation
biofuel crops, specifically based on sweet sorghum.
There is significant exploitation potential in the world and
for Europe which is important for EU biofuel targets.
South, Central and Eastern Europe are particular areas that
EUBIA has identified as suitable for sweet sorghum crop
cultivation.
EUBIA also pushes forward the
development and deployment of integrated bio-refineries based
on sweet sorghum. The economics of such bio-complexes are
extremely interesting and could lead, thanks to the many
co-products generated, to a bioethanol market price of 450-500
€/ton (17-19 €/GJ, or 700-800 €/toe)
For more information about
bioethanol BAFF http://www.baff.info/
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