User:SarcasticDwarf/Ethanol fuel

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For other forms of alternative energy, see energy development.

Ethanol fuel is a biofuel alternative to gasoline. It can be combined with gasoline in any concentration up to pure ethanol (E100). Anhydrous ethanol, that is, ethanol with at most 1% water, can be blended with gasoline in varying quantities to reduce consumption of petroleum fuels. Worldwide automotive ethanol capabilities vary widely and most spark-ignited gasoline style engines will operate well with mixtures of 10% ethanol (E10)^[1].

In Brazil, ethanol-powered and flexible-fuel vehicles are manufactured to be capable of operation by burning hydrated ethanol, an azeotrope of ethanol (around 93% v/v) and water (7%). Hydrated ethanol may also be mixed with gasoline in flexible fuel vehicles but a minimum amount of ethanol (granted by legally regulated gasoline type C) is required to avoid problems with the mixture.

Ethanol is increasingly used as an oxygenate additive for standard gasoline, as a replacement for methyl t-butyl ether (MTBE), the latter chemical being difficult to retrieve from groundwater and soil contamination. At a 10% mixture, ethanol reduces the likelihood of engine knock, by raising the octane rating. The use of 10% ethanol gasoline is mandated in some cities where the possibility of harmful levels of auto emissions are possible, especially during the winter months.^[2] Ethanol can be used to power fuel cells, and also as a feed chemical in the transesterification process for biodiesel.

Ethanol can be mass-produced by fermentation of sugar or by hydration of ethylene from petroleum and other sources. Current interest in ethanol lies in production derived from crops (bio-ethanol), and there's discussion about whether it is a sustainable energy resource that may offer environmental and long-term economic advantages over fossil fuels, like gasoline or diesel. It is readily obtained from the starch or sugar in a wide variety of crops. Ethanol fuel production depends on availability of land area, soil, water, and sunlight.

There is considerable ongoing debate about how useful bio-ethanol will be in replacing fossil fuels in vehicles. One research paper in the UK suggested that to replace 5% of fuel used in the UK with bio-ethanol would require 20% of the UKs arable land.^[3]

In 2004, around 42 billion liters of ethanol were produced in the world,^[4] most of it being for use in cars. Brazil produced around 16.4 billion liters and used 2.7 million hectares of land area for this production (4.5% of the Brazilian land area used for crop production in 2005^[5]). Of this, around 12.4 billion liters were produced as fuel for ethanol-powered vehicles in the domestic market.

Contents 1 Chemistry 2 Sources 2.1 Production Process 2.2 Fermentation 2.3 Distillation 2.4 Dehydration 3 Technology 3.1 Ethanol-based engines 3.2 Ethanol fuel mixtures 3.3 Fuel Economy 4 Controversy 5 Environment 5.1 Energy balance 5.2 Air pollution 5.2.1 Manufacture 5.2.2 Greenhouse gas abatement 5.3 Land use 5.4 Renewable resource 5.5 Replacement of petroleum 5.6 Alternatives 6 Research 6.1 Economics 6.2 Common crops associated with ethanol production 6.3 Ethanol from algae 7 Notes 8 See also 9 External links

[edit] Chemistry

During ethanol fermentation, glucose is decomposed into ethanol and carbon dioxide.

C₆H₁₂O₆ → 2C₂H₆O + 2CO₂

During combustion ethanol reacts with oxygen to produce carbon dioxide, water, and heat: (other air pollutants are also produced when ethanol is burned in the atmosphere rather than in pure oxygen)

2C₂H₆O + 6O₂ → 4CO₂ + 6H₂O + heat

Together, these two equations add up to the following:

C₆H₁₂O₆ + 6O₂ → 2CO₂ + 4CO₂ + 6H₂O + heat

This is the reverse of the photosynthesis reaction, which shows that the three reactions completely cancel each other out, only converting light into heat without leaving any byproducts:

6 CO₂ + 6 H₂O + light → C₆H₁₂O₆ + 6 O₂

[edit] Sources

Main article: Energy crop

Bioethanol is obtained from the conversion of carbon based feedstock. Agricultural feedstocks are considered renewable because they get energy from the sun using photosynthesis. Ethanol can be produced from a variety of feedstocks such as sugar cane, bagasse, miscanthus, sugar beet, sorghum, grain sorghum, switchgrass, barley, hemp, kenaf, potatoes, sweet potatoes, cassava, sunflower, fruit, molasses, corn, stover, grain, wheat, straw, cotton, other biomass, as well as many types of cellulose waste and harvestings, whichever has the best well-to-wheel assesment.

Five countries have developed bioethanol fuel programs: Brazil, Colombia, China, Sweden and the United States.

Because of the climate conditions, different countries are using different feedstocks. As of 2007, ethanol is almost entirely produced from corn (maize)^[6]. As of 2006, technology does not exist that makes it economically competitive to produce ethanol from the most promising crop: the cellulosic feedstock (see cellulosic ethanol).^[7]

About 5% (in 2003) of the ethanol produced in the world is actually a petroleum product.^[8] It is made by the catalytic hydration of ethylene with sulfuric acid as the catalyst. It can also be obtained via ethylene or acetylene, from calcium carbide, coal, oil gas, and other sources. Two million tons of petroleum-derived ethanol are produced annually. The principal suppliers are plants in the United States, Europe, and South Africa.^[9] Petroleum derived ethanol (synthetic ethanol) is chemically identical to bio-ethanol and can be differentiated only by radiocarbon dating.^[10]

Ethanol can be produced in different ways, using a variety of feedstocks.^[11] Brazil uses sugarcane as primary feedstock. For information on Brazil's method of ethanol production, see ethanol fuel in Brazil. More than 90% of the ethanol produced in the U.S. comes from corn (see Renewable Fuels Association's list of United States ethanol plants).

Crops with higher yields of energy, such as switchgrass and sugar cane, are more effective in producing ethanol than corn^{[citation needed]}. Ethanol can also be produced from sweet sorghum, a dryland crop that uses much less water than sugarcane, does not require a tropical climate and produces food and fodder in addition to fuel. Sweet sorghum cultivar improvement and cultivation is emphasized in India.^[12][13]

[edit] Production Process

The basic steps for large scale production of ethanol are: microbial (yeast) fermentation of sugars, distillation, dehydration (required unless distillation is done well and/or repeatedly), and denaturing (optional). Prior to fermentation, some crops require saccharification or hydrolysis into carbohydrates. Saccharification of cellulose is called cellulolysis (see cellulosic ethanol). Other pre-production steps can be necessary for certain crops like corn which requires refinement into starch and liquification.

[edit] Fermentation

Main article: Ethanol fermentation

Ethanol is produced by microbial fermentation of the sugar. Subsequent processing is the same as for ethanol from corn. Production of ethanol from sugarcane (sugarcane requires a tropical climate to grow productively) returns about 8 units of energy for each unit expended compared to corn which only returns about 1.34 units of fuel energy for each unit of energy expended.^[14]

Carbon dioxide, a potentially harmful greenhouse gas, is emitted during fermentation and combustion. However, this is cancelled out by the greater uptake of carbon dioxide by the plants as they grow to produce the biomass.^[15] When compared to gasoline, depending on the production method, ethanol releases less or even no greenhouse gases.^[16][17]

[edit] Distillation

For the ethanol to be usable as a fuel, water must be removed. Most of the water is removed by distillation, but the purity is limited to 95-96% due to the formation of a low-boiling water-ethanol azeotrope. The 96% m/m (93% v/v) ethanol, 4% m/m (7% v/v) water mixture may be used as a fuel, and it's called hydrated ethyl alcohol fuel (álcool etílico hidratado combustível, or AEHC in Portuguese). In 2006/2007, an estimated 17 billion liters (4.5 billion gallons) of hydrated ethyl alcohol fuel will be produced, to be used in ethanol powered vehicles.^[18]

[edit] Dehydration

Currently, the most widely used purification method is a physical absorption process using molecular sieve for excemple ZEOCHEM Z3-03 (a special 3A molecular sieve for EtOH dehydration. Another method, azeotropic distillation, is achieved by adding the hydrocarbon benzene which also denatures the ethanol (to render it undrinkable for duty purposes). A third method involves use of calcium oxide as a desiccant.

Ethanol is not typically transported by pipeline for three important reasons. Current production levels will not support a dedicated pipeline. The costs of building and maintaining a pipeline from Midwestern United States to either coast are prohibitive. Any water which penetrates the pipeline will be absorbed by the ethanol, diluting the mixture.^[19] Also, ethanol is corrosive to the current pipeline structure. Thus, an entirely new infrastructure is required to allow for long-term transportation and this is not economically viable. Biobutanol can be transported by pipelines.

[edit] Technology

[edit] Ethanol-based engines

Ethanol is most commonly used to power automobiles, though it may be used to power other vehicles, such as farm tractors and airplanes. Ethanol (E100) consumption in an engine is approximately 34% higher than that of gasoline (the energy per volume unit is 34% lower)^[20][21][22]. However, higher compression ratios in an ethanol-only engine allow for increased power output and better fuel economy than would be obtained with the lower compression ratio.^[23] In general, ethanol-powered engines are tuned to give similar power and torque output to gasoline-powered engines. In flexible fuel vehicles, the lower compression ratio requires tunings that give the same output when using either gasoline or hydrated ethanol. For maximum use of ethanol's benefits, a compression ratio of nearly 15:1 should be used^{[citation needed]}, which would render that engine unsuitable for gasoline usage. When ethanol fuel availability increases to the point where high-compression ethanol-only vehicles are practical, the fuel efficiency of such engines should be the same or greater than current gasoline engines.^{[citation needed]}

A 2004 MIT study,^[24] and paper published by the Society of Automotive Engineers,^[25] present the possibility of a definite advance over hybrid electric cars' cost-efficiency by using a high-output turbocharger in combination with continuous dual-fuel direct injection of pure alcohol and pure gasoline in any ratio up to 100% of either. Each fuel is stored separately, probably with a much smaller tank for alcohol, the peak cost-efficiency being calculated to occur at approximately 30% alcohol mix, at maximum engine power. The estimated cost advantage is calculated at 4.6:1 return on the cost of alcohol used, in gasoline costs saved, when the alcohol is used primarily as an octane modifier and is otherwise conserved. With the cost of new equipment factored in the data gives a 3:1 improvement in payback over hybrid, and 4:1 over turbo-diesel (comparing consumer investment yield only). In addition, the danger of water absorption into pre-mixed gasoline and supply issues of multiple mix ratios can be addressed by this system.

[edit] Ethanol fuel mixtures

For more details on this topic, see Common ethanol fuel mixtures.

To avoid engine stall, the fuel must exist as a single phase. The fraction of water that an ethanol-gasoline fuel can contain without phase separation increases with the percent of ethanol. This is shown for 25 C (77 F) in a gasoline-ethanol-water phase diagram, Fig 13 of [3]. This shows, for example, that E30 can have up to about 2% water. If there is more than about 71% ethanol, the remainder can be any proportion of water or gasoline and phase separation will not occur. However, the fuel mileage declines directly with water content. The increased solubility of water with higher ethanol content permits E30 and hydrated ethanol to be put in the same tank since any combination of them always results in a single phase. Somewhat less water is tolerated at lower temperatures. For E10 it is about 0.5% v/v at 70 F and decreases to about 0.23% v/v at -30 F as shown in Figure 1 of [4].

In many countries cars are mandated to run on mixtures of ethanol. Brazil requires cars be suitable for a 25% ethanol blend, and has required various mixtures between 22% and 25% ethanol, as of October 2006 23% is required. The United States allows up to 10% blends, and some states require this (or a smaller amount) in all gasoline sold. Other countries have adopted their own requirements.

Beginning with the model year 1999, an increasing number of vehicles in the world are manufactured with engines which can run on any fuel from 0% ethanol up to 100% ethanol without modification. Many cars and light trucks (a class containing minivans, SUVs and pickup trucks) are designed to be flexible-fuel vehicles (also called dual-fuel vehicles). Their engine systems contain alcohol sensors in the fuel and/or oxygen sensors in the exhaust that provide input to the engine control computer to adjust the fuel injection to achieve stochiometric (no residual fuel or free oxygen in the exhaust) air-to-fuel ratio for any fuel mix. The engine control computer can also adjust (advance) the ignition timing to achieve a higher output without pre-ignition when higher alcohol percentages are present in the fuel being burned.^{[citation needed]}

[edit] Fuel Economy

For 2006 vehicles with flexible fuel engines, fuel economy (measured as miles per gallon -MPG- , or liters per 100 km) is directly proportional to energy content.^[26] Ethanol contains approx. 34% less energy per gallon than gasoline, and therefore will result in a 34% reduction in miles per gallon.^[20][21][22] For E10 (10% ethanol and 90% gasoline), the effect is small (~3%) when compared to conventional gasoline,^[27] and even smaller (1-2%) when compared to oxygenated and reformulated blends.^[28] However, for E85 (85% ethanol), the effect becomes significant. E85 will produce lower mileage than gasoline, and will require more frequent refueling. Actual performance may vary depending on the vehicle. The EPA-rated mileage of current USA flex-fuel vehicles^[29] should be considered when making price comparisons, but it must be noted that E85 is a high performance fuel and should be compared to premium.

However, this analysis applies only to currently designed flex-fuel engines. Ethanol has a much higher octane rating (octane rating of 105 for E85 versus 87 for regular unleaded gasoline). Because currently marketed flex-fuel vehicles must be capable of efficiently burning both gasoline and E85, their engines must be designed to tolerate lower octane rated petroleum-based fuels. Typically this means that the engine must be designed to operate at a lower compression ratio. However, engines that are designed to run on E85 or higher ethanol alone can be designed to better exploit the higher octane rating of the fuel by incorporating higher compression ratios. This results in higher energy efficiencies, though those engines are no longer able to burn conventional gasoline.^{[citation needed]} The higher energy efficiencies of these engines offsets the lower energy content of the alcohol, resulting in approximately the same number of miles per gallon of ethanol fuel as a similar engine designed to run on gasoline. Designing an engine that is capable of running on both E85 and gasoline while changing the compression ratios of the stroke cycle to make maximum use of either fuel is possible, but so far not feasible on a mass-produced scale.

[edit] Controversy

• Ethanol-based fuels are not compatible with some fuel system components.^[30][31]
• Examples of extreme corrosion of ferrous components,^[31] and internal separation of portions of rubber fuel tanks have been observed in some vehicles using ethanol fuels.^{[citation needed]}
• Formation of salt deposits, jelly-like deposits on fuel strainer screens
• Can negatively affect electric fuel pumps by increasing internal wear^[31] and undesirable spark generation.^{[citation needed]}
• Is not compatible with capacitance fuel level gauging indicators and may cause erroneous fuel quantity indications in vehicles that employ that system.^[32]
• Not always compatible with marine craft, especially those that use fiberglass tanks.^[33][34]
• Decreases fuel-economy by 15-30%; this can be avoided using certain modifications that would, however, render the engine inoperable on regular petrol without the addition of an adjustable ECU, or use of multiple ECUs to run the engine on multiple fuel types. ^[35][22]
• Support for biofuels could keep petroleum prices high in the USA (NY Times - [5])

[edit] Environment

[edit] Energy balance

Main article: Ethanol fuel energy balance

One thing that is often considered when evaluating fuels is the energy balance -- that is, how much energy goes in (not all of which could fuel a vehicle) versus how much comes out.

In the case of production from corn in the US the U.S. Department of Energy has concluded that it does, stating in a recent report "the net energy balance of making fuel ethanol from corn grain is 1.34; that is, for every unit of energy that goes into growing corn and turning it into ethanol, we get back about one-third more energy as automotive fuel."^[36] The report also indicates that using a crop with a higher sugar content than corn, such as sugar beets, would result in production with a much higher positive net energy balance.

Some scientists^[37] argue that the energy balance in production from corn is negative when all factors are considered. Professors Tad Patzek and David Pimentel are the best-known academics to make this argument. These arguments have been challenged in a report from the U.S. Department of Energy as being based on decades-old data and not considering recent advances in production or the use of more efficient source crops for ethanol fermentation.^[38] In January 2006, the journal Science published a study from U.C. Berkeley which concluded that ethanol does have a positive net energy balance, but noted that corn-based ethanol has " ... greenhouse gas emissions similar to those of gasoline".^[39]

Note that these reports refer to the use of corn (largely in America where corn is subsidised) to produce bioethanol. In Brazil where sugar cane is used, the yield is higher, and conversion to ethanol is many times more energy efficient than corn.^[14] Additionally, it is hoped that Biotechnology may improve the energy gain of bioethanol.^[40]

It is also important to note that ethanol is not the only product created during production, and the energy content of the by-products must also be considered. Corn is typically 66% starch. The remaining 33% is not fermented and is called distillers grain. This grain is high in fats and proteins, which makes a good animal feed. ^[41]

[edit] Air pollution

Compared with conventional unleaded gasoline, ethanol is a particulate-free burning fuel source that combusts cleanly with oxygen to form carbon dioxide and water. The Clean Air Act requires the addition of oxygenates to reduce carbon monoxide emissions in the United States. The additive MTBE is currently being phased out due to ground water contamination, hence ethanol becomes an attractive alternative additive.

Use of ethanol, produced from current (2006) methods, emits a similar amount of carbon dioxide but less carbon monoxide than gasoline.^[42] If all bioethanol-production energy came from non-fossil sources the use of bioethanol as a fuel would add no greenhouse gas.^[43]

[edit] Manufacture

In 2002 , monitoring of ethanol plants revealed that they released VOCs (volatile organic compounds) at a higher rate than had previously been disclosed.^[44] The Environmental Protection Agency (EPA) subsequently reached settlement with Archer Daniels Midland and Cargill, two of the largest producers of ethanol, to reduce emission of these VOCs. VOCs are produced when fermented corn mash is dried for sale as a supplement for livestock feed. Devices known as thermal oxidizers or catalytic oxidizers can be attached to the plants to burn off the hazardous gases. Smog causing pollutants are also increased by using ethanol fuel in comparison to gasoline.

[edit] Greenhouse gas abatement

Corn ethanol has received much support on environmental grounds primarily because of its role in reducing greenhouse gas emissions. However, the evidence for this claim is mixed.

A recent ten-year forecast of ethanol production by the USDA places 2017 corn ethanol production at 12 billion gallons and growing at only 2% per year. This estimate, together with a parameter publishing in the Proceedings of the National Academy of Sciences (PNAS), indicates that this near-maximum level of ethanol production will abate GHG emissions by 0.13% (~1/10 of 1%) of current US GHG emissions. However, this does not hold for all greenhouse gases. Another study has suggested that replacement of 100% petroleum fuel with E85 (a fuel mixture comprised of 85% ethanol and 15% petroleum) would significantly increase ozone levels, thereby increasing photochemical smog and aggravating medical problems such as asthma.[6][7]

This value reflects increases in corn acreage and the use of 30% of the corn crop for ethanol. It also apparently takes into account anticipated improvements in corn yields and ethanol production. The PNAS value is a 12% reduction in greenhouse gas emission relative to the "net emissions of production and combustion of an energetically equivalent amount of gasoline."

The January 2006 Science article from UC Berkeley's ERG, estimated this parameter to be 13% after reviewing a large number of studies. However, in a correction to that article releases shortly after publication, they reduce the estimated value to 7.4%. None of the other values needed to complete the calculation are controversial.

GREET model maintained by Argonne National Labs in Chicago has produced a series of publications on GHG abatement through ethanol. The latest of the studies is [8]

[edit] Land use

If the world switches from fossil fuels to ethanol, demand and prices for food and feedstocks will increase; indeed, increasing use of ethanol in the United States has already increased corn prices 50% in some parts of rural Mexico.^[45] Large-scale production of agricultural alcohol requires substantial amounts of cultivable land with fertile soils and water. Clearance of new land often involves burning which can result in a very large emission of carbon dioxide. This clearing leads to a loss of wildlife habitat though deforestation, and a decline in soil fertility due to reduction of organic matter.^[46] Growing demand for ethanol fuel, perceived as an environmentally sound alternative to fossil fuel, poses a challenge to the conservation of endangered species in such countries as Brazil, Indonesia and Malaysia. ^[47][48]

[edit] Renewable resource

Ethanol is considered "renewable" because it is primarily the result of conversion of the sun's energy into usable energy. Creation of ethanol starts with photosynthesis causing the feedstocks such as switchgrass, sugar cane, or corn to grow. These feedstocks are processed into ethanol (see production).

The environmental and economic benefits of non-cellulosic ethanol - including corn ethanol - have been heavily critiqued by many, including Brad Ewing of Environmental Economics & Sustainable Development^[49] and Lester R. Brown of Earth Policy Institute.^[50] The main criticism dwells on the increasing costs of corn for food as the demand for ethanol production increases. It remains to be seen

^[vague] if ethanol production can overcome these problems.

Current, first generation processes for the production of ethanol from corn use only a small part of the corn plant: the corn kernels are taken from the corn plant and only the starch, which represents about 50% of the dry kernel mass, is transformed into ethanol. Two types of second generation processes are under development. The first type uses enzymes to convert the plant cellulose into ethanol while the second type uses pyrolysis to convert the whole plant to either a liquid bio-oil or a syngas. Second generation processes can also be used with plants such as grasses, wood or agricultural waste material such as straw.

[edit] Replacement of petroleum

Only about 5% of the fossil energy required to produce bioethanol from corn in the United States is obtained from non-US petroleum.^[51] Current (2006) United States production methods obtain the rest of the fossil energy from domestic coal and natural gas. Even if the energy balance were negative, US production involves mostly domestic fuels such as natural gas and coal so the need for non-US petroleum would be reduced. Developed regions like the United States and Europe, and increasingly the developing nations of Asia, mainly India and China, consume much more petroleum and natural gas than they extract from their territory, becoming dependent upon foreign suppliers as a result.

[edit] Alternatives

A switch to battery electric vehicles combined with solar power and nuclear power may be cheaper and less damaging to the environment.^{[citation needed]} Vehicles directly powered from starches (via hydrogen release and fuel cells), such as corn starch, are also being considered, as their total system efficiency is almost three times higher than converting the starch to ethanol and burning it.[9]

[edit] Research

[edit] Economics

The United States Department of Energy, finds that for every unit of energy put towards ethanol production, 1.3 units are returned.^[52] Another study found that corn-grain ethanol produced 1.25 units of energy per unit put in.^[53] As yields improve or different feedstocks are introduced, ethanol production may become more economically feasible in the US. Currently, research on improving ethanol yields from each unit of corn is underway using biotechnology. By utilizing hybrids designed specifically with higher extractable starch levels, the energy balance is dramatically improved. Also, as long as oil prices remain high, the economical use of other feedstocks, such as cellulose, become viable. By-products such as straw or wood chips can be converted to ethanol. Fast growing species like switchgrass can be grown on land not suitable for other cash crops and yield high levels of ethanol per acre.^{[citation needed]}

[edit] Common crops associated with ethanol production

Note: U.S. motor gasoline consumption is 384.7 million gallons per day or 140 billion gallons per year. ^[54] Total arable land in the U.S. is 460 million acres. ^[55] Figures are for gross ethanol yield; they do not account for fuel used for crop production or ethanol processing.

Crop	Yield (litres ethanol/ha)	Yield (gallons/acre)	Greenhouse-gas savings (% vs. petrol)	Comments
Miscanthus	7,300	780	37 - 73	Low-input perrenial grass. Ethanol production depends on development of cellulosic technology.
Switchgrass	3,100 - 7,600	330 - 810	37 - 73	Low-input perrenial grass. Ethanol production depends on development of cellulosic technology. Breeding efforts underway to increase yields. Higher biomass production possible with mixed species of perennial grasses.
Poplar	3,700 - 6,000	400 - 640	51 - 100	Fast-growing tree. Ethanol production depends on development of cellulosic technology. Completion of genomic sequencing project will aid breeding efforts to increase yields.
Sugar cane	5,300 - 6,500	570 - 700	87 - 96	Ethanol being produced on a commercial scale using existing technology. Newer processing plants burn residues not used for ethanol to generate electricity. Only grows in tropical and subtropical climates.
Sweet sorghum	2,500 - 7,000	270 - 750	No data	Low-input annual grass. Ethanol production possible using existing technology. Grows in tropical and temperate climates, but highest ethanol yield estimates assume multiple crops per year (only possible in tropical climates). Does not store well. [10] [11] [12] [13]
Corn	3,100 - 3,900	330 - 420	10 - 20	High-input annual grass. Used as feedstock for most bioethanol produced in USA. Only kernals can be processed using available technology; development of commercial cellulosic technology would allow stover to be used and increase ethanol yield by 1,100 - 2,000 litres/ha.

Source (except sorghum): Nature 444 (Dec. 7, 2006): 670-654.

[edit] Ethanol from algae

Similar to the research done on biodiesel, making ethanol from algae has the higher potential production efficiency, and unlike more complex organisms, the time it takes to improve energy output for algae is much shorter.

In 2006-2-23, Veridium Corporation announced the technology to convert exhaust carbon dioxide from the fermentation stage of ethanol production facilities back into new ethanol and biodiesel. The bioreactor process is based on a new strain of iron-loving blue-green algae discovered thriving in a hot stream at Yellowstone National Park.^[56]

In 2006-11-14, US Patent Office approved Patent 7135308, a process for the production of ethanol by harvesting starch-accumulating filament-forming or colony-forming algae to form a biomass, initiating cellular decay of the biomass in a dark and anaerobic environment, fermenting the biomass in the presence of a yeast, and the isolating the ethanol produced.^[57]

[edit] Notes

[edit] See also

Alcohol fuel Biobutanol, a gasoline replacement. Bioconversion of biomass to mixed alcohol fuels Biodiesel Biofuel Biomass Butanol from Clostridium acetobutylicum Cellulosic ethanol Corn Ethanol Energy crop Energy development Ethanol fuel in Brazil Ethanol fuel in Australia Ethanol fuel in the United States

Hydrogen fuel Hydrogen vehicle Liquid fuels List of energy topics MTBE Oil crisis P-series fuels Sugarcane Timeline of alcohol fuel Vegetable oil economy Well-to-wheel

[edit] External links

• Fuel Sheet - Ethanol, Biofuels, Oil, and Natural Gas
• Fermentative production of lactic acid from biomass: an overview on process developments and future perspectives
• How E85 Ethanol Flex Fuel Works.
• U.S. Department of Energy: ethanol.
• Federal Aviation Administration: 10/27/06 Special Airworthiness Information Bulletin - Automobile gasoline containing alcohol (Ethanol or Methanol) is not allowed to be used in aircraft in USA.
• National Pollutant Inventory - Ethanol fact sheet
• Clean Fuels Development Coalition [14]
• Henry Ford, Charles Kettering and the Fuel of the Future (history of ethanol) [15]
• Renewable and Appropriate Energy Laboratory's survey article *Ethanol Can Contribute to Energy and Environmental Goals (.pdf format). Published in Science, January 27, 2006
• DrivingEthanol.org
• E85 Ethanol Fuel
• Thermodynamics of the Corn-Ethanol Biofuel Cycle Tad W. Patzek, Department of Civil and Environmental Engineering, University of California, Berkeley
• How far can you drive on a bushel of corn? Crunching the numbers on alternative fuels. Popular Mechanics May, 2006 issue
• Digging into the Ethanol Debate Wall Street Journal Online, June 9, 2006. Summary of the production efficiency debate, with references.
• American Coalition for Ethanol
• Ethanol: Myths and Realities

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