Bioethanol
From Biocrawler, the free encyclopedia.
Ethanol can be used as fuel for automobiles either alone or as an additive to gasoline.
Ethanol can be blended with gasoline in varying quantities to reduce the consumption of petroleum fuels, as well as to reduce air pollution. The resulting fuel is known as gasohol. Two common mixtures are E10 and E85 which contain 10% and 85% ethanol, respectively.
Ethanol is also increasingly used as an oxygenate additive for standard gasoline, as a replacement for methyl t-butyl ether (MTBE), the latter chemical being responsible for considerable groundwater and soil contamination. Ethanol can also be used to power fuel cells.
Ethanol derived from crops (bio-ethanol) is a potentially sustainable energy resource that may offer environmental and long-term economic advantages over fossil fuel. It is readily obtained from the sugar or starch in crops such as maize and sugarcane. However, current bio-ethanol production methods use a significant amount of energy compared to the energy value of the produced fuel. For this reason, it is not feasible to replace current fossil fuel consumption entirely by bio-ethanol. <ref>In 2005, United States gasoline consumption was about 150 billion gallons per year. [1] (http://auto.howstuffworks.com/question417.htm) An acre of corn can produce approximately 200 gallons (gasoline equivalent) per year. The United States would have to place roughly 750 million acres of corn into production to fully meet this demand. For comparison, this is nearly double the total area currently used for all crops in the US (430 million acres) and about one third of the total land area of the United States (2.3 billion acres). [2] (http://www.ers.usda.gov/StateFacts/US.htm) There are currently about 80 million acres of corn planted in the United States.
For bio-ethanol to be sustainable, an even greater acreage would have to be put into production to replace our fossil fuel dependence. Assuming a required input energy of 100 (gasoline equivalent) gallons per acre, bio-ethanol production achieves only a net 100 gallons per acre, rather than the 200 gallon per acre figure used above. A sustainable bio-ethanol program for the United States would require 1.5 billion acres; more than half the land area of the entire country. </ref>
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Sources
Ethanol for industrial use is often synthesized from petroleum feedstock, typically by the catalytic hydration of ethylene with sulfuric acid as the catalyst. This process is cheaper than the traditional fermentation associated with alcoholic beverages. It can also be obtained via ethene or acetylene, from calcium carbide, coal, oil gas, and other sources.
Three countries have developed significant bioethanol fuel programs: Brazil and Colombia (from sugarcane), and the United States (from maize). Ethanol can be produced from a variety of other crops, such as sugar beet, sorghum, switchgrass, barley, hemp, kenaf, potatoes, cassava and sunflower, as well as many types of cellulose waste. This large-scale production of agricultural alcohol for fuel requires substantial amounts of cultivable land with fertile soils and water. It is less attractive for densely occupied and industrialized regions like Western Europe, or for regions where desire for increased farmland puts pressure on important natural resources like rainforests. Smaller quantities of fuel alcohol can be made from the stalks, wastes, clippings, straw, corn cobs, and other farm waste now used for fertilizer, animal feed, or electric power plant fuels. In fact, using a mix of, say, corn and corn plant stalks/waste would mean that industrialised countries like the US could get all the ethanol they need without cultivating any more farmland specifically for ethanol feedstockCitation needed (however more land would still be needed to replace the lost plant wastes, used by many farmers as a cheap and clean source of fertiliser and animal feed.)
Production
Ethanol can be produced either by petrochemical feedstock or by fermentation [3] (http://www.nrel.gov/biomass/proj_biochemical_conversion.html).
Ethanol produced by fermentation results in a solution of ethanol in water. For the ethanol to be usable as a fuel, water must be removed. The oldest method is simple distillation, but the purity is limited to 95-96 % due to the formation of a low-boiling water-ethanol azeotrope. It is not possible to obtain ethanol of purity > 96 % by distilling any more dilute solution.
For blending with gasoline, purities of 99.5 to 99.9% are required, depending on temperature, to avoid separation. Currently, the most widely used purification method is a physical absorption process using molecular sieves.
In the past, when farmers distilled their own ethanol, they sometimes used radiators as part of the still. The radiators often contained lead, which would get into the ethanol. Lead entered the air during the burning of contaminated fuel, possibly leading to neural damage. However this was a relatively minor source of lead since at the time tetraethyl lead was used as a mainstream gasoline additive. Today, ethanol for fuel use is produced almost exclusively from purpose-built plants, avoiding any lead presence.
Ethanol fuel blends
Generally, the higher the ethanol component of a gasohol blend, the lower its suitability for standard car engines. Pure ethanol reacts with or dissolves certain rubber and plastic materials and must not be used in unmodified engines. Additionally, pure ethanol has a much higher octane rating (116 AKI, 129 RON) than ordinary gasoline (86/87 AKI, 91/92 RON), requiring changes to the compression ratio or spark timing to obtain maximum benefit. [4] (http://www.ethanol.org/autoracing.html) To change a pure-gasoline-fueled car into a pure-ethanol-fueled car, larger carburetor jets (about 30-40% larger by area) are needed. (Methanol requires an even larger increase in area, to roughly 50% larger.) Ethanol engines also need a cold-starting system to ensure sufficient vaporization for temperatures below 13 °C (55 °F) to maximize combustion and minimize uncombusted nonvaporized ethanol. On the other hand, if 10 to 30% ethanol is mixed with gasoline, no engine modification is typically needed. Many modern cars can run on these mixtures very reliably.
E10 gasohol, the most common variant, has been introduced nationwide in Denmark, and in 1989, Brazil produced 12 billion liters of fuel ethanol from sugar cane, which was used to power 9.2 million cars. It is also commonly available in the Midwestern United States and is the only type of gasoline allowed to be sold in the state of Minnesota. Similar blends include E5 and E7. These concentrations are generally safe for recent, unmodified automobile engines, and some regions and municipalities mandate that the locally-sold fuels contain limited amounts of ethanol. One way to measure alternative fuels in the US is the "gasoline-equivalent gallons" (GEG). In 2002, the U.S. used as fuel an amount of ethanol equal to 137 petajoules (PJ), the energy of 1.13 billion US gallons (4,280,000 m³) of gasoline. This was less than 1% of the total fuel used that year.[5] (http://www.eia.doe.gov/cneaf/alternate/page/datatables/table10.html)
The term "E85" is used for a mixture of 15% (by volume) gasoline and 85% ethanol. This mixture has an octane rating of about 105. This is down significantly from pure ethanol but still much higher than normal gasoline. The addition of a small amount of gasoline helps a conventional engine start when using this fuel under cold conditions. E85 does not always contain exactly 85% ethanol. In winter, especially in colder climates, additional gasoline is added (to facilitate cold start). E85 has traditionally been similar in cost to gasoline, but with the large oil price rises of 2005 it has become common to see E85 sold for as much as $0.70 less per gallon than gasoline, making it highly attractive to the small but growing number of motorists with cars capable of burning it.
Beginning with the model year 1999, an increasing number of vehicles in the world are manufactured with engines which can run on any gasoline from 0% ethanol up to 85% ethanol without modification. Many light trucks (a class containing minivans, SUVs and pickup trucks) are designed to be dual fuel or flexible fuel vehicles, since they can automatically detect the type of fuel and change the engine's behavior, principally air-to-fuel ratio and ignition timing to compensate for the different octane levels of the fuel in the engine cylinders.
Local production and use of ethanol
Ethanol fuel in Brazil
Today, Brazil is the largest producer and consumer of ethanol fuel in the world. Since the 1980s, Brazil has developed an extensive domestic ethanol fuel industry upon sugarcane production and refining. Brazil produces approximately 4 billion gallons of ethanol per year. Ethanol factories in Brazil maintain a positive (+34%) energy balance by burning the non-sugar waste from sugarcane.
Ethanol fuel in Colombia
Colombia’s fuel ethanol program got a start in 2002 when the government passed a law which mandates oxygen enrichment of gasoline. This was initially done to reduce carbon monoxide emissions from cars. Later regulations exempted biomass-derived ethanol from some taxes on gasoline, thus making ethanol cheaper than gasoline. This trend was reinforced when petroleum prices went up starting in 2004 and with it the interest in renewable fuels (at least for cars). In Colombia the price of both gasoline and ethanol are controlled by the government. Complementing this ethanol program is a biodiesel program to oxygenate diesel fuel and produce a renewable fuel from vegetable oil.
Initially all the interest in ethanol production has come from the existing sugar industry, as it is relatively easy to add an ethanol back end to a sugar mill and the energy usage is similar to that needed to produce sugar. The government aims to gradually convert the nation’s auto fuel supplies to a mixture of 10 percent ethanol and 90 percent gasoline. Ethanol plants are being encouraged by tax breaks. There has been interest in ethanol plants from yuca (cassava) and from new sugar cane plantations, but producing inexpensive carbohydrates has not been achieved.
The first fuel ethanol plant in Colombia began production in October 2005, with output of 300,000 liters a day in the Cauca department. By March 2006 five plants, all in the Cauca Valley, are operational with a combined capacity of 1,050,000 liters per day or 357 million liters per year. In the Cauca Valley of Colombia sugar is harvested year round and the new distilleries have very high availability. The total investment in these plants is $100 million. By 2007, Colombia hopes to have a capacity of 2,500,000 liters per day, which is the requirement for adding 10% ethanol to the gasoline. The ethanol fuel produced is currently used in the main cities close to the Cauca Valley, such as Bogota, Cali, and Pereira. There is not enough production for the rest of the country.
Ethanol fuel in the United States
One criticism of ethanol usage in the United States is its availability. Roughly 600 gas stations, out of a total of 200,000 carry E85 pumps. If a wide adoption strategy were to be implemented, far greater availability would have to come to fruition. Another aspect of its availability is that it is currently only available in the relatively sparsely populated midwest, where the ethanol is refined. As of April 27, 2006 in the US, there are 4485.9 million gallons per year capacity for ethanol production with capacity of 2229.5 million gallons per year under construction. [6] (http://www.ethanolrfa.org/industry/locations/)
Regulations and subsidies
In Brazil, Colombia and the United States, the use of ethanol from sugar cane and grain as car fuel has been heavily promoted by government programs. Some individual U.S. states in the corn belt began subsidizing ethanol from corn (maize) after the Arab oil embargo of 1973. The Energy Tax Act of 1978 authorized an excise tax exemption for biofuels, chiefly gasohol. The excise tax exemption alone has been estimated as worth US$1.4 billion per year. Another U.S. federal program guaranteed loans for the construction of ethanol plants, and in 1986 the U.S. even gave ethanol producers free corn. Colombia's ethanol program was started by a law which would exempt biomass-derived ethanol from some taxes on gasoline.
In August 2005, President Bush signed a comprehensive energy bill which included a requirement to increase the production of ethanol and biodiesel from 4 to 7.5 billion US gallons (15,000,000 to 28,000,000 m³) within the next ten years. It is expected that in the short term the majority of this increase will come from ethanol produced from corn.
Directive 2003/30/EC of the European Parliament promotes the replacement of fossil fuels by biofuels: amongst them bio-ethanol to be blended into petrol. The United Kingdom has adopted a national policy of encouraging the use of biofuels including ethanol[7] (http://www.odpm.gov.uk/index.asp?id=1143908).
Ethanol and hydrogen
Hydrogen is being analyzed as an alternative fuel, creating a hydrogen economy. Because hydrogen in its gaseous state takes up a very large volume when compared to other fuels, logistics becomes a difficult problem. One possible solution is to use ethanol to transport the hydrogen, then liberate the hydrogen from its associated carbon in a hydrogen reformer and feed the hydrogen into a fuel cell. Alternatively, some fuel cells (DEFC Direct-ethanol fuel cell) can be directly fed by ethanol or methanol. As of 2005, fuel cells are able to process methanol more efficiently than ethanol.
In early 2004, researchers at the University of Minnesota announced the invention of a simple ethanol reactor that would feed ethanol through a stack of catalysts, and output hydrogen suitable for a fuel cell. The device uses a rhodium-cerium catalyst for the initial reaction, which occurs at a temperature of about 700 °C. This initial reaction mixes ethanol, water vapor, and oxygen and produces good quantities of hydrogen. Unfortunately, it also results in the formation of carbon monoxide, a substance that "chokes" most fuel cells and must be passed through another catalyst to be converted into carbon dioxide. (The odorless, colorless, and tasteless carbon monoxide is also a significant toxic hazard if it escapes through the fuel cell into the exhaust, or if the conduits between the catalytic sections leak.) The ultimate products of the simple device are roughly 50% hydrogen gas and 30% nitrogen, with the remaining 20% mostly composed of carbon dioxide. Both the nitrogen and carbon dioxide are fairly inert when the mixture is pumped into an appropriate fuel cell. The carbon dioxide is released back into the atmosphere, where it can be reabsorbed by plant life. No net carbon dioxide is released, though it could be argued that while it is in the atmosphere, it does act as a greenhouse gas.
EEI has developed a new method for producing butanol from biomass. This process involves the use of two separate micro-organisms in sequence to minimize production of acetone and ethanol byproducts. Interestingly, this process produces significant amounts of hydrogen as well as butanol. [8] (http://www.butanol.com)[9] (http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=/netahtml/search-adv.htm&r=1&f=G&l=50&d=ptxt&S1=(butanol.TTL.+AND+'environmental+energy')&OS=TTL/butanol+AND+)
Energy balance
For ethanol to contribute significantly to transportation fuel needs, it would need to have a positive net energy balance. To evaluate the net energy of ethanol four variables must be considered: the amount of energy contained in the final ethanol product, the amount of energy directly consumed to make the ethanol (such as the diesel used in tractors), the quality of the resulting ethanol compared to the quality of refined gasoline and the energy indirectly consumed (in order to make the ethanol processing plant, etc). Although a topic of debate, some research that ignores energy quality suggests it takes as much or more fossil fuel energy (in the forms of diesel, natural gas and coal) to create an equivalent amount of energy in the form of ethanol. In other words, the energy needed to run the tractors, produce the fertilizer, process the ethanol, and the energy associated with the wear and tear on all of the equipment used in the process (known as fixed asset depreciation to economists) may be more than the energy derived from burning ethanol. Two important flaws are cited in response to that argument: (1) the energy quality is ignored, the economic effects of which are large. Principal economic effects of energy quality comparison are the cleanup costs of soil contamination stemming from gasoline releases to the environment and medical costs from air pollution resulting from refining and burning gasoline. and (2) the inclusion of development of ethanol plants instills a bias against that product based strictly upon the pre-existence of gasoline refining capacity. The real decision should be based upon the long term economic and social returns. The first counter-argument, however, is contested. Burning a gallon of cleaner ethanol is still pointless if it implicitly requires burning 2 gallons of dirty gasoline to create that ethanol in the first place.
Much of the current academic discussion regarding ethanol currently revolves around issues of system borders. This refers to how complete of a picture is drawn for energy inputs. There is debate on whether to include items like the energy required to feed the people tending and processing the corn, to erect and repair farm fences, even the amount of energy a tractor represents. In addition, there is no consensus on what sort of value to give the rest of the corn (such as the stalk), commonly known as the 'coproduct.' Some studies leave it on the field to protect the soil from erosion and to add organic matter, while others take and burn the coproduct to power the ethanol plant, but do not address the resulting soil erosion (which would require energy in the form of fertilizer to replace). Depending on the ethanol study you read, net energy returns vary from .7-1.5 units of ethanol per unit of fossil fuel energy consumed. For comparison, that same one unit of fossil fuel invested in oil and gas extraction (in the lower 48 States) will yield 15 units of gasoline, a yield an order of magnitude better than current ethanol production technologies, ignoring the energy quality arguments above. [10] (http://www.bu.edu/cees/people/faculty/cutler/articles/Net_%20Energy_US_Oil_gas.pdf).
Extraction is not the same as production. Each gallon of extracted oil is a gallon of depleted oil. To fairly compare the energy balance of gas production to ethanol production, one must also calculate the energy required to produce oil from the atmosphere and feed it back into the earth, a process that would make gasoline production fractionally efficient compared to ethanol. It is suggested that an energy balance of 200%, or two units of ethanol per unit of fossil fuel invested, is needed before ethanol mass-production will become economically feasible.
Switching to a system with negative fuel energy balance could increase the consumption of non-alcohol fuels. Such a system may only be worth considering as a way of exploiting and converting non-liquid fuels through the production of ethanol for transportation use, such as coal, natural gas, or biofuel from crop residues. (Indeed, many U.S. proposals assume the use of natural gas for distillation and fertilizer production.) However, many of the expected environmental and sustainability advantages of alcohol fuels may not be realized in a system with negative fuel balance. Before conclusions are drawn on the energy fuel balance calculations it would be necessary to factor in the annual medical costs associated with air pollution from gasoline and soil remediation costs of the gasoline alternative; combined the annual costs of these penalties to gasoline are on the order of one to ten billion dollars per annum in the U.S. and potentially treble that value worldwide.
Even a positive but small energy balance would be problematic: if the net fuel energy balance is 50%, then, in order to eliminate the use of non-alcohol fuels, it would be necessary to produce two units of alcohol for each unit of alcohol delivered to the consumer.
In this regard, geography is the decisive factor. In tropical regions with abundant water and land resources, such as Brazil and Colombia, the viability of production of ethanol from sugarcane is no longer in question; in fact, the burning of sugarcane residues (bagasse) generates far more energy than needed to operate the ethanol plants, and many of them are now selling electric energy to the utilities. However, while there may be a positive net energy return at the moment, recent research suggests that the sugercane plantations are not sustainable in the long run, as they are depleting the soil of nutrients and carbon matter (Reijnders 2004).
The picture is different for other regions, such as most of the United States, where the climate is too cool for sugarcane. In the U.S., agricultural ethanol is generally obtained from grain, chiefly corn.
Environmental effects
Air pollution
Compared with conventional unleaded gasoline, ethanol has fewer carbon monoxide emissions, but larger emissions of volatile organic compounds such as formaldehyde and acetaldehyde. [11] (http://www.dep.state.pa.us/DEP/DEPUTATE/POLLPREV/AFIG/emissions_062596.htm) 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 so that ethanol remains the only alternative additive, despite evidence that it is not effective in improving air quality. [12] (http://www.rppi.org/ethanolmandates.html)
Bio-ethanol production contributes to additional air pollution beyond that from the combustion of ethanol fuel. While growing crops removes carbon from the atmosphere, one study shows that the total corn-for-ethanol cycle releases 40% more carbon dioxide into the atmosphere than use of the equivalent amount of gasoline. [13] (http://petroleum.berkeley.edu/papers/patzek/CRPS416-Patzek-Web.pdf)
All of these studies focus on the use of the product in an internal combustion engine, neglecting the production of the fuel prior to use in an engine. The production of ethanol takes approxamitely 167 percent of the energy it produces in an engine, whereas the production of gasoline takes 80 percent of the energy it takes to produce. This, in addition to the pollutants generated in the refining process (effectively zero when refining gasoline to substantive quantities in ethanol production), also means that ethanol is more expensive to produce than gasoline. [14] (http://www.mnsu.edu/news/read.php?id=old-1115755777)
In considering the potential for pollution reduction with ethanol, however, it is equally important to consider the potential for environmental contamination stemming from the manufacture of ethanol. In 2002, monitoring of ethanol plants revealed that they released volatile organic compounds at a much higher rate than had previously been disclosed [15] (http://www.cbsnews.com/stories/2002/05/03/tech/main508006.shtml). The Environmental Protection Agency (EPA) subsequently reached settlement with Archer Daniels Midland and Cargill, two of the largest producers of ethanol, to reduce emissions. However, the fact that these plants emitted carcinogens (such as formaldehyde) and other pollutants at a high volume must be considered as a serious concern.
Effects of ethanol on agriculture
There is evidence that rainforests are being cleared to make land available for growing crops for bioalcohol.[16] (http://www.dft.gov.uk/stellent/groups/dft_roads/documents/page/dft_roads_028393-04.hcsp) This has been aggravated by an increase in the demand for biofuels in Europe.
More generally, environmentalists have a long list of objections to many modern farming practices, especially those practices most useful for making bioethanol more competitive ("factory farming"). If more third-world land were to be converted to agriculture to feed ethanol fuel demand, there is the possibility of trading today's automotive pollution for tomorrow's farm pollution. Ethanol could become a pollution export scenario, in which poor, ethanol-producing countries suffer the deforestation, extinction pressures, fertilizer runoff, etc. of heavy agricultural expansion, while the rich, heavily motorized ethanol consumers reap the environmental rewards.
Renewable resource
If bio-ethanol production can be made at least neutral in net energy consumed, then it can play an important role in converting energy from difficult to consume sources (e.g., natural gas, solar electric, wind power) to more convenient ones (ethanol).
However, using current farming and production methods, bio-ethanol (from corn) cannot be considered a viable renewable energy source because it either has a net negative energy balance or it has too small of a positive energy balance to be a practical replacement for fossil fuels.
Economics
Some economists have argued that using bioalcohol as a petroleum substitute is economically infeasible because the energy required to grow the corn and other crops used as fuel is greater than the amount ultimately produced. They argue that government programs that mandate the use of bioalcohol are agricultural subsidies.
Another way of stating this is that the price of corn-derived ethanol may be too high to compete with gasoline even though the net energy balance at the pump is positive (assuming corn derived ethanol and oil at $70-$75). This is strictly considering corn as the feedstock. 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 dramtically improved. Also, as long as oil prices remain high, the economical use of other feedstocks, such as cellulose become viable. Bi-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.
Dependency on foreign oil
A somewhat related argument is that developed regions like the United States and Europe, and increasingly the developing nations of Asia, mainly India and China, consume much more fossil fuels than they can extract from their territory, therefore becoming dependent upon foreign suppliers as a result. Even if the energy balance is negative, US production involves mostly domestic fuels such as natural gas and coal, so the impact on oil importation is still positive.
See also
- List of energy topics
- biodiesel
- biofuel
- biomass
- butanol from Clostridium acetobutylicum
- MTBE
- sugarcane
- liquid fuels
- oil crisis
- Timeline of Alcohol Fuel
- cellulosic ethanol
- Landless Movement (Movimento dos Sem-Terra) under Politics of Brazil
External links
- Ethanol Facts (http://www.ethanolfacts.com), provided by the National Corn Growers Association.
- U.S. Department of Energy: Biomass Program (http://www.eere.energy.gov/biomass/).
- U.S. Department of Energy: Clean Cities (http://www.eere.energy.gov/cleancities/). Includes info on flexible fuel vehicles.
- Zen Alcohol Stoves (http://zenstoves.net/Stoves.htm). Includes info on alcohol fuels for stove use.
- Ethanol as Fuel (http://freeenergynews.com/Directory/Ethanol/) - Documentation that Ethanol consumes more energy to make than is derived from its burning.
- American Coalition for Ethanol: www.ethanol.org. Advocacy group.
- Methanol Institute: [17] (http://www.methanol.org/altfuel/press/pr970521.html) Article about methanol in race cars.
- National Pollutant Inventory - Ethanol fact sheet (http://www.npi.gov.au/database/substance-info/profiles/35.html)
- How To Run Your Car On Alcohol Fuel (http://terrasol.home.igc.org/alky/alky.htm) - A 1982 book, now published online, with information on converting gasoline cars to use ethanol.
- Farm Industry News: Hydrogen Corn Economy (http://farmindustrynews.com/news/hydrogen-corn-economy/). Article about converting ethanol to hydrogen.
- Making Alcohol Fuel (http://journeytoforever.org/biofuel_library/ethanol_motherearth/me1.html) - A website that covers the use and production of ethanol as a fuel.
- the Ethanol Source (http://www.theEthanolSource,) - A website that covers use, production and other information on ethanol as a fuel.
- Renewable Fuel Association [18] (http://www.ethanolrfa.org)
- National Ethanol Vehicle Coalition [19] (http://e85fuel.com) Shows locations of E85 fuel pumps in the USA
- Clean Fuels Development Coalition [20] (http://cleanfuelsdc.org)
- Set America Free Coalition (http://www.setamericafree.org)
- Pimentel: Ethanol - Inefficient Fuel (http://whatsnextnetwork.com/technology/index.php/2005/07/08/unfortunately_ethanol_and_biodiesel_may)
- Debunking Pimentel: Ethanol - Efficient Fuel (http://www.ncga.com/ethanol/debunking/index.htm)
- Ethanol Fuel News and Discussion (http://www.thewatt.com/modules.php?name=News&new_topic=7,)
- Henry Ford, Charles Kettering and the Fuel of the Future (history of ethanol) [21] (http://www.radford.edu/~wkovarik/papers/fuel.html)
- "How to Beat the High Cost of Gasoline. Forever!" (http://money.cnn.com/magazines/fortune/fortune_archive/2006/02/06/8367959/index.htm?cnn=yes), Fortune (January 24, 2006)
- Renewable and Appropriate Energy Laboratory's (http://rael.berkeley.edu/) survey article Ethanol Can Contribute to Energy and Environmental Goals (http://rael.berkeley.edu/EBAMM/FarrellEthanolScience012706.pdf) (.pdf format). Published in Science, January 27, 2006
- David Cohn, "Ethanol's New Cheap Trick (http://www.seedmagazine.com/news/2006/03/ethanols_new_cheap_trick.php)", Seed Magazine (http://www.seedmagazine.com)" March 31, 2006
- Flexible Fuel Vehicle List [22] (http://www.sugre.info/tools.phtml?id=515#)
- Ethanol in Brazil [23] (http://www.nytimes.com/2006/04/10/world/americas/10brazil.html?_r=1&oref=slogin)
- ICM Incorporated - Ethanol Plant Design (http://www.icminc.com/)
- DrivingEthanol.org (http://www.drivingethanol.org/)
- Cellulose Ethanol Production (http://www.sunopta.com/bioprocess/default.htm)
- Ethanol forums (http://www.ethanolforums.com)
- E85 Blog (http://www.e85blog.com)
- FuturePundit.com - Is Corn Ethanol A Good Energy Source? (http://www.futurepundit.com/archives/002722.html)
- Thermodynamics of the Corn-Ethanol Biofuel Cycle (http://petroleum.berkeley.edu/papers/patzek/CRPS416-Patzek-Web.pdf) Tad W. Patzek, Department of Civil and Environmental Engineering, University of California, Berkeley
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