Ethanol fuel is ethyl alcohol, the same type of alcohol found in alcoholic beverages, used as fuel. It is most often used as a motor fuel, mainly as a biofuel additive for gasoline. The first production car running entirely on ethanol was the Fiat 147, introduced in 1978 in Brazil by Fiat. Ethanol is commonly made from biomass such as corn or sugarcane. World ethanol production for transport fuel tripled between 2000 and 2007 from 17×109 liters (4.5×109 U.S. gal; 3.7×109 imp gal) to more than 52×109 liters (1.4×1010 U.S. gal; 1.1×1010 imp gal). From 2007 to 2008, the share of ethanol in global gasoline type fuel use increased from 3.7% to 5.4%. In 2011 worldwide ethanol fuel production reached 8.46×1010 liters (2.23×1010 U.S. gal; 1.86×1010 imp gal) with the United States of America and Brazil being the top producers, accounting for 62.2% and 25% of global production, respectively. US ethanol production reached 57.54×109 liters (1.520×1010 U.S. gal; 1.266×1010 imp gal) in 2017-04.
Ethanol-blended fuel is widely used in Brazil, the United States, and Europe (see also Ethanol fuel by country). Most cars on the road today in the U.S. can run on blends of up to 10% ethanol, and ethanol represented 10% of the U.S. gasoline fuel supply derived from domestic sources in 2011. Furthermore, many cars today are flexible-fuel vehicles able to use 100% ethanol fuel.
Since 1976 the Brazilian government has made it mandatory to blend ethanol with gasoline, and since 2007 the legal blend is around 25% ethanol and 75% gasoline (E25). By December 2011 Brazil had a fleet of 14.8 million flex-fuel automobiles and light trucks and 1.5 million flex-fuel motorcycles that regularly use neat ethanol fuel (known as E100).
Bioethanol is a form of renewable energy that can be produced from agricultural feedstocks. It can be made from very common crops such as hemp, sugarcane, potato, cassava and corn. There has been considerable debate about how useful bioethanol is in replacing gasoline. Concerns about its production and use relate to increased food prices due to the large amount of arable land required for crops, as well as the energy and pollution balance of the whole cycle of ethanol production, especially from corn. Even though this debate has the counterpart of animal agriculture being already a source of massive arable land, therefore making ethanol a lower resource consumer in constrast.  Recent developments with cellulosic ethanol production and commercialization may allay some of these concerns.
Cellulosic ethanol offers promise because cellulose fibers, a major and universal component in plant cells walls, can be used to produce ethanol. According to the International Energy Agency, cellulosic ethanol could allow ethanol fuels to play a much bigger role in the future.
Ethanol fermentation is not 100% selective with side products such as acetic acid and glycols. They are mostly removed during ethanol purification. Fermentation takes place in an aqueous solution. The resulting solution has an ethanol content of around 15%. Ethanol is subsequently isolated and purified by a combination of adsorption and distillation.
During combustion, ethanol reacts with oxygen to produce carbon dioxide, water, and heat:
Starch and cellulose molecules are strings of glucose molecules. It is also possible to generate ethanol out of cellulosic materials. That, however, requires a pretreatment that splits the cellulose into glucose molecules and other sugars that subsequently can be fermented. The resulting product is called cellulosic ethanol, indicating its source.
Most ethanol is produced by fermentation.
About 5% of the ethanol produced in the world in 2003 was actually a petroleum product. 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 short tons (1,786,000 long tons; 1,814,000 t) of petroleum-derived ethanol are produced annually. The principal suppliers are plants in the United States, Europe, and South Africa. Petroleum derived ethanol (synthetic ethanol) is chemically identical to bio-ethanol and can be differentiated only by radiocarbon dating.
Bio-ethanol is usually obtained from the conversion of carbon-based feedstock. Agricultural feedstocks are considered renewable because they get energy from the sun using photosynthesis, provided that all minerals required for growth (such as nitrogen and phosphorus) are returned to the land. Ethanol can be produced from a variety of feedstocks such as sugar cane, bagasse, miscanthus, sugar beet, sorghum, grain, 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 harvesting, whichever has the best well-to-wheel assessment.
An alternative process to produce bio-ethanol from algae is being developed by the company Algenol. Rather than grow algae and then harvest and ferment it, the algae grow in sunlight and produce ethanol directly, which is removed without killing the algae. It is claimed the process can produce 6,000 U.S. gallons per acre (5,000 imperial gallons per acre; 56,000 liters per hectare) per year compared with 400 US gallons per acre (330 imp gal/acre; 3,700 L/ha) for corn production.
Currently, the 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 and yeast fermentation 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.
Although there are various ways ethanol fuel can be produced, the most common way is via fermentation.
The basic steps for large-scale production of ethanol are: microbial (yeast) fermentation of sugars, distillation, dehydration (requirements vary, see Ethanol fuel mixtures, below), and denaturing (optional). Prior to fermentation, some crops require saccharification or hydrolysis of carbohydrates such as cellulose and starch into sugars. Saccharification of cellulose is called cellulolysis (see cellulosic ethanol). Enzymes are used to convert starch into sugar.
Ethanol is produced by microbial fermentation of the sugar. Microbial fermentation currently only works directly with sugars. Two major components of plants, starch and cellulose, are both made of sugars—and can, in principle, be converted to sugars for fermentation. Currently, only the sugar (e.g., sugar cane) and starch (e.g., corn) portions can be economically converted. There is much activity in the area of cellulosic ethanol, where the cellulose part of a plant is broken down to sugars and subsequently converted to ethanol.
For the ethanol to be usable as a fuel, the yeast solids and the majority of the water must be removed. After fermentation, the mash is heated so that the ethanol evaporates. This process, known as distillation, separates the ethanol, but its purity is limited to 95–96% due to the formation of a low-boiling water-ethanol azeotrope with maximum (95.6% m/m (96.5% v/v) ethanol and 4.4% m/m (3.5% v/v) water). This mixture is called hydrous ethanol and can be used as a fuel alone, but unlike anhydrous ethanol, hydrous ethanol is not miscible in all ratios with gasoline, so the water fraction is typically removed in further treatment to burn in combination with gasoline in gasoline engines.
There are three dehydration processes to remove the water from an azeotropic ethanol/water mixture. The first process, used in many early fuel ethanol plants, is called azeotropic distillation and consists of adding benzene or cyclohexane to the mixture. When these components are added to the mixture, it forms a heterogeneous azeotropic mixture in vapor–liquid-liquid equilibrium, which when distilled produces anhydrous ethanol in the column bottom, and a vapor mixture of water, ethanol, and cyclohexane/benzene.
When condensed, this becomes a two-phase liquid mixture. The heavier phase, poor in the entrainer (benzene or cyclohexane), is stripped of the entrainer and recycled to the feed—while the lighter phase, with condensate from the stripping, is recycled to the second column. Another early method, called extractive distillation, consists of adding a ternary component that increases ethanol's relative volatility. When the ternary mixture is distilled, it produces anhydrous ethanol on the top stream of the column.
With increasing attention being paid to saving energy, many methods have been proposed that avoid distillation altogether for dehydration. Of these methods, a third method has emerged and has been adopted by the majority of modern ethanol plants. This new process uses molecular sieves to remove water from fuel ethanol. In this process, ethanol vapor under pressure passes through a bed of molecular sieve beads. The bead's pores are sized to allow adsorption of water while excluding ethanol. After a period of time, the bed is regenerated under vacuum or in the flow of inert atmosphere (e.g. N2) to remove the adsorbed water. Two beds are often used so that one is available to adsorb water while the other is being regenerated. This dehydration technology can account for energy saving of 3,000 btus/gallon (840 kJ/L) compared to earlier azeotropic distillation.
Recent research has demonstrated that complete dehydration prior to blending with gasoline is not always necessary. Instead, the azeotropic mixture can be blended directly with gasoline so that liquid-liquid phase equilibrium can assist in the elimination of water. A two-stage counter-current setup of mixer-settler tanks can achieve complete recovery of ethanol into the fuel phase, with minimal energy consumption.
Ethanol is hygroscopic, meaning it absorbs water vapor directly from the atmosphere. Because absorbed water dilutes the fuel value of the ethanol and may cause phase separation of ethanol-gasoline blends (which causes engine stall), containers of ethanol fuels must be kept tightly sealed. This high miscibility with water means that ethanol cannot be efficiently shipped through modern pipelines, like liquid hydrocarbons, over long distances.
The fraction of water that an ethanol-gasoline fuel can contain without phase separation increases with the percentage of ethanol. For example, 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 does not occur. The fuel mileage declines with increased 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 21° C and decreases to about 0.23% v/v at −34° C .
While biodiesel production systems have been marketed to home and business users for many years, commercialized ethanol production systems designed for end-consumer use have lagged in the marketplace. In 2008, two different companies announced home-scale ethanol production systems. The AFS125 Advanced Fuel System from Allard Research and Development is capable of producing both ethanol and biodiesel in one machine, while the E-100 MicroFueler from E-Fuel Corporation is dedicated to ethanol only.
Ethanol contains approx. 34% less energy per unit volume than gasoline, and therefore in theory, burning pure ethanol in a vehicle reduces miles per US gallon 34%, given the same fuel economy, compared to burning pure gasoline. However, since ethanol has a higher octane rating, the engine can be made more efficient by raising its compression ratio. Using a variable geometry or twin scroll turbocharger, the compression ratio can be optimized for the fuel, making fuel economy almost constant for any blend.
For E10 (10% ethanol and 90% gasoline), the effect is small (~3%) when compared to conventional gasoline, and even smaller (1–2%) when compared to oxygenated and reformulated blends. For E85 (85% ethanol), the effect becomes significant. E85 produces lower mileage than gasoline, and requires more frequent refueling. Actual performance may vary depending on the vehicle. Based on EPA tests for all 2006 E85 models, the average fuel economy for E85 vehicles was 25.56% lower than unleaded gasoline. The EPA-rated mileage of current United States flex-fuel vehicles should be considered when making price comparisons, but E85 is a high performance fuel, with an octane rating of about 94–96, and should be compared to premium.
High ethanol blends present a problem to achieve enough vapor pressure for the fuel to evaporate and spark the ignition during cold weather (since ethanol tends to increase fuel enthalpy of vaporization). When vapor pressure is below 45 kPa starting a cold engine becomes difficult. To avoid this problem at temperatures below 11 °C (52 °F), and to reduce ethanol higher emissions during cold weather, both the US and the European markets adopted E85 as the maximum blend to be used in their flexible fuel vehicles, and they are optimized to run at such a blend. At places with harsh cold weather, the ethanol blend in the US has a seasonal reduction to E70 for these very cold regions, though it is still sold as E85. At places where temperatures fall below −12 °C (10 °F) during the winter, it is recommended to install an engine heater system, both for gasoline and E85 vehicles. Sweden has a similar seasonal reduction, but the ethanol content in the blend is reduced to E75 during the winter months.
Brazilian flex fuel vehicles can operate with ethanol mixtures up to E100, which is hydrous ethanol (with up to 4% water), which causes vapor pressure to drop faster as compared to E85 vehicles. As a result, Brazilian flex vehicles are built with a small secondary gasoline reservoir located near the engine. During a cold start pure gasoline is injected to avoid starting problems at low temperatures. This provision is particularly necessary for users of Brazil's southern and central regions, where temperatures normally drop below 15 °C (59 °F) during the winter. An improved flex engine generation was launched in 2009 that eliminates the need for the secondary gas storage tank. In March 2009 Volkswagen do Brasil launched the Polo E-Flex, the first Brazilian flex fuel model without an auxiliary tank for cold start.
In many countries cars are mandated to run on mixtures of ethanol. All Brazilian light-duty vehicles are built to operate for an ethanol blend of up to 25% (E25), and since 1993 a federal law requires mixtures between 22% and 25% ethanol, with 25% required as of mid July 2011. In the United States all light-duty vehicles are built to operate normally with an ethanol blend of 10% (E10). At the end of 2010 over 90 percent of all gasoline sold in the U.S. was blended with ethanol. In January 2011 the U.S. Environmental Protection Agency (EPA) issued a waiver to authorize up to 15% of ethanol blended with gasoline (E15) to be sold only for cars and light pickup trucks with a model year of 2001 or newer.
Beginning with the model year 1999, an increasing number of vehicles in the world are manufactured with engines that 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 using ethanol blends up to 85% (E85) in North America and Europe, and up to 100% (E100) in Brazil. In older model years, their engine systems contained 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. In newer models, the alcohol sensors have been removed, with the computer using only oxygen and airflow sensor feedback to estimate alcohol content. The engine control computer can also adjust (advance) the ignition timing to achieve a higher output without pre-ignition when it predicts that higher alcohol percentages are present in the fuel being burned. This method is backed up by advanced knock sensors – used in most high performance gasoline engines regardless of whether they are designed to use ethanol or not – that detect pre-ignition and detonation.
Since 1989 there have also been ethanol engines based on the diesel principle operating in Sweden. They are used primarily in city buses, but also in distribution trucks and waste collectors. The engines, made by Scania, have a modified compression ratio, and the fuel (known as ED95) used is a mix of 93.6% ethanol and 3.6% ignition improver, and 2.8% denaturants. The ignition improver makes it possible for the fuel to ignite in the diesel combustion cycle. It is then also possible to use the energy efficiency of the diesel principle with ethanol. These engines have been used in the United Kingdom by Reading Buses but the use of bioethanol fuel is now being phased out.
A 2004 MIT study and an earlier paper published by the Society of Automotive Engineers identified a method to exploit the characteristics of fuel ethanol substantially more efficiently than mixing it with gasoline. The method presents the possibility of leveraging the use of alcohol to achieve definite improvement over the cost-effectiveness of hybrid electric. The improvement consists of using dual-fuel direct-injection of pure alcohol (or the azeotrope or E85) and gasoline, in any ratio up to 100% of either, in a turbocharged, high compression-ratio, small-displacement engine having performance similar to an engine having twice the displacement. Each fuel is carried separately, with a much smaller tank for alcohol. The high-compression (for higher efficiency) engine runs on ordinary gasoline under low-power cruise conditions. Alcohol is directly injected into the cylinders (and the gasoline injection simultaneously reduced) only when necessary to suppress ‘knock’ such as when significantly accelerating. Direct cylinder injection raises the already high octane rating of ethanol up to an effective 130. The calculated over-all reduction of gasoline use and CO2 emission is 30%. The consumer cost payback time shows a 4:1 improvement over turbo-diesel and a 5:1 improvement over hybrid. The problems of water absorption into pre-mixed gasoline (causing phase separation), supply issues of multiple mix ratios and cold-weather starting are also avoided.
In a 2008 study, complex engine controls and increased exhaust gas recirculation allowed a compression ratio of 19.5 with fuels ranging from neat ethanol to E50. Thermal efficiency up to approximately that for a diesel was achieved. This would result in the fuel economy of a neat ethanol vehicle to be about the same as one burning gasoline.
In June 2016, Nissan announced plans to develop fuel cell vehicles powered by ethanol rather than hydrogen, the fuel of choice by the other car manufacturers that have developed and commercialized fuel cell vehicles, such as the Hyundai Tucson FCEV, Toyota Mirai, and Honda FCX Clarity. The main advantage of this technical approach is that it would be cheaper and easier to deploy the fueling infrastructure than setting up the one required to deliver hydrogen at high pressures, as each hydrogen fueling station cost US$1 million to US$2 million to build.
Nissan plans to create a technology that uses liquid ethanol fuel as a source to generate hydrogen within the vehicle itself. The technology uses heat to reform ethanol into hydrogen to feed what is known as a solid oxide fuel cell (SOFC). The fuel cell generates electricity to supply power to the electric motor driving the wheels, through a battery that handles peak power demands and stores regenerated energy. The vehicle would include a tank for a blend of water and ethanol, which is fed into an onboard reformer that splits it into pure hydrogen and carbon dioxide. According to Nissan, the liquid fuel could be an ethanol-water blend at a 55:45 ratio. Nissan expects to commercialize its technology by 2020.
The world's top ethanol fuel producers in 2011 were the United States with 13.9×109 U.S. gallons (5.3×1010 liters; 1.16×1010 imperial gallons) and Brazil with 5.6×109 U.S. gallons (2.1×1010 liters; 4.7×109 imperial gallons), accounting together for 87.1% of world production of 22.36×109 U.S. gallons (8.46×1010 liters; 1.862×1010 imperial gallons). Strong incentives, coupled with other industry development initiatives, are giving rise to fledgling ethanol industries in countries such as Germany, Spain, France, Sweden, China, Thailand, Canada, Colombia, India, Australia, and some Central American countries.
|Annual fuel ethanol production by country |
Top 10 countries/regional blocks
(Millions of U.S. liquid gallons per year)
|United States||Corn ethanol||1.3|
|United States||Cellulosic ethanol†||2–36††|
† experimental, not in commercial production
†† depending on production method
All biomass goes through at least some of these steps: it needs to be grown, collected, dried, fermented, distilled, and burned. All of these steps require resources and an infrastructure. The total amount of energy input into the process compared to the energy released by burning the resulting ethanol fuel is known as the energy balance (or "energy returned on energy invested"). Figures compiled in a 2007 report by National Geographic Magazine point to modest results for corn ethanol produced in the US: one unit of fossil-fuel energy is required to create 1.3 energy units from the resulting ethanol. The energy balance for sugarcane ethanol produced in Brazil is more favorable, with one unit of fossil-fuel energy required to create 8 from the ethanol. Energy balance estimates are not easily produced, thus numerous such reports have been generated that are contradictory. For instance, a separate survey reports that production of ethanol from sugarcane, which requires a tropical climate to grow productively, returns from 8 to 9 units of energy for each unit expended, as compared to corn, which only returns about 1.34 units of fuel energy for each unit of energy expended. A 2006 University of California Berkeley study, after analyzing six separate studies, concluded that producing ethanol from corn uses much less petroleum than producing gasoline.
Carbon dioxide, a greenhouse gas, is emitted during fermentation and combustion. This is canceled out by the greater uptake of carbon dioxide by the plants as they grow to produce the biomass. When compared to gasoline, depending on the production method, ethanol releases less greenhouse gases.
Compared with conventional unleaded gasoline, ethanol is a particulate-free burning fuel source that combusts with oxygen to form carbon dioxide, carbon monoxide, water and aldehydes. 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. Current production methods include air pollution from the manufacturer of macronutrient fertilizers such as ammonia.
A study by atmospheric scientists at Stanford University found that E85 fuel would increase the risk of air pollution deaths relative to gasoline by 9% in Los Angeles, US: a very large, urban, car-based metropolis that is a worst-case scenario. Ozone levels are significantly increased, thereby increasing photochemical smog and aggravating medical problems such as asthma.
Brazil burns significant amounts of ethanol biofuel. Gas chromatograph studies were performed of ambient air in São Paulo, Brazil, and compared to Osaka, Japan, which does not burn ethanol fuel. Atmospheric Formaldehyde was 160% higher in Brazil, and Acetaldehyde was 260% higher.
The calculation of exactly how much carbon dioxide is produced in the manufacture of bioethanol is a complex and inexact process, and is highly dependent on the method by which the ethanol is produced and the assumptions made in the calculation. A calculation should include:
Such a calculation may or may not consider the following effects:
The January 2006 Science article from UC Berkeley's ERG, estimated reduction from corn ethanol in GHG to be 13% after reviewing a large number of studies. In a correction to that article released shortly after publication, they reduce the estimated value to 7.4%. A National Geographic Magazine overview article (2007) puts the figures at 22% less CO2 emissions in production and use for corn ethanol compared to gasoline and a 56% reduction for cane ethanol. Carmaker Ford reports a 70% reduction in CO2 emissions with bioethanol compared to petrol for one of their flexible-fuel vehicles.
An additional complication is that production requires tilling new soil which produces a one-off release of GHG that it can take decades or centuries of production reductions in GHG emissions to equalize. As an example, converting grass lands to corn production for ethanol takes about a century of annual savings to make up for the GHG released from the initial tilling.
Large-scale farming is necessary to produce agricultural alcohol and this requires substantial amounts of cultivated land. University of Minnesota researchers report that if all corn grown in the U.S. were used to make ethanol it would displace 12% of current U.S. gasoline consumption. There are claims that land for ethanol production is acquired through deforestation, while others have observed that areas currently supporting forests are usually not suitable for growing crops. In any case, farming may involve a decline in soil fertility due to reduction of organic matter, a decrease in water availability and quality, an increase in the use of pesticides and fertilizers, and potential dislocation of local communities. New technology enables farmers and processors to increasingly produce the same output using less inputs.
Cellulosic ethanol production is a new approach that may alleviate land use and related concerns. Cellulosic ethanol can be produced from any plant material, potentially doubling yields, in an effort to minimize conflict between food needs vs. fuel needs. Instead of utilizing only the starch by-products from grinding wheat and other crops, cellulosic ethanol production maximizes the use of all plant materials, including gluten. This approach would have a smaller carbon footprint because the amount of energy-intensive fertilisers and fungicides remain the same for higher output of usable material. The technology for producing cellulosic ethanol is currently in the commercialization stage.
Converting biomass to electricity for charging electric vehicles may be a more "climate-friendly" transportation option than using biomass to produce ethanol fuel, according to an analysis published in Science in May 2009 Researchers continue to search for more cost-effective developments in both cellulosic ethanol and advanced vehicle batteries.
For each billion ethanol-equivalent gallons of fuel produced and combusted in the US, the combined climate-change and health costs are $469 million for gasoline, $472–952 million for corn ethanol depending on biorefinery heat source (natural gas, corn stover, or coal) and technology, but only $123–208 million for cellulosic ethanol depending on feedstock (prairie biomass, Miscanthus, corn stover, or switchgrass).
As ethanol 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. 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 unit area.
|Crop||Annual yield (Liters/hectare, US gal/acre)||Greenhouse-gas savings
|Sugar cane||6800–8000 L/ha,
|87%–96%||Long-season annual grass. Used as feedstock for most bioethanol produced in Brazil. Newer processing plants burn residues not used for ethanol to generate electricity. Grows only in tropical and subtropical climates.|
|37%–73%||Low-input perennial grass. Ethanol production depends on development of cellulosic technology.|
|37%–73%||Low-input perennial 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.|
|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.|
|Sweet sorghum||2500–7000 L/ha,
|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 (possible only in tropical climates). Does not store well.|
|10%–20%||High-input annual grass. Used as feedstock for most bioethanol produced in USA. Only kernels 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 those indicated): Nature 444 (7 December 2006): 673–676.|
[a] – Savings of GHG emissions assuming no land use change (using existing crop lands).
One rationale given for extensive ethanol production in the U.S. is its benefit to energy security, by shifting the need for some foreign-produced oil to domestically produced energy sources. Production of ethanol requires significant energy, but current U.S. production derives most of that energy from coal, natural gas and other sources, rather than oil. Because 66% of oil consumed in the U.S. is imported, compared to a net surplus of coal and just 16% of natural gas (figures from 2006), the displacement of oil-based fuels to ethanol produces a net shift from foreign to domestic U.S. energy sources.
According to a 2008 analysis by Iowa State University, the growth in US ethanol production has caused retail gasoline prices to be US $0.29 to US $0.40 per gallon lower than would otherwise have been the case.
The American Le Mans Series sports car championship introduced E10 in the 2007 season to replace pure gasoline. In the 2008 season, E85 was allowed in the GT class and teams began switching to it.
Australia's V8 Supercar championship uses Shell E85 for its racing fuel.
Stock Car Brasil Championship runs on neat ethanol, E100.
Project Gaia is a U.S. non-governmental, non-profit organization involved in the creation of a commercially viable household market for alcohol-based fuels in Ethiopia and other countries in the developing world. The project considers alcohol fuels to be a solution to fuel shortages, environmental damage, and public health issues caused by traditional cooking in the developing world. Targeting poor and marginalized communities that face health issues from cooking over polluting fires, Gaia currently works in Ethiopia, Nigeria, Brazil, Haiti, and Madagascar, and is in the planning stage of projects in several other countries.
Ethanol research focuses on alternative sources, novel catalysts and production processes. INEOS produced ethanol from vegetative material and wood waste. The bacterium E.coli when genetically engineered with cow rumen genes and enzymes can produce ethanol from corn stover. Other potential feedstocks are municipal waste, recycled products, rice hulls, sugarcane bagasse, wood chips, switchgrass and carbon dioxide.
BioEthanol for Sustainable Transport (BEST) was a four-year project financially supported by the European Union for promoting the introduction and market penetration of bioethanol as a vehicle fuel, and the introduction and wider use of flexible-fuel vehicles and ethanol-powered vehicles on the world market. The project began in January 2006 and continued until the end of 2009, and had nine participating regions or cities in Europe, Brazil, and China.Biofuel in Australia
Biofuel is fuel that is produced from organic matter (biomass), including plant materials and animal waste. It is considered a renewable source of energy that can assist in reducing carbon emissions. The two main types of biofuel currently being produced in Australia are biodiesel and bioethanol, used as replacements for diesel and petrol (gasoline) respectively. As of 2017 Australia is a relatively small producer of biofuels, accounting for 0.2% of world bioethanol production and 0.1% of world biodiesel production.In 2016-17, biofuels contributed only 0.5% of the total liquid and gaseous transport fuel energy mix in Australia.Total commercial biofuel production for 2018 is estimated at 290 million liters (ML): 250ML of ethanol and 40ML of biodiesel.This article mainly deals with biofuels for personal vehicles, though cooking, heating and electricity generation can also use biofuel. Historically in Australia cooking and home heating have been accomplished by burning wood, a biofuel. 909,000 households in Australia still used firewood as their main heating method in 2005, with a further 300,000 using firewood occasionally.Biofuel in Sweden
Biofuels are renewable fuels that are produced by living organisms (biomass). Biofuels can be solid, gaseous or liquid, which comes in two forms: ethanol and biodiesel and often replace fossil fuels. Many countries now use biofuels as energy sources, including Sweden. Sweden has one of the highest usages of biofuel in all of Europe, at 32%, primarily due to the wide-spread commitment to E85, bioheating and bioelectricity.
Sweden's energy usage is divided into three sectors: housing and services, industry, and transport and is used in three different ways: to produce heating, electricity and vehicle fuels. In 2014 Sweden has used 555 TWh of energy, 130 of which came from biofuels.Increased biofuel usage is the main reason why Sweden has managed to decrease greenhouse gas emissions by 25% between 1990 and 2014.Common ethanol fuel mixtures
Several common ethanol fuel mixtures are in use around the world. The use of pure hydrous or anhydrous ethanol in internal combustion engines (ICEs) is only possible if the engines are designed or modified for that purpose, and used only in automobiles, light-duty trucks and motorcycles. Anhydrous ethanol can be blended with gasoline (petrol) for use in gasoline engines, but with high ethanol content only after minor engine modifications.
Ethanol fuel mixtures have "E" numbers which describe the percentage of ethanol fuel in the mixture by volume, for example, E85 is 85% anhydrous ethanol and 15% gasoline. Low-ethanol blends, from E5 to E25, although internationally the most common use of the term refers to the E10 blend.
Blends of E10 or less are used in more than 20 countries around the world, led by the United States, where ethanol represented 10% of the U.S. gasoline fuel supply in 2011. Blends from E20 to E25 have been used in Brazil since the late 1970s. E85 is commonly used in the U.S. and Europe for flexible-fuel vehicles. Hydrous ethanol or E100 is used in Brazilian neat ethanol vehicles and flex-fuel light vehicles and hydrous E15 called hE15 for modern petrol cars in the Netherlands.Corn ethanol
Corn ethanol is ethanol produced from corn biomass and is the main source of ethanol fuel in the United States. Corn ethanol is produced by ethanol fermentation and distillation. Corn ethanol results in lower greenhouse gas emissions than gasoline and is fully biodegradable, but environmental concerns ; approximately 40.5% of the U.S. corn croplands are used for ethanol production.Cosan
Cosan is a public listed company, a Brazilian conglomerate producer of bioethanol, sugar and energy . The company operates in Brazil, Argentina, Uruguay, Paraguay, Bolivia and United Kingdom.David Blume
David Blume is an American permaculture teacher and entrepreneur. He has been an especially prolific public speaker, and is a vocal advocate for production of ethanol fuel, especially at local, small and medium scales.Direct-ethanol fuel cell
Direct-ethanol fuel cells or DEFCs are a category of fuel cell in which ethanol is fed directly into the cell. They have been used as a model to investigate a range of fuel cell concepts including the use of PEM.E85
E85 is an abbreviation typically referring to an ethanol fuel blend of 85% ethanol fuel and 15% gasoline or other hydrocarbon by volume.
In the United States, the exact ratio of fuel ethanol to hydrocarbon may vary according to ASTM 5798 that specifies the allowable ethanol content in E85 as ranging from 51% to 83%. This is due to the lower heating value of neat ethanol making it difficult to crank engines in relatively cold climates without pre-heating air intake, faster cranking, or mixing varying fractions of gasoline according to climate. Cold cranking in cold climates is the primary reason ethanol fuel is blended with any gasoline fraction.
In Brazil, ethanol fuel is neat at the pumps, hence flexible-fuel vehicles (FFV) including trucks, tractors, motorbikes and mopeds run on E100. The 85% fraction is commonly sold at pumps worldwide (outside the US), and when specifically supplied or sold as E85 is always 85% ethanol (at pumps or in barrel). Having a guaranteed ethanol fraction obviates the need for a vehicle system to calculate best engine tune according to maximise performance and economy.
In countries like Australia where E85 is always 85% ethanol (and pump fuel with varying fractions is called "flex fuel"), performance motoring enthusiasts and motor racing clubs/championships use E85 extensively (without the need for any FFV certification). Use of alcohol (ethanol and methanol) in motor racing history parallels the invention of the automobile, favoured due to inherent combustion characteristics such as high thermal efficiency, raised torque and with some advanced engines, better specific fuel consumption. In the United States, government subsidies of ethanol in general and E85 in particular have encouraged a growing infrastructure for the retail sale of E85, especially in corn growing states in the Midwest.Ethanol fuel energy balance
In order to create ethanol, all biomass needs to go through some of these steps: it needs to be grown, collected, dried, fermented, and burned. All of these steps require resources and an infrastructure. The ratio of the energy released by burning the resulting ethanol fuel to the energy used in the process, is known as the ethanol fuel energy balance (sometimes called "Net energy gain") and studied as part of the wider field of energy economics. Figures compiled in a 2007 National Geographic Magazine article point to modest results for corn ethanol produced in the US: 1 unit of energy input equals 1.3 energy units of corn ethanol energy. The energy balance for sugarcane ethanol produced in Brazil is much more favorable, 1 to 8. Over the years, however, many reports have been produced with contradicting energy balance estimates. A 2006 University of California Berkeley study, after analyzing six separate studies, concluded that producing ethanol from corn uses marginally less petroleum than producing gasoline.Ethanol fuel in Brazil
Brazil is the world's second largest producer of ethanol fuel. Brazil and the United States led the industrial production of ethanol fuel in 2014, together accounting for 83.4 percent of the world's production. In 2014 Brazil produced 23.4 billion liters (6.19 billion U.S. liquid gallons), representing 25.2 percent of the world's total ethanol used as fuel.Brazil is considered to have the world's first sustainable biofuels economy and the biofuel industry leader, a policy model for other countries; and its sugarcane ethanol "the most successful alternative fuel to date." However, some authors consider that the successful Brazilian ethanol model is sustainable only in Brazil due to its advanced agri-industrial technology and its enormous amount of arable land available; while according to other authors it is a solution only for some countries in the tropical zone of Latin America, the Caribbean, and Africa.Brazil’s 40-year-old ethanol fuel program is based on the most efficient agricultural technology for sugarcane cultivation in the world, uses modern equipment and cheap sugar cane as feedstock, the residual cane-waste (bagasse) is used to produce heat and power, which results in a very competitive price and also in a high energy balance (output energy/input energy), which varies from 8.3 for average conditions to 10.2 for best practice production. In 2010, the U.S. EPA designated Brazilian sugarcane ethanol as an advanced biofuel due to its 61% reduction of total life cycle greenhouse gas emissions, including direct indirect land use change emissions.
There are no longer any light vehicles in Brazil running on pure gasoline. Since 1976 the government made it mandatory to blend anhydrous ethanol with gasoline, fluctuating between 10% to 22%. and requiring just a minor adjustment on regular gasoline engines. In 1993 the mandatory blend was fixed by law at 22% anhydrous ethanol (E22) by volume in the entire country, but with leeway to the Executive to set different percentages of ethanol within pre-established boundaries. In 2003 these limits were set at a minimum of 20% and a maximum of 25%. Since July 1, 2007 the mandatory blend is 25% of anhydrous ethanol and 75% gasoline or E25 blend. The lower limit was reduced to 18% in April 2011 due to recurring ethanol supply shortages and high prices that take place between harvest seasons. By mid March 2015 the government raised temporarily the ethanol blend in regular gasoline from 25% to 27%.The Brazilian car manufacturing industry developed flexible-fuel vehicles that can run on any proportion of gasoline (E20-E25 blend) and hydrous ethanol (E100). Introduced in the market in 2003, flex vehicles became a commercial success, dominating the passenger vehicle market with a 94% market share of all new cars and light vehicles sold in 2013. By mid-2010 there were 70 flex models available in the market, and as of December 2013, a total of 15 car manufacturers produce flex-fuel engines, dominating all light vehicle segments except sports cars, off-road vehicles and minivans. The cumulative production of flex-fuel cars and light commercial vehicles reached the milestone of 10 million vehicles in March 2010, and the 20 million-unit milestone was reached in June 2013. As of June 2015, flex-fuel light-duty vehicle cumulative sales totaled 25.5 million units, and production of flex motorcycles totaled 4 million in March 2015.The success of "flex" vehicles, together with the mandatory E25 blend throughout the country, allowed ethanol fuel consumption in the country to achieve a 50% market share of the gasoline-powered fleet in February 2008. In terms of energy equivalent, sugarcane ethanol represented 17.6% of the country's total energy consumption by the transport sector in 2008.Ethanol fuel in Hawaii
Ethanol is not presently manufactured in Hawaii. Between April 2, 2006 and June 26, 2015, Hawaii State law (Hawaii Revised Statutes Chapter 486J-10 and Hawaii Administrative Rules Chapter 15-35) required all gasoline sold for vehicles to contain 10% ethanol (E-10). In 2015, the requirement was repealed (Act 161, Session Laws of Hawaii 2015). In 2010, E-85 (85% ethanol) became available on a military base for flex fuel use. About 45,000,000 US gallons (170,000,000 l; 37,000,000 imp gal) of ethanol were imported from the Caribbean or continental US in 2009.Ethanol fuel in the Philippines
The Philippines Biofuels Act 2006 requires oil companies to use biofuels in all "liquid fuels for motors and engines sold in the Philippines." All gasoline sold in the country must contain at least 5 percent ethanol by February 2009, and by 2011, the mandated blend can go up to 10 percent. The new law is expected to bring a number of benefits to the country:
"Commercial production of ethanol from sugarcane, cassava or sorghum will help the island nation diversify its fuel portfolio and help to ensure its energy security. It could also generate employment, particularly in rural regions, as investors put up biofuel crop plantations and processing plants. Also, the shift to these plant-based fuels for transportation will help reduce pollution."
Four feedstocks—sugarcane, corn, cassava and sweet sorghum—were initially identified for ethanol production, but sugarcane is expected to be the predominant source of ethanol. The Philippines is a sugar-producing country, and sugarcane is grown mainly in the islands of Negros, Luzon, Panay and Mindanao. Despite growing demand for sugar, there are still an estimated 90,750 hectares (224,000 acres) of sugarcane available that can be used for ethanol production, and high-yielding varieties of sugarcane are available.Ethanol fuel in the United States
The United States became the world's largest producer of ethanol fuel in 2005. The U.S. produced 13.9 billion U.S. liquid gallons (52.6 billion liters) of ethanol fuel in 2011, an increase from 13.2 billion U.S. liquid gallons (49.2 billion liters) in 2010, and up
from 1.63 billion gallons in 2000. Brazil and U.S. production accounted for 87.1% of global production in 2011. In the U.S, ethanol fuel is mainly used as an oxygenate in gasoline in the form of low-level blends up to 10 percent, and to an increasing extent, as E85 fuel for flex-fuel vehicles.The ethanol market share in the U.S. gasoline supply grew by volume from just over 1 percent in 2000 to more than 3 percent in 2006 to 10 percent in 2011. Domestic production capacity increased fifteen times after 1990, from 900 million US gallons to 1.63 billion US gal in 2000, to 13.5 billion US gallons in 2010. The Renewable Fuels Association reported 209 ethanol distilleries in operation located in 29 states in 2011, and 140 under construction or expansion as of December 2011, that upon completion, would bring U.S. total installed capacity to 15.0 billion US gallons. Most expansion projects are aimed to update the refinery's technology to improve ethanol production,
energy efficiency, and the quality of the livestock feed they produce.By 2011 most cars on U.S. roads could run on blends of up to 10% ethanol(E10), and manufacturers had begun producing vehicles designed for much higher percentages. However, the fuel systems of cars, trucks, and motorcycles sold before the ethanol mandate may suffer substantial damage from the use of 10% ethanol blends. Flexible-fuel cars, trucks, and minivans use gasoline/ethanol blends ranging from pure gasoline up to 85% ethanol (E85). By early 2013 there were around 11 million E85-capable vehicles on U.S. roads. Regular use of E85 is low due to lack of fueling infrastructure, but is common in the Midwest. In January 2011 the U.S. Environmental Protection Agency (EPA) granted a waiver to allow up to 15% of ethanol blended with gasoline (E15) to be sold only for cars and light pickup trucks with a model year of 2001 or later. The EPA waiver authorizes, but does not require stations to offer E15. Like the limitations suffered by sales of E85, commercialization of E15 is constrained by the lack of infrastructure as most fuel stations do not have enough pumps to offer the new E15 blend, few existing pumps are certified to dispense E15, and no dedicated tanks are readily available to store E15.Ethanol production was expected to continue to grow over the next several years, since the Energy Independence and Security Act of 2007 required 36 billion US gallons of renewable fuel use by 2022. The target for ethanol production from cellulosic feedstocks was 16 billion US gallons a year. The corn ethanol target was 15 billion US gallons by 2015. Ethanol industries provided jobs in agriculture, construction, operations and maintenance, mostly in rural communities.In early 2009 the industry experienced financial stress due to the effects of the economic crisis of 2008. Motorists drove less, gasoline prices dropped sharply, capacity rose and less financing was available.Historically most U.S. ethanol has come from corn and the required electricity for many distilleries came mainly from coal. Debate ensued about ethanol's sustainability. The primary issues related to the large amount of arable land required for crops and ethanol production's impact on grain supply, indirect land use change (ILUC) effects, as well as issues regarding its energy balance and carbon intensity considering its full life cycle. Recent developments with cellulosic ethanol production and commercialization may allay some of these concerns.Flexible-fuel vehicle
A flexible-fuel vehicle (FFV) or dual-fuel vehicle (colloquially called a flex-fuel vehicle) is an alternative fuel vehicle with an internal combustion engine designed to run on more than one fuel, usually gasoline blended with either ethanol or methanol fuel, and both fuels are stored in the same common tank. Modern flex-fuel engines are capable of burning any proportion of the resulting blend in the combustion chamber as fuel injection and spark timing are adjusted automatically according to the actual blend detected by a fuel composition sensor. Flex-fuel vehicles are distinguished from bi-fuel vehicles, where two fuels are stored in separate tanks and the engine runs on one fuel at a time, for example, compressed natural gas (CNG), liquefied petroleum gas (LPG), or hydrogen.
The most common commercially available FFV in the world market is the ethanol flexible-fuel vehicle, with about 60 million automobiles, motorcycles and light duty trucks manufactured and sold worldwide by March 2018, and concentrated in four markets, Brazil (30.5 million light-duty vehicles and over 6 million motorcycles), the United States (20 million by the end of 2016), Canada (1.6 million by 2014), and Europe, led by Sweden (243,100). In addition to flex-fuel vehicles running with ethanol, in Europe and the US, mainly in California, there have been successful test programs with methanol flex-fuel vehicles, known as M85 flex-fuel vehicles. There have been also successful tests using P-series fuels with E85 flex fuel vehicles, but as of June 2008, this fuel is not yet available to the general public. These successful tests with P-series fuels were conducted on Ford Taurus and Dodge Caravan flexible-fuel vehicles.Though technology exists to allow ethanol FFVs to run on any mixture of gasoline and ethanol, from pure gasoline up to 100% ethanol (E100), North American and European flex-fuel vehicles are optimized to run on E85, a blend of 85% anhydrous ethanol fuel with 15% gasoline. This upper limit in the ethanol content is set to reduce ethanol emissions at low temperatures and to avoid cold starting problems during cold weather, at temperatures lower than 11 °C (52 °F). The alcohol content is reduced during the winter in regions where temperatures fall below 0 °C (32 °F) to a winter blend of E70 in the U.S. or to E75 in Sweden from November until March. Brazilian flex fuel vehicles are optimized to run on any mix of E20-E25 gasoline and up to 100% hydrous ethanol fuel (E100). The Brazilian flex vehicles are built-in with a small gasoline reservoir for cold starting the engine when temperatures drop below 15 °C (59 °F). An improved flex motor generation was launched in 2009 which eliminated the need for the secondary gas tank.History of ethanol fuel in Brazil
The history of ethanol fuel in Brazil dates from the 1970s and relates to Brazil's sugarcane-based ethanol fuel program, which allowed the country to become the world's second largest producer of ethanol, and the world's largest exporter. Several important political and technological developments led Brazil to become the world leader in the sustainable use of bioethanol, and a policy model for other developing countries in the tropical zone of Latin America, the Caribbean, and Africa. Government policies and technological advances also allowed the country to achieve a landmark in ethanol consumption, when ethanol retail sales surpassed 50% market share of the gasoline-powered vehicle fleet in early 2008. This level of ethanol fuel consumption had only been reached in Brazil once before, at the peak of the Pró-Álcool Program near the end of the 1980s.Renewable energy in Brazil
As of 2018, renewable energy accounted for 79% of the domestically produced electricity used in Brazil. Brazil relies on hydroelectricity for 65% of its electricity , and the Brazilian government plans to expand the share of biomass and wind energy (currently 6%) as alternatives. Wind energy has the greatest potential in Brazil during the dry season, so it is considered a hedge against low rainfall and the geographical spread of existing hydroelectric resources.
In January 2015, a drought in Brazil that cut water to the country's hydroelectric dams prompted severe energy shortages. This crisis ravaged the country's economy and led to electricity rationing.Brazil held its first wind-only energy auction in 2009, in a move to diversify its energy portfolio. Foreign companies scrambled to take part.
The bidding lead to the construction of 2 gigawatts (GW) of wind production with an investment of about $6 billion over the following two years.
Brazil's technical potential for wind energy is 143 GW due to the country's blustery 7,400 kilometres (4,600 mi) kilometres coastline where most projects are based.
The Brazilian Wind Energy Association and the government have set a goal of achieving 20 GW of wind energy capacity by 2020 from the current 5 GW (2014). The industry hopes the auction will help kick-start the wind-energy sector, which already accounts for 70% of the total in all of Latin America.According to Brazil's Energy Master-plan 2016-2026 (PDE2016-2026), Brazil is expected to install 18,5GW of additional wind power generation, 84% in the North-East and 14% in the South. Brazil started focusing on developing alternative sources of energy, mainly sugarcane ethanol, after the oil shocks in the 1970s.
Brazil's large sugarcane farms helped the development.
In 1985, 91% of cars produced that year ran on sugarcane ethanol.
The success of flexible-fuel vehicles, introduced in 2003, together with the mandatory E25 blend throughout the country, have allowed ethanol fuel consumption in the country to achieve a 50% market share of the gasoline-powered fleet by February 2008.Top Alcohol
Top Alcohol refers to two different classes in professional drag racing: Top Alcohol Dragster and the Top Alcohol Funny Car. Commonly known as "alky" cars, both are akin in design to the premier Top Fuel classes, but less powerful (about 3,500 bhp (2,600 kW; 3,500 PS)). In Top Alcohol Dragster, the cars used supercharged ("blown") engines, burning alcohol (methanol). Top Alcohol Funny Cars look similar to Fuel Funny Cars, with about half the power of a Top Fuel car. In this class only alcohol cars with three-speed transmissions are allowed.Top Alcohol was devised in the 1970s as a replacement for the Top Gas class, which was similar but burned gasoline. Initially, alcohol dragsters competed against Funny Cars in a category known as Pro Comp, before a separate class, Top Alcohol Funny Car, was created in the 1980s. It was within IHRA's version of this class use of ethanol fuel was pioneered with great success by Mark Thomas, an Ohio farmer who became a five-time champion within that organization. Despite this, ethanol has failed to capture the imagination of racers; the majority opt for more traditional methanol. Today both Top Alcohol Dragster and Top Alcohol Funny Car compete in NHRA drag racing. They are classed not as professional but as sportsman within the USA but in Europe they are classed as a professional category within the FIA Drag Racing Championships. Top Alcohol classes also compete outside of North America, most notably in Australia and Europe. In Europe they are called Top Methanol Dragsters and Top Methanol Funny Cars.Vinasse
Vinasse is a byproduct of the sugar or ethanol industry. Sugarcane, or Sugar beet is processed to produce crystalline sugar, pulp and molasses. The latter are further processed by fermentation to ethanol, ascorbic acid or other products. Juice sugarcane can also be processed directly by ethanol fermentation. After the removal of the desired product (alcohol, ascorbic acid, etc.) the remaining material is called vinasse. Vinasse is sold after a partial dehydration and usually has a viscosity comparable to molasses. Commercially offered vinasse comes either from sugar cane and is called cane-vinasse or from sugar beet and is called beet-vinasse. Vinasse produced from sugar cane is also called dunder.In the process of distillation of the alcohol and as a result of the heating in the distillation process, in the pulp of the beet reactions of condensation and predominantly molecular ruptures take place. This causes a high fulvic acid concentration in this byproduct. One use of vinasse is in thermophilic digesters. In Brazil thermophilic digester is a source of biogas using pure and hot vinasse as the source of production of methane. In the past, vinasse was a problem in production of ethanol, but vinasse is also a good fertilizer (at least for some time) and a source of methane that can be used to generate heat or electricity. Moreover, other uses of vinasse involving also the formulation of nutritive solutions for hydroponics, formulation of culture media for plant tissue culture and culture media for algal growth.Vinasse composition
Treated vinasse is originated by a decantation and filtration process.