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.
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 tons 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.
In Brazil, flex-fuel vehicles are capable of running on pure ethanol. In the US, tolerance of ethanol depends on the individual vehicle. Anhydrous ethanol can be blended with gasoline in varying quantities to reduce the consumption of petroleum fuels, as well as to reduce air pollution. In Brazil, by law all fuels are at least 25% ethanol.
Ethanol is 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 sustainable energy resource that offers environmental and long-term economic advantages over fossil fuel (gasoline). 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.
Bio-ethanol is 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 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 assessment.
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 and yeast 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.
Glucose (a simple sugar) is created in the plant by photosynthesis.
- 6CO2 + 6H2O + light → C6H12O6 + 6O2
- C6H12O6 → 2C2H6O + 2CO2 + heat
After doubling the ethanol combustion reaction because two molecules of ethanol are produced for each glucose molecule, there are equal numbers of each type of molecule on each side of the equation, and the net reaction for the overall production and consumption of ethanol is just:
- light → heat
The heat of the combustion of ethanol is used to drive the piston in the engine by expanding heated gases. It can be said that sunlight is used to run the engine.
Air pollutants are also produced when ethanol is burned in the atmosphere rather than in pure oxygen. Harmful nitrous oxide gases are produced.
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.
When all 200 American ethanol subsidies are considered, they cost about $7 billion USD per year (equal to roughly $1.90 USD total for each a gallon of ethanol). When the price of one agricultural commodity increases, farmers are motivated to quickly shift finite land and water resources to it, away from traditional food crops.
The U.S. has invested more than $1 billion to spur the growth of a strong, sustainable domestic biofuels industry. This investment promises to reduce America's gas consumption by 20 percent within a decade, promoting a cleaner environment and keeping more of our energy dollars right here at home. We continue to aggressively pursue technologies to create advanced biofuels, and we're working diligently on constructing the biofuels section bridge away from oil. On September 24, John Mizroch, acting assistant secretary for Energy Efficiency and Renewable Energy, U.S. Department of Energy, credited corn-based biofuels production with paving the way for use of "nextgeneration, non-feedstock" sources such as cellulosic energy crops. The oil market continues to fluctuate in dramatic fashion, baffling experts, investors and policy makers. Just last month, gas prices surged in the immediate aftermath of Hurricane Ike, and we all experienced sticker shock at the pumps — with some stations in the U.S. charging as much as $5.09 a gallon. IkeÕs destructive force on the Gulf Coast, which represents about 20% of the nation's oil processing capacity, painfully reinforced the effects of supply disruption as well as the limitations we face by spending $1 billion dollars per day on imported oil.
Ethanol can be produced in different ways, using a variety of feedstocks. Brazil uses sugarcane as primary feedstock. More than 90% of the ethanol produced in the U.S. comes from corn. Crops with higher yields of energy, such as switchgrass and sugar cane, are more effective in producing ethanol than corn. 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.
Ethanol is produced by yeast fermentation of the sugar extracted from sugarcane or sugar beets. 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. Thus sugarcane nets 7/.34 or about 20 times as much energy as corn. (corn produces an additional 0.33 units of energy in the form of high-protein livestock feed).
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% ethanol, 4% 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 2002, almost 5 billion liters (1,3 billion gallons) of hydrated ethyl alcohol fuel were produced in Brazil, to be used in ethanol powered vehicles.
For blending with gasoline, purity of 99.5 to 99.9% is required, depending on temperature, to avoid separation. Currently, the most widely used purification method is a physical absorption process using molecular sieves. Another method, azeotropic distillation, is achieved by adding the hydrocarbon benzene which also denatures the ethanol (so no extra methanol/petrol/etc. is needed to render it undrinkable for duty purposes). However, benzene is a powerful carcinogen and so will probably be illegal for this purpose soon.
POET, the largest ethanol producer in the world according to the Renewable Fuels Association, is an established leader in the biorefining industry through project development, design and construction, research and development, plant management, and marketing. The 20-year old company currently operates 25 production facilities in the United States with one more under construction. The company produces and markets more than 1.47 billion gallons of ethanol annually.
The POET Biorefining facilities located in Glenville, Hanlontown, Preston, Lake Crystal, and Bingham Lake, Minn. in conjunction with the Ethanol Promotion and Information Council (EPIC) and Dave Syverson Ford, joined together to give the Devries family a brand new F150 crew cab flexible-fuel vehicle (FFV) valued at nearly $36,000 on Tuesday, October 7, 2008 during the filming of the show.
All levels of ethanol-infused fuel emit less carbon monoxide and other greenhouse emissions than standard fuel and meet EPA requirements. However, the higher levels of ethanol available through mid-level blends offer more impressive results. Research is finding that using the ideal ethanol blend for a given vehicle dramatically reduces emissions.Not only is ethanol generally less expensive than regular gasoline, but it has been shown to increase the gas mileage many non-flex and flex-fuel vehicles (FFVs) obtain. Since these alternative fuels are compatible with many of today's vehicles, soon consumers will forego a trip to their local car dealership to save money at the pump... using these new mid-level ethanol blends will mean paying less to drive farther.
For vehicles with current design flexible fuel engines, fuel economy (measured as miles per gallon (MPG), or liters per 100km) is directly proportional to energy content. Ethanol contains approx. 34% less energy per gallon than gasoline, and therefore will get 34% fewer miles per gallon. 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. However, for E85 (85% ethanol), the effect becomes significant. E85 will produce approximately 27% lower mileage than gasoline, and will require more frequent refueling. Actual performance may vary depending on the vehicle.
Fuel system design must be compatible with the percent of ethanol permitted. All current production spark ignition vehicles are designed to be compatible with up to 10% ethanol. Pure ethanol reacts with or dissolves certain rubber and plastic materials and must not be used in fuel systems that are not designed for it.
Pure ethanol has a much higher octane rating (116 AKI, 129 RON) than ordinary gasoline (86/87 AKI, 91/92 RON), allowing higher compression ratio and different spark timing for improved performance. To change a pure-gasoline-fueled car into a pure-ethanol-fueled car, larger carburetor jets (about 30-40% larger by area), or fuel injectors are needed. (Methanol requires an even larger increase in area, to roughly 50% larger.)
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. 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. Because of this requirement it is speculated that all cars can run blends up to about 30% (so that manufactures do not have to stock parts incompatible with ethanol next to parts compatible), but it is not known if this is true.