Biofuels are transportation fuels made from organic materials. These fuels are usually blended with petroleum, but they can also be used in their pure form. Ethanol and biodiesel are the leading forms of biofuel, and, compared to the fossil fuels they replace, are cleaner-burning and produce fewer air pollutants or carbon emissions.
Ethanol is an alcohol fuel made from the sugars found in a wide range of feedstocks. Most of the ethanol used today is distilled from starch and sugar based feedstocks, including corn, sugarcane, and potatoes. Three commercial plants are opening in 2014 to produce cellulosic ethanol, which is made from the fibrous or cellulosic material in plants.
Nearly all gasoline sold now in the U.S. contains some ethanol. About 99% of the fuel ethanol consumed in the U.S. is added to gasoline in mixtures of up to 10% ethanol and 90% gasoline. Any gasoline powered engine in the U.S. can use E-10 (gasoline with 10% ethanol), but only specific types of vehicles can use mixtures with greater than 10% ethanol. The U.S. Environmental Protection Agency (EPA) ruled in October 2010 that cars and light trucks of model year 2007 and after are capable of running on a 15% ethanol blend. Some other vehicles can utilize even higher blends.
Biodiesel is a fuel made from vegetable oils, fats, greases, and advanced feedstocks like algae, and it can be used in any standard diesel engine. Fuel grade biodiesel is produced to strict industry specifications and is safe, biodegradable, and produces lower levels of most air pollutants than petroleum-based fuels. Most of the biodiesel used in the United States is made from soybean oil, as well as from waste animal fat and grease.
Advanced biofuels (like cellulosic ethanol and algae-based biodiesel) are generally derived from non-edible feedstocks such as forestry and agricultural residues, perennial grasses, algae, and other “energy crops” as well as municipal solid waste. In addition to the benefit of relying on non-food sources for their generation, these biofuels produce much higher energy yields. Conventional biofuels yield 23 – 35% more energy than is used to generate them, while cellulosic biofuels yield 400 – 900% more energy.
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