Bioenergy is renewable energy made from any organic material from plants or animals. Sources of bioenergy are called "biomass," and include agricultural and forestry residues, municipal solid wastes, industrial wastes, and terrestrial and aquatic crops grown solely for energy purposes. Biomass is an attractive petroleum alternative because it is a renewable resource that is more evenly distributed over the Earth's surface than finite energy sources, and it may be exploited using more environmentally friendly technologies. Today, biomass resources are used to generate electricity and power, and to produce liquid transportation fuels, such as ethanol and biodiesel. Ethanol is the most widely used liquid transportation fuel, or biofuel. Currently, a majority of ethanol is made from corn, but new technologies are being developed to make ethanol from a wide range of renewable agricultural and forestry resources.
Biodiesel is made by combining alcohol (usually methanol) with vegetable oil (usually soybeans and peanuts), animal fat, or recycled cooking grease. It can be used as an additive (typically 20%) to reduce vehicle emissions or in its pure form as a renewable alternative fuel for diesel engines and home heating oil.
According to tests conducted by the U.S. Department of Energy, when used as a vehicle fuel, biodiesel offers some tailpipe and considerable greenhouse gas (GHG) emission benefits over conventional gasoline and diesel fuels.