Biomass is organic matter that can be used to provide heat, make fuel, and generate electricity. Wood, the largest source of biomass, has been used to provide heat for thousands of years. Many other types of biomass are used as an energy source, such as plants, residue from agriculture or forestry, and the organic component of municipal wastes. Landfill gas is also considered a biomass source. Biomass resources can be replenished through cultivation of what are known as energy crops, such as fast-growing trees and grasses.
Biomass can be converted directly into liquid fuels, called biofuels, to meet transportation needs. The two most common biofuels are ethanol and biodiesel. Ethanol is made by the fermentation of any biomass rich in carbohydrates, such as corn. It is mostly used as a fuel additive to reduce a vehicle's emissions. Biodiesel is made using vegetable oils, animal fats, algae, or recycled cooking greases. It can be used as a diesel additive to reduce emissions or its pure form to fuel a vehicle.
Biomass is also used to generate electricity. This is accomplished through the direct combustion of wood, municipal solid waste, and other organic materials; co-firing with coal in high efficiency boilers; or combustion of biomass that has been chemically converted into fuel oil. In the lumber and paper industries, wood scraps are sometimes directly fed into boilers to produce steam for their manufacturing processes or to heat their buildings. The co-firing of coal with biomass in power plants has environmental benefits since co-firing can significantly reduce emissions. Biomass accounts for 76 percent of renewable electricity generation and 1.6 percent of total U.S. electricity supply.
Gas for generating electricity can be produced from biomass. Gasification systems use high temperatures to convert biomass into a gas that is used to fuel a turbine. The decay of biomass in landfills also produces methane gas that can be captured and burned in a boiler to produce steam for electricity generation or for industrial processes.
For a map showing biomass and biofuel resources in the U.S., see page 6-3 in the National Energy Policy report, May2001.