We have used biomass energy, or “bioenergy” —the energy from plants and plant-derived materials —since people began burning wood to cook food and keep warm. Wood is still the largest biomass energy resource today, but other sources of biomass can also be used. These include food crops, grassy and woody plants, residues from agriculture or forestry, oil-rich algae, and the organic component of municipal and industrial wastes. Even the fumes from landfills can be used as biomass energy sources. —National Resources Defense Council website