Bioenergy is stored energy from the sun contained in materials such as plant matter and animal waste, known as biomass. Biomass is considered renewable because it is replenished more quickly when compared to the millions of years required to replenish fossil fuels. The wide variety of biomass fuel sources includes agricultural residue, pulp/paper mill residue, urban wood waste, forest residue, energy crops, landfill methane, and animal waste.

Energy in the form of electricity, heat, steam, and fuels can be derived from these sources through conversion methods such as direct combustion boiler and steam turbines, anaerobic digestion, co-firing, gasification, and pyrolysis. The co-firing method mixes biomass with coal, and may be the best near-term economic opportunity for biomass, particularly in combined heat and power applications, which make the most efficient use of biomass.