The term "biomass" refers to all organic material that is directly or indirectly produced through photosynthesis and has not been altered via geological processes (in contrast to fossil biomass, e.g. oil, coal, natural gas). When biomass is utilised for the production of energy, the amount of CO2 that is released is limited to the amount that has been previously integrated in the biomass with the aid of solar energy through photosynthesis. Biomass can be used for producing heat, combined electricity and heat, and fuel.
A distinction is made between dry woody biomass and moist biomass with a low wood content. Forms of dry woody biomass include forest and hedgerow wood, waste wood and solid waste from trade and industry and private households. Combustion and gasification are suitable processes for utilising biomass for energy production. Gasification is suitable for farmyard manure (liquid manure and dung), harvest residue and biogenic waste from the foodstuffs and catering industries, and from private households. Energy can be produced from the various types of waste material through fermentation.