Seite - 129 - in Water, Energy, and Environment - A Primer

8.5 BIOMASSENERGY Biomass energy is both an old and a future technology. As a feedstock, biomass is defined by Wikipedia as ‘biological material derived from living, or recently living organisms.’ It includes plantmaterial and animal (andhuman)wastes. 8.5.1 Sourcesofbiomass Combustionofbiomasshasbeenused throughouthumanhistory toprovideheat,eversincethediscoveryoffire,andit is theoldest form of renewable energy. Wood has long been a source of biomass energy and is still widely used today for heating and cookingpurposes. More recently, other ways to obtain useful energy from biomass have been developed, including gasification and conversion to liquid fuels. Each of these applications is discussedbelow, as is biomass’ significant potential. A considerable amount of biomass is produced globally each year, about half in the oceans and half on land. It is biologically produced matter based on carbon (as well as hydrogen and oxygen). Estimated annual production involves about 100 trillion kilogramsof carbon.An important point to keep inmind is that the chemical arrangements of these organicmaterials can be changed, an important focus of biomass research. 8.5.2 Wood Wood, in the form of trees, tree stumps, branches, wood chips, andyard clippings remains the largest source of biomass energy today. In many developing countries it is still the only combustion fuel source for domestic use. Other common fuel sources include municipal solid wastes, animal wastes (e.g., ‘cow chips’ or bio-digestedmanure), and landfill gas (primarily methane and carbon dioxide). In recent years pellet fuels, made from compressed biomass, have been used increasingly for heating in power plants, homes, and other applications. Wood Renewableenergy 129