Biomass, as a renewable energy source, is biological material
A biomaterial is any matter, surface, or construct that interacts with biological systems. The development of biomaterials, as a science, is about fifty years old. The study of biomaterials is called biomaterials science. It has experienced steady and strong growth over its history, with many...

 from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel
Biofuel is a type of fuel whose energy is derived from biological carbon fixation. Biofuels include fuels derived from biomass conversion, as well as solid biomass, liquid fuels and various biogases...


In the first sense, biomass is plant matter used to generate electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

 with steam turbines & gasifiers or produce heat, usually by direct combustion. Examples include forest residues (such as dead trees, branches and tree stump
Tree stump
After a tree has been cut and felled, the stump or tree stump is usually a small remaining portion of the trunk with the roots still in the ground. Stumps may show the age-defining rings of a tree. The study of these rings is known as dendrochronology....

s), yard clippings, wood chips and even municipal solid waste
Municipal solid waste
Municipal solid waste , commonly known as trash or garbage , refuse or rubbish is a waste type consisting of everyday items we consume and discard. It predominantly includes food wastes, yard wastes, containers and product packaging, and other miscellaneous inorganic wastes from residential,...