Biomass, mainly in the form of wood, is the oldest form of energy used by humans. Biomass is used to meet a variety of energy needs, including generating electricity, heating homes, fueling vehicles, and providing process heat for industrial facilities. Biomass potential includes wood and animal and plant wastes. Biomass, mainly now represents only 3% of primary energy consumption in industrialized countries. World production of biomass is estimated at 146 billion metric tons a year, mostly wild plant growth. Energy from biomass fuels is used in the electric utility, lumber and wood products, and pulp and paper industries. Biomass conversion may be conducted on two broad pathways: chemical decomposition and biological digestion. The conversion technologies for utilizing biomass can be separated into four basic categories: direct combustion processes, thermochemical processes, biochemical processes, and agrochemical processes. Biological processes are essentially microbic digestion and fermentation.