Biomass is the oldest form of energy in the world. For thousands of years, since man discovered fire, it has been used to burn wood for light, heat, and cooking. In fact, wood accounted for 90% of the energy used in the United States until the mid-1800s. It was then replaced by coal, natural gas, petroleum, and other energy sources.

Biomass is any organic matter that can be used as an energy source. Organic means anything that is alive or was alive a short time ago. Organic materials are also renewable energy sources, they include things like trees, plants, sugar cane, animal waste, manure, and some types of garbage.

Biomass gets its energy from the sun through a process called photosynthesis. Plants such as trees, crops, and grass absorb and store the sun's radiant energy in their leaves and roots. The plants then convert this energy into chemical energy in the form of sugar which is a carbohydrate. When people and animals eat plants (biomass) or products made from plants such as wheat, they are using the carbohydrates for energy. When we burn wood, waste, and other plant matter, it releases the stored chemical energy in the form of heat.

Biomass is burned to generate steam that turns a generator that produces electricity. The process of producing energy from biomass is called Bioenergy.

Power plants that use garbage and other waste are called waste-to-energy plants.

Biomass can also be converted into a gas called biogas, or into liquid biofuels, such as ethanol and biodiesel.