Biomass is the organic non-fossil material of biological origin, collectively. For example, plants (including trees) and animals are biomass, as are the materials they produce, such as animal droppings and wood. The most successful animal of the earth, in terms of biomass, is the Antarctic krill, Euphausia superba, with a biomass of probably over 500 million tonnes, roughly twice the total biomass of humans.
Biomass is sometimes burned as fuel for cooking and to produce electricity and heat. Biomass used as fuel often consists of underutilized types, like chaff and animal waste. This is often considered a type of alternative energy although it is not a non-polluting one. In some industrialized countries, like Germany, paradoxically, food is cheaper than fuel compared by price per joule. Central heating units supplied by food grade wheat or maize are available.