The weight of living organisms. Forests are biomass factories, producing plant, animal, and microbial biomass.

The weight of living material. Most commonly used as a measure per unit area of land or per volume of water. Commonly includes the dead parts of living organisms, e.g. the bark and heart wood of trees and the hair, claws etc. of animals which are strictly 'necromass'.

Literally, "living weight", refers to mass having its origin as living organisms (i.e., plants or animals).

Forestry and agricultural residues and crops (such as willow) which are used as a fuel to produce electricity and heat.