What is Biomass?

Biomass in ecology, is the mass of living biological organisms in a given area or ecosystem at a given time. Biomass can refer to species biomass, which is the mass of one or more species, or to community biomass, which is the mass of all species in the community. It can include microorganisms, plants or animals. The mass can be expressed as the average mass per unit area, or as the total mass in the community.

How biomass is measured depends on why it is being measured. Sometimes, the biomass is regarded as the natural mass of organisms in situ, just as they are.

For example, in a salmon fishery, the salmon biomass might be regarded as the total wet weight the salmon would have if they were taken out of the water. In other contexts, biomass can be measured in terms of the dried organic mass, so perhaps only 30% of the actual weight might count, the rest being water. For other purposes, only biological tissues count, and teeth, bones and shells are excluded.

In stricter scientific applications, biomass is measured as the mass of organically bound carbon (C) that is present. [1]

As a simple definition biomass refers to the organic material on Earth that has stored sunlight in the form of chemical energy. Biomass is a compound word. The meanings of its individual compounds are the following:


Bio is an abbreviation of biological, which means relating to living organisms.


Mass is a property of a physical system or body, giving rise to the phenomena of the body's resistance to being accelerated by a force and the strength of its mutual gravitational attraction with other bodies. Instruments such as mass balances or scales use those phenomena to measure mass. The SI unit of mass is the kilogram (kg).

Primary biomass:

In general primary biomass means the total weight of plant biomass in the Earth. This type of biomass has been produced by autotroph organisms. An autotroph ("self-feeding or "producer"), is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) from simple substances present in its surroundings, generally using energy from light (photosynthesis also known as phyto-mass) or inorganic chemical reactions (chemosynthesis).

Secondary biomass:

In general it is the total weight of animal biomass in the Earth, often called as zoo-mass. In fact secondary biomasses are organism which feeds on primary biomass also known as heterotrophic organisms. A heterotroph is an organism that cannot fix carbon and uses organic carbon for growth. This contrasts with autotrophs, such as plants and algae, which can use energy from sunlight (photoautotrophs) or inorganic compounds (lithoautotrophs) to produce organic compounds such as carbohydrates, fats, and proteins from inorganic carbon dioxide. These reduced carbon compounds can be used as an energy source by the autotroph and provide the energy in food consumed by heterotrophs. Ninety-five percent or more of all types of living organisms are heterotrophic .

The main and by products of animal husbandry are also concern to this group.

Tertiary biomass:

Products by-products and waste of primary and secondary biomass processing industry and the organic waste from human living areas. The biomass which is mixed and therefore cannot be referred to its origin or so aged, that the original composition is basically changed are also refers to this group.

References: 1. IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "Biomass".