2.1 Classification of biomass

2.1.1 Definition of biomass

As stated in Chapter 1.1, “What Is Biomass?,” the word “biomass” consists of “bio” + “mass”, and originally used in the field of ecology simply referring to amount of animal and plant. After the oil shocks, the meaning of the word was widened beyond ecological field and came to include the meaning “biological resources as energy sources”, since it was vigorously proposed that alternative (new) energy sources should be promoted. There is still no strict definition of biomass, and the definition differs from one field to another. From the perspective of energy resources, a common definition is “a general term for animal and plant resources and the wastes arising from them, which have accumulated in a certain amount (excluding fossil resources)”. Accordingly, biomass encompasses a wide variety including not only agricultural crops, timber, marine plants, and other conventional agriculture, forestry, and fisheries resources, but also pulp sludge, black liquor, alcohol fermentation stillage, and other organic industrial waste, municipal waste such as kitchen garbage and paper waste, and sewage sludge. Because some countries do not classify municipal waste as biomass, care is needed in the use of statistical data.