There is no established way of categorizing biomass, which is defined differently according to the field; categorization changes depending on the purpose and application. Generally there are two ways to categorize biomass: one is biological categorization based on types of existing biomass in nature (such as categorization according to ecology or type of vegetation), and the other is based on the use or application as resources. The latter is highly significant in terms of making effective use of energy (resources).

2.1.3 An example of biomass categorization (in terms of use and application)

An example of biomass categorization appears in Fig. 2.1.2. In this categorization, biomass includes not only the conventional product and waste from agriculture, forestry, and fisheries, but also plantation biomass. Categorization according to source is important for designing biomass usage systems.

Biomass

Conventional Biomass Resources

Agriculture, Forestry (Woody), Fishery, Livestock farming

Food, Materials, Medicine, Timber, Pulp, Chip, e. t.c

Biomass Wastes (Derivatives)

Agricultural, Forestry, Fishery, Livestock residues (wastes)

Rice straw, Cattle manure, Lumber mill, Sawdust, Sewage sludge Black liquor

Plantation Biomass

Forestry Eucalyptus, Poplar, Willow, Oil palm Herbaceous Sugarcane, Switchgrass, Sorghum, Corn, Rapeseed Aquatic Giantkelp, Water hyacinth, Algae

Fig. 2.1.2. Biomass categorization (in terms of use and application).

Moisture content is a major factor to consider when using biomass, especially as energy. Because moisture content is defined differently in each field, care is needed in reading indications of moisture content. In the energy field, moisture content is often defined as follows.

(moisture content) = (moisture weight) / (total weight) x 100 [%]

(total weight) = (biomass dry weight) + (moisture weight)

Using this definition, moisture content never exceeds 100%. In the forestry and ecology fields, moisture content is often defined as follows:

(moisture content) = (moisture weight) / (biomass dry weight) x 100 [%] (2.1.3)

As a rule, this handbook employs Eq. (2.1.1) for definition of the moisture content. Biomass comprises natural macromolecular compounds such as cellulose, lignin, and proteins, and many kinds of biomass have high moisture content, because the origin of biomass is living organisms. Fig. 2.1.3 shows the moisture content of various biomass types. There is a wide range, from biomass types like dry wood and paper waste with about 20% moisture content, to those with over 95% moisture content, such as microalgae, fermentation residue, and sludge. For the purpose of energy conversion, one must choose a process adapted to the moisture

content.

Fig. 2.1.3. Relation of moisture contents and heating value.

Further information

Ogi, T. in “Biomass Handbook”, Japan Institute of Energy Ed., Ohm-sha, 2002, pp.2-6 (in Japanese)