There are many kinds of biomass, which may be classified into woody type, agricultural one, food residual one, domestic waste one, biomass produced overseas and others.

1.

Woody biomass includes waste wood from lumber mill, scrap wood derived from destructed building structures, thinned wood derived from mountain forest management and others.

2.

Agricultural biomass includes "hulls", "straws" derived from rice/wheat production and others.

3.

Food residual biomass includes dregs left after making of juice, coffee and tea as well as sludge and wastes discharged from food processing plants and others.

4.

Domestic waste biomass includes kitchen garbage, discarded plastic products, sewage sludge and others. (MSW : Municipal Solid Waste)

5.

Typical biomass from overseas includes dregs from palm oil mill and Jatropha oil mill.

Is there anything good expected from utilization of biomass? As for biomass, there is an idea of "carbon neutral". This idea is based on the concept that combustion of biomass generates CO₂ whereas growing trees absorb this CO₂, and so its concentration in atmospheric air does not increase, thus securing its zero emission. Amount of biomass can be increased by means of forestation and so biomass can be called one of the important renewable energy resources.

In past days kitchen garbage was incinerated merely for disposal, while in recent days the heat produced by burning of garbage has been utilized to generate electricity. Such utilization system is very important for Japan poor in natural resources.

Biomass secures "carbon neutral".