2.6.1 Types of woody biomass material and its characteristics

Forest industry provides woody biomass material as by-products such as logging residues and as main-products which is cut directly from trees and forests. The planted forests are usually thinned out to maintain the growth space among stumps. These thinning trees are expected to utilize for biomass energy materials, because they have no commercial values and leave in a stand after thinning operation. A cutting cycle in the temperate zone is around 50 to 100 years and wood residues of 0.36 m3 blanches and 0.22 m3 stumps are left after producing 1 m3 logs. These residues are utilized for modern and traditional biomass energy source in many countries.

Woodfuel accounts for about 53 percent of total round wood produced in the world. However woodfuel accounts for only several percent in industry countries at present, tough industry countries used to depend on woodfuel until 1960s. In Japan case, hardwood forests located near rural communities used to be main resources for fuelwood and charcoal. Nowadays hardwood forests have not been utilized as woody resources, because hardwood timber value is cheaper compared with softwood. Though hardwood forests have not industrial values so far, they have high potential to provide renewable energy sources to mitigate global warming. Aside from this, fast growing species, such as willow (Salix), poplars (Populus), and birch (Retula), have been planted to produce biomass energy materials.