Sustainable Use of Regional Wood Biomass in Kushida River Basin, Japan

The amount and cost of wood biomass produced from the Kushida River basin in Japan were simulated under current and modified forestry scenarios by combining the forest ecosystem and cost calculation models at semi-compartment level; in addition, an analysis was carried out comparing the sustainable supply against heat demands in the basin. The forest ecosystem model (BGC-ES) simulates biomass growth, the effects of thinning and clear-cutting practices, and the amount of harvest from these practices. The cost calculation model estimates the cost of each stage of wood biomass production, which depends on the productivity of forestry machines and the forest location. The available amount was determined by an economic comparison between the energy density of wood chips and fossil fuel. The available wood chips were assumed to be converted to heat at a boiler plant. The current forestry scenario (thinning schedule, rotation length, and managed area) was not efficient for the production of wood chips. The economic available amount was <1 % of the potential production from the basin forests. Modified scenarios (arranging the thinning schedule to promote secondary growth, increasing the rotation length, and increasing the managed area) improved the economic availability of the basin forest (up to about 40 %). In these scenarios, the available amount indicated that saturation was determined by the maximum cost of the wood chips. The available amount of wood chip production that can be sustainably supplied by the basin forest was simulated and compared with the household and agricultural demands for heat in the basin.