Types and moisture content of wood residuals from wood processing plants like sawmills or plywood mills can vary widely. Larger residuals are chipped and sold for pulp or wood composites like log slabs from sawmills or peeled cores from plywood mills. Smaller residuals like bark, sawdust, planer dust, or veneer residuals are utilized as livestock bedding in nearby farms, as boiler fuel in the mill, or as compost. Only 7% of the estimated 12 million m3 of wood residuals produced in 2005 was uselessly burned or otherwise wasted.

In large scale mills, even zero emission production is possible by recycling residuals for electric power generation or steam for wood drying. But for small sawmills without drying facilities or precut mills, a residuals utilization system such as a small-scale round accumulation system, must be established. Recently, wooden pellet production from bark or sawdust, which is easy to handle and has higher energy density, has been increasing.

Fig. 2.12.1. Wood flow in Japan.

2.12.2 Residuals from wood utilization

In the 2005 estimates, 22 million m3 of residuals were produced in the construction, furniture, transportation, and civil engineering sectors. Residuals from civil engineering include trees felled during construction works.

Only 10% of residuals were recycled as materials; 1.6 million m3 for particle board etc., and 0.8 million m3 for pulp. The “Construction Recycle Law” mandates that construction-derived wood wastes from construction and civil engineering sectors are to be separated and recycled. In 2005, an estimated 62.8% of the 15 million m3 of residuals produced is recycled in some way, mostly, for energy generation, except for the volume reducing by incineration.

In the first commitment period of the Kyoto Protocol, the rise of petroleum prices has given many industries like power plants, steel mills, cement mills, and paper mills added incentive to start wooden residuals for energy production. Recycling companies also benefit easily, because they can collect a disposal fee for residuals from wood utilization. The objectives of the “Construction Recycle Law” will undoubtedly be achieved, and there may even be a shortage of wood residuals.

Material-recycling for conserving resources must have top priority. However, residuals with adhesives or paint cannot be used for pulp chips, and almost no waste wooden boards are material-recycled. Also small or composite wooden residuals, which cost much to be material-recycled, should be crushed and used as fuel chips. So, more than half of wood residuals could be energy-recycled without wasting, which in turn could reduce fossil fuel consumption by more than 1 million tons-C.