Using cedar plantation materials for wood-based composites in Japan

The standing timber volume in plantation forests in Japan is currently estimated at about 2.3 billion m(3) and it is increasing. Finding effective ways for utilizing these valuable wood resources is one of the most important issues in forest management and to the wood industry in Japan. Cryptomeria japonica (L.f) D.Don (Sugi or Japanese cedar) is the primary plantation forest species planted in Japan. There are several examples of major timber construction using Sugi, such as domes and bridges. Three recent examples are the Ohdate-Dome with a diameter of 178m built in 1997 using Sugi glulam timber, the Miyazaki-Dome constructed in 2004 using Sugi glulam, and a large king-post truss bridge built in 2003 with 140m length. Laminated veneer lumber (LVL) and parallel strand lumber (PSL) are still other examples of engineered lumber products that use Sugi as a raw material. Recently another new technology, known as SST, was developed in Japan and is intended to encourage the utilization of low quality logs. In some respects, SST is similar to PSL in that it is composed of long strands, but the wood strands are made by tearing and splitting the small diameter logs. In the Japanese composite panel market, the production of domestic softwood plywood has been rapidly increasing, and the plywood industry has started to peel Sugi logs to produce thicker panels for structural use, especially for the floor systems in residential housing. In another attempt to promote forest sustainability, several under-utilized plantation species were shown to effectively reinforce Sugi plywood. This new type of plywood is environmentally friendly because it combines veneers from Sugi and other under-utilized plantation species to achieve superior mechanical properties over all-Sugi plywood. Also mat-formed panels can now be manufactured using Sugi as a raw material. While a part of sawmill residue is actually used for commercial particleboard and medium-density fiberboard (MDF) productions, oriented strandboard (OSB) made from Sugi is a product that achieves much higher mechanical properties than those of particleboard or MDF. Strandboard using conifers has been recently manufactured in a series of small-scale mills as a trial for commercial production. This work has shown that fast-grown plantation Sugi can provide high mechanical performance when used as the base strand-material in mat-formed structural OSB panel products.