Abstract
Objective. Wood is generally considered to be an eco-friendly material because it is renewable and carbon-neutral. Wood is said to require less energy to produce than aluminum, steel and concrete. However, the environmental loads of wood have not been assessed on a life-cycle basis. In studying CO2 emissions of wood and wood products, it is necessary to use life-cycle assessment (LCA). In this study, we estimated the CO2 emissions based on life cycle inventory analysis for log production of Japanese larch from ground clearance to final cutting, using models of forest management for planted forest in Hokkaido.
Results and Discussion. The CO2 emissions from log production were estimated to range from 6.1 kg/m3 to 15.2 kg/m3. In terms of the classes of site, the emissions were the greatest for second-class, followed by the first-class and the special-class. In terms of control of stands density, the emissions were lower for low-density than for medium-density. In using machinery to clear the ground, the emissions were the greatest for excavators with brush cutter attachments, followed by excavators with grapple rake attachments, bulldozers, and shoulder bush cutter. No significant differences in emissions were observed between the planting densities of 2000 trees/ha and 2500 trees/ha. Emissions from silviculture were found to differ greatly according to the machinery used to clear the ground; there were estimated to account for 3% to 29% of overall emissions.
Conclusions. From the point of view of reducing the CO2 related to log production, it is better to afforest areas that are higher class, and to control the stands at low densities. Also, it is not recommended to use heavy machinery such as bulldozers and excavators to clear the ground. The CO2 emissions associated with log production were estimated to account for 0.8% to 2.0% of CO2 fixed in the log.
