Environmental impacts of cross-laminated timber production in Japan

Japan has promoted a policy to use lumber in various types of buildings since 2010. As cross-laminated timber (CLT) is one of the engineered timber products, an amount of CLT production has been increasing in Japan under this policy. The purpose of this study is to produce generic life cycle assessment data for CLT production in Japan and to propose measures for reducing environmental impacts of CLT production. The system boundary includes from material production to CLT production (cradle-to-gate). The operational data at three major Japanese companies are collected in the fiscal year of 2018. The evaluated environmental impact categories are climate change, ozone layer depletion, eutrophication, acidification, photochemical oxidant, land occupation, and land transformation. The results show that electricity used in wood laminae production had the largest impact to climate change and the roundwood production had the second largest. The sensitivity analysis clarified that the use of fossil fuels during the drying process greatly increased CLT’s environmental impacts. The policies to promote the introduction of biomass boilers for sawmills are appropriate for reducing environmental impacts. If CLT is used for more than 30 years, greenhouse gas reduction due to temporary carbon storage will be greater than that of the CLT production. It is also recommended to extend the life of buildings using CLT and/or to use CLT for a long time through the reuse of CLT panels to avoid releasing biogenic carbon to the atmosphere.