(Paper under reviews: Etoh & Sasaki 2010)

Abstract

Under the Marrakesh Accord of the Kyoto Protocol, Japan is allowed to use forest carbon sinks as reduction option for meeting its greenhouse gas reduction commitment. Due to inactive management coupled with slow forest growth, intensive thinning is being implemented to accelerate the growth so that carbon sinks could reach the capped amount of 47.7 TgCO2 year-1. Beginning in 2007, special budgets were allocated for a 6-year intensive thinning on about 3.3 million ha of young stands. However, because a large proportion of thinned wood and wood waste are not utilized, we argue that thinning alone is not a viable option for reducing carbon emissions as unused thinned wood and wood waste gradually emit methane. We assessed carbon emission reduction potentials when woody biomass from thinned wood is fully utilized for bioenergy generation as compared with the generation of the same amount of energy produced under coal, oil, and natural gas scenarios. Our analytical results show that if all thinned wood and wood waste are utilized to generate energy, about 78.7, 74.9, and 56.12 TgCO2 year-1 could be prevented from emitting depending on emission scenarios or about 39.9, 37.9, and 27.9% of Japan’s reduction commitment to the Kyoto Protocol. On the other hand, if thinned wood and wood waste are not utilized, about 21.6 TgCO2 year-1 would be released due to thinning. Our results suggest that Japan should implement thinning to increase carbon sinks in the forests only if appropriate policies to promote the utilization of woody biomass from such thinning are introduced.