Carbon emission reduction potentials through thinned wood in Japan

Abstract

Substituting fossil fuel with woody biomass for bioelectricity production has great potentials for carbon emission reductions while increasing forest productivity to increase carbon sequestration and improve ecological functionalities. Until recently, study on such potentials was very limited. Beginning in 2007, Japan’s special budgets were allocated for a 6-year intensive thinning on about 3.3 million ha of young stands for increasing carbon sinks in Japanese forests to meet the capped amount of 47.7 Tg CO2 year-1 allowed under the Marrakesh Accord. Because of only 30% of the thinned wood were used for sawntimber, CO2 and CH4 must have been emitted from the disposed thinned wood and wood waste. Such emissions and reduction potentials need to be assessed to provide future alternatives for climate change mitigation. We assessed carbon emission reduction potentials when woody biomass from thinned wood is fully utilized for bioelectricity production 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 disposed thinned wood and wood waste are utilized to generate energy, about 62.6, 58.3, and 37.8 Tg CO2 year-1 could be prevented from emitting depending on emission scenarios or about 33.2, 30.9, and 20.0% of Japan’s reduction commitment to the Kyoto Protocol. On the other hand, if thinned wood and wood waste are not utilized, about 13.4 Tg CO2 year-1 would be released due to thinning. Our results suggest that incentives to reducing emission reductions in forest sector in the future climate change mitigation agreements will likely lead to large emission reductions, otherwise leakages due to thinning are unavoidable.