記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Environmental Science and Technology  

Decarbonizing materials production presents a major challenge to achieving a carbon-neutral society. The current carbon-neutral roadmap for materials generally assumes an uncertain dissemination of innovative production technologies, making the changes in material flows required for a carbon-neutral society unclear. This study introduces three material reduction scenarios and an input-output optimization model to explore material flows in Japan for achieving carbon neutrality by 2050 without disseminating innovative technologies. The results indicate that Japanese carbon emissions could reach neutrality by 2050 if the country can manage a yearly material reduction of 4% together with the decarbonization of electricity generation. To achieve this, the material efficiency of consumption must increase nearly 4-fold, and the material circulation rate must be doubled. Achieving such a rapid improvement in material efficiency and circularity is as challenging as the early large-scale deployment of material decarbonization technologies. Therefore, the critical choice in the remaining years is whether to bet heavily on innovative material decarbonization or prioritize technologies and policies accelerating material efficiency.

DOI： 10.1021/acs.est.4c08719

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Cleaner Production  

Despite the recent increase in vehicle electrification, the transport sector remains a major contributor to the rise in global CO2 emissions. Using dynamic product lifecycle (LC) models, we analyzed the relationship between LC-CO2 emissions and the proportion of electric vehicle (EV) sales in Japan, where the introduction of EVs could increase LC-CO2 emissions. We considered the contributions of vehicle fuel efficiency and vehicle lifetime to LC-CO2 emissions under three scenarios—changes in sales, improvements in fuel efficiency, and changes in vehicle lifetimes. Our findings show that promoting EVs and decarbonization in the electricity sector will decrease CO2 emissions during the driving phase. However, even if the energy mix follows the net zero emission target, emissions from the vehicle manufacturing phase will largely remain, and the manufacturing emissions from electric will account for over 50% of the total emissions in 2050, even when the vehicle lifetime is extended by 5 years. Although the decarbonization of the power sector and vehicle electrification are important steps toward reducing LC-CO2 emissions, they are insufficient. Thus, to reduce LC-CO2 emissions, including those from the manufacturing phase, the Japanese government needs to focus on decarbonizing the supply chain and extending vehicle lifetime, especially that of EVs, as well as reducing driving phase emissions.

DOI： 10.1016/j.jclepro.2024.140658

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