Material Efficiency and Circularity Goals to Achieve a Carbon-Neutral Society by 2050

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.