How can C&D waste recycling do a carbon emission contribution for construction industry in Japan city?

Japan has made a legislative commitment to achieve carbon neutrality by 2050. The construction industry in Japan contributes 30% of the carbon emissions and is the key sector for achieving carbon neutrality. Building abandonment and vacancy has become an urgent problem in Japan. However, less attention has been paid to the carbon emissions of building demolition, especially the recycling of Construction and Demolition (C&D) waste. This study clarifies the flow of C&D waste and accounts for the carbon emission of C&D waste disposal by Life Cycle Assessment and IPCC method. The contribution of C&D waste recycling to carbon emission reduction under three scenarios (Baseline scenario, Large area scenario, Long lifespan scenario) is predicted by modeling the building stock flow. The results show that in Kitakyushu, a decarbonization pioneer region, the disposal of C&D waste will generate 35,896 tons of CO2 in 2019, and the recycled products could reduce emissions by 7,845 tons for the construction industry. Disposing of concrete and steel is the major source of carbon emissions of 94.1%, recycling of steel is the biggest driver of emissions reduction. Kitakyushu will soon face rapid growth in C&D waste, contributing to a 1.9-6.8% carbon reduction in the construction industry. From a material cycle perspective, a reasonable building stock and an extended building lifespan are more conducive to achieving carbon neutrality.