CO2 uptake estimation in Japan's cement lifecycle

Carbon dioxide (CO 2 ) uptake by cement-containing products has attracted significant interest as an important source of CO 2 absorption. This study provides an advanced estimation of CO 2 uptake during the cement lifecycle in Japan by incorporating dynamic material stock-flow analysis into the model. Concrete stock-flow and CO 2 uptake from 1870 to 2070 are estimated by reflecting country-specific characteristics such as concrete mix design, surface-to-volume ratio of buildings, presence or absence of coating resins and/or covering materials, and exposure climate. Annual CO 2 uptake in the cement lifecycle was estimated to be 2.6 million tonnes/year in 2020, corresponding to 13.9% of CO 2 emissions from calcination during cement production. Annual CO 2 uptake by in-use concrete accounted for 86.8% of the total in 2020, whereas that by end-of-life concrete was relatively small throughout the estimation period. CO 2 uptake is expected to increase slightly in the late 2020s, then decrease to 2.3 to 2.4 million tonnes/year by 2070. Our results were lowered by comparing those of previous studies, suggesting that the most critical aspect was affected by the local climate. The high-precision analysis highlighted the importance of integrating local climate factors, surface-to-volume ratio of structures based on the domestic design guidelines and examples, and modeling of end-of-life concrete, providing fundamental knowledge for incorporating CO 2 uptake into the carbon-neutral strategy of Japanese cement industry. • CO 2 uptake in Japan's cement lifecycle is estimated from 1870 to 2070. • Material stock-flow analysis of concrete is conducted. • Annual CO 2 uptake accounted for 13.9% of annual CO 2 emission in 2020. • Further development of domestic database is required.