CO2 uptake estimation in Japan’s cement lifecycle

Abstract

Carbon dioxide (CO₂) uptake by cement-containing products has attracted significant interest as an important source of CO₂ absorption. This study provides an advanced estimation of CO₂ uptake during the cement lifecycle in Japan by incorporating dynamic material stock-flow analysis into the model. Concrete stock-flow and CO₂ 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 CO₂ uptake in the cement lifecycle was estimated to be 2.6 million tonnes/year in 2020, corresponding to 13.9% of CO₂ emissions from calcination during cement production. Annual CO₂ 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. CO₂ 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 CO₂ uptake into the carbon-neutral strategy of Japanese cement industry.