Global CO 2 uptake by cement from 1930 to 2019

[摘要] Because of the alkaline nature and high calcium content of cements in general, they serve as a CO 2 -absorbing agent through carbonation processes, resembling silicate weathering in nature. This carbon uptake capacity of cements could abate some of the CO 2 emitted during their production. Given the scale of cement production worldwide (4.10 Gt in 2019), a life-cycle assessment is necessary to determine the actual net carbon impacts of this industry. We adopted a comprehensive analytical model to estimate the amount of CO 2 that had been absorbed from 1930 to 2019 in four types of cement materials, including concrete, mortar, construction waste, and cement kiln dust (CKD). In addition, the process CO 2 emission during the same period based on the same datasets was also estimated. The results show that 21.02 Gt CO 2 (95 % confidence interval, CI: 18.01–24.41 Gt CO 2 ) had been absorbed in the cements produced from 1930 to 2019, with the 2019 annual figure mounting up to 0.89 Gt CO 2  yr −1 (95 % CI: 0.76–1.06 Gt CO 2 ). The cumulative uptake is equivalent to approximately 55 % of the process emission based on our estimation. In particular, China's dominant position in cement production or consumption in recent decades also gives rise to its uptake being the greatest, with a cumulative sink of 6.21 Gt CO 2 (95 % CI: 4.59–8.32 Gt CO 2 ) since 1930. Among the four types of cement materials, mortar is estimated to be the greatest contributor (approximately 59 %) to the total uptake. Potentially, our cement emission and uptake estimation system can be updated annually and modified when necessary for future low-carbon transitions in the cement industry. All the data described in this study, including the Monte Carlo uncertainty analysis results, are accessible at https://doi.org/10.5281/zenodo.4459729 (Wang et al., 2021).

[学科分类] 眼科学