Carbon uptake by cement in China: Estimation and contribution to carbon neutrality goals

Cement is a widely used construction material globally. Its manufacturing contributes to anthropogenic CO2 emissions significantly. However, its alkaline compounds can absorb CO2 from the surrounding environment and engage in a carbonation reaction, thereby functioning as a carbon sink. As a major cement producer and consumer, China has an important responsibility to rigorously investigate and accurately account for cement carbon uptake. This study presents a comprehensive analytical model of cement carbon uptake from China, revealing a substantial increase in carbon uptake from 1930 to 2021, peaking at 426.77 MtCO2 (95% Confidence Interval: 317.67-874.33 Mt CO2) in 2021. The uptake accounts for 8.10% to 45.40% of China's annual land sink and 2.51% to 4.54% of the global land sink. The cumulative carbon uptake by cement is approximately 7.06 Gt CO2 (95% CI: 5.22-9.44 Gt CO2) during this period, offsetting 50.7% of the total emissions (13.91 Gt CO2, 95% CI: 12.44-17.00 Gt CO2) from the cement industry. Notably, cement mortar contributed to most absorption (65.64%). From a life cycle perspective, the service stage of cement materials is the period where the largest CO2 sink is formed, accounting for 90.03% of the total. Therefore, the potential for carbon sequestration in cement materials and their waste is enormous. Additionally, the model improves the accuracy of cement carbon accounting, supporting both China and global carbon neutrality assessments. Thus, it is crucial for China to achieve its carbon neutrality goals sooner by prioritizing the environmental benefits of cement materials and wastes, and accelerating the development and commercialization of CO2 sequestration technologies for cement and its by-products.