A framework for integrating cement carbonation sink into national greenhouse gas inventories

Cement carbonation has been recognized as an important carbon sink. However, this sink has not yet been integrated into national greenhouse gas inventories for lack of standard annual accounting framework. This gap has resulted in both overestimation of net emissions in the cement sector and the imbalance of the global carbon budget. Here, we establish a tiered accounting framework for integrating the cement carbonation sink into the IPCC guidelines for national greenhouse gas inventories. We develop annual cement carbon absorption factors to ensure the time boundary consistency between the cement carbonation sink and the IPCC guidelines. We establish a decision tree to guide the selection of appropriate methods according to data availability. Furthermore, the feasibility and robustness of the framework are validated through comparison of the carbonation sink calculated by the Tier 1 and Tier 2 methods in 50 countries. We find that ratios of cement carbonation sink to emissions range from 31.4% to 91.2%, highlighting the necessity of the standard accounting framework for carbonation sink. We conclude that our cement carbonation sink inventory framework is helpful for improving the completeness of cement process emissions accounting method in IPCC guidelines.