Toward a better practice for estimating the CO2 emission factors of cement production: An experience from China

CO2 emission estimation of cement production is an underlying tool to identify the CO2 sources, to evaluate the reduction efforts and to set prospective reduction targets for the Chinese cement industry. However, lack of domestic data has limited the reliability and accuracy of CO2 emission estimation for Chinese cement industry. To develop an accurate and comprehensive CO2 emission factor for Chinese cement industry, this study established a factory-level database of 197 cement production lines from 21 provinces covering various capacity scales. On the basis of this database, process, fuel, electricity and synthesized emission factor were computed. Furthermore, bootstrap simulation and Monte Carlo simulation were applied to evaluate the uncertainty of these factors. After corrections for cement kiln dust (CKD), incomplete decomposition, organic carbon and inorganic carbon, the medians of process, fuel and direct emission factors are 525, 369, and 919 kg CO2/t clinker, respectively. Electricity emission factor is 74.9 kg CO2/t clinker. The final synthesized emission factor for cement product is 761 kg CO2/t cement with uncertainties of [−34.8%, +31.69%]. In this study, two revised calculation methods for the process emission factor are applied. Two calculation methods for the fuel emission factor are adopted as well. These practices seek to improve the reliability and accuracy of cement CO2 emission factor. The simulated results indicate that the revised output method produces more accurate estimation for the process emission factor than the revised input method and unrevised output method. For fuel emission factor, the CC (carbon content) method is more accurate than the NCV (net calorific value) method. Simulated results are also compared with other authoritative estimation to validate the reliability of the CO2 emission factors calculated in the present study.