Factory-level measurements on CO2 emission factors of cement production in China

Cement is a primary component of concrete and is consumed extensively for construction and transportation infrastructures worldwide. Cement is largely produced and consumed locally but has global impact in terms of both energy consumption and greenhouse gas emissions. China is both the largest producer of cement and the biggest emitter of CO2 emissions in the world. It has been widely recognized that uncertainties of China׳s CO2 emissions were poorly quantified and clear discrepancies can be identified among different sources. These discrepancies arise from many uncertainties, including system boundary and statistical standards, availability of production data (especially for the clinker and cement outputs), and emission factors. We argue that the emission factors (EFs, either default values or adjusted ones) are the most important here and highlight the importance of clearly defining the CO2 accounting and reporting boundaries for determining the emission factors. We therefore developed a factory-level measurement for different types of clinker and cement production, primarily using onsite surveys and sampling, with the objective of distinguishing process-, combustion- and electricity-related emission factors on a factory level. It is a bottom-up CO2 emission inventory for China using the uniform formula and calculators and the first time factory-level sampling method (BFSM) based on three tiers of production lines, provincial and national integrations. Our results indicate that China׳s carbon emissions from cement production might be overestimated in the previous estimates because they overlooked the technology transition from the wet process to the dry process, differences in lime content and clinker-to-cement ratios, raw materials and fuels substitutions, and usages of blend additives.