Cement industry is one of the largest anthropogenic carbon dioxide (CO₂) emitters. China is the biggest cement producer in the world. Therefore it is essential to accurately calculate the CO₂ emission amounts. The calculation of CO₂ emission amount is based on CO₂ emission factors (EFs).  

Dr. GENG Yuanbo and his colleagues at Key Lab for Resources Use and Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research (IGSNRR), Chinese Academy of Sciences (CAS) found Raw Material Carbonate Method is more accurate and simpler than other methods to calculate CO₂ emission factors related to the new suspension pre-heater and pre-calciner kilns, based on inorganic carbon and organic carbon. This work was published in Journal of Cleaner Production. 

The calculation methods of CO₂ EFs (process-related emission factors) include two categories: clinker method（Also called as the output method）and raw material method (Also called as the input method) in cement production. Clinker method determines the CO₂ emission factors according to the amount of calcium oxide (CaO) and magnesium oxide (MgO) in clinker. Though the data is easy to access, the result is hard to guarantee correctness.  

“The reason is that the source of calcium oxide (CaO) and magnesium oxide (MgO) are indefinable, this method usually roughly estimates or ignores either CaO and MgO in cement kiln dust, bypass dust, and coal ash, or the non-carbonates components in the form of CaO and MgO in the raw materials,” said Dr. GENG.  

In addition, organic and inorganic carbon residues exist in almost all of the clinker due to incomplete decomposition of carbonate and incomplete combustion of fuel, so the carbonate decomposition rate and organic carbon combustion rate should be considered during the process of calculation.  

Researchers determined the inorganic carbon (carbonate) in raw materials and the corresponding decomposition rate, calculated the process-related CO₂ EFs with raw material carbonate method, measured the organic carbon in coal and the corresponding combustion rate and calculated combustion-related CO₂ EFs, which improved the accuracy of the two EFs.  

This work was supported by the Strategic Priority Research Program – Climate Change: Carbon Budget and Related Issues of the Chinese Academy of Sciences

Figure: Calculating process of direct CO2emissions and corresponding CO2emission factors (Image by GENG Yuanbo’s group)

Reference:

Geng Y, Wang Z, Shen L & Zhao J. Calculating of CO₂emission factors for Chinese cement production based on inorganic carbon and organic carbon. Journal of Cleaner Production, 2019, 217: 503-509.