Life cycle assessment of beneficial use of calcium carbide sludge in cement clinker production: A case study in China

Abstract

The use of calcium carbide sludge (CCS) as a substitute for limestone is an effective method for reducing CO2 emissions in the cement industry. In this study, a life cycle assessment (LCA) was performed to assess the greenhouse gas (GHG) emission reduction potential of CCS cement clinker compared to that of Portland cement clinker. The results showed that the global warming potential (GWP) of CCS cement clinker was approximately 31% lower than that of Portland cement clinker. However, this may have other environmental impacts owing to the extra energy used for CCS pretreatment. The environmental impacts of three typical CCS cement clinker production scenarios were compared, and the results demonstrated that Scenario 2 (CCS pretreated by mechanical dehydration and dried using a coal-drying machine) was the best among these three scenarios from the perspective of environmental performance. An optimization scheme for CCS pre-drying system (using waste heat from clinker kiln for drying CCS) in Scenario 2 was also proposed and had the potential to decrease the environmental impact. Finally, sensitivity analysis revealed that other factors (e.g., CCS transport distance, CCS content) may affect the GHG emissions and other environmental impacts of CCS cement clinker, which should be considered in practical applications. This case study demonstrates that non-carbonate alternative materials should be actively explored for their application in the cement industry, and a series of emission-reduction technologies should be developed for GHG generated from industrial process.