Life Cycle Assessment Of Cement Kiln Co-processing With Classified Domestic Waste

In the context of carbon peaking and neutrality goals,as well as green development,the cement industry is required to reduce carbon emissions and the utilization of non-renewable resources.The cement kiln co-processing of domestic waste has attracted widespread attention because it not only realizes the recycling,reduction,and harmlessness of waste but also provides resources and energy for cement production.Domestic waste classification provides a new idea for the low-carbon transformation of the cement industry.However,the environmental and economic feasibility of cement kiln co-processing with classified domestic waste is uncertain.This study conducted a life cycle assessment of cement kiln co-processing with classified domestic waste from both environmental and economic perspectives,aiming to provide theoretical support to national policy makers and cement enterprise managers and accelerate the green and sustainable development of the cement industry.Firstly,this study formulated a roadmap for cement kiln co-processing of classified domestic waste,selected Yicheng District,Zaozhuang City,Shandong Province as the study area,and completed the layout of waste collection sites through ArcGIS to fully consider the impact of waste transportation.Combining the current waste disposal methods in China,four scenarios were set up by incorporating both waste disposal and clinker production into the system boundary.Secondly,the calorific value of the alternative fuel(New RDF)was calculated according to the specific components of urban and rural separated domestic waste,the amount of waste blended as an alternative fuel was determined according to the thermal substitution rate(30%),and the amount of waste blended as an alternative raw materials was determined according to the cement clinker rate value.Then,the life cycle assessment method was used to quantitatively analyze the environmental impact of each scenario from six environmental impact categories:global warming potential(GWP100),abiotic resource depletion(ADP fossil),acidification potential(AP),eutrophication potential(EP),human toxicity potential(HTP)and photochemical smog and ozone generation potential(POCP).It identified the main stages of creating environmental problems and the major environmental problems caused,and proposed solutions to the problems.Finally,the internal costs and environmental costs of each scenario were accurately calculated,and the economic benefits were measured by life cycle costs.Considering the factors of economic development and technological progress,the changes of marginal abatement costs of CO2,SO2,NOx,CH4 and CO after the implementation of cement kiln co-processing with classified domestic waste in the future were explored.The results showed that(1)The calorific value of the New RDF made from classified waste was calculated to be 18977.76 kJ/kg.Under the premise of clinker quality,the cement kiln can co-processing 149.302 kg of food waste and 88.035 kg of residual waste by producing 1 t of clinker.(2)Co-processing of classified domestic waste in cement kiln had the lowest environmental impact in terms of GWP100,ADP fossil,AP,EP and POCP compared to conventional waste disposal methods.(3)The increase in electricity consumption for waste screening,crushing and preparation of New RDF caused a separate increase in HTP.It was considered that China’s current coal-based power structure had caused shortcomings in HTP.It was predicted that the HTP caused by co-processing will be reduced by 56.29%and 83.38%by 2030 and 2060 respectively after the transformation of power structure.(4)Considering waste transportation and New RDF preparation,the environmental burden of cement kiln co-processing with classified domestic waste was reduced by 7.86%compared with the conventional production of clinker,and the environmental impact caused by waste transportation was minimal.The environmental impact of clinker calcination stage of co-processing was still the largest,and the GWP100 and HTP were the main environmental problems associated with co-processing.(5)Compared with the conventional waste disposal methods,co-processing of classified domestic waste in cement kiln had the lowest life cycle cost.Compared with the conventional production of clinker,the internal and external costs of co-processing were reduced,and the life cycle cost decreased by 2.16%,with resource and energy cost being the main factor affecting the life cycle cost.Based on China’s cement production of 2.39 billion tons in 2020 and the promotion ratio of 3.5%,the cost savings of using this technology can be 736 million RMB.The marginal abatement costs of five pollutants were negative,indicating that cement kiln co-processing with classified domestic waste produced a wide range of energy-saving benefits along with emission reduction.