Optimization Treatment Path Of Municipal Solid Waste And Environmental Impact Assessment In Zhengzhou City

With the rapid development of China’s economy and the acceleration of urbanization,the total amount of municipal solid waste(MSW)in China has increased rapidly.In 2019,the total amount of MSW in the country has reached 240.0 million tons,and 45.6%of the MSW was disposed in sanitary landfills.MSW landfills occupy a large amount of urban land space,causing serious environmental problems such as"garbage siege" and soil and water pollution.Thus,the Ministry of Ecology and Environment issued the work plan for the construction of a zero-waste city,vigorously promoting the reduction,recycling and harmless treatment of MSW,giving full play to the synergistic effect of pollution reduction and carbon reduction,and putting forward higher requirements for the treatment of urban household waste.Therefore,it is urgent to find a more scientific and environmentally friendly way to dispose of MSW.In this study,Zhengzhou was selected to study the optimal treatment path for MSW.Firstly,through calculation and field research data,a list of greenhouse gas and air pollutant emissions from MSW disposal in Zhengzhou was established.Secondly,this study used life cycle assessment method(LCA)to establish a life cycle inventory including MSW landfill treatment and incineration treatment,and evaluated eight environmental impacts of the two treatment methods,including global warming potential(GWP),acidification potential(AP),eutrophication potential(EP),freshwater ecotoxicity potential(FAETP),human toxicity potential(HTP),photochemical ozone creation potential(POCP),abiotic depletion potential(ADP),and terrestric ecotoxicity potential(TETP).After that,this study used the gray GM(1,1)prediction model to predict the future MSW production in Zhengzhou.By setting the baseline scenario,the scenario of increasing the proportion of incineration power generation,the scenario of MSW classification and treatment,and the scenario of increasing the proportion of composting,analyzing the environmental impact and energy-saving and emission reduction benefits of each scenario,in order to explore the optimal treatment path.The main conclusions are as follows:(1)In recent years,the output of MSW in Zhengzhou has grown rapidly,and landfill is the main treatment method,emitting a large amount of greenhouse gases and air pollutants.In 2019,the total MSW reached 268.9×104 tons,of which 66.5%was landfilled.Through the establishment of greenhouse gas and air pollutant emission inventory of MSW treatment in 2019,the greenhouse gas emission of MSW treatment in Zhengzhou was 333.0×104 tons of CO2-eq,and the MSW landfill was the main emission source,accounting for 92.0%of the emission.The emissions of NOx,H2S and CO from MSW treatment in Zhengzhou were 852.0 tons,618.0 tons and 512.0 tons respectively.NOx and heavy metal pollutants mainly come from MSW incineration power plant,while H2S and CO are mainly produced by MSW landfill.(2)The LCA results show that MSW incineration treatment will produce significant GWP and HTP environmental impacts,and the incineration process is the main pollutant generating process.The GWP and HTP are the main types of environmental impact in MSW incineration power plant,and their contribution rate to the overall environmental impact is as high as 69.7%.The contribution rate of MSW to the comprehensive environmental impact during the incineration process reaches 97.0%,which is far greater than that of the MSW transportation.process,fly ash treatment process and wastewater treatment process.In addition,the environmental impact of MSW incineration power generation in Zhengzhou is smaller than that of sanitary landfill.(3)The scenario of MSW classification and treatment(S3)has the smallest comprehensive environmental impact and significant energy saving and emission reduction benefits.Compared with the baseline scenario(S1),the scenario of increasing the proportion of incineration power generation(S2),and the scenario of increasing the proportion of composting(S4),the comprehensive environmental impact of S3 in 2030 is reduced by 29.2%,3.7%,and 15.1%,respectively.In terms of environmental impact,compared with scenario S1,POCP had the best improvement,achieving 84.9%reduction in emissions,followed by GWP with 49.4%reduction.Compared with scenario S1,Scenario S3 can reduce greenhouse gas emissions by 3.4×106 CO2-eq,reduce air pollutants NH3,VOCs and H2S emissions by 208.4 tons,177.9 tons and 1022.9 tons,and reduce diesel use by 17.1 kt.In the future,Zhengzhou should accelerate the classification of MSW,reduce the landfill treatment of MSW and increase the proportion of incineration power generation treatment and resource treatment.This study carried out an environmental impact assessment on the MSW optimal treatment path in Zhengzhou,which can help decision makers master the current situation of MSW generation and treatment in Zhengzhou.It provides theoretical support for Zhengzhou government departments to promote the classification of MSW,accelerate the establishment of MSW collection,transportation and disposal system covering the whole society and realize the optimal treatment of MSW.