Research On The Accounting Method And Application Of Carbon Emissions In Life Cycle Of Urban Stormwater System

Under the background of"dual carbon",coping with the greenhouse effect has become one of the most important issues in the process of urban development in China.The water system is a vital resource base and life support system in the economy and society.However,with the rapid growth of water use,regional water systems are facing enormous challenges,including the inability of water conservancy facilities and water and drainage networks to meet the growing demand for water,as well as increasing energy consumption and carbon emissions from water systems.In order to promote the collaborative optimization of water energy and carbon emission reduction,plan the stormwater system based on low-carbon ecological construction,and jointly contribute to the construction of sponge city and the goal of"dual carbon",taking the urban stormwater system as the research object,the carbon emission accounting method of the stormwater system at the facility,area and urban scale was proposed,and the carbon emission accounting software of the stormwater system that can realize automatic calculation was established.Furthermore,the carbon emissions of stormwater system in sponge cities in the study area were quantified,the key factors affecting carbon emission characteristics were analyzed,and the carbon emission reduction strategy of stormwater system was constructed.It has certain guiding significance for correctly understanding carbon emissions in the stormwater field and exploring carbon emission reduction paths.The main results are as follows:（1）Applying the life cycle assessment（LCA）to analyze the carbon emission inventory of the whole life cycle process of the stormwater system from production,transportation,construction,operation and use of stormwater infrastructure materials to final disposal in three stages:construction,operation and maintenance,asset replacement and demolition.Based on the LCA method,a facility-scale carbon emission calculation method is proposed,the carbon emissions of stormwater infrastructure are quantitatively analyzed,and the impacts of construction,operation and maintenance,asset replacement and demolition stages in different life cycle stages are compared,and a quick check table of typical stormwater infrastructure carbon emission intensity is obtained.Furthermore,the carbon emission calculation methods at the district scale and the city scale are proposed,and the carbon emission intensity of some typical stormwater infrastructure construction investment is obtained.（2）A comprehensive dataset of greenhouse gas emissions from the whole life cycle of localized stormwater system was established,and a user-realized automatic calculation of stormwater system carbon emission accounting software was developed according to the established carbon emission accounting method of the whole life cycle of the stormwater system,namely"Greenhouse Gas Accounting Software for the Full Life Cycle of Stormwater System（2023）"（hereinafter referred to as"stormwater system discharge software"）.It includes a database of greenhouse gas emission coefficient factors with relatively complete data,including seven major sectors,including materials,transportation,and calculation,which can more comprehensively and accurately estimate the carbon emissions and carbon sinks of stormwater systems in actual cases,which are initially reflected in the form of Excel.（3）In order to verify the feasibility of carbon emission calculation method and stormwater system discharge software,the carbon emissions in the construction,operation and maintenance stage of sponge city stormwater system in sponge city were quantified by taking the current situation of sponge city planning in Beijing as a reference and the sponge city planning area of 100 km²as the research area,and the correlation between control indicators such as the proportion of sponge city area,the total runoff control rate,and the proportion of pressure flow pipe network and carbon emissions was analyzed.The results show that the carbon emissions in the construction stage of sponge cities are mainly concentrated in the material production stage,and the embodied carbon of most facilities accounts for more than 80%of the total carbon emissions in the construction stage,and the carbon emissions related to construction are relatively small.At the same level of stormwater control,the carbon emissions of gray stormwater infrastructure are higher than those of green stormwater infrastructure;The carbon emissions（in terms of CO₂）in the construction stage of the study area during the 30 a lifetime were 173,600 tons,and due to the significant carbon sink role of green stormwater infrastructures,the carbon emissions in the operation stage were negative,which was-167,100 tons.（4）The proportion of sponge city area,the total annual runoff control rate and the drainage mode were the key factors affecting the carbon emissions in the construction and operation of sponge city,and for every 1%increase in the proportion of sponge city area and the total annual runoff control rate,the carbon emissions in the whole life period were reduced by about 1,900 tons and 2,500 tons,respectively,and the proportion of pressure flow pipe network decreased by 1%.The average lifetime carbon emission reduction is about 200tons.（5）From the perspective of the full life cycle of stormwater systems,the entire process of construction,operation and maintenance,asset replacement,and demolition is always accompanied by carbon emission activities.After conducting carbon accounting for stormwater systems,the optimization of emission reduction strategies is also particularly important.Based on the characteristics of carbon emissions from stormwater systems,this paper proposes technical paths and strategies for carbon emission reduction in stormwater systems from three directions:carbon reduction,carbon replacement,and carbon sequestration,starting from the entire process of"from cradle to grave.".When it comes to stormwater systems,their complex composition and numerous carbon emission activity units determine the multiple sites and corresponding technologies that can be used to reduce carbon emissions.It is further separated into four categories of action strategies,namely,source control,process management,resource optimization,and plant carbon sequestration.Analyze technical solutions,action strategies,and corresponding implementation characteristics to provide reference for formulating carbon emission reduction plans for stormwater systems.In view of the realization of the goal of"carbon peaking and carbon neutrality"and the promotion of the concept of sponge city,the problems of high carbon emission,high energy consumption and carbon emission reduction limitations existing in the traditional drainage mode,focusing on the functional needs of increasing green stormwater infrastructure to improve the diversified improvement and utilization of stormwater and carbon emission reduction,and studying the carbon accounting,emission characteristics and carbon emission reduction expansion methods and methods of stormwater system,which has important academic value and practical significance for correctly understanding the carbon emission level in the stormwater field,exploring the carbon emission reduction path in the stormwater field,and serving the"dual carbon"goal.It provides theoretical support and decision-making basis for the formulation of carbon emission reduction targets and the measurement of energy conservation and emission reduction potential of stormwater systems,and provides practical guidance and reference for the evaluation of low-carbon construction of stormwater systems.