塑料作为现代社会的重要基础材料之一，生产、消费和废弃量持续增长，其全生命周期的资源与环境影响也愈发受到关注。在气候变化日益严峻、各国高度关注碳中和的大背景下，我国也于2020年提出“双碳”国家目标。作为全球最大塑料生产和消费国，我国塑料碳减排势在必行。只有深入了解我国塑料碳排放现状，才能更具针对性地制定碳减排决策。因此本研究基于LCA-MFA耦合方法构建了中国主要品类塑料生命周期碳排放模型，对中国塑料碳排放总量进行了系统测算和多视角结构分析，具有重要的学术价值和政策意义。 本研究首先基于生命周期评价方法，分塑料品类构建了涵盖主要中间体、主要工艺路线的塑料生命周期碳排放强度测算框架。通过对大量文献、环评等资料的收集整理，构建了中国本土化的、含时间序列的塑料碳排放强度数据集，并与同类研究结果进行了分析对比。测算结果表明：在“从摇篮到大门”阶段， 2015-2019年中国PE、PP、PS、PVC、ABS、PET生产碳排放强度区间分别为2.9-3.4、3.7-4.7、2.4-3.5、3.3-5.4、4.2-5.1、3.1-4.6 tCO2/t制品。原材料开采-单体生产过程、能源供应对应的间接碳排放是最主要的碳排放来源，因此推动化工生产各阶段的节能增效对塑料碳减排具有重要意义。在废塑料处置阶段，不同品类废塑料处置方式对应的碳排放强度均呈现出简单焚烧＞能量回收＞材料回收＞填埋的特征，2019年这四种方式对应的碳排放强度区间分别为1.4-3.1、0.8-2.2、0.2、0.04 tCO2/t废塑料。 在此基础上，结合课题组开发的塑料动态物质流模型，基于LCA-MFA耦合方法构建了中国塑料生命周期碳排放模型，应用该模型测算了2015-2019年中国六大塑料碳排放总量。测算结果表明：中国六类塑料碳排放总量从2015年2.5亿吨CO2增长至2019年2.8亿吨CO2，2019年在中国温室气体排放总量中占比约2%。从塑料品类来看，PP、PVC和PE是主要的碳排放贡献者，2019年总占比达79%。从生命周期各阶段来看，2019年原材料开采-树脂生产、制品制造和废塑料处置阶段的碳排放占比分别为82.4%、9.4%和8.2%，其中原生塑料生产的高能耗导致的高碳排放强度是主要原因；废塑料处置阶段的碳排放占比在废塑料能量回收比例增加的驱动下呈持续增长趋势。基于对现阶段中国塑料碳排放特征的评估分析，本研究从降低塑料生产、消费量增速和降低塑料生命周期碳排放强度等角度提出了三点针对性的政策建议。

As one of the important basic materials in modern society, the production, use and disposal of plastics have been increasing continuously. The life cycle resource and environmental impacts have also attracted worldwide attention. Meanwhile, the increasingly severe climate change calls for strong actions, and China proposed its carbon peak and neutrality targets in 2020. As the world's largest plastic producer and consumer, the carbon emission reduction implemention in China’s plastic industry is imperative. However, the targeted decisions can only be made based on in-depth understanding of the current situation of China’s plastic carbon emissions. Therefore, based on the LCA-MFA coupling method, this study constructed China’s plastics life cycle carbon emission model, and carried out a systematic calculation and then multi-perspective structural analysis of the total carbon emissions of China’s plastics, which has important academic value and policy significance. Based on the LCA method, this study firstly constructed life cycle carbon emission intensity measurement framework by plastic categories. Then by integrating a large number of literatures and environmental impact assessments, a localized and time-series data set of plastic carbon emission intensity was constructed. The results were analyzed and compared with the results of similar researches. Our results showed that: in the stage of “from the cradle to gate”, the carbon emission intensity of China's PE, PP, PS, PVC, ABS and PET in 2015 -2019 were 2.9-3.4, 3.7-4.7, 2.4-3.5, 3.3- 5.4, 4.2-5.1 and 3.1-4.6 tCO2/t products. The process from raw material extraction to monomer production, and the indirect carbon emissions corresponding to energy supply were the most important sources of carbon emissions. Therefore, it is of great significance to promote energy conservation and efficiency in various chemical production processes. In the waste plastic disposal stage, the carbon emission intensity corresponding to smiple incinereation, energy recovery, material recycling and landfill of different plastics were 3.1, 0.8-2.2, 0.2, 0.04 tCO2/t waste plastics in 2019. On this basis, combined with the previously developed plastic dynamic material flow model, this study constructed China’s plastic life cycle carbon emission model based on the LCA-MFA coupling method. Then the total carbon emissions of China's six major plastics from 2015 to 2019 were calculated by applying this model. The results showed that the total carbon emissions of China’s plastics increased from 250 million tons CO2 in 2015 to 280 million tons CO2 in 2019, accounting for 2% of China's total GHG emissions in 2019. PP, PVC and PE were the main contributors to carbon emissions, accounting for 79% in 2019. From the perspective of life cycle stages, the proportion of the resin production, product manufacturing and waste plastic disposal stage was 82.4%, 9.4% and 8.2% respectively in 2019. The high carbon emission intensity resulted from energy consumption of virgin plastic production was the main reason. Driven by the increasing proportion of incineration, the proportion of carbon emissions in the waste plastic disposal stage continued to increase. Based on the evaluation of China’s plastic carbon emission characteristics, this study put forward three targeted carbon emission reduction policy recommendations from the perspective of slowing down growth in plastic production and consumption and reducing plastic life cycle carbon emission intensity.