Low carbon potential of urban symbiosis under different municipal solid waste sorting modes based on a system dynamic method

Urban symbiosis (UrS) is an innovative application of circular economy focusing on municipal solid waste (MSW). However, few studies have been conducted to forecast the impact of UrS on climate change under different MSW sorting policies such as four-category/two-category MSW separation standards and high/low sorting rates from a long-term and dynamic perspective. This study develops a system dynamics model to simulate the greenhouse gas (GHG) emission reduction potential and the energy saving potential of UrS under different MSW sorting modes in Shanghai for the period of 2020–2050. The results show that UrS with four-category MSW separation and a high sorting rate (scenario S1) has the highest energy saving and GHG reduction potential at both annual level and accumulative level, approximately 10.75 times the energy saving and 146.30% of the GHG emission reduction compared with the Business-As-Usual (BAU) scenario in 2050. Meanwhile, the scenario of two-category MSW sorting and a high sorting rate (S3) can further help reduce 12.84% GHG emissions than the scenario of four-category MSW sorting and low sorting rates (S2) in 2050. Among all the UrS measures, waste plastic recovery can contribute the most GHG emission and energy consumption reductions, with figures of approximately 2.15 Mt and 17.28 Mtce, respectively. Finally, policy recommendations on strengthening implementation of four-category MSW separation, making efficient two-category MSW separation as a backup plan, and promoting reutilization of waste plastic and Refuse Plastic & Paper Fuel technology are proposed.