Waste sorting policy impact on mercury emissions from municipal solid waste incineration: Evidence from China

Mandatory waste sorting policy in Beijing (2020) lowered mercury inputs to the representative MSWI plant by 67.7 % versus 2019 through removal of batteries and other Hg-rich articles. The front-end change propagated through the entire system, cutting stack emissions 82 % (1.35 ± 0.6 → 0.24 ± 0.05 µg m/³) and decreasing the Hg²⁺ fraction from 45.5 % to 28 %. Higher post-sorting plastic loads elevated chlorine, promoting in-furnace oxidation of Hg⁰; the resultant Hg²⁺ was efficiently captured by existing wet scrubbing/fabric filters. Mass-balance and speciation data show that source separation functions as a chemical pre-treatment that shifts mercury toward easily removable forms, amplifying downstream control performance without hardware retrofits.Implications: This study provides the first field-scale proof that waste-classification policy can govern mercury emission chemistry. By altering waste composition at the source, mandatory sorting oxidizes elemental mercury and enhances removal efficiency, offering decision-makers a low-cost, proactive tool to meet stringent Hg limits while advancing circular-economy goals.