The growing importance of waste-to-energy (WTE) incineration in China's anthropogenic mercury emissions: Emission inventories and reduction strategies

Waste-to-energy (WTE) incineration has been increasingly adopted for municipal solid waste (MSW) disposal in China, which already accounts for nearly 40% of the global installed capacity and electricity generation from WTE. This review identifies the growing importance of WTE incineration as a source of anthropogenic mercury emissions in China, summarizes the mercury control practices at WTE facilities, estimates the inventories of mercury emissions from WTE and those after the implementation of the more stringent air emission standards, and recommends key measures to further reduce the mercury emissions from WTE industry in China. WTE incineration in China was estimated to have a mean current mercury emission factor (EF) of 0.083 g/tonne (with 95% confidence intervals of 0.056-0.116 g/tonne) based on the mercury contents in MSW and the typical removal efficiencies of air pollution control devices (APCDs). The total mercury emissions from WTE incineration were estimated to be around 6.1 tonnes in 2016, and were predicted to reach 10.6 tonnes by 2020 based on its fast growth. The recently adopted more stringent emission standard for mercury can help curb the growth in mercury emissions from WTE incineration, while the gradual implementation of the Minamata Convention on Mercury is expected to contribute to significant reduction in the emissions of mercury from WTE incineration in the long run. Current estimations for mercury emission inventories from WTE incineration in China carry large uncertainty due to the overall scarcity of data. Thus, more work should be conducted to better monitor and quantify the mercury contents in MSW, and the mercury removal efficiencies of APCDs and the emission rates of mercury at WTE facilities. Meanwhile, China also needs to develop effective recycling and waste-sorting programs to divert the mercury-containing waste items from entering the incinerators and thus reduce the mercury emissions while promoting waste disposal by WTE.