LCA as a decision support tool for the environmental improvement of organic fraction of municipal solid waste composting in China

Composting is an effective way to manage Organic fraction of municipal solid waste (OFMSW). Subpar compost quality and negative environmental impacts pose the main challenges to OFMSW composting. Adding bulking agents (BAs) is crucial in OFMSW composting. Nevertheless, the overall environmental impacts of composting of OFMSW and BAs from cradle to grave based on an industrial composting plan have never been thoroughly studied. A LCA was conducted on an OFMSW industrial composting plant (1000 MT/day) with different types and ratios of BAs. The BAs included ternary-BAs (i.e. corn stover, watermelon straw, and yard trimmings) with ratios of 5%, 10%, and 20%, as well as singular BAs (yard trimmings) with a ratio of 20%. Additionally, two byproduct usage pathways were also investigated: 100% by-product incineration (Plan A) and one part of the byproduct is dried for reuse as BAs in the next batch while another part is incinerated (Plan B). Results showed that the favorable strategies for mitigating global warming potential, ecotoxicity potential, and acidification/eutrophication potential are 5% ternary BAs, 10% ternary BAs, and 20% yard trimmings, respectively. Compared with Plan B, Plan A has a smaller environmental impact. OFMSW composting with 20% ternary BAs benefits from long periods of high temperature but leads to higher gas emissions and a lower mass of compost. It should be noticed that "One-size-fits-all" policies and regulations for reducing the environmental footprint of OFMSW composting management should be avoided in China.