Municipal solid waste composting with amendments reduces heavy metals hazard, ecological risks and greenhouse gases emission

Abstract Open dumping and landfilling of municipal solid waste (MSW) in India cause environmental hazards and greenhouse gases (GHGs) emissions. Therefore, studies require to assess the potential of aerobic composting of MSW to minimize these risks. This study evaluates the potential of MSW composting with or without some amendments (i.e. G-gypsum, ES-elemental sulphur and RS-rice straw) in minimizing these risks. The composition, physicochemical characteristics including heavy metals (HMs), the potential pollution hazards and GHGs emissions were assessed for the MSW collected from domestic and industrial sites of Haryana, India. Industrial MSW had higher pH (7.31) and HMs concentrations (e.g. Cr, Cd, Cu, Ni, Pb and Zn), than domestic MSW. HMs were found within the critical limits for both sites except Cr and Cu in industrial MSW. Composting lowered the HMs and ecological risk and increased N, P, K and organic carbon. Co-composting with amendments like gypsum, elemental sulphur and rice straw improved C:N ratio, nutrients concentration and accelerated the degradation process. The pollution indices enrichment factor, contamination factor, geoaccumulation index, ecological risk and potential ecological risk index indicated lower ecological risk and HMs concentration in domestic site MSW. On-site GHGs emission significantly differed in space and seasons. Emission of CO2, CH4 and N2O from domestic landfill site were 20%, 27% and 64% higher than industrial and higher in monsoon season, followed by summer and winter, respectively. The highest GHGs emission was from center (heap top) (924.58 mg m-2 h-1), followed by middle (805.23 mg m-2 h-1) and peripheral (717 mg m-2 h-1) area of sites. Use of ES and RS amendments in co-composting reduced up to 41% GHGs emission than landfill emissions. MSW co-composting with elemental sulphur and rice straw can be a potentially safer alternative for the management of both domestic and industrial MSW than open landfill dumping.