Insights into carbon loss reduction during aerobic composting of organicsolid waste: A meta-analysis and comprehensive literature review

Carbon neutrality is now receiving global concerns for the sustainable development of human societies, of which howto reduce greenhouse gases (GHGs) emissions and enhance carbon conservation and sequestration becomes increas-ingly critical. Therefore, this study conducted a meta-analysis and literature review to assess carbon loss and to explorethe main factors that impact carbon loss during organic solid waste (OSW) composting. The results indicated that over40 % of carbon was lost through composting, mainly as CO2-C and merely as CH4-C. Experimental scale, feedstock va-rieties, composting systems, etc., all impacted the carbon loss, and there was generally higher carbon loss under opti-mal conditions (i.e., C/N ratio (15-25), pH (6.5-7.5), moisture content (65-75 %)). Most mitigation strategies inconventional composting (CC) systems (e.g., additive supplementary, feedstock adjustment, and optimized aeration,etc.) barely mediated the TC and CO2-C loss but dramatically reduced the emission of CH4-C through composting.Among them, feedstock adjustment by elevating the feedstock C/N ratio effectively reduced the TC loss, and chemicaladditives facilitated the conservation of both carbon and nitrogen. By comparison, there was generally higher carbonloss in the novel composting systems (e.g. hyperthermophilic and electricfield enhanced composting, etc.). However,the impacts of different mitigation strategies and novel composting systems on carbon loss reduction throughcomposting were probably underestimated for the inappropriate evaluation methods (composting period-dependentinstead of maturity originated). Therefore, further studies are needed to explore carbon transformation throughcomposting, to establish methods and standards for carbon loss evaluation, and to develop novel techniques and sys-tems for enhancedcarbon conservation through composting.Overall,the results ofthis study could providea referencefor carbon-friendly composting for future OSW management under the background of global carbon neutrality