A comprehensive review on the decentralized composting systems for household biodegradable waste management

Municipal solid waste primarily consists of household biodegradable waste (HBW). HBW treatment is a crucial step in many countries due to rapid urbanization. Composting is an effective technique to treat HBW. However, conventional composting systems are unable to produce matured compost (MC), as well as releasing huge amounts of greenhouse and odorous gases. Therefore, this review attempts to suggest suitable composting system to manage HBW, role of additives and bulking agents in composting process, identify knowledge gaps and recommend future research directions. Centralized composting systems are unable to produce MC due to improper sorting and inadequate aeration for composting substrate. Recently, decentralized compost systems (DCS) are becoming more popular due to effective solid waste reduction at the household and/or community level itself, thereby reducing the burden on municipalities. Solid waste sorting and aeration for the composting substrate is easy at DCS, thereby producing MC. However, Mono-composting of HBW in DCS leads to production of immature compost and release greenhouse and odorous gases due to lower free air space and carbon-to-nitrogen ratios, and higher moisture content. Mixing HBW with additives and bulking agents in DCS resulted in a proper initial substrate for composting, allowing rapid degradation of substrate due to longer duration of thermophilic phase and produce MC within a shorter duration. However, people have lack of awareness about solid waste management is the biggest challenge. More studies are needed to eliminate greenhouse and odorous gases emissions by mixing different combinations of bulking agents and additives (mainly microbial additives) to HBW in DCS.