Effect of physico-chemico-biological and operational parameters on composting of organic fraction of municipal solid waste and gaseous products emission: review

Composting enables microbial decomposition of biodegradable organic fractions of municipal solid waste (OFMSW) and converts them into a valuable resource having profuse application in agriculture and horticulture. The efficiency of composting, primarily, would depend upon physico-chemico-biological properties of the feedstock (moisture content, particle size and organic matter) and operational parameters (temperature, aeration rate and frequency, presence of bulking agents and microorganisms). However, lack of appropriate selection of the initial physico-chemico-biological properties of municipal solid waste (MSW) and inadequate maintenance of operational conditions during composting results in generating low-quality end products with undesirable characteristics, such as phytotoxicity and nutrients-deficiency. Also, the release of toxic elements, greenhouse gases and volatile organic compounds (odorants) into the environment are other major issues related to composting technology, which need immediate attention of the researchers. Hence, a critical synthesis of the literature has been conducted to understand the effect of different (i) physical (particle size, moisture content), (ii) chemical (pH, elemental composition), (iii) biological (type of microorganisms, enzymatic activities) and (iv) operational (temperature, aeration strategy, turning frequency, addition of bulking agents) parameters on the composting of OFMSW and emission of major gaseous products. Furthermore, by utilizing the available data in the literature, several trends have been developed to depict the impact of substrate characteristics and operational conditions on compost quality and emission of gaseous products. These relationships would be instrumental in devising general recommendations on the selection of initial properties of MSW to (i) obtain superior quality compost and (ii) reduce the emission of harmful gaseous products during composting