The effect of leaching and bulking agents on the quality of municipal solid waste compost

Compost quality varies greatly depending on the feedstocks used and the composting process. Thus, improving the quality of compost is highly important for producing a high-quality agricultural product. Accordingly, the effect of leaching and addition of wheat straw (WS) and wood shaving (WSH) as bulking agents (BAs) on the organic fraction of municipal solid waste (OFMSW) was evaluated through assessing their effects on composting process and final product quality. Two pilot-scale experiments were prepared, each consisting of 3 piles of 1.2 m³. The first experiment (A) has three plies: A1 =  (100% OFMSW), A2 =  (88.5% OFMSW + 11.5% WS) and A3 =  (90.1% OFMSW + 9.9% WSH). The second one (B), where OFMSW was subjected to leaching, has also three piles: B1 =  (100% OFMSW), B2 =  (96.2% OFMSW + 3.8% WS) and B3 =  (97.1% OFMSW + 2.9% WSH). The results showed that the addition of BAs and leaching treatments accelerated the starting step, raised the temperature and decomposing process, and reduced the duration of the thermophilic phase. The addition of BAs, primarily WS, increased compost stability and maturity in terms of greater total organic carbon (TOC) 22.8-25.5%, total kjeldahl nitrogen (TKN) 1.73-2.37%, germination index (GI) 84.6-107.2%, and reduced C/N 10.8-14 ratio and CO₂ evolution rate 2.67-3.69 mg CO₂ - C/g OM/d. The use of the leaching process and BAa decreased EC values and heavy metal content in the final products. The implementation of these experimental approaches can be used successfully to reduce the undesired high salt and heavy metal content in the final composts.