Drum composting of municipal solid waste

The high initial C/N ratio (> 30) found in Indian municipal solid waste (MSW) leads to more time required for composting (> 3 months), with poor-quality compost production. Therefore, the effects of MSW amended with cattle manure (trial 1) and tree leaves (trial 2) were compared with unamended MSW (control) in a rotary drum composter. The initial C/N ratios of trial 1 and trial 2 were kept at 22, as compared to 32 for the MSW control sample. It was observed that trial 1 produced high-quality and stable compost within 20 days. It showed higher final total nitrogen (2.2%), final total phosphorus (3.2 g/kg) and low electrical conductivity (2.7 dS/m). At the end of 20 days, higher degradation caused lower final oxygen uptake rate (OUR) (1.8 mg/g volatile solids (VS)/day), final CO2 evolution (1.0 mg/g VS/day) and final C/N ratio (7.8). Trial 2 produced good-quality and stable compost resulting in 1.9% of total nitrogen, 2.7% of total phosphorus and low OUR (2.0 mg/g VS/day), CO2 evolution (1.5 mg/g VS/day) and C/N ratio (10.1) after 20 days ofcomposting. However, the control sample with an initial C/N ratio of 32 showed higher OUR (3.6 mg/g VS/day) and CO2 evolution (2.6 mg/g VS/day) comprising a lower concentration of total nitrogen (1.6%) and total phosphorus (2.3 g/kg), which indicated an unstable and low-quality product as compared to trials 1 and 2. Therefore, results showed that the characteristics of MSW amended with cattle manure and tree leaves significantly influence the compost quality and process dynamics in a rotary drum composter.