Evolution of chemical and biological characterization during thermophilic composting of vegetable waste using rotary drum composter

Vegetable waste usually contains high levels of organic matter, moisture and nutrients that make the waste unsuitable for disposal in municipal landfills. Composting of vegetable waste is in practice by many urban local bodies, and therefore, it was composted along with cow dung and sawdust in a 550-L batch scale rotary drum composter. Four different trials of varying waste combinations of vegetable waste, cow dung and sawdust, i.e., trial 1 (5:4:1), trial 2 (6:2:1), trial 3 (7:2:1) and trial 4 (8:1:1) were composted by adding 10 kg of dry leaves as bulking agent with a total mass of 100 kg. With proper combinations of organic waste mix, a maximum temperature of 66.5 C was observed in trial 1 and 61.4 C in trial 2, when compared to other two trials with prolonged thermophilic period. Due to such elevated temperature, higher degradation was observed in trials 1 and 2 with inactivation of pathogens to considerable amounts. Furthermore, final compost had total nitrogen of 2.31 and 3.01 %, total phosphorous of 4.30 and 3.27 % and final carbon-to-nitrogen ratio of 15 and 12, in trials 1 and 2, respectively. Carbon dioxide evolution and oxygen uptake rate of compost samples was analyzed for its stability and was observed to reduce completely at the end of 20 days with lower emission rates.