Stability and microbial community analysis during rotary drum composting of vegetable waste

Background Disposal of vegetable waste in landfills andillegal sites leads to emission of greenhouse gases andleachate production, thereby imposing major environmentalissues. As an alternative, this waste can be successfullyrecycled for its high nutrient content using compostingprocess.Results Five trials were made with the ratio of 6:3:1 oftrial 1 (50 kg), trial 2 (70 kg), trial 3 (90 kg), trial 4(120 kg) and trial 5 (150 kg) by adding 10 kg of dry leavesin each of the trials as bulking agent. Due to activemicrobial population and high biodegradable organicmatter in vegetable waste, early thermophilic phase wasobserved within 18–24 h of the composting process in allof the trials with a maximum of 61.4 C in trial 3. Totalmesophilic heterotrophs were observed in the range of7.1 9 1011 CFU g-1 and gradually reduced to 2.65 9 106CFU g-1 at the end of 20 days, which was considered dueto prolonged thermophilic phase maintained in trial 3. Anaverage of 54–56 C temperature was maintained for7 days in trial 3, with spore-forming population in the orderof 3.82 9 109 CFU g-1 contributing to higher organicdestruction. The populations of fungus, actinomycetes andstreptomycetes were observed to reduce during thermophilicphase and remained in the order of 2.85 9 104,3.8 9 106 and 4.1 9 105 CFU g-1, respectively, at the endof 20 days. CO2 evolution and OUR were in the order of0.89 and 0.32 mg g-1 VS d-1, respectively, in trial 3denoting maximum degradation of organic matter andstabilization of compost. Indicator organisms were foundwell with the standard limits due to elevated temperature.Conclusions Combinations of waste materials played amajor role in favoring microbial succession. Temperaturein the compost system had major effect on the survival ofthe microbial populations. Elevated temperatures favoredhigher degradation of organic matter, thereby stabilizingthe compost within proposed time of composting and alsodestructing the indicator pathogens.