A cost-effective microbial slurry technology for rapid composting of municipal solid wastes in waste dump sites in India and its feasibility for use in Australia

Abstract

This short article reports on commercial composting ‘slurry’ now available in India. The slurry culture containing active decomposer bacteria and enzymes is spread on the surface of the garbage and inside the heaps in windrows constructed at waste dump sites. The microbes produce hydrolysing enzymes to break down the long chain complexes of the organic substrates. About 1 kg of ‘slurry’ culture in the colloidal emulsion form mixed with 20 litres of water is sprayed on about 3 m of solid waste. For one tonne of waste 200 litres of slurry water are needed. The waste heaps are turned once in 7 to 10 days for proper aeration and the inoculant slurry is sprayed at each turning to enhance decomposition and to maintain the proper moisture level which is usually 45–55 percent. The process is exothermic and the windrows reach a temperature of 70°–75°C within 24–36 hours, killing many harmful pathogens and repelling all birds, stray animals, flies and mosquitos from the dump site. The entire process is completed within 4–6 weeks and as the decomposition is completed the temperature falls to normal. About 40–45 percent of the undecomposed matter is of recyclable materials, and of the rest about 25–30 percent requires safe disposal in adjacent land-fill sites. The problem of emission from tip gases and of leachate and discharge of effluents is greatly reduced. The foul odor of the tip also disappears within 2–3 days of sanitization. The compost produced is rich in sodium, potassium and phosphorous as well as certain trace elements, and contains active nitrogen fixing and phosphate solubulising bacteria.