STUDY OF BIODEGRADATION OF ORGANIC WASTE FOR SMALL COMMUNITIES

Abstract

In India, every year, approximately 36.5 million tonnes of degradable organic matter is generated in urban areas, and only a fraction (less than 10%) is intermittently processed in mechanical compost plants (Shekdar, 1999) and remaining (more than 90% ) of waste is disposed of in uncontrolled dumps (Selvem and Rajshekhar, 2002). This assessment/ management of solid waste is even poor in small town and villages. In the present study the biodegradation potential of organic waste using vermicomposting and biomethanation is being investigated. For vermicomposting two different earthworm species were used, one exotic species Eisenia fetida and one native species Perionyx excavates.Vermicomposting was performed on two different substrate, vegetable waste and sludge obtained from biomethanation of vegetable waste. For vegetable waste after vermicomposting the C/N ratio reduced to 13, TOC reduced from 54 to 27 and 32% increase in earthworm biomass was observed. Similarly for sludge from biomethanation, the initial C/N ratio reduced from 19 to 8, TOC reduced from 37% to 32%, and 30% increase in earthworm biomass was observed. Biomethanation study was performed using two different substrates, cattle manure and vegetable waste. Two different sets of experiments were performed on both the substrate. Effect of mixing and square wave temperature variation on biogas generated and other allied parameters were studied. During the course of both sets of experiment HRT of 15 days, OLR of 0.5 Kg/m3/day and TS of 1% was maintained. During mixing experiment the maximum gas output was noticed for continuous mixing for both the substrate. Initial/final mixing and intermittent mixing gave same results in terms of biogas generation and stability of the reactor. Identical results were observed for experiments with square wave temperature variation (24°C — 32 °C) for both the substrate. The volume of biogas generated increased at higher operating temperature, and reduction of VFA accumulating inside the reactor during this period suggests efficient conversion to biogas.