AD-MTECH-10-403

Assessment of various substrates for biogas production
Mane Archana Baburao, M.Tech, 10, 69 pp.
Department of CTARA
Indian Institute of Technology Bombay, Powai, Mumbai 400 076.
Supervisor(s): Bakul Rao, Anand Rao

Biogas, as a renewable energy source, is gaining importance in todays era of global warming and depleting sources of fossil fuels. Biogas is produced by anaerobic digestion (digestion in the absence of oxygen) of organic material which can be available from various wastes such as agro industrial waste,urban and rural wastes, human and animal waste and aquatic plants.

This study deals particularly with characterisation of fruit and vegetable waste and the comparison of the performance of bi- phasic biogas digester while using the fruit and vegetable waste as a substrate with that of monophasic digester. Biphasic biogas reactors were fabricated from acrylic material which consisted of acidification tank of 14.4 liter capacity and methanisation tank of 36 liter capacity. The monophasic biogas reactor was of the same capacity as that of the methanisation tank. The experimental set up consisted of two acidification tanks and four methanisation tanks and one monophasic biogas reactor. A common acidification reactor was used for feeding two methanisation tanks. The start-up inoculant (10\%) was from the biogas reactor using deoiled cake as a substrate.

The characterization of fruit and vegetable waste (cabbage leaves, potato skin, banana skin, waste tomato,cauliflower leaves, lady finger remains, cucumber skin, spinach remains, watermelon skin, sweet lemon skin, mango skin, orange skin, onion skin, carrot skin, cluster beans remains) and influent and effluent was carried out by following the APHA standards. The characterization of fruit and vegetable waste includes determination of Total solids, Volatile solids and C/N ratio. The total solids vary in the range of 5-44 % w/w, volatile solids in the range of 80-90% w/w and C/N ratio (dry basis) from 6.5 to 212. The characterisation of fruit and vegetable waste helped in determination of possible combination of easily available substrates for experimentation, which will yield C/N ratio of 25 and organic loading rate of 6% and 8% total solids.

Experiments were carried out to understand the effect of two parameters namely hydraulic retention time and organic loading rate on biogas production in the fabricated biphasic biogas reactor and monophasic biogas reactor. The operating conditions were organic loading rate of 6% and 8% and hydraulic retention time of 10 and 12 days and temperature of 55 ºC.

Characterisation of the influent and effluent, which consisted of determination of Total solids and COD, was carried out to measure the performance of the biogas digester in terms of reduction in TS and organic matter present in the influent.