International Journal of Scientific Engineering and Technology (ISSN : 2277-1581) Volume 2 Issue 4, pp : 216-221 1 April 2013 IJSET@2013 Page 216 Catalytic Effect of Tungsten on Anaerobic Digestion Process for Biogas Production from Fruit and Vegetable Wastes Das. A 1 , Mondal.C 2 1 Master of Bioprocess Engineering, Department of Chemical Engineering, Jadavpur University, West Bengal, India. 2 Department of Chemical Engineering, Jadavpur University, West Bengal, India. 1 enggaritra@hotmail.com Abstract – In the recent years global energy crisis increased at a fast pace. Demand for the use of fossil fuels for cooking and other commercial activities increased along with the increasing population of India. Use of renewable sources of energy viz. biogas for cooking etc can somewhat be an alternative for the excessive demand of fossil fuels like LPG. In this study, the catalytic effect of tungsten for maximizing biogas have been presented. Essentially, anaerobic digestion process have been conducted in batch reactors for a retention time of 15 days at a constant temperature of 27°C. Necessary cumulative and differential plots between yield of biogas and retention time have been studied for individual anaerobic digestion processes at different slurry and catalyst concentrations so as to observe the optimum slurry and catalyst concentration for maximum biogas production. Maximum yield of biogas have been obtained with 5% slurry concentration at 1.5g/l catalyst concentration. Keywords – catalytic effect, anaerobic digestion, retention time, slurry concentration, catalyst concentration. I.INTRODUCTION Biological conversion of wastes has been demonstrated as one of the most advantageous and effective method of reducing pollution. Anaerobic treatment of solid municipal wastes, especially food wastes is a cost effective technology (1, 2). Although the concept of biogas production is not new but process design for efficient energy production is not fully understood and research & development work is still going on to improve efficiency, reliability and applicability using various biomass (3). Moreover, in India FVW constitute about 5.6 million tonnes annually and currently these wastes are disposed by dumping on the outskirts of cities (4). Most promising alternative process of pyrolysis and incineration is to digest or degrade the organic matter using anaerobic digestion (5, 6). Anaerobic digestion is a biochemical process in which complex organic wastes (FVW) are converted to a mixture of methane and carbon dioxide collectively called biogas (3). Technically it is a four step process (7) namely hydrolysis, acidogenesis, acetogenesis and methanogenesis. Generally two categories of micro-organisms are involved for this type of conversion. The first among them is the acid formers which convert macro molecules like carbohydrates, proteins, starches, cellulose, lipids etc to organic acids (step one and step two). In the third step these organic acids are converted to acetate & finally in the fourth step the acetate is converted to methane & carbon dioxide by a group of organisms called methanogens. Solid retention time for batch digestion is pretty high (8). Time required for first two steps is very high that comsumes most of the time. Production of biogas can be enhanced by addition of trace elements that serve as micro nutrients for the anaerobic micro organisms. Supplementation of essential trace elements has been shown to maintain and stimulate the digestion process(9- 15). Enzymes required for biochemical reactions contain these trace elements in the form of co enzymes and co factors. The roles of trace elements have been reviewed in several publications (16, 17). However, information on the specific trace element requirement for anaerobic digestion process is still limited. The purpose of current study was to present the catalytic effect of tungsten on anaerobic digestion process and also to find the optimum slurry concentration at which maximum biogas yield have been obtained being catalyzed by tungsten at a definite concentration. II. MATERIALS AND METHODS A.Collection and preparation of sample Fruit and vegetable wastes (FVW) have been collected from local market and also from regular household activities like peeling , prior to cooking. Then these wastes have been cut into small pieces and subjected to sun drying for 5 days followed by drying in a hot air oven for 5 to 6 hours at a