The Anaerobic Digestion of Waste Food Materials by Using Cow Dung: A New Methodology to Produce Biogas

Abstract

From kitchen and dining place lots of food wastes are generated and these create many problems if these are disposed directly by dumping. Instead of dumping, the aforesaid wastes can be utilized in a better way to produce valuable products such as biogas. In the open literature, different methodologies of digestion by using bacteria or microorganisms have been described. The use of bacteria or microorganism increases the cost of conversion. However, the literature does not disclose any information on the process which describes the digestion of the food waste without the use of microorganism directly. Hence, in the current work, an attempt has been made to digest food waste and to produce biogas by using a novel technique which does not use the bacteria directly. In the current work, nourishment waste was gathered from various messes of National Institute of Technology Rourkela and these were given as the feedstock to our reactor which functions as an anaerobic digester framework to deliver biogas. For the production of biogas, food waste was mixed with cow dung at different ratios and the cow dung acts as an inoculum in the current case as it contains both methanogenic and acid-forming bacteria. By using a gas analyzer, after experimentation, the composition of the gas was analyzed and the achieved composition confirms that the obtained gas is the biogas. The result shows that the rate of biogas production is influenced by the pH, temperature and solid-to-water ratio. The biogas production rate is found to be maximum at an intermediate solid-to-water ratio of 1:2 and at the neutral range of pH. Furthermore, the biogas production rate increases from 110 to 142 ml with the rising temperature from 25 to 40 °C, and with the further increment in temperature, the methane production rate declines. In addition to the above, the process behavior at different conditions has been modeled by using response surface methodology technique and also the optimum conditions (T = 44.03 °C, R = 0.44 and pH 7.02) for the maximum production of biogas has been determined.