Biogas production from canteen waste

Abstract

Abstract Day by day as the population increases, food waste keeps on growing. This waste needs to be managed in order to reduce the number of landfills and to use food waste efficiently. Among the various processes available, Anaerobic Digestion (AD) of food waste is one of the alternatives for processing food waste. The two biggest obstacles to anaerobic digestion of food waste are high biodegradability and high C/N ratio. The C/N ratio determines the ratio between substrate and nutrients; the latter is essential for microbial synthesis and for providing alkalinity through ammonia metabolism. Biogas, a product of the anaerobic digestion process, is a clean and renewable form of energy that can replace conventional energy sources that cause ecological-environmental problems and at the same time are depleted more quickly. The aim of this work was to increase the nitrogen content to enhance the production of biogas from canteen waste. During the process, two digesters of the same capacity were operated. Anaerobic digestion of canteen waste along with addition of ammonium chloride was carried out in Digester 1 while AD of only canteen waste was carried out in Digester 2. The amount of biogas produced in Digester 1 was in the range of 0.04 m3/kg–0.075 m3/kg, while in Digester 2 the volume range was 0.02 m3/kg–0.04 m3/kg. The average biogas produced in digester 1 consisting of canteen waste and nitrogen source was 0.053 m3/kg while biogas production in digester 2 with only canteen waste was 0.030 m3/kg. So, biogas produced by addition of nitrogen source was 77 % higher than that of only canteen waste. From this study we obtained a higher amount of biogas by addition of ammonium chloride as an external nitrogen source. Nitrogen demand of methanogens was fulfilled by additional supply of nitrogen resulting in increased quantity of biogas. Therefore, in anaerobic digestion addition of ammonium chloride was beneficial for food waste digestion. Hence, nitrogen content in canteen waste turned out to be the main parameter affecting anaerobic digestion of canteen waste which is justified in this research.