Biogas production from food waste from a prototype biogas digester

Abstract

Food waste from a school feeding nutrition program, if not correctly disposed, has a high level of pollution. Food waste can be utilised as a substrate for biogas production. The aim of the research was to construct a low-cost biogas digester for Bongumusa FET School in Mpumalanga province in South Africa and to assess its performance when fed with available food waste. A prototype biogas digester was designed, constructed and fed with food waste namely: vegetable peels, mealie meal, samp, rice, pilchards and fruit peels. The food waste was crushed and mixed with water before it was fed into the biogas digester. Cow dung was used as inoculum for the food waste. The temperature of slurry, the pH and biogas production were measured during a retention time of thirty days. It was observed that the initial pH dropped at the start of the experiment and this was attributed to the volatile fatty acid formation in acidogenesis and acetogenesis. The pH began to rise gradually as the volatile fatty acids were consumed by the methanogens to methane and carbon dioxide. From the results, it was observed that food waste is a good source of biogas for the school. In addition, the food waste was found to be an attractive method for environmental protection and energy saving for Bongumusa FET School. The biogas from the food waste can be used to replace imported Liquid Petroleum Gas (LPG) that is used in the school for heating purposes.