Anaerobic Digestion of Vegetable Wastes Using Biochemical Methane Potential Assays

Abstract

Solid wastes generation is a major problem in Mauritius in terms of wastes disposal with vegetable wastes representing 40–46 % the organic waste stream by mass. This study focused on the anaerobic digestion (AD) of vegetable wastes using biochemical methane potential (BMP) assays to assess the performance of AD processes in treating these wastes in a sustainable manner. 2,000 mL plastic bottles were used as anaerobic digesters for the assays and the vegetable wastes comprising of carrots, potatoes, cabbage and beetroots were ground and seeded with inoculum in a ratio 4:1 (volume basis). The inoculum used was mature sludge taken from an anaerobic digester treating cattle wastes. The inoculated substrates were then fed in the digesters, purged with N2 and sealed with rubber septum. The AD process was allowed to run over a hydraulic retention time (HRT) of 20 days. Results showed a total solids (TS) reduction of 62.1 %, volatile solids (VS) reduction of 66.4 % and COD reduction of 64.9 % which demonstrated effective degradation of the substrates during the digestion process. The biogas yield was 0.360 L/g VS fed and this value was in agreement with published data. These results hence showed that vegetable wastes can be effectively treated by AD. The next phases of the study consist in investigating the AD process of wastewater treatment sludge and the effects of sonication on AD of vegetable wastes and sludge, with special emphasis on process parameters.KeywordsAnaerobic digestionBiogasBiochemical methane potential assayChemical oxygen demandVolatile solids