VARIATION OF COCOA LEAVES, COW DUNG, RICE BRAN AND WATER HYACINTH SUBSTRATES FOR THE MICROBIAL PRODUCTION OF BIOGAS

Abstract

Varied quantities of cocoa leaves, cow dung, rice bran and water hyacinth were investigated for biogas production potential. Samples were subjected to microbiological analysis using standard technique, proximate and mineral composition analysis. The samples were sundried and milled separately. Six hundred grams (600g) of cocoa leaves, cow dung, rice bran and water hyacinth in the ratio: 3:1:1:1, 1:3:1:1, 1:1:3:1, 1:1:1:3 and 1:1:1:1 (negative control). Slurry was subjected to anaerobic digestion for thirty days (30days). Microbiological parameters monitored during the digestion were; microbial population, isolation and identification, while physiochemical parameters monitored were pH and temperature. The weight and volume of biogases produced were measured and gases were subjected to chromatographic analysis. Percentage constituents of the biogases produced were compared with that of the domestic gas sold in the market (positive control). The methane percentage of the biogases produced by the substrates quantity ratio represented A, B, C, D and E were 57.05%, 63.15%, 60.05%, 63.93% and 52.92% respectively while that of the domestic cooking gas sold in the market was 59.80%. The Biogas produced from co-substrates with the highest quantity of Cow dung; Rice Bran as well as co-substrate with equal quantity of cocoa leaves, cow dung, rice bran and water hyacinth contained higher percentage of methane than the domestic gas. These biogases could be considered for cooking gas in preference to the commonly sold domestic cooking gas. This could contribute to the reduction of environmental pollution and conversion of waste to wealth.