CO-DIGESTION OF COW DUNG WITH SOME CEREAL BIOMASS FOR BIOGAS PRODUCTION

Abstract

Co-digesting different ratios of cereal biomass with a known quantity of cow dung was investigated. Four cereal biomass obtained from local traders in Ido-Ekiti were used for anaerobic digestion. The cereal biomass includes millet shaft, sorghum shaft, corn cob, and rice husk. They were grounded evenly for homogeneity, mixed in the ratio 4:1:3:2, and 2:3:4:1. Cow dung obtained from FUTA University Farm was soaked for seven days and used as fungal inoculum, by mixing it with the two biomass of varied concentrations, while the four cereal biomass were used as bacteria inoculum. Control experiment was set up without adding cow dung. Four anaerobic digesters were used for the anaerobic digestion of the cereal biomass for thirty days. Physicochemical parameters such as pH, temperature, pressure, total solids and proximate composition were determined. The pH varies from 3.7 to 6.8, temperature varied from 28oC to 44oC throughout the digestion process, the pressure varies from 0pa to 1300pa while thethe total solids varied from 19.20mg/l to 89.30mg/l. Bacteria and fungi populations in the digesting materials ranged from 1.0 x 107 to 8.0 x 107cfu/ml and 0.0 x 106 and 7.0 x 106sfu/ml respectively. Twenty three microorganisms were isolated before, during and after the digestion process. The bacteria among them were Lactobacillus delbrueckii, Micrococcus luteus, Streptococcus pneumoniae, Corynebacterium diptheriae, Clostridium perfringes, Lactobacillus fermenti, Staphylococcus aureus, Bacillus cereus, Escherichia coli, Salmonella enterica, Enterobacter aerogenes, Proteus vulgaris and Methanosarcina barkeri. The fungi isolated were Aspergillus flavus, Aspergillus niger, Aspergillus fumigatus, Rhizopus stolonifer, Penicilium italicum, Mucor mucedo, Fusarium graminearum, Mould monalia, Rhizopus oryzae, and Aspergillus oryzae. The proximate composition result from the least to the highest value includes the following, ash, moisture, fat, fibre, protein and carbohydrate from 0.52% to 28.84%, 10.77% to 85.70%, 1.80% to 9.13%, 4.11% to 32.69%, 0.59% to 11.17%, and 2.77% to 29.07% respectively. The mineral content includes, sodium from 3.84% to 16.88%, potassium from 3.29% to 89.46%, calcium, 0.01% to 52.37%, magnessium 0.66% to 81.60% while the phosphorus was 11.41% to 168.33%. The two digesters which contains cow dung has the highest methane value of 65.159% and 65.143% respectively while the two control experiments had the lowest methane value of 58.49% and 57.36% respectively. These results showed that cow dung has significant impact on the co-digestion with the cereals’ biomass.