Biogas Production from Co-Digestion of a Cellulosic Feedstock and Piggery Manure

Nigeria has energy crisis, hence, there is urgent need to diversify the country's energy resources towards the renewable alternatives for economic and social transformation. Biogas generated from the anaerobic digestion of local biomass resources, will increase national energy security, reduce dependence on fossil fuels and as well mitigate the environmental and ecological impacts of the organic wastes polluting our environment. The methane-producing potentials of rice husk co-digested with piggery manure and also using them as single substrate each under anaerobic condition at 35- 40oC were studied. The results of the molecular identification of the microorganisms used for the studies based on 16S rRNA gene sequences and biochemical characterization showed that Bacillus, Cellulomonas and Pseudomonas species were the dominant bacterial group while the methanogenic archae were Methanosarcina and Methanobrevibacter species. The result of the proximate composition of rice husk showed that the volatile solids, Carbon, nitrogen, ash content and carbonnitrogen ratio were 68.5%, 42.5%, 0.84%, 19.20% and 51:1 respectively. Five hundred (500) gram of rice husk was pretreated by steaming at 120oC for 30 minutes, dried at 80oC and ground into powder with a disc mill prior to anaerobic digestion. The result of co-digestion of rice husk with piggery manure at 50% ratio showed that the methane yield was 30.50 cm3/g VS at hydraulic retention time of 35 days while the methane yield using rice husk and piggery manure as single substrate each were 18.4 cm3/g VS and 24.4 cm3g VS at hydraulic retention time of 45 and 38 days respectively. The results of the studies have shown that co-digestion of rice husk and piggery manure has higher biogas yield than using them as single substrates. The one-way analysis of variance of biogas yield results showed that there was significant difference between the biogas yield obtained from co-digestion and that obtained from using both substrates as single substrates at 95% confidence level.