ENHANCEMENT OF METHANE PRODUCTION BY CODIGESTION OF KERATIN AND CELLULOSIC FEEDSTOCKS AT MESOPHILIC AND THERMOPHILIC CONDITIONS USING MICROBIAL CONSORTIA

ABSTRACT
Nigeria has energy crisis, hence, there is urgent need to diversify the country’s energy resources towards renewable alternatives for economic and social transformation. Biogas generated from the anaerobic digestion of local biomass resources, will increase national energy security as well as reduce dependence on fossil fuels. Optimization of methane production by codigestion of poultry feather and sawdust using microbial consortia were investigated. The results of the molecular identification of the microorganisms used for the studies based on 16S rRNA gene sequences and biochemical characterization showed that
Geobacillus stearothermophillus, cellulomonas flavigena, Burkholderia fungorum, Bacillus licheniformis, Streptococcus salivarius and Pseudomonas aeruginosa were the major bacterial isolates while the predominant methanogenic archaeal isolates were Methanosarcina thermophilla and Methanobrevibacter smithii which are capable of metabolizing acetate to methane and carbon dioxide under anoxic condition. The result of the proximate analysis of the complex media sources showed that sawdust had the volatile
solid content and carbon-nitrogen ratio (C/N) of 93.80% and 145:1 respectively while poultry feather had volatile solids and carbon-nitrogen ratio of 96.50% and 4:1 respectively. Four bacterial consortia (1, 2, 3 and 4) were formulated from the combination of the hydrolytic, acidogenic and methanogenic bacteria isolated from cowdung and chicken feather dump-sites in different ratios. The results of methane production after the adsorption and absorption purification process favoured co-digestion of the two substrates at optimum temperature (55oC) with the highest methane production of 14.675 cm3/g VS realized from the combination of 50% chicken feather with 50% sawdust at hydraulic retention time of 22 days and pH of 7.30 by consortium 4, followed by consortium 3 with methane production of 13.455 cm3/g VS. The co-digestion of 50% chicken feather with 50% sawdust which gave the highest methane yield had carbon-nitrogen (C/N) ratio of 19:1. The results of the evaluation of the consortia using statistical analysis showed that consortium 4 containing more of the methanogens has the best methane-yielding potential followed by consortium 3 while the difference in methane yield between consortium 2 and 1 was not significant. The results of the composition analysis of the biogas samples produced by the consortia using infrared gas analyzer at the mesophillic and thermophillic conditions showed that the highest concentration of 74.52% methane was realized at the thermophillic condition from 50% chicken feather blend with sawdust using consortium 4. One-way analysis of variance of the results on methane production from different treatments showed that methane production was significantly (P ≤ 0.05) dependent on the microbial consortia, nature of substrate and digestion temperature. The results of the studies have shown that the substrates though complex in nature are veritable sources of renewable fuel especially when pretreated and co-digested.