Co-digestion of Livestock Wastes for Biogas Production

Abstract

Co-digestion of cow dung, poultry dropping and pig manure was carried out in batch digesters at mesophilic temperature for twenty-eight days to determine the biogas generating potentials. The wastes were also digested individually for the same period and under the same conditions. The physicochemical and bacteriological characteristics were determined using standard techniques. The range of P H, temperature, percentage moisture content, percentage chemical oxygen demand, percentage carbon content, and the bacterial loads of the wastes slurries before digestion were 6.4-6.8, 28.0 0 C-29.0 0 C, 80.0-80.2, 9.2-11.0, 32.0-46.0 and 3.7 x 10 6 cfu/ml-6.2 x 10 6 cfu/ml respectively and 6.6-7.5, 27.6 0 C-28.5 0 C, 80.2-91.6, 7.0-9.4, 35.0-58.0 and 1.6 x 10 6 cfu/ml-5.2 x 10 6 cfu/ml respectively at the end of digestion. The biogas yield from the digestion of the cow dung, poultry dropping and pig manure individually were 185ml, 220ml and 170ml respectively while the co-digestion of the substrates yielded more biogas. The cumulative biogas yield from the digestion was 2780ml. The slurry containing 48g: 144g: 48g of cow dung, poultry dropping and pig manure gave the highest biogas yield. This study showed that though the digestion of a single livestock waste can yield some biogas, co-digestion of such wastes has the potential to generate more biogas.