Anaerobic co-digestion of palm oil mill effluent with cow manure for biogas production

Abstract

Palm oil mill effluent and cow manure are excellent substrates for biogas production in anaerobic digesters though the biogas yield from a single substrate is not high. However, mixing palm oil mill effluent with cow manure (CM) or any other kind of waste materials in co-digestion can optimize the production of biogas. In this research work, the biogas potentials from palm oil mill effluent and cow manure as a single substrate as well as co-substrates was investigated. In addition the effect of chemical oxygen demand (COD) and volatile solids (VS) removal efficiencies towards biogas production and its methane content was also investigated. Anaerobic batch digesters were used for the digestion and were operated at room temperature (28oC to 34°C) for 21 days. The digesters were operated at different POME – CM compositions, they are; 100% POME, 100% C.M, 60% POME + 40% C.M, 70% POME +30% CM and 80% POME + 20% CM. Approximately 717 mL, 443 mL, 864 mL, 1875 mL and 1504 mL of the biogas yields could be obtained, respectively, after 21 days of digestion. Average methane content of the biogas was 44.17%, 40.59%, 46.12%, 61.13% and 50.56%, respectively. Maximum cumulative biogas production after 21 days of digestion was obtained as 1875ml with maximum methane content as 61.13% in the mixture containing 70% POME + 30% CM. Co-digestion of 70% POME + 30% CM improved the removal efficiency up to 75% COD & 68% VS with its corresponding methane content of 61.13% which has been recognized as the optimum for biogas production as well as methane content. Biogas yield was improved by 21%, 162% and 110% v/v using the co-digestion as compared to the digestion of POME alone and 95%, 323% and 240% v/v as compared to the digestion of CM alone respectively. These results showed that biogas and its methane content production can be enhanced efficiently through co-digestion process.