Enhancement of Biogas Potential for Slaughterhouse Waste by Co-digestion with Animal Wastes

Abstract

The aim of the current study was to investigate biogas production from the slaughterhouse waste codigested with animal wastes. Slaughterhouses generate organic wastes that are environmentally hazardous due to high contents of biological contaminants. The use of anaerobic digestion of the slaughterhouse waste can achieve twin objectives of waste treatment and energy production as biogas. The process is however, limited by low biogas potential of slaughterhouse waste. The study evaluated the effect of co-digesting the slaughterhouse, chicken and pig wastes on biogas potential. The co-digestion test with combination ratio of 1:1, slaughterhouse waste and chicken waste produced the highest value of biogas potential of 636 L/kg-VS, which was almost double that from pure slaughterhouse waste. In addition, the substrate biodegradability, the biogas productivity and the yield were most improved at 1:1 co-digestion. The digestate from the process had high nutrient contents and a maximum of; 0.8, 2.6 and 2.7% of dry matter for total nitrogen, phosphate and Potassium respectively. The kinetic analysis of the co-digestion process using modified Gompertz equation indicated a correlation between the waste biodegradability and biogas yield. The enhancement of the C/N ratio in the slaughterhouse waste by co-digestion with these wastes could be responsible for the improvement of the biogas production and yield. Future studies should focus on how the nutrient rich digestate can be appropriately applied as bio-fertilizer and on how co-digestion affects the pathogens in slaughterhouse wastes.