Enrichment of pig dung with selected crop wastes for the production of biogas

Abstract

Effect of pig dung enriched with selected crop wastes for the production of biogas was investigated. Bean husks, peels of yam, cassava and plantain were processed with fresh dung of pig in a combined ratio of 1:4 (crop wastes: pig dung); on wet weight basis. The mixture was digested for 16 days. Bacterial, fungal and yeast burden in the biogas ranged from 1.5 x 1011cfu/ml to 3.5 x 1011cfu/ml, 0.8 x 107sfu/ml to 1.4 x 107sfu/ml and 1.8 x 107sfu/ml to 2.4 x 107sfu/ml respectively. The pH of the digesting materials ranged from 5.2 to 7.1 in which the pH initially decreased and subsequently increased as the digestion progressed. Temperature range of 26oC - 34 oC was recorded during the digestion process. The gas yield ranged from 85.5mmH2O to 314.5mmH2O. The chemical analysis of biogas evolved from the mixture of pig dung and selected crop wastes was 70.6% for CH4, 13.2% for NH3, 5.3% for H2S, 4.7% for CO2 and trace of other unknown gases which were found to be low. It was observed that the quantity of the pig dung and the mixture of the selected crop wastes fed into the digester had significant effect on the biogas generated (< 0.05). Therefore, the utilization of pig dung and the selected crop wastes for the production of biogas is of dual benefits. It serves as waste reduction strategy to improve the environment while the residue from the digester has fertilizing value which can be used as soil conditioner