Comparative analysis of biogas and yields from cattle, sheep, poultry wastes and their combinations

Abstract

Comparative analysis of biogas yields from cattle, sheep and poultry wastes and blends were carried out at mesophilic temperature range (30oC–40oC) in a laboratory scaled conventional digestive system coupled with batch flow micro digesters. The system was made of air – impermeable plastic containers with effective volume of 4 l. Experiments were carried out in three replicates and at varying total solid concentrations (5%, 15% and 25%) and monitored for 8 days detention period (anaerobically digested); one day lag period observed for bacteria activation on the slurries. Biogas yields were compared as well as the variation of the total solid (TS) concentrations with together with their combinations. Seven batch type anaerobic laboratory-scale digesters were used. Biogas measurement was by water displacement method. Hydrogen ion concentration, ash content of the pulverised materials before and after digestion were determined. Results showed that the composite blends of the three livestock (cattle + sheep + poultry) wastes have the highest biogas potential at 15% total solids concentration which peaked during the fourth day. There was a significant difference at 5% confidence level (P > .05) between the digestion of carbon before and after digestion and hence increase in C:N ratio was observed which favoured complete digestion with positive correlation of all the proximate analysis parameters before and after digestion.