Investigation of slaughterhouse waste anaerobic digestion in a pilot-scale mesophilic reactor

Slaughterhouses generate highly polluted effluents, and if not treated before discharge can cause major adverse environmental and public health impacts. Treatment of this waste by anaerobic digestion can reduce those impacts while producing a potentially valuable source of energy. The purpose of this study was to investigate this process efficiency under pilot operating conditions for a more accurate scaling up. Blood waste from a slaughterhouse was treated in a pilot-scale digester of 30 dm(3) total volume under mesophilic temperature conditions. Operating parameters such as pH, alkalinity, organic loading, volatile fatty acids, biogas composition, total and volatile solids were monitored in order to study the behavior of the fermentation process. The results show that no significant inhibition were caused by the accumulation of volatile fatty acids, due to the high buffering capacity of treated sludge. An efficient reduction of organic matter was obtained with a COD decrease of about 67% within 40 days of fermentation. The biogas produced was of a good quality with high CH4 yields (above 70%) and low CO2 yields, corresponding to a biomethane potential of 225.9 dm(3) CH4/kg TVS. Logistic model described accurately the methane production kinetic and enables an easy process scaling up for industrial applications.