Batch Optimization of Biogas Yield from Pasteurized Slaughterhouse By-Products Incorporating Residues from Bioethanol Industry

Abstract

Batch anaerobic digestion of pasteurized pig slaughterhouse waste (SW) and corn sieving waste (CSW), and anaerobic co-digestion of CSW/SW were studied at lab scale employing several carbon to nitrogen ratio (C/N) and total solids (TS) content. Mixtures with highest biogas yield and suitable process inhibition parameter values were scaled up to pilot scale. Results showed that SW and CSW co-digestion improved biogas yield over that obtained from mono-digestion of both substrates. Thus, CSW demonstrates to be a proper substrate to balance C/N and improves biogas yield. Also, all studies reveal that the best biogas yield for each C/N mixture was achieved for the lowest TS content. Moreover, SW/CSW mixture with C/N 15 and 5% TS achieved the highest biogas yield and the best inhibition parameters values. Pilot scale assay demonstrates that biogas yield, methane yield and degradability for C/N 15 mixture were 41%, 25%, and 24% higher than those using C/N 20. Also, the methane content was similar for both C/N 15 and C/N 20 at pilot scale, however, other gasses composition (H2, CO2) presented variations. Kinetic analysis was employed to test cumulative methane production observed for mixtures tested at pilot scale.