Bioenergy Potential and Kinetic of Biogas Production in Anaerobic Digestion of Slaughterhouse Effluent

Abstract

A great amount of wastewater is generated each day from the slaughterhouse located in the harbor area (Togo). This amount of wastewater is a source of environmental pollution and degradation of water quality, as it is discharged with no treatment. The wastewater produced by slaughterhouses is biodegradable with a ratio between biological oxygen demand (BOD5) and chemical oxygen demand (COD) (BOD5/COD) > 0.5. Anaerobic co-digestion was used in this study to assess the bio-energy potential and kinetics of biogas production during processing. An effective anaerobic digestion design shows that over 90% of organic material was removed when inoculation and the carbon/nitrogen (C/N) ratio were adjusted. Biogas production was significantly affected by COD concentration, inoculation and C/N ratio. The cumulative volume of biogas increased from 415 mL to 2,150 mL as the substrate/inoculum (S/I) ratio has decreased from 2.028 to 0.337, while the cumulative volume of biogas increased from 1,140 mL to 5,250 mL as the C/N ratio increased from 6 to 22. The biogas produced has a high calorific value, as the methane content is 74% after simple purification with a concentrated solution of NaOH. Among the three kinetic models used to describe biogas production, a modified Gompertz model was found to be the best with R2 between 0.983 and 0.993. Then, the logistical model with R2 between 0.902 and 0.928 and the first order kinetic model with R2 between 0.552 and 0.704