Integration of mesophilic biogas plant in the animal slaughter process under real limitations: Techno-economic evaluation of a colombian bovine slaughterhouse.

Abstract

Anaerobic digestion (AD) has been a widely tested alternative for the management and valorization of wastewater from the animal slaughter process. However, the integration of AD in slaughterhouses depends on technical and economic aspects. In Colombian slaughterhouses AD integration is limited by the availability of land. In the present study, a techno-economic evaluation of the AD of offal wastewater (OWW) stream in a laboratory scale mesophilic tubular digester was carried out. The digester was operated at organic loading rates (OLR) of 0.28, 0.50, 1.0, 1.5 and 2.0kg VS/m3 d. Boilers and a CHP (combined heat and power) system were considered for energy integration of biogas. For the economic study, the cost structure of a Colombian slaughterhouse was considered. The AD of OWW at 2.0kg VS/m3 d OLR was unstable with risk of inhibition. Increasing the OLR from 0.28 to 1.5kg VS/m3 d caused a reduction in the specific biogas production (SBP) from 0.474 to 0.069m3/kg VS However, the biogas production rate (BPR) remained constant at around 0.105m3/m3dig d for OLRs>0.28kg VSm3 d. Therefore, OWW anaerobic digestion in low-cost mesophilic biogas plants is technically feasible with OLRs between 0.28 and 1.5kg VS/m3 d. The implementation of boilers is economically favorable for OLR≥1.0kg VS/m3 d. Nevertheless, feasibility is very sensitive to variations in the cost structure. The implementation of CHP was feasible in the range of OLRs evaluated and its viability is not affected by changes in assumed costs.