Simultaneous Synergy in CH4 Yield and Kinetics: Criteria for Selecting the Best Mixtures during Co-Digestion of Wastewater and Manure from a Bovine Slaughterhouse

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

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 2.0 kg 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 2.0 kg VS/m³ d OLR was unstable with risk of inhibition. Increasing the OLR from 0.28 to 1.5 kg VS/m³ d caused a reduction in the specific biogas production (SBP) from 0.474 to 0.069 m³/kg VS However, the biogas production rate (BPR) remained constant at around 0.105 m³/m³dig d for OLRs > 0.28 kg VSm³ d. Therefore, OWW anaerobic digestion in low-cost mesophilic biogas plants is technically feasible with OLRs between 0.28 and 1.5 kg VS/m³ d. The implementation of boilers is economically favorable for OLR ≥ 1.0 kg 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.

A comprehensive techno-economic analysis of income-generating sources on the conversion of real sheep slaughterhouse waste stream into valorized by-products

The present analysis was conducted as the first research to assess the techno-economic viability of the value-added by-products (struvite, blood meal, bone meal, and raw sheepskin) from a medium-scale sheep slaughterhouse facility with a slaughtering capacity of 300 sheep per day. For this aim, a comparative technical and economic feasibility analysis was performed to assess the synergistic use of slaughterhouse-oriented rendering wastes and struvite recovery from real sheep abattoir effluent within the framework of detailed cost breakdown, break-even point, and payback period analyses. The experimental findings clearly showed that under the optimal conditions (chemical combination of MgCl₂.6H₂O + NaH₂PO₄.2H₂O, a molar ratio of Mg²⁺:NH₄⁺-N:PO₄^3--P = 1.2:1:1, a reaction pH of 9.0, an initial ammonium concentration of 240 mg NH₄⁺-N/L, and a reaction time of 15 min), struvite precipitation could effectively remove about 73%, 64%, 59%, and 82% of NH₄⁺-N, TCOD, SCOD, and color, respectively, from the real sheep slaughterhouse waste stream. Based on various up-to-date techno-economic items considered within the break-even point analysis, the sheep slaughterhouse facility was estimated to achieve the targeted net income (€100/day) for any selling prices of €1041.30/ton, €640.05/ton, €263.72/ton, and €1.012/hide, respectively, for struvite, blood meal, bone meal, and raw sheepskin. Steel construction and chemicals were determined as the most costly components for CAPEX (capital expenditures) and OPEX (operating expenditures), respectively, and selling prices of bone meal and raw sheepskin were found to be the most critical income items on the profitability of the slaughterhouse facility. Co-monetary assessment of the struvite process and valorized compounds corroborated the economic viability of the proposed project with the payback periods of about 6.3 and 5.5 years, respectively, for the current market and the profit-oriented conditions without subsidy. The findings of this feasibility analysis, as the first of its own, could be used as guideline for simplifying the decision-making with regards to the feasibility of similar facilities and commercialization of profitable by-products.