Energy Efficiency Optimization in Biogas Production from Cattle Rumen Digesta Through Process Simulation Using Aspen Plus

This study optimizes energy efficiency in biogas production from cattle rumen digesta (CRD) using Aspen Plus process simulation. CRD, an underutilized abattoir byproduct, showed favorable characteristics with 72.6% volatile solids and a C/N ratio of 22.48. The simulation integrated NRTL thermodynamic techniques with RCSTR/RStoic reactor modules to model the four anaerobic digestion phases: hydrolysis, acidogenesis, acetogenesis, and methanogenesis. The validated model predicted methane yields of 0.0382 kg/hr compared to experimental yields of 0.0335 kg/hr (12.3% difference), representing acceptable agreement under optimal conditions; deviations ranged from 12.3% to 25.4% across all HRT conditions. Energy analysis revealed an electrical potential of 4.46 kWh/day, equivalent to ₦9,366/month, with payback period less than one year. Heat integration reduced external heating requirements by 30%, lowering net energy demand and improving overall system efficiency. Sensitivity analysis identified optimal conditions at 25 days hydraulic retention time and 1.5 kg VS/m³/day organic loading rate, yielding stable pH (6.8–7.2) and VFA concentrations below 1,500 mg/L. Simulated methane yields (0.0341–0.0382 kg/hr) compare favourably with published values for similar feedstocks (0.035–0.045 kg/hr). Model validation across seven case studies showed deviations ranging from 0.3% to 12.4%, confirming robustness and scalability. This study provides a validated, CRD-specific framework for waste-to-energy system design and demonstrates the effectiveness of process simulation in optimizing renewable energy production from abattoir waste.