Development of a Biogas-Based Power Generation System for Swine Farms: Performance and Economic Evaluation

This study presents the development, purification, and performance evaluation of a biogas-powered electricity generation system designed for medium-scale swine farms. A conventional Hino V-22C diesel engine was modified to operate in spark-ignition mode using purified biogas with methane content ranging from 65 to 70%, obtained through a PSA upgrading system. The compression ratio was reduced from 18.5:1 to 14.7:1 to accommodate the lower heating value and combustion characteristics of biogas. An oxygen-sensor-based emergency fuel supply (EFS) system was integrated, activating when λ > 19.0 and deactivating when λ < 17.0, to enhance combustion stability under high-load operation. The corrected higher heating value (HHV ≈ 20–21 MJ/kg) and consistent fuel mass flow rate (0.036 kg/s) were used for revised thermodynamic calculations. Field testing over 524 operating hours demonstrated stable power generation between 80 and 120 kW. The EFS system increased thermal efficiency by approximately 22.7%, achieving a peak efficiency of 11.66% at 100 kW. A techno-economic assessment, including sensitivity analysis (±20% biogas yield and ±10% electricity price), confirmed economic viability with a breakeven period of 15.79 months. The system offers a reliable and scalable renewable energy solution for agricultural applications, contributing to methane mitigation and improved waste-to-energy utilization.