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Abstract
This study conducted 30 kW-generator experiments at a small biogas plant on a swine farm to serve as a preliminary study for the construction of a 300-kW power plant for a larger scale biogas plant in the near future. The experimental results showed that the optimum biogas flow rate for the engine was around 240 to 260 L/min, and the maximum power generation, the corresponding thermal efficiency, and the percentage of consumed CH4 were 26.8 kW, 28.7%, and 95.4%, respectively, at a biogas supply rate of 260 L/min. With 3% oxygen-enriched air, the maximum power generation, thermal efficiency, and percentage of consumed CH4 increased up to 28.2 kW, 30.2%, and approximately 100%, respectively, for a biogas supply rate of 260 L/min, and the engine can operate normally at a lower limited fuel supply rate of 220 L/min. The heat exchanger could recover 923 kJ/min of heat from the flue gas, leading to an overall efficiency of 47.3%, at a biogas supply rate of 240 L/min. With the total swine population (around 4.3 million heads) from the farm scale of over 1,000 heads of pigs in Taiwan, the estimation, based on the data obtained from this study, shows the economic benefits of using biogas, including an annual electricity generation of 2.67 × 108 kWhe (corresponding to electricity charge savings of US$ 26.7 million), where natural gas charge savings total US$ 8.7 million, and the carbon dioxide reduction totals 180,000 tons.