Calculating the efficiency of a biogas plant by the energy and exergy analysis method

In this study, energy and exergy analysis methods and the first and second law efficiencies of thermodynamics were examined using real-time data of a biogas facility in Bingöl province. The biogas facility produces biogas under mesophilic conditions by processing 650 m3/day of liquid dairy cow manure, and electricity, hot water and steam energy are produced from the biogas obtained. In addition to dairy cow manure, the facility also processes other animal and plant-based wastes, but since these wastes come in variable quantities at variable periods, calculations were made on dairy cow manure, which is the main raw material with the highest amount by mass in the loading plan and is loaded regularly every day. The biogas facility was examined in four sections, and the first and second law efficiencies of all equipment in each of these sections were calculated separately. The facility has four biogas engines with 1067 kW electricity production power, three main digesters and one final digester reactor with a volume of 7000 m3. It has been concluded that the energy balance efficiency of the biogas plant in anaerobic digestion systems varies between 90-98%, the first law efficiency in the energy balance of the biogas engine cogeneration system is 70.2% and the second law efficiency is 48.8%. The power produced by the biogas engine, hot water energy and exhaust gas recovery powers were compared with the catalog values, and it was concluded that the realized values were 96.1% similar to the catalog data.