Techno-Economic Assessment of Gas Turbine Cogeneration Cycles Utilizing Anaerobic Digestion Products for Biogas Fuel

This work presents the development of an integrated approach for the techno-economic assessment of recuperated gas turbine cycles utilizing anaerobic digestion (AD) products of animal manure and energy crops for biogas fuel. The overall approach consists of a series of modeling methods applicable to AD and biogas fuel yield, thermodynamic evaluation of cogenerated gas turbine cycles, exergy analysis, and economic evaluation of powerplant operation. The developed method is applied for the techno-economic analysis of an AD plant yielding biogas fuel supplied to a recuperated gas turbine. The influence of gas turbine technology level on the economic sustainability of cogenerated powerplants powered by AD products is investigated. The obtained results suggest that the dominant cycle variables affecting the electrical performance of integrated digestion–cogeneration systems are the gas/air temperatures at the combustor outlet and recuperator air side (AS) exit, respectively. It is demonstrated that the profitability of the investment is highly dependent on electrical power output and the feed-in tariff used for electrical energy. It is argued that the desired split between electrical and thermal power output is dependent on the gas turbine technology level. It is shown that optimizing the cogenerated cycle for maximum electrical power output is key in terms of securing investment sustainability. A general review of the acquired results indicates that anaerobic treatment of animal manure and energy crops to produce biogas fuel can constitute a sustainable investment. This applies especially for cases that substantial volumes of substrates are available to ensure stable powerplant operation.