Eco-friendly power generation process using Allam cycle and cryogenic carbon capture for biogas upgrading

The growing energy demand has led to increased fossil fuel consumption in the power generation sector, thereby intensifying concerns over environmental degradation. Accordingly, various economic strategies and research initiatives have been directed toward bioenergy as a viable alternative. This study investigates a biogas-based power generation system by evaluating its energy efficiency, environmental impact, and economic feasibility in conjunction with various renewable energy sources. To upgrade biogas, a cryogenic desublimation process is employed, utilizing cold energy recovered from an air separation unit. The resulting biomethane and oxygen are subsequently fed into the Allam cycle, a regenerative Brayton cycle, for high-efficiency power generation. The overall energy efficiency of the proposed process ranges from 44.33 % to 54.15 %, depending on the share of renewable electricity utilized. The integrated desublimation and oxy-fuel combustion system achieves a high carbon capture rate, recovering 99.78 % of the carbon originally contained in the biogas. When various renewable energy sources are considered, the process yields negative carbon emissions, ranging from −740.45 g_CO2eq/kW to −471.51 g_CO2eq/kW. A conventional techno-economic analysis determined a levelized cost of electricity (LCOE) of $95.3/MWh, primarily driven by the high biogas cost of $12.8/MMBtu. In particular, at a biogas price of $16/MMBtu, the LCOE remains within the range of $81.6/MWh to $120.0/MWh on average, even when the variability of renewable energy sources is additionally considered. In addition to its environmental advantages, the proposed process is compatible with existing oxy-fuel combustion facilities, suggesting its potential as a substitute for current fossil-fuel-based power generation systems.