High Efficiency and Zero Emissions Biogas-to-power: Solid Oxide Fuel Cells and Advanced Biogas Cleaning

The biogas sector is growing rapidly, with a significant rise in biogas and biomethane production expected. While there is a noticeable trend towards medium to large-scale biogas plants, especially for bio-methane upgrading, smaller facilities remain crucial for on-site heat and electricity generation. However, conventional internal combustion engines face efficiency challenges in small-medium biogas plants. This study explores the viability of solid oxide fuel cells (SOFCs) for distributed combined heat and power generation, given their superior energy conversion efficiency and lower emissions. Biogas-SOFC systems require effective biogas purification to remove inherent sulfur-based contaminants which are detrimental for fuel cells. This study assesses the techno-economic impact of biogas cleaning on the levelized cost of electricity (LCOE) for 3-kW and 100-kW SOFC applications, comparing a single-vessel and a two-vessel (lead-and-lag) configuration. Using a validated mathematical adsorption model, the study predicts contaminant concentration profiles and extends experimental results to larger scales. Results indicate that for a 3-kW plant, cleaning unit costs significantly affect the plant’s economy (27-41%), with higher costs for the second vessel increasing the LCOE. For a 100-kW plant, SOFC costs dominate, and despite higher initial costs (3% higher), the lead-and-lag layout reduces operational costs (2-3%), resulting in a slightly lower LCOE compared to single-vessel configurations. Overall, the LCOE remains below 0.12 €/kWh for all configurations for a 3-kW system and below 0.07 €/kWh for a 100-kW plant.