Techno-economic Analysis of a Solid Oxide Fuel Cell Installation in a Biogas Plant Fed by Agricultural Residues and Comparison with Alternative Biogas Exploitation Paths

Abstract In this work, the comparison between three biogas exploitation paths is analyzed from both an energetic and economic point of view. As main current available Combined Heat and Power (CHP) options, a traditional Internal Combustion Engine (ICE) and a Solid Oxide Fuel Cell (SOFC) are compared. Furthermore, biogas upgrading (UPG) is analyzed as a discussed and innovative alternative to electrical production. Currently, main issues related to the agricultural biomass plants can be addressed to: the reduced subsidies for the electrical production, especially in case of energy crops feeding, the wasted thermal energy, which usually cannot find a user in the surroundings and the emissions from traditional Internal Combustion Engines (ICEs), which usually exceed limits and require the use of a post-combustor. The analysis has been applied to a typical biogas plant fed with agricultural residues in Piedmont. Data on current biogas production, methane content and auxiliaries consumption have been collected. Electrical and thermal load for the plant have also been analyzed, in order to calculate the net efficiency of the system. Results show positive effects of the SOFC system from an energy point of view with respect to traditional systems. The advantages in terms of electrical production and low maintenance costs are able to generate a higher incomes on a yearly basis, even if the high investment costs still generates, in the current scenario, a higher PayBack Time (PBT). Analyzing a future scenario with target fuel cell costs, which have been almost reached in countries where the market is grown (e.g. USA and Asia), the investment reaches interesting economic benefits even if compared to traditional systems. The bio-methane choice analyzed shows an interesting investment cost but with lower net yearly incomes which cumulatively generates a slow investment recovery time in the current scenario.