INTEGRATING DARK FERMENTATION AND SOFC TECHNOLOGY: OPTIMIZING BIOHYDROGEN UTILIZATION FOR GREEN ENERGY

The generation of hydrogen by means of dark fermentation of organic waste and its coupling with the production of electricity using Solid Oxide Fuel Cells is a promising approach to sustainable electrical energy production. Dark fermentation represents a renewable route to produce hydrogen-rich biogas from organic waste; however, the direct application of this biohydrogen in fuel cells is usually hindered by the energy-intensive purification steps needed. This work explores the possibility of directly converting biohydrogen produced in dark fermentation to power using SOFC technology without the conventional purification steps. The paper focuses on the experimental results of laboratory testing of SOFCs with biohydrogen -like fuel composition. The SOFC under study uses Ni-YSZ as the anode material, and La0.6Sr0.4Co0.8Fe0.2O3-δ as the cathode, with a Gadolinia-Doped Ceria buffer layer to prevent phase degradation. Electrochemical tests were carried out under varying fuel compositions: a standard mixture of 10% H2 and 90% Ar, and a CO2-contaminated mix of 10% H2, 20% CO2, and 70% Ar. The results indicate that the inclusion of CO2 influences the current-voltage characteristics, with up to an 8% reduction in power density at 900°C due to the mass transfer resistance from the Reverse Water Gas Shift reaction. However, the CO2-containing mixture demonstrated improved performance at lower temperatures (600–650°C), suggesting potential optimization pathways for SOFC operation under carbon-rich conditions. In addition, a Life Cycle Assessment was conducted for the process using a cradle-to-grave approach, incorporating data from dark fermentation hydrogen production, purification, and electricity generation via SOFC. The process yielded a contribution to Climate Change of 4.15 kg CO2eq/kWh. High contributions to GHG emissions were observed from key processes such as hydrogen purification, compression and storage, as well as electricity generation, collectively accounting for more than 80% of the total GWP. This is largely attributed to the energy-intensive nature of these processes and the upstream emissions associated with the production and manufacturing of their components. Water consumption was measured at 0.444 m3/kWh, predominantly driven by biomass preparation and cooling systems. The analysis also highlighted significant impacts on land use, 0.733 m2a crop eq. and ozone depletion, 5.82×10⁻⁶ kg CFC-11 eq, with the anaerobic fermenter identified as the main contributors across multiple environmental categories. Combining experimental findings with LCA results, this study underlines the importance of optimizing hydrogen purification and SOFC efficiency to improve environmental performance. Improvement in feedstock selection, process integration, and energy recovery mechanisms is indispensable for emission and resource consumption reduction. Furthermore, the results confirm the good potential for the integration of dark fermentation and SOFC technologies within a circular economy approach, thus providing a promising route toward organic waste valorization and green energy production. To underscore these findings, a comparative assessment was carried out against PEMFC, a widely adopted conventional technology for electricity production. The results of this study will provide the basis for scaling up such technologies and furthering their industrial applications, thus contributing to a global transition toward sustainable and renewable energy systems.