Running solid oxide fuel cells on biogas

The feasibility of operating a solid oxide fuel cell on biogas has been studied over a wide compositional range of biogas, using a small tubular solid oxide fuel cell system operating at 850 °C. In addition the response of the SOFC towards waste ammonia has been studied. It is possible to run the SOFC on biogas, even at remarkably low levels of methane, at which conventional heat engines would not work, thus offering a valuable and environmentally friendly use for poor-quality biogas that is currently wasted by detrimental venting to the atmosphere. The power output varies with methane content of the biogas, with maximum power production occurring at 45% methane, corresponding to maximal production of H2 and CO through internal dry reforming. Direct electrocatalytic oxidation of methane does not contribute to the power output of the cell. For biogas with higher methane contents methane decomposition becomes significant, leading to increased H2 production, and hence transiently higher power production, and deleterious carbon deposition and thus eventual cell deactivation. SOFCs are tolerant to ammonia, actually utilising the ammonia present in biogas to produce electrical power, at the same time acting as an environmental clean-up device breaking down the ammonia pollutant to N2 and water, with no formation of any undesirable nitrogen oxides.