In-Situ H2S reduction in biogas fuel for solid oxide fuel cell applications by using cow urine

Biogas, generated from small scale digesters, is a traditional energy source for satisfying the thermal energy demand in off-grid communities. Recent developments in small scale solid oxide fuel cells (SOFCs) technology and progress in research and development of dry reforming, opens perspectives to couple small scale SOFCs with already existing digesters to meet both thermal and electrical energy demand, enabling power access to off-grid communities.However, one of the major challenges for SOFC integration to small scale digesters is the effect of biogas impurities, such as H2S, on the performance of SOFCs. Previous work has shown that local operational practices could influence the biogas quality and particularly the H2S content in the biogas. The here presented research expanded on the use of cow urine instead of water as solvent in manure digestion as a potential operational strategy that enables in-situ reduction of H2S in the evolving biogas. This research investigated the following hypotheses: 1) urine addition results in a high pH that favours HS- over H2S, 2) given the presence of metal elements in the cow urine, insoluble metal sulphides are being formed, reducing the biogas H2S content. The research was carried out by measuring cow urine composition of various samples, assessing the effects of different urine/water/manure mixtures on the evolving biogas-H2S concentration, and verifying the experimental findings with phreeqC equilibrium speciation. Bio-kinetic modelling, using the anaerobic digestion model nr 1 (ADM1), was subsequently performed to explore the influence of different feed compositions on the H2S content in the biogas..............