H2S removal from biogas using bioreactors: a review

International audienceThis review aims to provide an overview of the bioprocesses used for the removal of H2S from biogas. The ability of aerobic and anoxic bioreactors (biotrickling filters, bioscrubbers, and a combination of chemical scrubbers and bioreactors) to perform the degradation of H2S is considered. For each operating mode (aerobic and anoxic), the bioprocesses are presented, the operating conditions affecting performance are summarized, the state of the art of research studies is described and commercial applications are given. At laboratory-scale, whatever their operating mode, biological processes are effective for biogas cleaning and provide the same performance. The clogging of the packed bed due to the deposit of elemental sulfur S0 and biomass accumulation clearly represents the main drawback of bioprocesses. Although elimination capacities (EC) determined at laboratory-scale can be very high, EC should not be higher than 90 g m-3 h-1 at industrial-scale in order to limit clogging effects. For aerobic processes, the need to control the oxygen mass transfer accurately remains a key issue for their development at full-scale. As a result, the aerobic processes alone are probably not the most suitable bioprocesses for the treatment of biogas highly loaded with H2S. For anaerobic bioprocesses using nitrate as an electron acceptor, the scale-up of the laboratory process to a full-size plant remains a challenge. However, the use of wastewater from treatment plants, which constitutes a cheap source of nitrates, represents an interesting opportunity for the development of innovative bioprocesses enabling the simultaneous removal of H2S and nitrates