Hydrogen sulfide affects the performance of a methanogenic bioelectrochemical system used for biogas upgrading.

Methanogenic bioelectrochemical systems (BESs) can convert carbon dioxide (CO ₂ ) to methane (CH ₄ ) and may be used for anaerobic digester biogas upgrading. However, the effect of hydrogen sulfide (H ₂ S), a common biogas component, on BES performance is unknown. Thus, the objective of this study was to assess the effect of H ₂ S addition to the cathode headspace on BES performance at a range of initial gas-phase H ₂ S concentrations (0-6% v/v), as well as its effect on the anode and cathode microbial communities. As the initial cathode headspace H ₂ S increased from 0 to 2% (v/v), biocathodic CH ₄ production increased by two-fold to 3.56 ± 0.36 mmol/L-d, due to dissolved H ₂ S transport from the cathode to the anode where H ₂ S was oxidized. Elemental sulfur and sulfate were H ₂ S oxidation products detected in the anode. Above 3% initial cathode headspace H ₂ S, biocathodic CH ₄ production declined due to inhibition. A phylotype most closely related to Methanobrevibacter arboriphilus dominated the cathode archaeal communities. In the sulfide-amended BES, a phylotype similar to the exoelectrogen Ochrobactrum anthropi was enriched in both the anode and cathode, whereas phylotypes related to sulfate-reducing and sulfur oxidizing Bacteria were detected in the bioanode. Thus, sulfide transport and oxidation in the anode play an important role in methanogenic BESs treating sulfide-bearing biogas.
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