| Abstract | This study compares microbial and bioelectrochemical methods of biogas upgrade via CO₂ conversion to CH₄. First, an in situ approach for CO₂ conversion is investigated in an anaerobic reactor with a continuous supply of exogenous H₂. This approach increased CH₄ content of the biogas to 80–85%, yet also increased the effluent acetate concentration to 5,000–6,000 mg L⁻¹ due to homoacetogenic activity. In a second approach, an anaerobic biofilter was continuously fed with biogas and an exogenous supply of H₂, resulting in a CH₄ content of 85–90% and a H₂ consumption of 4.2–4.5 mol per mol of CO₂ removed. Finally, biogas upgrade via CO₂ to CH₄ conversion was demonstrated in the cathode compartment of a membraneless microbial electrosynthesis cell. This test resulted in a CH₄ purity of 85 – 90% and an energy consumption (per L of treated biogas) of 3.1 ± 1.6 Wh L⁻¹. |
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