Removal of H₂S and CO₂ from biogas by algae-assisted bioelectrochemical system with oxygenic and anoxygenic photosynthesis

Abstract

A bioelectrochemical system (BES) combining oxygenic and anoxygenic photosynthesis was investigated. The possibility of improving the composition of biogas by removing H 2 S and carbon dioxide in the anode zone of the bioelectrochemical system and obtaining additional energy has been established. The dynamics of HSremoval from model solutions in the BES anolyte at 3 operating modes were observed. Complete removal of sulfides in the anodic zone and the anaerobic photobioreactor was found in the BES operating option as a microbial fuel cell. At the same time, an increase in the concentration of sulfates was observed to varying degrees for the studied variants. The most probable mechanisms for the removal of H 2 S in this combined system are the oxidation of sulfides by sulfur photoautotrophic bacteria present in the mixed consortium to sulfates and the bioelectrochemical oxidation of hydrogen sulfide on the surface of the anode to elemental sulfur and its other forms. The obtained results with real biogas passed through the BES anolyte and the anaerobic photobioreactor (APBR) are also positive. A complete purification of the biogas from H 2 S and a significant removal of CO 2 (81 % -85 %) were achieved, where the CH 4 content in the biogas reached 94.1 % -96.2 %.