• Bioscrubber-High-Rate Algal Pond system effectively desulfurized biogas on sunlight. • Biodesulfurization showed to be a solar-light dependent process. • Enhanced oxygenic photosynthesis increased the H 2 S oxidation rates to sulfate. • Controlling dissolved oxygen loads to bioscrubber promoted efficient H 2 S removal. • High solar irradiation lowered biogas empty bed residence time in the bioscrubber. This study addresses the application of an alkaline bacteria-microalgal process for biogas desulfurization. The bacterial consortium, composed of the genus Thioalkalivibrio, in conjunction with the microalgae Picochlorum sp. and Scenedesmus sp., fosters hydrogen sulfide (H 2 S) removal from biogas and promotes its conversion to sulfate. The performance of a bioscrubber (BS) coupled with a high-rate algal pond (HRAP) exposed to outdoor conditions for the removal of various H 2 S loads from synthetic biogas was analyzed. During diurnal period, the oxygen produced by the microalgae in the HRAP, in conjunction with controlled dissolved oxygen loading rates to the bioscrubber enhanced (three times respect to data published elsewhere) the removal rates of H 2 S from biogas up to 15.2 g/m 3 h at gas residence time (GRT) of 4 min with H 2 S and CO 2 inlet concentrations of 5000 ppmv and 30%vol, respectively, achieving efficient H 2 S and CO 2 removal efficiencies of 99.9% and 80%, respectively. During the night, the supply of crude biogas was stopped to prevent sulfide accumulation and a decrease in pH. This sunlight-driven biodesulfurization process operates only during daylight hours, as it requires high external irradiance to sustain high oxygenic photosynthetic activity. Thus, the proposed microalgae-based desulfurization technology could serve as a supplementary unit to conventional systems, partially fixing CO 2 into biomass and increasing the methane concentration of the purified biogas.
González-Sánchez et al. (Fri,) studied this question.