Photoautotrophic removal of hydrogen sulfide from biogas using purple and green sulfur bacteria.

Biogas desulfurization based on anoxygenic photosynthetic processes represents an alternative to physicochemical technologies, decreasing the risk of O and N contamination. This work aimed at assessing the potential of Allochromatium vinosum and Chlorobium limicola for biogas desulfurization under different light intensities (10 and 25 klx) and HS concentrations (1 %, 1.5 % and 2 %) in batch photobioreactors. In addition, the influence of rising biogas flow rates (2.9, 5.8 and 11.5 L d in stage I, II and III, respectively) on the desulfurization performance in a 2.3 L photobioreactor utilizing C. limicola under continuous mode was assessed. The light intensity of 25 klx negatively influenced the growth of A. vinosum and C. limicola, resulting in decreased HS removal capacity. An increase in HS concentrations resulted in higher volumetric HS removal rates in C. limicola (2.9-5.3 mg L d) tests compared to A. vinosum (2.4-4.6 mg L d) tests. The continuous photobioreactor completely removed HS from biogas in stage I and II. The highest flow rate in stage III induced a deterioration in the desulfurization activity of C. limicola. Overall, the high HS tolerance of A. vinosum and C. limicola supports their use in HS desulfurization from biogas.