Integrated biogas desulfurization and membrane extraction for ammonium sulfate recovery

This study presents a novel integrated system for biogas purification and nutrient recovery, combining biological desulfurization with ammonia recovery using a hollow-fiber membrane contactor. Designed for anaerobic treatment of nitrogen- and sulfur-rich wastes, the system enables simultaneous hydrogen sulfide (H₂S) removal and ammonium sulfate production, improving environmental performance and resource recovery. A two-stage desulfurization unit scrubbed and biologically oxidized H₂S to sulfuric acid under controlled oxygen supply. The acid was neutralized by ammonia extracted from the biogas effluent through a hydrophobic membrane, forming ammonium sulfate without chemical additives. The system achieved over 95% H₂S removal, with outlet concentrations below 35 ppm, and accumulated up to 12.5 g/L (0.095 mol/L) ammonium sulfate. Operation remained stable over several months at pH 3.0, with mass balance and ion analyses confirming efficient sulfur conversion. Microbial analysis identified Acidithiobacillus and Alicyclobacillus as dominant sulfur oxidizers. Compared with conventional systems, the two-stage design avoided sulfur clogging and biogas dilution. This robust, scalable process couples gas purification with nutrient recovery, producing a concentrated fertilizer solution while minimizing chemical use and supporting circular resource utilization.