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ABSTRACT Shows an overview of the integrated biogas purification and nutrient recovery system. The diagram illustrates the coupling of a two-stage biological desulfurization unit with a hollow-fiber membrane contactor. Biogas containing H₂S enters the first scrubber, is oxidized to H₂SO₄, and the biologically produced acid reacts with NH₃ recovered from the effluent to form ammonium sulfate ((NH₄)₂SO₄), demonstrating simultaneous gas purification and nutrient 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.