Integrated Biogas Desulfurization and Membrane Extraction for Ammonium Sulfate Recovery
This study presents an integrated system for biogas purification and nutrient recovery, combining biological desulfurization with ammonia capture via a hollow-fiber membrane contactor. Designed for treating nitrogen- and sulfur-rich anaerobic effluents, the system enables simultaneous hydrogen sulfide (H2S) removal and ammonium sulfate production, improving environmental performance and resource recovery. A two-stage desulfurization unit scrubbed H2S and biologically oxidized it to sulfuric acid under controlled oxygen supply. This acid was subsequently neutralized by ammonia extracted from the biogas effluent via a hydrophobic membrane, forming ammonium sulfate. The system achieved H2S removal efficiencies above 95%, with outlet concentrations consistently below 35 ppm. The membrane contactor recovered ammonia effectively, producing up to 12.5 g/L (0.095 mol/L) ammonium sulfate without chemical additives. The process remained stable over several months, with pH maintained at 3.0. Mass balance and ion analyses confirmed efficient sulfur conversion.Microbial community analysis of the desulfurization unit identified Acidithiobacillus and Alicyclobacillus as key sulfur-oxidizing genera. These microorganisms played a central role in the biological oxidation of hydrogen sulfide to sulfuric acid, supporting stable long-term operation. Their dominance highlights the importance of maintaining favorable conditions (e.g., oxygen levels, pH) for autotrophic sulfur-oxidizing bacteria in achieving efficient biogas purification.Compared to conventional technologies, the two-stage configuration avoided common issues such as sulfur clogging and biogas dilution. The system offers a robust, scalable solution that supports circular resource utilization by generating a concentrated fertilizer while minimizing the need for external chemicals, making it suitable for full-scale implementation.