Hydrogen Sulfide Reduction in Biogas Using an Iron-Based Reagent from Laboratory to Full Scale

The study investigated whether a dose of a commercial iron-based reagent determined under controlled laboratory conditions could be used as a starting point for full-scale hydrogen sulfide control in biogas. Laboratory tests were conducted in a reactor with a working volume of 30 dm3, and technical validation was performed in an operating anaerobic digester with a process volume of approximately 7200 m3. The common parameter used for scale transfer was the mass dose of reagent relative to the sulfur load supplied with the sludge (DSF, kg reagent/kg S). An operational reference range of 300 ppm H2S ±10% (270–330 ppm) was adopted for biogas supplied to combined heat and power units. In the final phase of the laboratory experiment, at a volumetric dose of 2.0 dm3/m3, the H2S concentration stabilized at 312–318 ppm, corresponding to DSF = 4.91 kg reagent/kg S. Full-scale validation was initiated at a similar dose of 4.75 kg/kg S, after which dosing was gradually reduced on successive days. The lowest tested dose was 1.26 kg/kg S, and the H2S concentration on the final day of observation was 268 ppm. The CH4 fraction at full scale remained stable at 62.3–64.0%. Reducing DSF from 4.75 to 1.26 kg/kg S decreased the unit reagent cost from approximately 2.21 to 0.59 EUR/kg S. Within the 8-day full-scale validation, the laboratory-derived dose functioned as a suitable starting point for scale transfer, but the results do not establish a long-term optimum and do not support using the laboratory value directly as a fixed operating dose.