Technical and economical study of a full-scale biotrickling filter for H₂S removal from biogas

The present study evaluates the technical and economical feasibility of the H₂S elimination from an energy-rich gas using a full-scale biotrickling filter installed in a municipal waste water treatment plant. The study analyzes the continuous operation of a 4.5 months period, treating 80 m³ h^-1 of biogas with an average H₂S concentration of 3000 ppm_v. The bioreactor was operated at a gas contact time of 180 seconds and maximum elimination capacities of 170 g H₂S m^-3 h^-1 were obtained without any occurrence of neither biological nor mass transfer limitation. Elemental sulfur and sulfate were the main detected byproducts of the H₂S treatment. The main drawback observed during the studied period was related to the air flow supply. This caused a removal efficiency decrease and an excess of sulfur production. A comparative cost-benefit analysis of the more applied chemical oxidation processes with the biological treatment was performed. Savings chemicals indicated that the payback time of the substitution treatment was about 4.5 years. Cost savings ranged between 11000€ per year, or 2.6€ per kg H₂S treated. The results of this study have shown how to solve the main operational problems detected in the proposed system and the cost-benefit analysis suggests a significant benefit by replacing the current chemical treatment by the biological alternative not only from an environmental point of view, but also from an economical perspective.