Desulfurization of biogas from a closed landfill under acidic conditions deploying an iron-redox biological process

Abstract

Desulfurization processes play an important role in the use of biogas in the emerging market of renewable energy. In this study, an iron-redox biological process was evaluated at bench scale and pilot scale to remove hydrogen sulfide (H2S) from biogas. The pilot scale system performance was assessed with real biogas emitted from a closed landfill to determine the desulfurization capacity under outdoor conditions. The system consisted of an Absorption Bubble Column (ABC) and a Biotrickling Filter (BTF) with useful volumes of 3 L and 47 L, respectively. An acidophilic mineral-oxidizing bacterial consortium immobilized in polyurethane foam was utilized to regenerate Fe(III) ion, which in turn accomplished the continuous H2S removal from inlet biogas. The H2S removal efficiencies were higher than 99.5% when H2S inlet concentrations were 120–250 ppmv, yielding a treated biogas with H2S < 2 ppmv. The ferrous iron oxidation rate (0.31 g·L−1·h−1) attained when the system was operating in natural air convection mode showed that the BTF can operate without pumping air. A brief analysis of the system and the economic aspects are briefly analyzed.