Methane biofiltration for the treatment of a simulated diluted biogas emission containing ammonia and hydrogen sulfide

Fugitive methane emissions impair the physical and chemical stability of the atmosphere. Biological systems, such as biofilters, have been proposed as a feasible technology for the abatement of CH₄ in diluted emissions (<5% [CH₄]). Other gases, such as NH₃ and H₂S, are also present in these emissions; and they could be detrimental for the performance of biological CH₄ abatement strategies. The objective of this work was to establish the magnitude of the impact on the biofiltration of CH₄ due to the presence of NH₃ and H₂S. A methane biofiltration system operating at load of 10 gCH₄m^-3h⁻¹ was affected by the presence of NH₃ and H₂S in a synthetic diffuse stream, where the elimination capacity (5.5 gCH₄m^-3h⁻¹) and efficiency (55%) varied significantly. A combination of 100 ppmv of NH₃ and 100 ppmv of H₂S decreased the capacity by 17% with respect to the unexposed biofilter while 500 ppmv of NH₃ and 300 ppmv of H₂S shrink the capacity by 26%. Separately, H₂S decreased the methane elimination capacity by 11% under 150 ppmv and 20% when 300 ppmv was supplied. In the case of NH₃, the presence of 100 ppmv and 300 ppmv of NH₃ increases the methane elimination capacity by 35% and 16%, respectively. A reduction of 32% in the elimination capacity was observed under 1000 ppmv of NH₃. We contribute with numerical evidence by which methane biofiltration was affected by secondary gases on a concentration range similar to those in waste methane diffuse stream, establishing the concentration ranges of H₂S and NH₃ at which it is possible to optimize the process of methane biofiltration and under which performance could be reduced.