A Two-Stage Biogas Desulfurization Process Using Cellular Concrete Filtration and an Anoxic Biotrickling Filter

A two-stage desulfurization process including an abiotic filtration using cellular concrete waste (first stage) and an anoxic biotrickling filter filling with an inoculated expanded schist material (second stage) was investigated to remove H2S in mimic biogas with limited O2 amount (ranged from 0.5 to 0.8%). The two-stage process was able to satisfactorily remove H2S for all experimental conditions (RE > 97%; H2S concentration = 1500 mg m−3; total Empty Bed Residence Time (EBRT) = 200 s; removal capacity (RC) = 26 g m−3 h−1). Moreover, at a total EBRT = 360 s (i.e., 180 s for each stage), the H2S loading rate (LR) was almost treated by the bed of cellular concrete alone, indicating that abiotic filtration could be applied to satisfactorily remove H2S contained in the gas. According to the H2S concentration entering the biotrickling filter, the majority end-product was either elemental sulfur (S0) or sulfate (SO42−). Thus, the ability of the abiotic filter to remove a significant part of H2S would avoid the clogging of the biotrickling filter due to the deposit of S0. Consequently, this two-stage desulfurization process is a promising technology for efficient and economical biogas cleaning adapted to biogas containing limited O2 amounts, such as landfill biogas.