Long-term evaluation of activated carbon as an adsorbent for biogas desulfurization.

In this study, granular activated carbon (GAC) was used as an adsorbent for biogas desulfurization. Biogas containing 932-2,350 ppm of H2S was collected from an anaerobic digester to treat the wastewater from a dairy farm with about 200 cows. An adsorption test was performed by introducing the biogas to a column that was packed with approximately 50 L of commercial GAC. The operation ceased if the effluent gas had an H2S concentration of over 100 ppm. The GAC was replaced by a given weight of new GAC in a subsequent test. According to the results, for H2S concentrations in the range of 932-1,560 ppm (average+/-SD = 1,260+/-256 ppm), 1 kg of the GAC yielded biogas treatment capacities of 568+/-112 m(3) and H2S adsorption capacities of 979+/-235 g. For the higher influent H2S concentrations of 2,110+/-219 ppm, the biogas treatment and H2S-adsorption capacities decreased to 229+/-18 m(3) and 668+/-47 g, respectively. An estimation indicated a requisite cost of US$16.5 for the purification of 1,000 m(3) of biogas containing 2,110 ppm of H2S. This cost is approximately 5% of US$330, the value of 1,000 m(3) of biogas. ImplicationsBiogas generated from anaerobic digesters of animal manure and municipal wastewater sludge contains hydrogen sulfide which must be removed before it can be combusted in electricity-generation engines. This study demonstrated that commercial activated carbon adsorption can be an economical and effective approach for removing hydrogen sulfide from biogas. In this study, granular activated carbon (GAC) was used as an adsorbent for biogas desulfurization. The biogas containing 932-2,350 ppm of H2S was collected from an anaerobic digester for treating wastewater collected from a 200 dairy farm. The adsorption test was performed by introducing the biogas to a PVC column packed with a commercial GAC of around 50 L. Operation ceased if the effluent gas had an H2S concentration of over 100 ppm. A given weight of new GAC was replaced for a successive test.