Development of an Activated Carbon from Anaerobic Digestion By-product to Remove Hydrogen Sulfide from Biogas

The production of biogas through the anaerobic digestion of cattle manure and its subsequent use in the generation of electricity on large Ontario farms is currently economically attractive. While larger farms have advantages of scale, there are substantially more small farms for which individually designed and engineered biogas systems are prohibitively expensive. Although biogas has numerous benefits, it contains hydrogen sulfide, an odourous, poisonous and corrosive gas, which emits sulfur oxides upon combustion. Larger systems can afford to use specialized biogas engines which tolerate some levels of hydrogen sulfide. For smaller scale systems to be financially attractive the hydrogen sulfide needs to be removed inexpensively, allowing for more flexibility in engine choice for electricity generation. In this work, the solid by-products from the anaerobic digestion process were used to create activated carbon, which has a high capacity for hydrogen sulfide. Not only does the carbon adsorb hydrogen sulfide, it allows for the surface oxidation of hydrogen sulfide to elemental sulfur and sulfate. Since the sulfur is in a beneficial form for fertilizer use, and there are no chemicals added to create the carbon, the spent sulfur-containing carbon can be land applied, eliminating any spent carbon disposal costs.MAS