“…The anaerobic fermentation of biomass, wastes, and other organic residues generates methane and carbon dioxide, biogas, whose composition depends on the biomass used and the operating conditions. Apart from methane and CO 2 , nitrogen, H 2 S, and NH 3 are produced. ,, On the basis of these facts, for the sake of simplification, we assume that biogas is mainly methane, CO 2 , H 2 S, NH 3 , and N 2 . The first stage consists of removing H 2 S. A bed of Fe 2 O 3 operating at 298–373 K is used.…”