TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The OMS structure of the manganese oxide material is one of OMS-1 and OMS-2, where OMS-1 has a 3x 3 tunnel structure and a tunnel size of 6.9 Angstrom and OMS-2 has a 2x 2 tunnel structure and a tunnel size of 4.9 Angstrom . The manganese oxide material has mixed valence and manganese in the OMS structure of the manganese oxide material has an oxidation state of +3 and +4. The manganese oxide material is doped with at least one doping metal inserted into tunnels of the OMS structure, where the amount of the doping metals is 0-50% of a total metal content of the desulfurizer material, and the doping metals comprise at least one of transition metals, alkali metals or alkali earth metals. The doped manganese oxide material comprises copper-OMS-2, cobalt-OMS-2 or iron-OMS-2. The manganese oxide material is doped with a first doping metal in an amount of 0-50% of the total metal content of the desulfurizer material and with a second doping metal in an amount of 0-25% of the total metal content of the desulfurizer material. Preferred Method: In the desulfurizing method, the step of removing sulfur-containing compounds is performed by an oxidation process or a catalytic oxidative desulfurization process. The desulfurizing method further comprises heating at least one fuel before conveying the fuels to the desulfurizing beds. In the desulfurizing method, the step of conveying comprises conveying a first fuel to the desulfurizer assembly and conveying a second fuel to the desulfurizer assembly, where the first fuel has a different composition from the second fuel, and the method further comprises: heating a biogas digester using waste heat output from the fuel cell system; generating a biogas fuel in the biogas digester; and processing the biogas fuel to output the first fuel comprising processed biogas fuel before conveying the first fuel to the desulfurizer assembly. The processing step comprises removing hydrogen sulfide from the biogas fuel, removing moisture from the biogas fuel and removing siloxanes from the biogas fuel. The method further comprises controlling at least one of: flow rates of first fuel and second fuel to the desulfurizer assembly; and flow of first fuel and second fuel through the desulfurizer beds in the desulfurizer assembly.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The desulfurizer assembly comprises many desulfurizer beds, including a first desulfurizer bed and a second desulfurizer bed, where the first desulfurizer bed and the second desulfurizer bed comprises one of the same desulfurizer material and different desulfurizer materials. The fuel cell system further comprises: a cleanup assembly for processing fuel before the fuel is conveyed to the desulfurizer assembly, where the cleanup assembly comprises at least one of an hydrogen sulfide removal unit for removing hydrogen sulfide from the fuel, a moisture conditioning unit for removing moisture from the fuel and a siloxane removal unit for removing siloxanes from the fuel; and a heating assembly for at least one of heating a biogas digester providing fuel to the cleanup assembly and pre-heating desulfurized fuel output from the desulfurizer assembly. The heating assembly pre-heats the desulfurized fuel using anode exhaust or cathode exhaust, and the heating assembly is further configured to receive water and to humidify the desulfurized fuel with the received water. The fuel cell system is configured to operate on at least two fuels different compositions and the fuel cell system further comprises: a first fuel supply assembly for supplying a first fuel to the fuel polishing assembly; and a second fuel supply assembly for supplying a second fuel, having a different composition from the first fuel, to the desulfurizer assembly, where the second fuel is not conveyed through the cleanup assembly. The first fuel is biogas fuel output from a biogas digester and fuel cell system further comprises a heating assembly for heating the biogas digester so as to maintain the temperature the biogas digester at a predetermined temperature. The fuel cell system further comprises a control assembly for controlling at least one of: flow rates of first fuel and second fuel through the first and second supply assemblies, respectively; and flow of first fuel and second fuel through the desulfurizer beds in the desulfurizer assembly. EXAMPLE - No suitable example given.