Fuel cells have a high electrical efficiency and low pollutant emissions, comparatively. Because of low number of units they are very expensive. They are working in base of oxyhydrogen reaction: !fuel cell reaction.jpg! By use of a reformer biogas is transformed into hydrogen-rich gas. In the fuel cell there are two gas-filled compartments, separated by a polymer membrane. Hydrogen is ionized at the anode. Emerged hydrogen protons are able to diffuse the membrane. Parallel the mobilized electrons of ionization process drift by a conductor into the other gas-filled compartment, the cathode, where the electrons ionize the oxygen. At this place the oxygen combines itself with the hydrogen protons into water. This drifting of electrons in the conductor produces electrical power. This process afford heat and electrical power.