In this thesis work are studied different scenarios for the analysis of a plant producing biogas from sewage sludges. The Collegno’s WWTP, with its relative hourly values, is considered as the base plant for the research. In the most complete scenario it is analysed a layout made up of the following components: - Upgrading system able to split CO2 and CH4 composing biogas, to ensure the trade with the natural gas grid. - Methanator in which the reaction of methanation occurs: thanks to this reaction it is possible to obtain further methane adding carbon dioxide to hydrogen. - Electrolyser system, which exploits water electrolysis: a process that produces hydrogen and oxygen from water molecules.