Nowadays in Europe there is a growing attention on renewable energy sources (RES), especially solar and wind power. The increasing development of RES has put emphasis on the problem of surplus power production, due to the randomness of natural phenomena. At the same time, plenty of European Countries, such as Italy, are continuously encouraging the usage of biofuels, e.g., biomethane. The aim of this thesis is to understand whether it is possible to produce biofuels in sustainable ways. Downstream of the Anaerobic Digestion, performed in Wastewater Treatment Plants, biogas is naturally produced by microorganisms. Therefore, this work focuses on the possibility to convert biogas or gas mixtures (carbon dioxide and hydrogen in ratio of 1:4) into biomethane by Hydrogenotrophic methanogens.