Given the goal of achieving carbon neutrality by 2050 and the widespread adoption of renewable energy sources, it is crucial to examine technologies that reduce environmental impact while maximizing efficiency. The aim of this work is to develop a fed-batch continuous-stirred tank reactor at laboratory-scale wherein a mesophilic ex-situ biomethanation process occurs. This process utilizes a feedstock comprising digestate from a wastewater treatment plant and a gaseous mixture of H2/CO2 in a 4:1 ratio. The work is structured into four parts. The first part addresses the current status of renewable energy sources in the European Union and the directives related to their utilization, including the Renewable Energy Directive.