The need to decarbonize industrial processes and to increase the utilization of renewable resources, either energy and raw materials, has led to the development of new production processes. The focus of this paper is to evaluate the environmental impacts of an innovative 1 kW pilot plant for methane production, following the life cycle thinking approach. The process is based on the coupling of an alkaline water electrolysis, which generates syngas using a carbon source, with a methanation reactor that converts the syngas to methane. The life cycle assessment (LCA) takes into account the pilot plant construction materials, electricity and reactants used, for a functional model of a mole of methane produced per hour of operation. Data from the pilot plant, in particular reaction conversions, were used complemented with data from the literature and inventory databases. Energy and the construction materials used to build the experimental unit are the main factors influencing the environmental performance. Several scenarios were defined varying the electricity source and the carbon source, showing the results that the energy source is more relevant to reduce the process environmental impacts. The results can be used to scale-up and to better implement the combined electrolysis methanation process in industrial practice. •A Life Cycle Assessment of methane production in an innovative combined electrolyzer/methanation reactor process was done.•Energy and construction materials are the main factors influencing the environmental performance.•Several scenarios were analyzed varying the energy source and carbon source.•Replacing the energy source to fully renewable has the largest reduction of the environmental impact.