The main aim of this studies was to analyze selected technologies for the production of bio-based natural gas and to assess the effect of substituting natural gas present in the Spanish grid and used for electricity generation with gas that is generated based on renewable energy sources as well as to evaluate the influence of such substitution on future energy generation systems in Spain. For this purpose, a parametric analysis and economic analysis of the selected technologies was made, allowing to determine the CAPEX and OPEX, and finally the price of renewable natural gas.