[en] ADEME contributes to the discussions on France's proactive strategy, notably by examining possible trajectories for the French energies of the future and has been publishing energy-climate scenarios on a regular basis since 2013. This study, 'A 100% renewable gas mix in 2050?', conducted by ADEME in collaboration with GRDF and GRTgaz, follows on from the works published in 2016 - 2017, and concerns the second most consumed energy in France, gas. Herein, ADEME explores the conditions of the technical and economic feasibility of a gas system in 2050 based on 100% renewable gas. The work is based on ADEME's 2035-2050 energy scenario, with a level of final demand for gas in 2050 of around 300 TWh, compared with today's figure of 460 TWh. The results, based on sensitivity analyses and various renewable gas production mix scenarios, reveal that there is a theoretical potential source of renewable gas that could fulfil this lower demand for energy in 2050 at an overall cost of gas between euros 116 and euros 153/MWh. It would involve making some modifications to the gas system and notably development of the complementarity between the gas network and the electric grid. This confirms that to improve the sustainability of our energy system, we must strengthen the interactions between the energy vectors and optimise their synergies, at various territorial scales