The energy sector in particular should be leading the decarbonisation effort given the availability of technological solutions so that Europe moves towards a highly efficient, 100% renewable energy system. What could be the role of gas in this 2050 perspective? While natural fossil fuel gas should be phased-out, other gases emerge and are presented as renewable alternatives. What are their potential, properties, costs and benefits? Are they compatible with a net-zero carbon emission society by 2050?