The increase in temperature in last decades has been strictly related to carbon dioxide emission: a sharp decrease in fossil fuel use is needed to limit irreversible damages to the global ecosystem. EU is committed to achieve net zero emissions by 2050, as announced in the European Green Deal. Between fossil fuel sources, methane is the one with the least environmental impact. This led EU to choose NG as the ideal fossil fuel to start the energy transition. In 2021, around 40% of imported NG derived from Russia. In response to the invasion in Ukraine new NG contracts with other suppliers were stipulated, increasing energy security; in parallel a rise in other sustainable sources and alternative fuel to NG was programmed.