Emission-free electricity can also be used to produce hydrogen by means of electrolysis. Such renewable hydrogen can be used in hard to electrify applications such as heavy goods transport and high-temperature heat for industrial processes, and can also be converted to electricity by combustion in a power plant or by fuel cells, especially for mobile uses such as heavy goods transport. Renewable hydrogen can also be used to produce methane or synthetic liquid fuels. Hydrogen or renewable gases can be stored over long periods and by making use of already existing gas storage infrastructure, thus reducing the overall system cost, compared with full electrification of economic activities. Energy system integration – i.e. the use of electricity to produce renewable gases or electrify end uses directly – provides opportunities for emission-free energy in a wide range of sectors and for mitigating the variability of RES. The Commission strategies for energy system integration and for hydrogen set out a roadmap and action plan for decarbonisation of the EU energy system. The Commission’s methane strategy, adopted in October 2020, addresses energy-related methane emissions.