About fifty years have passed since Japan's gas supply industry became the first in the world to switch from coal and oil to LNG as a city gas feedstock. Since the Japanese government target of net-zero carbon emission in 2050 was announced in October 2020, it has now entered a new era of challenges to commit the requirement for decarbonization.
The Japan Gas Association announced the 'Carbon Neutral Challenge 2050' as a vision to contribute to meet both national and world target by converting the city gas supply to carbon neutral. One of the key technologies is “methanation” to produce e-methane. Various efforts are underway to commercialize e-methane and recent leading examples conducted by the Japan’s major city gas companies.

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In order to promote the carbon neutralization of gaseous energy, Tokyo Gas is working on the mass production and import of e-methane by constructing overseas supply chain, domestic local production for local consumption of e-methane, and also the development of innovative methanation technology for further expansion of social implementation of e-methane in the future.

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SOEC methanation technology can produce e-methane with extremely high energy conversion efficiency from non-fossil electricity using water and CO₂ as raw materials. Since the amount of electricity required, which accounts for a large portion of the production cost, is the lowest among various green fuels, it is expected to be an innovative technology with high potential for cost reduction. This paper describes the outline, features, our efforts, and future development of innovative SOEC methanation technology that enables low-cost production of e-methane (synthetic methane), a non-fossil fuel that is carbon neutral like biomass, etc., the advantages of e-methane as an overseas renewable energy power import carrier, and the significance and potential of the e-methane power generation.

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For carbon neutral society and CCU, methanation technology and e-methane contribute to accelerate utilization of renewable energy and green hydrogen by using existing natural gas infrastructure of storage, transportation and utilization. Since 1993, Hitachi Zosen Group has been developing high-performance methanation catalysts and methanation processes, and accumulating field demonstrations.

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In order to achieve carbon neutrality in Japan, the validity of the CO₂ reduction effect of synthetic fuels (e.g. e-methane, e-fuel, etc.) needs to be internationally recognized as an important means of energy-related carbon neutralization.
International standards for the calculation of greenhouse gas emissions throughout the LNG value chain will lead to international recognition of the CO₂ reduction potential of e-methane (i.e. captured CO₂ for feedstock of recycled carbon fuels can be offset of CO₂ emissions from final combustion), which is expected to contribute to the carbon neutralization of city gas.

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The “Clean Gas Certificate” program has been launched since April,2024. This private program covers synthetic methane (also called e-methane) and biomethane contained in biogas. The certification body certifies the environmental value that the CO₂ emitted from combustion of those gases does not increase atmospheric CO₂.
There are approximately 200 city gas suppliers in Japan, usually each of which is mutually independent and managed by each gas company locating in the city or region.
Clean gas certificate is designed to enable to convey the environmental value of those gases separated from the energy value for heat, to those which need environmental value-added city gas with no-accessible to actual clean gases. An overview of the Clean Gas Certificate is provided.

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