E-fuels are fuels made from ‘green’ hydrogen — i.e. produced by a process using the electrolysis of water — which is then combined with CO2 captured either at plant outlets or in the air, to produce methane, methanol or synthetic paraffinic fuels such as e-gasoline, e-gasoil or e-kerosene. Ammonia can also be produced, but by reacting hydrogen with nitrogen instead of CO2.
The problem is that this type of production consumes a huge amount of energy: the renewable electricity needed to produce hydrogen by electrolysis, the energy needed to capture the CO2, then the energy needed either for the methanation or hydrogenation reaction of the CO2 to obtain e-methane, or for the other synthesis reactions, often catalytic, to obtain e-fuels (petrol, diesel or paraffin).[1] The report by the energy industry states that most energy consumption is linked to hydrogen production: the efficiency of converting electricity into fuel is between 40% and 60%, depending on the electrolyser used.[2] So while the synthesis routes for reacting carbon dioxide with hydrogen are mature and well known, they still consume energy during the process. Above all, the production of these fuels relies on a hydrogen production and CO2 capture process which is not yet mature.
The major advantage of these liquid fuels is that they can replace conventional fossil fuels without any change in use. Their properties are similar to those of fossil fuels, but they have the advantage of being purer, i.e. containing less sulphur or aromatic particles (PAHs), which generate pollution. Although these fuels require CO2 for their manufacture, thus they do not eliminate it and simply recycle it. But, like fossil fuels, they emit nitrogen oxides and particles during combustion.
The potential of electrofuels is significant for maritime transport and aviation, as these two sectors are subject to increasingly restrictive European regulations, and direct electrification with batteries is hardly conceivable in the current state of science over very long distances. As a result, the maritime sector must both reduce the fuel consumption of its ships (since July 2023) and use fuels whose greenhouse gas content must be reduced by 2% in 2025 and by 80% in 2050. To meet these requirements, the world’s third largest shipping company, CMA-CGM (Compagnie maritime d’affrètement-Compagnie générale maritime), believes that battery-powered or hydrogen-powered electric solutions are too bulky to propel container ships. The shipping company will initially order ships that run on liquefied natural gas, but which could later run on biomethane or e-methane. The world’s second largest container shipping company, Maersk, announced in 2021 that it would invest in partnerships to produce e-methanol (from biogenic CO2)[3] to decarbonise the fuel used by its ships. It plans to commission 19 ships running on e-methanol between 2023 and 2025, to reach its target of 25% green fuel use by 2030, using biomethanol and e-methanol.
The major problem is green electricity availability to produce these fuels, given the competition from other sectors (transport, industry, housing) for green electricity.
In the air transport sector, the European Parliament recently adopted a directive requiring the incorporation of sustainable aviation fuels: 2% by 2025, 6% by 2030, 20% by 2035, and up to 70% by 2050. The term sustainable fuel covers liquid fuels, biofuels and synthetic fuels derived from hydrogen. Today, these are mainly oils or fats derived from hydrogenated food waste. France is ahead of the game, already requiring aircraft to use 1% sustainable fuel from 2022. However, biofuels are starting to run out, as production is not sufficient to meet demand. Air-France/KLM already had to purchase 17% of the world’s production of aviation biofuels to meet this obligation. In Europe, according to the ReFuelEU Aviation initiative, the production of sustainable fuels for aviation is currently estimated at 0.24 million tonnes, whereas the expected demand in 2030 could be 46 million tonnes. To meet European targets, we would therefore need to almost quadruple the production of green fuels by 2025, and multiply it by more than 10 by 2030.
