E-fuels are synthetic fuels produced using renewable electricity. The term encompasses a wide range of products, such as e-methanol, e-diesel, e-gasoline, e-naphtha, and e-kerosene—the latter also known as Sustainable Aviation Fuels (SAF). Since they are potentially climate-neutral, unlike fossil fuels, they are considered a key technology for decarbonizing the mobility sector.
Manufacturing
The production of e-fuels involves several stages. In the first step, renewable electricity is generated from wind, solar, or hydro power. This electricity is then used to split water into oxygen and green hydrogen through electrolysis.
E-Fuel Production (© eFUEL-TODAY)
In a subsequent step, this hydrogen is converted into synthetic fuels (CCU) using CO₂ from the atmosphere or from industrial processes. Depending on the desired end product, this process is carried out in different ways. For example, the Fischer-Tropsch synthesis is particularly well-suited for the production of e-diesel or e-kerosene, whereas directCO₂ hydrogenation is used in the production of e-methanol.
A great deal of energy is lost through the multiple conversion processes. As a result, only about 10–35 percent of the electrical energy originally used in the production and use of e-fuels reaches the end user. A vehicle powered by e-fuels therefore requires about five times more energy than an electric car.
Pros and Cons of E-Fuels
As so-called “drop-in” alternative fuels, e-fuels can be used in internal combustion engines without any further modifications. The refueling infrastructure can also generally continue to be used as is. This reduces the transition costs associated with the transformation. The greatest advantage of e-fuels, however, lies in their potential CO₂ neutrality: In the best-case scenario, combustion releases only those pollutants that were previously extracted from the environment during the synthesis process. The climate impact of e-fuels, however, depends crucially on the electricity used. Only if this electricity comes almost entirely from renewable sources (over 90 percent) can e-fuels have a positive climate impact compared to fossil fuels.
The biggest challenge facing e-fuels is their currently relatively high cost. This stems from the high energy requirements of their production and the still limited production capacity. Production costs currently range up to 8 euros per liter—significantly higher than the cost of fossil fuels. As a result, battery-electric or hydrogen-based powertrains for passenger cars are currently still significantly more energy-efficient.
Examples
- Synthetic methanol can be used directly as a fuel or as a basic chemical in industry. It is also considered a promising alternative fuel for ships.
- E-diesel is suitable for heavy-duty commercial vehicles and ships and is designed to integrate seamlessly with existing diesel technologies.
- E-kerosene (SAF) is being developed specifically for aviation and is considered a sustainable fuel alternative for current aircraft engines.
This video was created as part of the OTH Regensburg Hydrogen Atlas projectand illustrates the basic principle of the Fischer-Tropsch process for producing e-diesel or e-kerosene:
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