What are e-fuels?
E-fuels are synthetic liquid fuels that are produced from renewable energy sources. They are also known as “power-to-liquids.”
E-fuels are considered an environmentally friendly alternative to fossil fuels, such as diesel and gasoline. Right now (April 2023), the focus is on e-fuels, as they are part of the argument of Transport Minister Volker Wissing (FDP) to prevent the Europe-wide ban on combustion engines and to allow new registrations of vehicles with combustion engines even after 2035, provided that they can be powered by e-fuels.
How are e-fuels produced?
E-fuels are produced from renewable energy sources such as solar energy, wind or hydropower. The electricity produced from this is used to produce hydrogen or carbon monoxide. Hydrogen or carbon monoxide is then converted into liquid synthetic fuels with carbon dioxide.
There are various technologies in the production of e-fuels. They all usually include the following steps:
- electrolysis: Water is split into hydrogen and oxygen through electrolysis using electricity from renewable energy sources.
- Fischer—Tropsch synthesis: The hydrogen produced in this way is converted into a synthesis gas with carbon monoxide. In a so-called Fischer-Tropsch synthesis, this gas is converted into a liquid fuel, such as methanol or synthetic diesel. This process requires carbon dioxide (CO2), which can be obtained from air or exhaust gases.
- Further processing: In order to obtain the desired properties of the fuel, for example to produce biodiesel from methanol, the fuel is further processed accordingly (e.g. by esterifying methanol).
Benefits of e-fuels
E-fuels are said to have the potential to minimize CO2 emissions from internal combustion engines, as the carbon released from the atmosphere during production is absorbed. In addition, e-fuels can be used to operate combustion engines and thus offer an opportunity to help shape the transition to climate-neutral mobility.
The biggest benefits include:
- climate neutrality: Since e-fuels are produced from renewable energy sources, they are ideally climate-neutral because they do not emit any additional carbon dioxide (CO2) into the atmosphere.
- Compatible with existing infrastructure: With e-fuels, existing combustion vehicles can continue to operate.
- Independence from environmental influences: In contrast to wind and solar energy, e-fuels can be produced regardless of weather conditions or time of day.
- Potential storage medium: One challenge in the energy revolution is the storage of renewable energy. E-fuels could possibly be used here as a storage medium for excess electricity from renewable energy sources.
Criticism of e-fuels: These are the disadvantages
In addition to the advantages mentioned above, e-fuels also have a number of disadvantages. In particular, the focus is on significantly higher production costs compared to fossil fuels and the need for the large amount of renewable energy required to produce climate-neutral e-fuels. Compared to the direct use of solar energy, for example, e-fuels lag far behind in terms of energy efficiency.
For e-fuels to be climate-neutral, they must be produced using renewable energy sources. Since the amount of energy required for production is very high, electricity from renewable energy sources can become scarce and therefore expensive if there is a corresponding demand for e-fuels. Since the efficiency of e-fuels is also comparatively low, the available amount of renewable energy should be used in a better location.
E-fuels with comparatively low efficiency
Efficiency describes how efficiently a device, for example, uses energy. This means: How much of the energy spent on production/operation can actually be used?
E-fuels are currently expected to be efficient at 15%. In other words, less than of the energy used to produce e-fuels can actually be used afterwards. In comparison, have battery-electric vehicles (electric cars) an efficiency of 64% and are therefore the most efficient of all technologies.
This means that the amount of electricity that an electric car can travel 700 km is only enough for e-fuels for 100 km. Or: A 3 megawatt wind turbine can supply 1,600 electric cars, 600 hydrogen cars or 250 vehicles with e-fuels.
By the way: With an efficiency of just 20%, gasoline engines are also relatively poor.
You should also know that you are not traveling locally with e-fuels without emissions. Although CO2 is absorbed from the air during the production of e-fuels, this is released again when burned in the engine.
Can every combustion engine be powered by e-fuels?
The theory of the advocates is: With the help of e-fuels, I can also drive a car with an internal combustion engine in a climate-neutral way. This results in higher acceptance of the transport revolution, because the combustion car owned by many consumers can continue to operate - the expensive purchase of a new (e) car can be postponed.
This should mean that any vehicle with an internal combustion engine can be powered by e-fuels. In theory, this is also the case - as long as the engines are designed in such a way that they can withstand the higher flash point due to the higher viscosity of e-fuels. In addition, e-fuels are more corrosive than fossil fuels, so corrosion resistance must also be considered.
It is questionable whether this is the case with every car - who doesn't remember the uncertainties surrounding the introduction of E10 gasoline? Should retrofits become necessary to use e-fuels, one should ask oneself whether to skip this intermediate step and immediately electrify.
Are e-fuels the future of climate-neutral mobility?
E-fuels have great potential to reduce CO2 emissions in mobility. Due to the many disadvantages, such as high (energy and cost) expenses and low efficiency, e-fuels should not be given a priority position for private transport. In the transport sector, however, things are different: Where battery-electric drives make little sense (for example in aviation and shipping), e-fuels may be able to make an important contribution to reducing CO2 emissions and thus to climate protection.
For us at elvah, however, one thing is clear: In a future with climate-neutral mobility in private transport, we see electric cars in first place.