E-fuels are no cleaner than fossil fuels

Transport & Environment (T&E) had synthetic fuels made in the lab and tested their combustion. The result: e-fuels emit just as much nitrogen oxide (NOx), more carbon monoxide (CO), but fewer particles than fossil fuels.

E-fuels can be synthesized from hydrogen (ideally from green electricity) and CO2 (ideally from the atmosphere), i.e. artificially produced in the laboratory. Ideally, when they are burned, only as much CO2 is released as their production removed from the atmosphere. In this respect, they are considered CO2-neutral. Problem: Enormous amounts of green electricity are required to manufacture them or to generate the hydrogen and extract the CO2 from the atmosphere. You can read everything about the advantages and disadvantages of e-fuels here .,

But what about the pollutants? After all, they are also made of hydrocarbons and their advantage is that they burn in the same engines in the same way as their fossil counterparts. On the other hand, it would actually be conceivable to produce fuels that burn more cleanly than diesel and petrol of fossil origin by producing them in the laboratory - the ADAC, for example, claims that e-fuels burn "quite cleanly compared to conventional petrol and diesel".

Are e-fuels CO2-neutral and have cleaner emissions?

As an umbrella organization for non-governmental organizations from Europe that are committed to sustainable transport, "Traffic & Environment" (T&E) wanted to know whether this is actually the case - i.e. whether synthetic fuels burn cleaner than fossil fuels. That is why T&E commissioned the French research institute IFP √Čnergies nouvelles (IFPEN) to measure the pollutant emissions of combustion vehicles powered by e-fuels. The focus was on synthetic petrol, since a study by the Concawe organization had already been carried out on diesel.

However, synthetic petrol is not yet available. The IPFEN had to produce the almost 100 liters itself. Three types were created: 100 percent synthetic gasoline and two types with additives for better combustion. Synthetic petrol with a 10 percent ethanol content was primarily used for the tests, as is currently on the market as Super E10 in accordance with the EN228 standard. A Mercedes A180 with a 1.3-liter turbo engine, Otto particle filter and manual 6-speed gearbox served as the test vehicle. The car was year of production 2019, properly maintained and had 17,000 km on the odometer. With this vehicle, IPFEN drove WLTP cycles and RDE laps (Real Driving Emissions) in the laboratory.


A car running on e-fuel emits as many toxic nitrogen oxides as one running on conventional E10 fuel, according to T&E. For classification: Nitrogen oxides (NOx) are the main problem of traffic-related emissions, especially for the city air.Their effective reduction only made significant progress with the introduction of the Euro 6d Temp emissions standard after the emissions scandal. It is obvious that the combustion of e-fuels emits no less of it: The compound of the main air components nitrogen and oxygen (N, O) is formed primarily at high temperatures, such as those found in engine combustion chambers; they last particularly well in the exhaust gas when it cools down very quickly. ,

In a test by auto motor und sport , a Porsche 911 powered by e-fuel emitted less NOx than the comparison model filled with Super Plus (see picture gallery), but only on the Autobahn at 130 km/h. In city traffic, where the NOx emissions are particularly disturbing, there were hardly any differences.,

More CO and particulate matter, fewer particles

According to T&E, the combustion of synthetic gasoline produces almost three times as much carbon monoxide as compared to normal gasoline; it is considered harmful and affects the oxygen supply to the heart and brain. In the auto-motor-und-sport test, the e-fuel 911 emitted even less CO. At T&E, the car powered by e-fuel also emitted up to twice as much ammonia. It can combine with other particles in the air to form fine dust particles (PM2.5) for which there is no adequate limit value. Health risks from PM2.5 include asthma, heart disease and cancer.

Only the particle emissions fell drastically when using e-fuels in the test commissioned by T & E. In the auto-motor-und-sport test, the e-fuel vehicle emitted over 40 percent less particulate matter and over 20 percent less particulate matter than the Super Plus. The particle-reducing effect for gasoline direct injection engines without Otto particle filters (OPF), i.e. older existing vehicles, would be significantly higher.,


According to the tests commissioned by T&E, the exhaust gas from a gasoline engine running on e-fuel contains significantly fewer particles, but just as much nitrogen oxide and even more carbon monoxide and ammonia.

Vehicles that are operated with e-fuels do not emit more CO2 than they ideally absorbed from the atmosphere during their synthesis. But the CO2 balance also has the enormously high demand for green electricity as a snag - you can read the detailed description of the advantages and disadvantages of electricity-based, synthetic fuels here .

That's why Stef Cornelis, Director of T&E Germany, is even attacking the traffic light coalition's plans: "The coalition agreement stipulates that e-fuels will also be used in road traffic after 2035. That's a mistake, because they're not clean, they're not available and most automakers don't even want them in their new vehicles." The T&E boss would block the way to e-fuels for cars.


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