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E-Fuels: CO2-neutral fuels of the future

Tomorrow's car will be emission-free. Alternative fuels and drive systems offer the opportunity to reduce CO2 emissions and promote climate protection. Synthetic fuels are an important building block on the road to emission-free driving.

Since 2004, CO2 emissions and fuel consumption of newly registered passenger cars in Germany have already fallen by more than a quarter. In order to achieve the ambitious European climate targets, pollutant emissions must be reduced even further, especially in the transport sector. The industry has developed various technological solutions for this. Synthetic fuels, so-called e-fuels, play an important role for tomorrow's mobility as they can be used in combustion engines just like petrol or diesel. If they are generated from purely renewable energy, they enable quasi CO2-neutral travel - not only by car, but also by lorry, ship or aircraft. The technology is becoming increasingly important as even purely electrically powered means of transport generate a lot of CO2 emissions in their manufacture.

What are e-Fuels?

E-fuels are synthetically produced fuels made from electricity, water and carbon dioxide through the use of power-to-X technology, more precisely the power-to-liquid (PtL) process. The method makes use of a feedback process. As much carbon dioxide is captured during production as is later emitted again during consumption. This is only possible if the electricity used comes from renewable energies and the CO2 from the environment. The term originates from English and is the abbreviation for "electro-fuels". The overarching goal of the technology is the decarbonisation of the transport sector, whereby e-fuels can be used in a scalable manner in end products, that is, they can be used like petrol or diesel in internal combustion engines without having to do a lot of conversion.

How are synthetic fuels produced?

The basis for the production of e-fuels is power-to-liquid technology, in which green hydrogen is produced. In the chemical process, electricity, which is necessary for the upcoming electrolysis, is first generated from renewable sources. Electrolysis is a process in which the electricity forces a chemical separation of water into hydrogen and oxygen. To put it simply, elemental hydrogen is created when charged particles migrate to electrodes and are thus separated. With the addition of carbon dioxide, a synthesis gas which forms the basis for the following steps is then produced in a separate reaction. The carbon dioxide used can either be extracted from the environment or stored using Carbon Capture Utilisation and Storage technology, which uses CO2 from combustion exhaust gases. The synthesis gas as an intermediate product contains the elements carbon, oxygen and hydrogen, which are required for further processing. This gas is then synthesised by means of special processes.

One of the most commonly used procedures is the Fischer-Tropsch process. Here, a build-up reaction of the synthesis product takes place on special catalysts, whereby paraffins, alkenes and alcohols can form. This requires a high pressure of up to 40 bar and a high temperature of up to 350°C. The product must then be processed in refineries to obtain e-gasoline or e-kerosene. In the last step, the product has to be processed in refineries to obtain e-gasoline, e-diesel or e-kerosene - e-fuel. This manufacturing process is very energy-intensive. The amount of energy required can only be covered with difficulty by the renewable energies available in Germany. Accordingly, e-fuels will probably be produced in other countries and then, for the most part, be imported.

Are e-fuels climate neutral?

When PtL technology is used for e-fuels, approximately the same amount of carbon dioxide is captured during production as is emitted again during subsequent combustion - the carbon footprint is therefore balanced and the vision of emission-free driving is a reality in theory.

E-fuels are largely free of sulphur components, which makes subsequent filtering unnecessary and protects the environment. The use of synthetic fuels ideally reduces the use of fossil raw materials to zero if no crude oil, natural gas or coal is used throughout the entire production process.

The use of e-fuels can make a major contribution to achieving the adopted climate targets. Since they can be used immediately without having to build a new infrastructure, they can also be implemented in economically less developed countries. E-fuels can therefore sustainably decarbonise the transport sector, reduce greenhouse gas emissions and mitigate climate change.

Advantages and disadvantages of synthetic fuels compared to conventional fuels.

Advantages Disadvantages
can directly replace conventional fuel as existing infrastructure (filling stations, pipelines) and power units can be used energy efficiency is four to six times lower compared to combustion engines
higher quality than fossil fuels as only pure feedstock is used (no sulphur content) there are still air pollutant emissions
high energy density Currently still many times more expensive than fossil fuels
Can be transported cost-effectively over long distances  
Good stationary storability  
Existing fleets can be operated in a climate-neutral way  
Crude oil can be processed in conventional refineries