What are the 'e-fuels' that Germany wants to develop for cars and what other biofuels could replace gasoline

Germany has demanded that the European Commission allow combustion cars to continue to be sold beyond 2035 as long as they only use synthetic fuel, also called

, as a condition to prohibit the sale of all other non-electric vehicles, which will no longer be able to be shipped after that date.

But what does this new range of fuels consist of and what fuels and biofuels are being investigated to replace gasoline, diesel and kerosene?

What is a fuel?

"A fuel is a substance capable of combustion, a chemical reaction that generates energy and transforms it into mechanical energy through an internal combustion engine," explains Lluís Soler Turu, Ramón y Cajal researcher and expert in Chemical Engineering at the University Polytechnic of Catalonia (UPC).

Most of the fuels used in transportation are based on fossil fuels such as oil (where gasoline and diesel come from) and natural gas, which cause greenhouse gas (GHG) emissions that accelerate global warming.

The commitment to decarbonise transport, which causes around 27% of emissions, is firm, and for this reason the EU will ban the sale of combustion cars in 2035. The alternatives without emissions are electric vehicles and those with a hydrogen battery.

Parallel,

What is a synthetic fuel?

Rafael Cossent, an

expert at the Universidad Pontificia de Comillas, points out: “The aim is to obtain a hydrocarbon similar to those derived from petroleum from hydrogen (H), which is present, for example, in water (H₂O).

First you separate the oxygen and hydrogen molecules through electrolysis and then through a catalytic process you combine it with carbon dioxide (CO₂) and you get that synthetic fuel.”

Soler Turu, from the UPC, adds: "This synthetic fuel can be generated from hydrogen from any source —for example, from natural gas—, but if it has the category of e-fuel it means that it does not come from a fossil fuel and that you have used renewable energy as your primary energy, such as wind or solar”.

From there arise the

, the

and

, among others.

More information

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What problems have you got?

The main one is the price.

“Removing hydrogen from water still has a very high energy and economic cost, and then it has to be combined with CO₂ using catalysts that normally contain precious metals.

Fossil fuel is still much cheaper.

But with investment and political will, more efficient catalysts can be achieved”, summarizes Soler Turu.

In fact, the NGO Transport & Environment (T&E) has calculated that they would increase the average cost of filling a deposit in 2030 to 210 euros (50% more).

Berta Cabello, from Repsol, points out: "They are not yet in industrial production, but when they do, they will be able to help decarbonise."

They are called climate neutral because it is assumed that the CO₂ they emit is offset by that previously captured to make the fuel.

Carlos Bravo, T&E,

puts down: "We can say that they are low emissions, but not neutral, because they do emit some CO₂ in the exhaust pipes, and also nitrogen oxides (NOx) in the combustion process."

And he adds: “They are much less energy efficient than battery electric motors.”

Comparison of the energy efficiency of fuels and e-fuels carried out by the environmental NGO Transport & Environment.

Transport & Environment

Can it be used on current cars?

“Yes, although most of them are in the experimental phase, they can already be used in today's cars, planes, trucks and boats,” answers Cabello.

In fact, the hydrocarbon molecule obtained from the electrolysis of hydrogen and carbon dioxide is practically the same as that obtained from petroleum.

Hence another question arises: “To lift its veto, Germany said that there would be a guarantee that the combustion engine would not start if it is not a synthetic fuel.

But current engines are not capable of differentiating a synthetic fuel from a normal one.

It is an open door to fraud and to delaying the decarbonisation of transport”, complains Bravo, from T&E.

What role does green hydrogen play?

“Hydrogen is an energy vector, an accumulator capable of storing energy, just like a battery.

Although, unlike a battery, you can store it for years and it doesn't discharge”, replies Soler Turu, who is doing research on it at the Specific Hydrogen Research Center (CER-H₂).

How does it work?

“You generate renewable electricity and when there is a surplus you use it to split water (H₂O) into hydrogen and oxygen.

This green hydrogen is used to produce electricity again, which can be sent to a hydrogen cell: it is an electrical generator that combines hydrogen and oxygen to generate water, electricity to run an engine, and a bit of heat”, he continues. the scientist.

There is already a model of car with this technology —such as the Toyota Mirai—,

A driver refills biodiesel at a German gas station.

Sean Gallup (Getty Images)

What are biofuels?

They are fuels derived from organic matter.

The first generation —such as biodiesel— are obtained through crops such as palm or soybeans;

those of second, of organic residues;

those of third —very incipient—, of algae.

Marta García, from Ecologistas en Acción, points out: “First-generation ones need a lot of surface area to produce and are associated with deforestation.

For this reason, in 2019 the EU considered that those that are based on palm oil have a high risk of generating changes in land use”.

The second generation, or advanced, represent an advance because they reuse waste, although they are still a very small part of the total.

"The emissions in the exhaust pipe are the same, but it is a product that you did not use before and that you revalue," says Javier Andaluz, from the same NGO.

Bravo, from T&E, notes:

“Methane is a gas that warms the atmosphere more than CO₂.

So landfill methane is much better if you use it for combustion than to let it be released.

It could be used, for example, for heating in buildings”.

An Airbus A320 recharges with biofuel at Seville airport.

Jose Manuel Vidal (EFE)

Which will be used in each means of transport?

Cossent predicts: “The electric vehicle will take a large part of the cake in terms of light vehicles, such as cars and motorcycles.

Instead, synthetic fuels and green hydrogen will be used more for heavy transport, such as buses, trucks, ships and planes, which are generally more difficult to electrify.

In this sense, airlines are already testing

, a synthetic fuel that has already been tested, for example, by the Spanish Iberia.

"Airbus is also trying to burn hydrogen, instead of using a fuel cell, but it is still in a very early phase," adds the expert.

"Meanwhile, shipping is testing two other synthetic fuels, such as methanol and ammonia," he concludes.

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