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No universal climate solution : Internal combustion engine in a dead end

In some parts of the automotive and mineral oil industries, there is great hope that cars with internal combustion engines will run on climate-friendly synthetic fuels in the future. This means that one could stick with the current car drive and achieve the goal of decarbonization more quickly than with battery-powered e-cars, so the idea. A study published on Thursday in the journal “Nature Climate Change” now rejects this.

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At least as far as fuel produced on the basis of hydrogen is concerned, this is not an option for climate protection in the short or medium term. The production of such fuels is too inefficient, too costly and their availability too uncertain to be able to replace fossil fuels on a broad front, write the researchers led by Falko Ueckerdt from the Potsdam Institute for Climate Impact Research (PIK).

Hydrogen as a false promise

Hydrogen produced with green electricity is a versatile option for conversion into hydrocarbon fuels, but as a universal climate solution it is a false promise. "Hydrogen-based fuels are an impressively versatile energy source - but their costs and the associated risks are also impressive," said Ueckerdt.

The analysis published on Thursday is based on his team's own calculations based on existing literature.

For car traffic and the heating of buildings, direct electrification is cheaper and more efficient. The researchers recommend hydrogen-based fuels for aviation in the field of long-haul flights as well as parts of the chemical industry and steel production. Here the green hydrogen - obtained with renewable energies through electrolysis - is "indispensable", says Ueckerdt.

Scientists consider hydrogen-based fuels to be very promising as a long-term vision. With carbon prices rising, these fuels could likely become cost-competitive by 2040.

“In view of the urgency of reducing greenhouse gas emissions to stabilize the climate, 2040 would be too late for all those sectors in which direct electrification is possible,” say the authors. "Since the international and national climate targets require immediate emission reductions, direct electrification should come first in order to ensure a secure future for everyone," said co-author Gunnar Luderer.

Giving green hydrogen priority over electrification today, however, could paradoxically lead to further dependence on fossil fuels, warn the authors. "If we stick to combustion technologies - in the hope of being able to continue operating them with hydrogen-based fuels - and the new fuels then turn out to be too expensive and scarce, we will ultimately continue to fall back on oil and gas," says Ueckerdt. That in turn endangers the climate targets.

"We should therefore use the valuable hydrogen-based fuels as a priority for those applications for which they are indispensable: long-haul flights, parts of chemical production, steel production and possibly some industrial high-temperature processes," said Ueckerdt. These sectors and applications could hardly be electrified directly.

Five times more energy consumption than electric cars

Hydrogen-based fuels could be used in conventional combustion processes and engines - and thus directly replace fossil fuels. “In view of the limited availability, however, it would be wrong to believe that fossil fuels can be completely replaced in this way,” emphasized Luderer.

"If we use hydrogen-based fuels instead of direct electrification, two to fourteen times the amount of electricity is required, depending on the application and the respective technologies," says co-author Romain Sacchi from the Paul Scherrer Institute.

There are losses in efficiency both in the production processes for hydrogen-based fuels and in their consumption. “An internal combustion engine wastes a lot more energy than an electric one,” says Sacchi. With e-fuels, a car with a combustion engine consumes five times more energy than an electric car.

[If you would like to find out more about the topic of electromobility, you will find an overview with current articles that deal with it on our homepage.]

Based on the German electricity mix for 2018, the use of hydrogen-based fuels in cars, trucks or airplanes would cause around three to four times more greenhouse gas emissions than the use of fossil fuels.

“In contrast to this, electric cars or electric trucks cause greenhouse gas emissions that in most countries are already comparable to or lower than those of diesel or gasoline vehicles with today's electricity mix,” the authors write. The researchers have carried out a life cycle analysis that also includes the emissions associated with battery production in order to be able to show this.

Expert: No alternative to the electric car

In the meantime, there is broad consensus in research that so-called e-fuels are currently primarily useful for aviation and shipping, heavy traffic and certain areas of industry. Manfred Fischedick, Scientific Director of the Wuppertal Institute for Climate, Environment and Energy, told the Science Media Center: "Compared to directly electrically powered vehicles, the energy balance of cars with synthetic fuels is six to seven times worse."

This is due on the one hand to the conversion losses in the production of the fuels and on the other hand to the significantly poorer efficiency of internal combustion engines compared to the electric motor. In other words, six to seven times more electricity has to be used for the same mobility service, "says Fischedick.

Felix Creutzig from the Mercator Research Institute on Global Commons and Climate Change (MCC) Berlin sees no future for e-fuels: “Because of the high price and the lower efficiency in converting renewable energy into energy for use, synthetic fuels are no alternative to electric cars and will not be either. "

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