E-Fuels: Climate neutral, from biomass - the fuel of the future?

Created: 07/12/2022, 09:59 am

By: Matthew Schneider

At some point, even Verbenner engines could be fed with climate-neutral e-fuels.

© imago/Wolfgang Maria Weber

E-cars can use e-fuels efficiently and thus form a step towards climate neutrality.

In an interview, a researcher explains what fuel from electricity can do.

Munich - E-fuels are considered to be potentially climate-neutral fuels for combustion engines.

But what is behind the technology and how sensible is its use in today's vehicles?

Daniel Klüh researches synthetic fuels at the Technical University of Munich and knows quite a bit about it.

Mr. Klüh, what is meant by e-fuels?

Fuels that are produced using electricity.

The basis for this is usually hydrogen, which is produced from the splitting of water using electricity.

However, hydrogen can hardly be used in existing engines.

That is why it is allowed to react with carbon dioxide.

What's the result?

High-energy hydrogen-carbon compounds that are similar to fossil fuels.

Among other things, crude oil or synthetic natural gas can be produced.

The latter is easy to explain: The energy carrier in the natural gas that we use today is methane.

A molecule consists of one hydrogen (H) and four carbon (C) atoms.

So all you have to do is bring hydrogen and carbon dioxide (CO2) together in a reactor using a catalyst and you get methane that can be transported in existing lines and used in gas-powered cars, for example.

The product is called synthetic natural gas (SNG).

And the oil?

Under different reaction conditions with a different catalyst and carbon monoxide (CO) instead of carbon dioxide, you get a liquid that consists of hydrocarbon chains of different lengths – like petroleum.

From this, petrol and diesel can be separated in a refinery process.

In the future, e-fuels are to be produced from biomass

Where does the carbon for the processes come from?

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We need gaseous carbon, i.e. carbon monoxide or carbon dioxide.

You can theoretically filter it out of the air, but that's cumbersome and expensive.

It is better to use the exhaust gases from industrial plants.

Cement factories, for example, are particularly suitable because CO2 is produced here both during heating and during the manufacturing process itself.

But the point of e-fuels is that at some point they should only be produced from green electricity and biogenic carbon from biomass, so that the CO2 cycle is closed.

Therefore, in the future, sewage sludge incineration plants or wood chip thermal power stations will be available as sources.

How expensive have e-fuels been so far?

That always depends on the price of the electricity used for electrolysis.

In the real process, the energy yield is between 50 and 60 percent.

How high the costs are also depends on which taxes, duties and surcharges are levied on the electricity.

Most models calculate between four and eight cents per kilowatt hour.

This is the lower spectrum of industrial electricity prices.

In the end, these are two to three euros pure production costs per liter of e-fuels, with SNG it is around 70 euros per megawatt hour - in each case without taxes.

That's roughly three times pre-crisis gas prices and half current prices.

Politicians can influence the production costs with regulatory measures, similar to the CO2 price.

In addition, the costs in mass production are likely to fall significantly.

E-Fuels: System is less dependent on electricity prices

How can biomass help?

Fuel can also be produced by gasifying biomass, such as methanol, which consists of hydrogen, carbon and oxygen.

Gasification produces a gas mixture of hydrogen and too many carbon compounds.

The latter usually has to be separated, i.e. released into the air.

But if you bring in hydrogen from an electrolyser, you can process over 95 percent instead of just 50 percent of the carbon from the biomass into methanol.

This is important because global arable land and biomass availability is limited.

At the same time, the biomass brings in part of the required hydrogen.

This makes this system less dependent on electricity prices, which makes the process more economically stable and therefore more price-competitive.

Where is the best place to use e-fuels?

You have to see where it makes sense.

An e-car uses electricity far more efficiently than a combustion engine that uses e-fuels.

But you can hardly run an airplane or a ship on battery power because you need higher energy densities there.

Artificial fuels are probably the best alternative here.

How far e-fuels will spread will largely depend on how cheaply we can produce or import hydrogen.

But since climate neutrality is stipulated in Europe by 2050, instruments and subsidies are already being created today to establish e-fuels on the market.

The interview was conducted by Matthias Schneider.