Efuel: What is it, how is it made and can it save the internal combustion engine?

As governments around the world propose firm dates for the end of new petrol and diesel powered vehicles and search for alternative fuel sources, you might be forgiven for thinking we’re living in the end days of the internal combustion engine.

But the technology that’s literally driven the transport revolution for more than a century isn’t ready to give up just yet and could be thrown a lifeline by the development of synthetic fuels that are nearly as green as going electric.

In fact, the ‘mood music’ surrounding the use of combustion engines and e-fuels after the 2035 cut-off date for their sales is changing, according to industry insiders.

First up, the European Union has approved an exemption to the ban on new internal combustion engines that will allow vehicles running on e-fuels to remain on the market after 2035.

Closer to home, the 11-strong, cross-party Parliamentary Transport Committee, which examines the expenditure of the Department of Transport (DfT), have released a 54-page report entitled Fuelling the Future and among their conclusions they say: “It is our view that the case for full electrification in private cars is ‘the received wisdom’, and therefore needs further scrutiny and investigation.

Synthetic petrol, diesel and aviation fuels are all the subject of heavyweight pilot projects and are gaining interest fast as they eliminate the CO2 emissions from transport without the need for end-users to switch to new tech. Aviation in particular is backing the idea but motorsport is getting in on the action, with the World Rally Championship due to use 100% sustainable fuel as soon as next year.

While biofuels already offset their emissions to an extent, synthetic fuel takes a more direct approach by stripping CO2 from the air and combining it with hydrogen to create a petrol replacement.

By using wind, solar or hydro-electric to generate the electricity for the electrolysis, the process is sustainable, and while engines using the fuel still emit carbon, the same amount is reabsorbed in the fuel-making process.

The idea of using electricity to create synthetic petrol and then to burn that fuel in combustion engines might seem wasteful but the benefits are also significant, reusing existing infrastructures and giving new life to billions of combustion engines rather than reducing them to scrap. With similar power density to normal petrol, synthetic fuels also mean you don’t need to lug vast batteries around.

At the moment, there are several synthetic fuel projects underway. Porsche – part of the VW Group and hence a sister to Ducati – have invested in Siemens Energy’s Haru Oni pilot project, a prototype plant in Chile that uses wind power to make synthetic petrol. It’s due to make 130,000 litres next year, 55 million in 2024 and 550 million litres in 2026.

BMW, meanwhile, have invested in US firm Prometheus Fuels, which uses a different process but again creates petrol from air, water and electricity.

While many governments seem keen on switching from combustion tech to all-electric vehicles, it’s looking likely that a better approach is to adopt multiple technologies to reach carbon neutrality, applying them where they fit best. And perhaps most importantly of all, synthetic fuel should mean that more than 100 years’ worth of bikes have a future.

How is synthetic or efuel made?

One of the companies experimenting with efuel is Siemens Energy who explained the process they use from start to finish.

First of all, the firm captures CO2 by using large fans to draw ambient air through chemical filters. Next, this CO2 is combined with hydrogen taken from water to create the methanol that will form the basis of the synthetic petrol.

The methanol is then processed at the firm’s Haru Oni plant using an ‘MTG’ (methanol to gasoline) technology provided by Exxon Mobil. The resulting fuel is intended to be a direct replacement for fossil-derived petrol, eliminating the need for new engines and infrastructures.

Estimates range from as little as £1 per litre to more than £3 per litre by 2030, but that may be worth it as a lifeline for existing engines and an alternative in applications where battery power is unsuitable.

Porsche investment

German sports car specialists, Porsche, have opened a large efuel plant and research facility in Chile. Although Porsche are a car maker, they’re a member of the Volkswagen Group, which also includes Italian marque Ducati.

And Ducati have made no secret of the fact that they are looking efuels as an alternative to electrification in the medium-term.

Barbara Frenkel, member of the Executive Board for Procurement at Porsche, said: “Porsche is committed to a double-e path: e-mobility and eFuels as a complementary technology. Using eFuels reduces CO2 emissions.”

Michael Steiner, member of Porsche’s Executive Board for Development and Research, added: “The potential of eFuels is huge. There are currently more than 1.3 billion vehicles with combustion engines worldwide.

“Many of these will be on the roads for decades to come, and eFuels offer the owners of existing cars [and motorcycles] a nearly carbon-neutral alternative.

“As the manufacturer of high-performance, efficient engines, Porsche has a wide range of know-how in the field of fuels.”

Initially eFuel production of around 130,000 litres per year is planned and will be used in projects such as the Porsche Mobil 1 Supercup and at Porsche experience centres.

After the pilot phase, the first scaling-up process will take place with a projected 55 million litres per year being produced by the middle of the decade.

Around two years later the capacity is expected to reach 550 million litres.

Fuel from fresh air

A pilot project on the roof of research university ETH Zurich in Switzerland uses a miniature solar refinery to create hydrocarbon fuels.

ETH Zurich’s mini refinery uses sunlight as a direct part of the process of making fuel and so doesn’t need a vast amount of electricity, a stumbling block for some other methods.

A parabolic mirror in the system directs sunlight back onto another reflector, then focuses it onto the solar reactor, heating it to 1500°C. The reactor is made of cerium oxide, and this burst of heat forces it to release oxygen into the atmosphere.

Then the CO2 and H2O are added and the reactor strips oxygen from them leaving a mixture of hydrogen and carbon monoxide. This is called syngas and can be used as the basis for a variety of fuels.

Because heat is only needed for the initial step, the prototype has two solar reactors, with a movable mirror to switch the sunlight’s focus back and forth, doubling its efficiency. The prototype makes around 100 litres of syngas per day.

Stage three takes the syngas and runs it through a gas-to-liquid unit, which converts it to methanol. The university say it could be made into gasoline or kerosene using catalysts.

In terms of emissions, it’s carbon neutral, since burning it will only release as much CO2 as was originally used to create it. However, in a combustion engine there are other emissions, NOx, for instance, which comes from the reaction of nitrogen and oxygen in the air during combustion.

However, since CO2 is by far the largest proportion of vehicle emissions, neutralising that promises to make a vast difference.

If you’ve got visions of plonking a reactor like this on your own roof and having an endless supply of petrol, think again. The mini refinery can make around a teaspoonful of fuel per day. Filling your tank could take a while.

It’s calculated that to create a solar plant that could completely replace the 414 billion litres of kerosene used in aviation in 2019 (before the pandemic slashed air travel), you’d need 45,000km2 of desert. That’s equivalent to 0.5% of the Sahara.

The cost of the fuel would depend on the industrialisation of the process, but the scientists behind the project reckon that once solar fuels account for 10-15% of the market they’ll be competitive with fossil fuel prices.