Synthetic fuel, and the possibility that it could be a feasible alternative to battery electric vehicles (BEVs) technology or hydrogen-fuelled cars (FCEVs), has been causing something of a stir in the automobile world. For Porsche, synthetic fuel has been the focus of significant investment, but they aren’t the only leading auto firm taking synthetic fuels for a spin.

The German transport ministry is involved with a pilot project worth 500 million Euros under the leadership of the Karlsruhe Institute of Technology, and further afield Mazda became the first auto manufacturer to join the eFuel Alliance.

So, what are synthetic fuels, and what role can they play in the global race to reduce CO2 emissions?

What are synthetic fuels?

There are two types of synthetic fuels:

  • electro fuels (eFuels) made using captured carbon dioxide in a reaction with hydrogen, generated by the electrolysis of water;
  • synthetic biofuels made through the chemical or thermal treatment of biomass or biofuels.

There are several advantages to using these fuels to reduce carbon emissions. They can be manufactured as “plug-and-go” replacements for jet fuel, diesel, and petrol, meaning that existing engines would need only minor modifications to go about their business. This is because both the volume and energy density of synthetic fuels are similar to existing fuels, which is of particular relevance when comparing synthetic fuels to other alternatives to petroleum.

Synthetic fuels can be engineered to burn cleanly, reducing other pollutants associated with fossil fuel use, such as particulates and nitrogen oxides, though this benefit is solely relevant when comparing synthetic fuels to petroleum, as battery electric and hydrogen cell technologies don’t produce these at all. Furthermore, whereas EVs require specialized charging stations, synthetic fuels use current infrastructure for distribution, storage, and delivery to the vehicle.

The hope of eco fuels

Make no mistake, the internal combustion engine (ICE) is not going to be with us forever. The UK government has announced that the sale of new petrol and diesel cars will be banned from 2030, and the general emphasis of recent legislation around the globe, e.g. congestion zone introduction and emission performance standards, has been to discourage use of all petrol-guzzling vehicles.

There is a very real possibility that the shift to fully electric vehicles could lead to fuel-powered cars becoming obsolete, and render the dream of running a classic car a practical impossibility for all but the wealthiest of us. The possibility of alternative fuels for cars that can be CO2-neutral is a game changer from this perspective.

Porsche synthetic fuel advocate Dr Frank Walliser, VP of GT Cars and motorsport, has suggested that synthetic fuels can deliver an 85% reduction in carbon emissions. If this is indeed achievable, then ICE-powered vehicles can still have a place in a greener future.

Synthetic fuels vs. electric cars

Despite the potential of synthetic fuels to be carbon neutral, the process of producing eFuels requires a significant amount of energy. This energy would need to be entirely derived from renewable sources to achieve true CO2-neutral status. The energy efficiency of producing electricity to make synthetic fuel, which is then burned to power a vehicle, is much lower than the efficiency of loading the energy straight into the batteries of an electric vehicle.

According to the UK Department for Transport & Environment, “powering just 10% of the UK’s cars, vans, and small trucks with e-fuels in 2050 would require nearly three times as much renewable electricity than if they all ran on a battery”. This sadly means that we would need a whole lot more renewable electricity across the globe to make synthetic fuel vehicles viable in comparison to BEV cars.

There is also a serious affordability question around synthetic fuels. The International Council on Clean Transportation estimates that the cost per gallon of synthetic fuel would be over $13 by 2030, which is a substantial hike on the US average of just over $3 per gallon. Synthetic fuel manufacturer Bosch, on the other hand, estimates the cost to be substantially lower.

Where the BEV loses out significantly in comparison is in contexts where the relatively poor energy density of battery technology is of increased importance. Synthetic fuel delivers more energy by weight and volume than electric batteries. In maritime, air travel, and road freight contexts, this can make battery technology borderline unusable.

Airbus has invested significantly in electric aircraft, but let us consider that the Airbus A380 can fly 600 passengers 15,000 kilometres in a single flight. Even if you were to replace all the passengers and cargo with batteries, the range would still be less than 2,000 kilometres. Batteries weighing 30 times more than the required fuel would be needed to maintain its current range, meaning it would never get off the ground.

All things considered, synthetic fuels as alternatives to petrol are unlikely to displace the BEV as the preferred power source for the vast majority of new vehicles. Their development will, however, be crucial to reducing carbon emissions where the limitations of batteries are an issue. A happy by-product of this is that there is a good chance that, as their costs come down, synthetic fuels will enable us to continue to drive ICE-powered cars in the future.