E-fuels might be worse for pollution than regular petrol

Independent tests indicate synthetic petrol releases the same level of nitrogen-oxide and even more carbon monoxide and ammonia

E-fuels have been touted, in recent months, as the saviour of the petrol engine. As the world heads seemingly inexorably towards an electric motoring future, those who bemoan the loss of tuneful, thrilling petrol engines – especially the more overtly sporting ones made by the likes of Porsche, Ferrari, Lamborghini, et al – have been pinning their hopes on e-fuels to ride to combustion’s rescue.

What is an e-fuel? Essentially, it’s a synthetic fuel made using the Fischer-Tropsch process. That process – which chemically combines gases to form a liquid – takes hydrogen, extracted from water using renewable electricity, and combines it with carbon extracted from the atmosphere, to make a simple hydrocarbon. A hydrocarbon being the basis of petrol, it takes only a few more processes to create a synthetic fuel that can be used in almost any combustion engine.

One can immediately see the appeal. Not only does the process, in theory, use renewable energy to make the fuel, but the fuel itself is made up of carbon taken out of the air. So any carbon released when it’s burned is effectively in a loop – it’s a carbon-neutral petrol.

Of the world’s car makers, so far Mazda and Porsche have proven the keenest on the idea. According to Wojciech Halarewicz, vice-president for communications at Mazda Europe: “We believe that with the necessary investment, CO2-neutral e-fuels and hydrogen will make a credible and real contribution to emissions reduction, not only for newly registered cars but for the current fleet. This would open up a second and faster route to achieving climate neutrality in transport, hand in hand with continued electrification.”


While the carbon emissions benefits of an e-fuel seem obvious, as long as such fuels can be made using renewable energy, their development might have found a major stumbling block – nitrogen-oxide emissions.

Nitrogen-oxide, or NOX, is the colourless, odourless gas that was at the centre of the diesel emissions scandal.

According to tests carried out by eco think tank Transport & Environment (T&E), e-fuels cause just as much NOX to be emitted, and are actually worse when it comes to other pollutants such as carbon monoxide and ammonia. Julia Poliscanova, senior director for vehicles and e-mobility at T&E, told The Irish Times: “No amount of spin can overcome the science of burning hydrocarbons. As long as fuel is combusted in engines, toxic air will persist in our cities. Lawmakers who leave loopholes for e-fuels in emissions targets are condemning the public to decades more of avoidable air pollution.

“When burned, synthetic petrol causes almost three times more carbon monoxide – which deprives the heart and brain of oxygen – compared to petrol. The e-petrol powered car also emitted up to two times more ammonia, which can combine with other compounds in the air to form particles (PM2.5) for which there is no safe level of pollution. The health risks of PM2.5 include asthma, heart disease and cancer.”


It is possible that technology could yet save the e-fuel — after all, exhaust treatment systems such as AdBlue injection can reduce NOX emissions to negligible levels in current petrol and diesel engines, while particulate traps can filter out the emissions of soot. All that will add expense and technological complication, though, which will make the development of such fuels even more expensive.

On top of which, T&E claims that the need for such fuels to be made using renewable electricity currently makes them unviable. “Supplying just 10 per cent of new cars with e-fuels instead of electrifying them will require 23 per cent more renewable electricity generation in Europe, an independent study for T&E shows” said Poliscanova. “E-fuels have lost the race to clean up cars, but in truth it was never even close. Battery electric cars offer drivers the cleanest, most efficient and affordable way to decarbonise, while synthetic fuels are best suited to planes where electrification is not an option. The credibility of Europe’s clean-car policy is on the line and any diversion into e-fuels is a new lease of life for old polluting engines.”

What comes next is a debate over legislation. The EU is preparing new regulations that would ensure that all cars sold in Europe from 2035 must be zero-emissions. What the legislators must now wrangle with is whether that phrase includes all possible emissions, or just emissions of carbon.

Perhaps, ultimately, it’ll be cost that rules e-fuels out. If you think it’s harsh paying €1.99 for a litre of petrol, just imagine paying twice that. According to Stephanie Searle from the International Council on Clean Transport (one of the groups that uncovered Volkswagen’s diesel cheating in 2015): “Like many things, it’s too good to be entirely true. While e-fuels can be very low carbon if made from new, additional renewable electricity, they can’t be low-cost at the same time. The e-fuels production process is inherently inefficient, converting at best half of the energy in the electricity into liquid or gaseous fuels.

“Using middle-of-the-road assumptions, we’ve found that significant volumes of renewable e-fuels won’t be made for less than €3 or €4 per litre in 2030.”