As the industrialized world moves haltingly toward a zero-emissions future, gas-engine automobiles - especially older cars and trucks - face an uncertain fate. Despite advances in engine technology, they're still responsible for a not-insignificant amount of tailpipe emissions, and drilling for oil remains a hot-button political issue. While some advocate for the electrification of cars both new and old, synthetic fuels have entered the conversation in recent years, to the point where major legislation intended to convert automotive fleets to electric propulsion are now being amended to include provisions for the fuels.

So what are synthetic fuels, are they as clean as they claim to be, could they prove viable alternatives to electrification, and will they allow older cars to remain on the road indefinitely?

Source: PorscheSource: Porsche

What are synthetic fuels?

Synthetic fuels have been around for more than a century and the term covers a wide range of processes that return everything from jet fuel to diesel. Broadly, any liquid fuel not derived from crude oil is considered a synthetic fuel. Specifically, however, investment into producing synthetic fuels for automotive use centers around three main categories: e-fuels, biomass-derived fuels and fuels developed from plastic.

E-fuel, at its most basic, requires just two ingredients: carbon dioxide (CO2) and hydrogen. Those two can be combined to synthesize methanol, which can then be converted into gasoline using a process that ExxonMobil introduced in 1975. While the CO2 and hydrogen can be obtained from a number of sources - some not as climate friendly as others - the practice of extracting hydrogen from water via electrolysis using wind or solar power (and of pulling the CO2 straight from the atmosphere) leads some to describe e-fuels as a carbon-neutral fuel, only emitting as much CO2 when it is burned as was used in its creation.

Biomass-derived fuels can come from pretty much any biological source, including wood processing waste, manure, agricultural residue and even sewage. Subjected to pyrolysis, the biomass can produce methane, which can then be converted into gasoline in a process similar to e-fuel production.

Plastic-derived fuel proponents see their technology as the solution to another environmental problem: plastic waste pollution. Via a pyrolytic process, the collected plastic waste is then essentially converted back into petrochemicals resembling what the plastic was made from in the first place, which can then be refined into gasoline.

Ian Lehn, the founder of Boostane and the current chair of SEMA's Emerging Trends and Technology Network, said that the end results for synthetic fuels, especially e-fuels, present almost zero molecular differences from fossil fuel-derived fuels. "With synthetic fuels, you're starting from a clean slate," he said. "All we're doing with synthetic fuels is creating some sort of long chain hydrocarbon, but we're getting the carbon and the hydrogen from somewhere else other than petroleum."

Volkswagens fill up with Bosch's Blue Gasoline. Source: BoschVolkswagens fill up with Bosch's Blue Gasoline. Source: Bosch

Who is producing synthetic fuels?

Porsche has generated plenty of headlines over the last couple of years for its efforts to save the internal combustion engine with synthetic fuels. According to Porsche press materials, the company's search for a synthetic fuel "that would allow combustion engines to be operated in an almost CO2-neutral manner" led it to invest more than $100 million in Highly Innovative Fuels, an e-fuel company with a wind-powered plant in Chile that started producing usable synthetic fuel in December relying, in part, on Exxon-Mobil's methanol-to-gasoline technology.

"If you want to operate the existing fleet in a sustainable manner, eFuels are a fundamental component," Porsche research and development head Michael Steiner said in 2020. And as TechCrunch noted, keeping the existing fleet operable is of particular importance to Porsche, considering that 70% of the vehicles it has built in its 75 years are still on the road.

Ferrari and Lamborghini have announced their intentions to use e-fuels but appear not to have invested as much into the development of synthetics as Porsche. Mazda just this week announced that it is joining Toyota, Suzuki, and Subaru in the Research Association of Biomass Innovation to look into the biomass process.

Bosch has also partnered with Shell and Volkswagen to create what it calls a "low-carbon" gasoline dubbed Blue Gasoline, which consists of up to 33% synthetic fuel using renewables produced from the byproducts from production of pulp wood for paper.

While other existing petrol companies like Repsol have also stepped into e-fuels and other synthetics, interest and investment in synthetic fuels is also spurring a number of startups. Prometheus Fuels, which rolled out the commercial-scale design of its Faraday Reactor in October, has visions of distributing the reactors all across the country. Synhelion similarly looks to produce e-fuels using solar energy. Select Fuel, meanwhile, has partnered with Bertone to get its plastic-to-fuel technology into use in motorsports and high-end sports cars and Norwegian company QuantaFuel is looking to do the same. P1 Performance Fuels has introduced a hybrid of biomass and e-fuel processes.

Lehn noted that European companies have taken the lead on e-fuels over those in the U.S. because the dominant conversation here concerns gasoline versus electric vehicles (EVs). "Nobody's really saying there's a third option we should be looking at here," he said. "So if e-fuels were to land anywhere with the best chance of survival, it's going to be Europe." That said, he noted that there is a big push in the U.S. to develop synthetic aviation fuels to replace the 100-octane low-lead that's still dominant in general aviation, and that lower-octane synthetic fuels will inevitably follow should a successful high-octane fuel be developed.

Why all the investment in synthetic fuels now?

Synthetic fuels have been a topic of discussion among engineers for a long time, Lehn noted, but never got much media scrutiny because of their cost-prohibitive nature. "It was always such a stretch goal," he said.

Automotive electrification, however, appears to be the main driver of the sudden investment in synthetic fuels. It's no coincidence that synthetic fuels were barely making headlines until major carmakers started to introduce their own battery EVs on a wider scale a few years ago. Whether the investment in synthetic fuels is intended to supplement or forestall electrification, however, is the question.

As Steiner noted in that same 2020 conversation, "electric mobility... is taking us towards out sustainability targets at a slower pace than we would like." Porsche remains committed to electrification, he said, with a target of 80% electric car sales by 2030, but he also notes that internal combustion cars will remain viable for decades to come and that synthetic fuels can offer a greener alternative to conventional drilled oil.

The investments in synthetic fuels can also be seen as a response to the many bans on internal combustion vehicles that governments around the world have proposed. Germany, for instance, where Porsche, Bosch and the eFuel Alliance are based, had been on board with the European Union's (EU'S) ban on new car sales of internal combustion vehicles set to take place in 2035. Just within the last month, however, it led a group of EU member countries (including Italy) in lobbying against a complete ban and for one that would make exceptions for vehicles designed to run on synthetic fuels, demands that the EU appears to have met this week.

"I think with those 2035 rules coming into place, all of a sudden people started to realize that the internal combustion engine has a shelf life unless they start lifting their heads up and looking for another solution," Lehn said.

Can synthetic fuels be burned in an older car?

As synthetic fuel proponents note, the fuels are considered "drop-in" replacements for fossil fuels, indistinguishable down to the molecular level from the gasoline, diesel or jet fuel they are designed to replace. They are expected to produce no more and no less energy than conventional fuels.

"I don't see any catastrophic drawbacks to synthetic fuels," Lehn said. "The switch should be somewhat seamless for both current and older vehicles."

To prove that, P1 spent much of 2022 driving a Volkswagen Type 2 T1 around Germany using its e-fuel and reported no hiccups during the test.

Still, Lehn said he understands where the apprehension about synthetic fuels comes from, especially among ones of collector cars and other much older vehicles. "A lot of that comes with their experience with ethanol," he said.

The EU exemption for e-fuels stipulated that any internal combustion engine vehicles permitted would require some device to distinguish between synthetic fuels and fossil fuels, but exactly how that is possible nobody has yet addressed.

Lehn figures that will most likely be accomplished via an additive that governments will mandate for either conventional or synthetic fuels. "No sensor that you can affordably put on a vehicle can distinguish synthetic fuel from conventional fuel," he said.

Whether synthetic fuels would also be subject to ethanol blending requirements in the U.S. and other countries remains to be seen as well. "Governments might force ethanol in, but I don't see any benefit," Lehn said. "I mean, if the real purpose of ethanol supplementation is to offset the carbon footprint (of conventional fuels), then a true synthetic fuel created from renewables doesn't need any supplementation."

What are the drawbacks of synthetic fuels?

For all the talk about the carbon neutrality of synthetic fuels, that does not mean internal combustion engines will emit any less carbon by burning them - they will just emit the same carbon that was captured to produce the fuels (and, theoretically, the same carbon that could once again be made into synthetic fuel). Nor will synthetic fuels - if they are true drop-in fuels - produce any less of the other emissions like nitrogen oxides found in the exhaust of internal combustion engines unless those emissions result from the burning of impurities like sulfur found in conventional fuels.

In addition, as James Morris wrote for Forbes, "The elephant in the room comes from how synthetic fuels are made." In particular, with how hydrogen is made. The vast majority of hydrogen these days is produced by a process called steam reformation, a process that is still dependent on fossil fuels, while hydrogen production via electrolysis uses about four times as much electricity as what would be used to directly power a battery-EV. Add in the number of stages required to turn that hydrogen into e-fuel and to transport it around the world and the efficiency continues to dwindle, Morris wrote.

The case for synthetic fuels made from plastic waste may be even harder to prove after recent reporting by ProPublica revealed that chemical emissions from a plastic-sourced fuel that Chevron intends to produce under a U.S. Environmental Protection Agency biofuels program poses a cancer risk for one in four people.

Biomass synthetic fuels, according to comments that Robert Freaks of Strategic Biofuels made to SEMA, can easily replicate diesel and jet fuel as well as gasoline, but replicating the latter results in "a yield loss" at this time.

Whatever the environmental impact of synthetic fuels, they are expected to cost far more than conventional fuels. Early estimates that Morris cited had synthetic fuels costing as much as $13 per gallon. A more recent estimate from Transport and Environment pegs the cost at €2.80 per liter, or about $11.50 per gallon. Meanwhile, Porsche's figures show that synthetic gasoline at this early stage costs as much as $40 per gallon to produce. Steiner told TechCrunch that the price to produce fuel (not including taxes, fees, and other add-ons) is expected to drop to €2 per liter, or about $7.50 per gallon, once production ramps up.

Highly Innovative Fuels, Porsche's partner in the Chile plant, claims that e-fuels can be competitive with fossil fuels when sold in markets with carbon pricing structures. More direct incentives may be needed to make e-fuels competitive too: The International Council on Clean Transportation estimated that incentives of no less than €1.50 per liter (about $5.70 per gallon) "would be needed to deliver significant volumes of electrofuels."

When can we expect synthetic fuels?

While Porsche has made much hay about the recent start of e-fuel production and the pumping e-fuels direct from its plant in Chile into a 911, it's not likely most owners of internal combustion engine cars will be able to start burning synthetic fuels anytime soon. Highly Innovative Fuels claims that mass production of e-fuels is expected to begin in 2026 while Bosch more optimistically claims that by 2025 synthetic fuels could be in widespread use. Porsche plans to produce 130,000 liters (about 34,500 gallons) of e-fuel per year during its pilot phase, ramp up to 55 million liters (about 14.53 million gallons) per year by the middle of the decade, then scale that up to 550 million liters (about 145.3 million gallons) before 2030.

To put that into perspective, the U.S. alone consumes 369 million gallons of gasoline per day. The U.S. Energy Information Administration expects global liquid fuels consumption to top 100 million barrels per day in 2023, or 4.237 billion gallons per day. It's likely for that reason that Porsche has earmarked much of its e-fuel production for motorsports use rather than for everyday commuters or cars and coffee runs for older vehicles. Formula 1, by the way, has already committed to switching to synthetic fuels for the 2026 season while the World Rally Championship has already switched to synthetic fuels using P1 Performance Fuels products. The eFuels Alliance doesn't expect synthetic fuels to constitute more than half the liquid fuel market until the late 2030s, which Morris and others decry as far too late to make substantial inroads against climate change.

So will synthetic fuels save the internal combustion engine?

Both Bosch's Use Gackstatter and Porsche's Steiner admit that synthetic fuels aren't going to solve all of our mobility needs and that EVs remain critical to meeting greenhouse gas reduction targets set out in the Paris Climate Accords.

"There's nothing as efficient as an EV, period," Lehn said.

Even the most ardent EV enthusiast will admit, however, that there are issues with the technology, from sourcing the raw materials for the batteries to the lack of affordable EVs on the marketplace, preventing their widespread adoption before the 2035 bans on new internal combustion engine vehicles.

Synthetic fuels, on the other hand, can be implemented without any significant changes to the vehicle fleets or to the existing fuel distributor infrastructure, which makes them appealing to those ardent gas-powered car proponents.

"I believe synthetic fuels are the future if the internal combustion engine is to remain relevant," Lehn said.

And if that's the case, then synthetic fuels may be the best hope for keeping internal combustion cars - including the vast majority of collector cars - from becoming static museum pieces after the middle of the 21st century.

Editor's note: This article originally appeared on Hemmings Motor News.