What Is Synthetic Fuel and How Is It Made?

Synthetic fuel is any liquid or gaseous fuel manufactured from non-petroleum feedstocks, typically by combining hydrogen with a carbon source such as captured carbon dioxide. When the hydrogen comes from water electrolysis powered by renewable electricity and the carbon comes from CO₂ pulled out of the air or industrial exhaust, the result is often called an e-fuel or electrofuel. The appeal is straightforward: these fuels can be burned in ordinary engines, shipped through existing pipelines, and stored in conventional tanks, yet their production-to-tailpipe carbon footprint can approach net zero under the right conditions.

The Two Raw Ingredients

Every synthetic fuel starts with two things: hydrogen and carbon. The hydrogen is produced through electrolysis, a process that splits water into hydrogen and oxygen using electricity. When that electricity comes from wind, solar, or another renewable source, the hydrogen is labeled “green.” Electrolysis technology is advancing on several fronts, with researchers working to extend the lifespan of the equipment, improve efficiency, and reduce the amount of precious metals needed in catalysts, all of which would bring costs down over time.¹ One techno-economic study modeled PEM electrolyzers requiring around 800 megawatts of electrical input to produce enough hydrogen for a commercial-scale fuel plant, underscoring just how electricity-hungry the process is.²

The carbon side involves capturing CO₂, either from concentrated industrial sources like cement plants and power stations or directly from ambient air. Point-source capture is cheaper and more mature because the CO₂ concentration in smokestack exhaust is far higher than in the atmosphere. Direct air capture (DAC) is more expensive but has the advantage of not being tied to any particular factory’s location. Recent materials research has demonstrated sorbents that can grab CO₂ across a wide range of concentrations, from the roughly 15 percent found in post-combustion flue gas down to the approximately 400 parts per million in outdoor air.³

From Hydrogen and CO₂ to Liquid Fuel

Once you have green hydrogen and captured CO₂, you need a chemical pathway to stitch them together into something you can pump into a fuel tank. Two major routes dominate the field.

The first and oldest is Fischer-Tropsch (FT) synthesis. The hydrogen and CO₂ are first converted into syngas, a mixture of hydrogen and carbon monoxide. That syngas then passes over a catalyst at high temperature and pressure, where the molecules assemble into longer hydrocarbon chains, producing a range of liquid fuels including diesel and jet fuel. One way to generate the syngas step is through high-temperature co-electrolysis, where solid oxide electrolysis cells split both steam and CO₂ simultaneously to yield the needed hydrogen-carbon monoxide mixture in a single step.⁴ Fischer-Tropsch technology is not new; it was developed in the 1920s and scaled industrially for coal-to-liquids conversion. China, for example, operated demonstration-scale FT plants producing thousands of barrels per day of liquid products.⁵ What makes the modern version different is the feedstock: instead of coal, the carbon comes from captured CO₂ and the energy comes from renewables.

The second major route goes through methanol. Hydrogen and CO₂ react to form methanol, which is then converted into gasoline-range hydrocarbons through a methanol-to-gasoline (MtG) process using a zeolite catalyst.⁶ The methanol pathway has some practical advantages: methanol is easy to store and ship, and the conversion step can be bolted onto existing refinery hardware. Beyond these two headline routes, the same Power-to-X family of technologies can produce e-methane (a synthetic natural gas), e-ammonia, e-kerosene for jets, and other fuels, depending on the downstream chemistry applied to the hydrogen and CO₂ inputs.⁷

Why “Drop-In” Compatibility Matters

The single biggest selling point of synthetic fuels is that they are chemically identical, or nearly so, to the fossil fuels they replace. A synthetic diesel shares the same physical and chemical properties as petroleum diesel, meaning it works with storage tanks, pipelines, gas station pumps, and engines without modification.⁸ That compatibility extends to the roughly 1.4 billion cars already on the road worldwide, which could keep running on synthetic fuel rather than being scrapped or retrofitted with electric drivetrains.⁸

This drop-in quality also matters for energy storage and grid balancing. Synthetic fuels can serve as a way to store surplus renewable electricity in chemical form, then release it later, either by burning the fuel in a power plant or using it for transport when needed.⁹ In modeling frameworks exploring a net-zero future, the only input to the system is renewable electricity and the only useful output is a service: either electricity dispatched back to the grid on demand or fuel delivered to a vehicle.¹⁰

Where Synthetic Fuels Make the Most Sense

Electric batteries work well for passenger cars, but some sectors are far harder to electrify. Aviation, long-haul shipping, and heavy freight are the areas where synthetic fuels have the clearest role to play. A battery pack heavy enough to fly a transatlantic commercial flight does not exist with current technology. E-fuels produced via Fischer-Tropsch synthesis can be formulated to meet the same Jet A-1 specifications that conventional jet fuel must satisfy.¹¹ That means synthetic jet fuel could be loaded onto existing aircraft without engine modifications, a quality no other zero-carbon energy carrier currently offers for commercial aviation.

The original description of e-fuels captures this neatly: they are attractive not only because of their compatibility with existing infrastructure and internal combustion engines in aviation, shipping, and freight but also because of their large market potential in reducing carbon emissions from those sectors.¹² For passenger cars, where batteries are increasingly practical, synthetic fuels are a harder economic sell. The real value lies in domains where energy density, refueling speed, and infrastructure compatibility give liquid fuels an irreplaceable advantage.

The Carbon Loop and What “Net Zero” Actually Means Here

Synthetic fuels still produce CO₂ when burned. The climate argument rests on the idea that the carbon released at the tailpipe or exhaust stack is the same carbon that was captured during production, creating a closed loop rather than adding ancient carbon from underground fossil reserves. Carbon capture and utilization (CCU) technologies treat CO₂ as a raw material: after capturing it, a chemical or physical process converts it into fuels or other products, which eventually release that CO₂ back into the atmosphere. In principle, this cycle can achieve net-zero emissions.¹³

“In principle” is doing real work in that sentence. Whether a given batch of synthetic fuel actually delivers net-zero emissions depends on every step in the chain. If the electricity powering the electrolyzer comes partly from natural gas, the loop leaks. If the CO₂ is captured from a fossil source that would not have existed without the e-fuel plant, the accounting gets muddier. Life cycle analysis shows that a meaningful improvement in CO₂ emissions compared to fossil fuels is found only when the energy input is solar (or another renewable) and the CO₂ is drawn from the atmosphere rather than from fossil-powered processes.¹⁴ Anything short of that combination and you risk spending enormous energy to produce a fuel whose climate benefit is marginal.

Energy Efficiency and the Conversion Penalty

One of the hardest truths about synthetic fuels is how much energy gets lost along the way. Every conversion step, from electricity to hydrogen, from hydrogen plus CO₂ to syngas, from syngas to liquid fuel, throws away some energy as heat. Producing liquid hydrocarbons starting from CO₂ with existing technology requires substantially more energy input per unit of fuel than simply extracting and refining petroleum.¹⁴

A comparison of synthetic fuel pathways in a Swedish context found that hydrogen (used directly in a fuel cell vehicle rather than converted into a liquid) delivers the best well-to-wheel energy efficiency, because it skips the final and lossy conversion into a hydrocarbon. Synthetic methane and diesel, meanwhile, showed potential to be cost-competitive sooner, even though they waste more energy in production.¹⁵ This tension between efficiency and compatibility is central to the whole synthetic fuel debate: direct hydrogen use is more efficient, but liquid synthetic fuels work with the world as it already exists.

Among the different synthetic fuels themselves, not all are equally resource-hungry. A prospective life cycle assessment found that synthetic methane carries the lowest overall environmental burden because it requires less hydrogen and fewer processing steps. Synthetic diesel and petrol demand more hydrogen per kilogram of fuel (roughly 0.6 kilograms of hydrogen per kilogram of fuel), and the additional conversion steps like the reverse water-gas shift reaction and Fischer-Tropsch synthesis push electricity demand significantly higher.¹⁶

What Synthetic Fuels Cost Today

Cost is the main barrier standing between synthetic fuels and widespread adoption. Current production costs fall in the range of roughly 1.83 to 2.36 euros per kilogram, with a best-case scenario bringing that down to about 1.42 to 1.97 euros per kilogram and a worst-case scenario pushing it as high as 3.88 to 4.28 euros per kilogram.¹⁷ For context, conventional gasoline and diesel at the refinery gate cost a fraction of those figures. The two biggest cost drivers are electricity (which dominates because electrolysis is so power-intensive) and the price of captured CO₂. If renewable electricity prices continue to fall and carbon capture technology scales, the gap narrows. But it will not close on its own without policy support.

Water and Land Requirements

Electrolysis consumes water as well as electricity, and the broader supply chain has its own resource footprint. A study quantifying water and land use for alternative diesel and jet fuel production found that Fischer-Tropsch-derived fuel from rainfed biomass feedstocks has a lifecycle water consumption footprint of about 1.6 to 20 liters of water per liter of fuel produced, which is broadly comparable to conventional petroleum diesel at 4.1 to 7.4 liters per liter. However, when irrigated biomass enters the equation, water use can balloon by several orders of magnitude, reaching as high as 22,600 liters of water per liter of fuel.¹⁸ The lesson is that where you build the plant and how you source feedstocks matter enormously. A synthetic fuel facility in a water-scarce region using irrigated crops for part of its carbon input could create serious local resource conflicts, even if the fuel itself is carbon-neutral.

The Regulatory Push

Governments are beginning to build synthetic fuels into their climate strategies, most aggressively in Europe. The EU’s Renewable Energy Directive includes specific targets for fuels of non-biological origin (the bureaucratic label for e-fuels). The ReFuelEU Aviation Regulation mandates sustainable aviation fuel blending starting at 2 percent in 2025 and scaling to 63 percent by 2050. The FuelEU Maritime Regulation promotes e-methanol and e-ammonia in shipping.¹⁹ These mandates are significant because they create guaranteed demand, which gives investors and producers the confidence to build the first wave of commercial-scale plants.

In the United States, the approach is more fragmented. The Renewable Fuel Standard mandates biofuel blending at the federal level, while California’s Low Carbon Fuel Standard and similar programs in Oregon and Washington enforce carbon-intensity targets and generate tradeable credits that support low-carbon fuels, including e-fuels. The SAF Grand Challenge sets an ambition to scale sustainable aviation fuel to 10 percent of U.S. aviation fuel by 2030, aiming for full replacement by 2050.¹⁹ Whether these programs survive political cycles is an open question, but the direction of travel across most major economies is toward mandating or incentivizing synthetic fuels in hard-to-electrify sectors.

Tailpipe Emissions and Air Quality

Even though the climate case for synthetic fuels revolves around the carbon loop, there is a separate and underappreciated benefit at the tailpipe. Synthetic fuels tend to burn more cleanly than their petroleum counterparts because their chemical composition can be controlled more precisely during production. Testing of a blend containing 20 percent synthetic diesel mixed with 80 percent conventional diesel showed reductions compared to pure fossil diesel: carbon monoxide emissions dropped by about 24 percent, total hydrocarbons by 30 percent, nitrogen oxides by around 5.5 percent, and fine particulate matter (PM2.5) by 19 percent.¹³ Those reductions matter for urban air quality independently of the climate question, and they grow larger with higher blend ratios. For cities struggling with smog and respiratory health problems linked to diesel exhaust, even a partial shift toward synthetic blends could have measurable public health value before a full transition to zero-emission vehicles arrives.

Why Scale Is the Real Bottleneck

The chemistry behind synthetic fuels is well understood. The catalysts work. The conversion pathways have been demonstrated at pilot and demonstration scale. What has not been demonstrated is production at a volume that matters. Global demand for liquid fuels runs into billions of barrels per year. Current synthetic fuel production is measured in thousands of barrels at best. Closing that gap requires massive buildouts of renewable electricity generation, electrolyzer capacity, carbon capture infrastructure, and fuel synthesis plants, all simultaneously. Spain’s plans to add 52 gigawatts of new renewable capacity by 2050 illustrate the kind of grid expansion that countries are banking on to make green hydrogen affordable.² Even with that kind of build-out, the sheer electricity appetite of electrolysis means synthetic fuels will likely remain a premium product directed toward aviation, shipping, and heavy industry rather than a mass-market replacement for gasoline in passenger cars, where batteries are the simpler and cheaper route.

The tension between ambition and thermodynamics is hard to resolve. Every additional conversion step between renewable electricity and liquid fuel burns away energy and adds cost. That reality does not make synthetic fuels pointless, but it does make them a targeted solution rather than a universal one. The sectors that need them most are the ones where no good electrical alternative exists, and policy is increasingly being shaped around that insight.

1
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2
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