What Exactly Is Synthetic Fuel Made Of?

Synthetic fuel is made primarily of hydrogen and carbon that are chemically combined to form hydrocarbons—such as gasoline, diesel, or jet fuel—using hydrogen (often from water electrolysis) and carbon from carbon monoxide or captured carbon dioxide; other synthetic fuels include methanol, dimethyl ether, synthetic methane, and even ammonia. In practice, producers use water, CO or CO2, large amounts of electricity, and catalysts to synthesize clean, sulfur-free fuels that can be “drop-in” compatible with today’s engines and infrastructure.

The Core Ingredients

The building blocks of synthetic fuels are straightforward. Below are the essential inputs and materials that go into making modern synthetic fuels, especially the lower-carbon variants sometimes called e-fuels or Power-to-Liquids.

• Hydrogen (H2): Commonly produced by splitting water via electrolysis; “green hydrogen” uses renewable electricity.
• Carbon source (CO or CO2): Carbon monoxide from syngas or carbon dioxide captured from industrial flue gas or directly from air (DAC).
• Energy: Significant electricity (ideally renewable) and process heat to drive electrolysis and synthesis reactions.
• Catalysts: Materials such as iron or cobalt (Fischer–Tropsch), copper–zinc–alumina (methanol synthesis), and ruthenium or nickel in certain steps.
• Process gases and utilities: Water, oxygen (from electrolysis), and sometimes nitrogen (for ammonia-based fuels).
• Optional biomass or waste feedstocks: For “biomass-to-liquids” pathways using gasification to create syngas.

Together, these inputs enable producers to assemble carbon and hydrogen into energy-dense molecules that mirror conventional fuels but with cleaner composition and a potentially far lower lifecycle carbon footprint when powered by renewables.

What the Molecules Look Like

Synthetic fuel is not a single substance; it’s a family of molecules chosen for engine compatibility and performance. Here are the main classes you’ll encounter.

• Hydrocarbon “drop-in” fuels: Mixtures of alkanes and iso-alkanes similar to fossil fuels—gasoline-range (roughly C5–C12), jet/diesel-range (roughly C8–C20).
• Oxygenated fuels: Methanol (CH3OH), ethanol, dimethyl ether (DME), and oxymethylene ethers (OMEs) that can reduce soot and be blended or used in modified engines.
• Synthetic methane (CH4): A pipeline-compatible gas produced from H2 and CO2 (Sabatier reaction).
• Non-carbon fuel: Ammonia (NH3), made from nitrogen and hydrogen; contains no carbon and can be a fuel or hydrogen carrier for certain engines and fuel cells.

While hydrocarbons dominate for easy drop-in use, oxygenates and ammonia are gaining attention in niches where their properties—like clean combustion or simplified storage—offer advantages.

How the Ingredients Are Turned into Fuel

Producers combine hydrogen and carbon through well-established industrial chemistry. The main routes differ in intermediates and end products but share common steps of synthesis and refining.

1. Power-to-Liquids via Fischer–Tropsch (FT): Make green H2 by electrolysis; combine H2 with CO/CO2 to form syngas; run FT over iron/cobalt catalysts to create long-chain hydrocarbons; upgrade via hydrocracking/isomerization to jet/diesel/gasoline blends.
2. Methanol route (CO2-to-methanol): Convert H2 + CO2 to methanol, then transform to gasoline (MTG) or to olefins and longer hydrocarbons (MTO/oligomerization) or use methanol directly.
3. Synthetic methane (Sabatier): React H2 with CO2 over nickel catalysts to produce CH4 and water; compatible with existing gas grids and LNG systems.
4. Ammonia (Haber–Bosch): Combine green H2 with nitrogen from air to produce NH3; can be used in marine engines or cracked back to H2 for fuel cells.
5. Biomass/Waste-to-Liquids: Gasify biomass or municipal solid waste to syngas, clean it, then proceed via FT or methanol synthesis to liquid fuels.

Each pathway tailors the carbon–hydrogen assembly to specific fuel specs, with upgrades and blending steps to meet standards such as ASTM D7566 for sustainable aviation fuels.

What’s Actually Inside the Finished Fuels

Beyond the route, the final composition is engineered for performance, cleanliness, and compliance with fuel standards.

• Hydrocarbons: Predominantly paraffins/iso-paraffins; gasoline typically C5–C12, jet/diesel C8–C20.
• Very low contaminants: Negligible sulfur, nitrogen, and metals; FT fuels are also very low in aromatics, improving local air quality and reducing soot.
• Oxygen content (if oxygenates): Methanol, DME, and OMEs contain oxygen, which can aid cleaner combustion but changes energy content.
• Additives and blending components: Detergents, antioxidants, lubricity improvers, and blending with fossil or bio components to meet volatility, cold-flow, and stability specs.
• Energy density: Similar to fossil counterparts for hydrocarbons (e-kerosene ~42–43 MJ/kg); lower for oxygenates like methanol; ammonia is carbon-free but has distinct combustion traits.

The result is a fuel pool that can be tailored: ultra-clean diesel for low soot, synthetic kerosene for aviation, or oxygenates for targeted emissions benefits.

Sources and Terminology

“Synthetic fuel” spans several production families, which differ in climate impact depending on their feedstocks and power sources.

• E-fuels or Power-to-Liquids (PtL): Use renewable electricity, water, and captured CO2; the most promising for deep decarbonization of aviation and shipping.
• GTL and CTL: Convert natural gas (GTL) or coal (CTL) to liquids; synthetic by process, but not low-carbon unless paired with robust carbon capture and low-leakage supply chains.
• BtL: Biomass-to-liquids, which can be low-carbon if feedstock sourcing and land-use impacts are responsibly managed.
• RFNBOs: “Renewable fuels of non-biological origin,” a regulatory term in the EU for e-fuels made from renewable power and captured carbon.

In common usage today, “synthetic fuel” often implies the low-carbon e-fuel flavor, but the label can include fossil-derived routes unless explicitly qualified.

Environmental and Practical Implications

What synthetic fuels are made of directly shapes their climate and operational profile. Key implications include the carbon source, electricity mix, and fuel properties.

• Carbon balance: Near net-zero only if the carbon comes from sustainable sources (captured CO2/biogenic CO) and the electricity is renewable; otherwise emissions rise.
• Compatibility: Hydrocarbon e-fuels are drop-in for existing engines and infrastructure, aiding hard-to-electrify sectors like aviation and long-haul shipping.
• Air-quality benefits: Very low sulfur and aromatics reduce particulate and SOx emissions versus conventional fuels, especially with FT products.
• Scale and cost: Production is electricity-intensive and currently costly; scaling requires abundant low-carbon power, CO2 capture at scale, and supportive policies and offtake agreements.
• Diversification: Non-carbon options like ammonia and hydrogen can decarbonize niches but demand new engine/fuel-cell technologies and safety protocols.

As renewable power and CO2 capture scale up, the material choices behind synthetic fuels can translate into meaningful emissions cuts where direct electrification is difficult.

Bottom Line

Synthetic fuels are made from hydrogen and carbon—sourced from water and CO/CO2—and assembled over catalysts into hydrocarbons or oxygenates; when powered by renewable electricity and sustainable carbon, they deliver drop-in fuels with much lower lifecycle emissions.

Summary

Synthetic fuels combine hydrogen with carbon (or nitrogen, in the case of ammonia) to create energy-dense liquids and gases. The primary ingredients are green hydrogen, captured CO/CO2, substantial renewable electricity, and catalysts, yielding clean hydrocarbons like e-kerosene, diesel, and gasoline, as well as methanol, DME, synthetic methane, and ammonia. Composition is tuned to standards, with ultra-low contaminants and, for FT fuels, minimal aromatics. Climate performance depends on truly renewable inputs and sustainable carbon sourcing; done right, these fuels enable decarbonization of sectors that can’t easily electrify.

What are the ingredients in synthetic fuel?

Synthetic fuel or synfuel is a liquid fuel, or sometimes gaseous fuel, obtained from syngas, a mixture of carbon monoxide and hydrogen, in which the syngas was derived from gasification of solid feedstocks such as coal or biomass or by reforming of natural gas.

What is the problem with synthetic fuels?

The manufacturing process is complex, costly and energy intensive, which is a major barrier to uptake. As a result, synthetic fuels will remain expensive until infrastructure is scaled up.

How close are we to synthetic fuel?

While synthetic fuel technologies have big potential, there’s a lot of ground to cover before they step up as a replacement for fossil-derived fuels. New data from EU-based campaign group Transport & Environment (T&E) reveals current synthetic fuel supplies will power just 2% of cars on European roads.

Can normal cars run on synthetic fuel?

The result is a liquid fuel that has all of the properties of its natural equivalent, which produces only around 15% of the emissions. In theory, any vehicles that run on petrol or diesel could also work perfectly on the synthetic alternative.