What are the Sustainable Fuels Powering Decarbonisation?
Photo: FUELPHORIA
As the world races to cut emissions, a new class of synthetic fuels is stepping forward to power the sectors batteries can’t reach.
We might want to believe that switching from fossil fuels to renewable energy is as simple as turning on a light switch. But the reality is that moving towards a decarbonised future requires a transition, and solutions that bridge the gap between today’s fossil-based systems and tomorrow’s fully renewable world.
Achieving that depends on decarbonising sectors that cannot be easily electrified. Aviation, shipping, long-haul road transport, and high-temperature industrial processes like cement production all depend on high-energy-density fuels that batteries cannot replace at scale. These are often referred to as “hard-to-abate” sectors.
In response, a new category of synthetic fuels has moved from niche innovation to the centre of decarbonisation strategies: Renewable Fuels of Non-Biological Origin (RFNBOs). In Europe, RFNBOs are seen as key to bridging the gap in hard-to-abate sectors and are embedded in major EU policies such as ReFuelEU Aviation, FuelEU Maritime, and the Renewable Energy Directive (RED III), all designed to expand production and stimulate demand.
Fuels that “drop-in” to existing infrastructure
RFNBOs are often mentioned alongside advanced biofuels, but they are fundamentally different. While advanced biofuels are derived from waste and residue biomass, RFNBOs are liquid or gaseous fuels produced using renewable electricity and non-biological feedstocks.
Their production begins with electrolysis, where renewable electricity splits water into hydrogen and oxygen to create green hydrogen. This is then combined with captured carbon dioxide (CO₂) to form synthetic hydrocarbons.
Common RFNBOs currently under development include:
- E-methanol, a synthetic liquid fuel that can be used in shipping, heavy industry and chemical production.
- E-kerosene (also known as synthetic jet fuel or electro-kerosene), which can serve as a form of Sustainable Aviation Fuel (SAF).
- E-methane, a synthetic form of methane that can be injected into existing gas networks or used directly in gas-powered vehicle infrastructure like long-haul road transport or shipping.
Because these fuels closely resemble fossil fuels at the molecular level, many can be blended or used directly in today’s engines and infrastructure. This “drop-in” compatibility makes them particularly attractive during the energy transition.
To qualify as an RFNBO under EU law, these synthetic fuels must meet strict requirements. It must be produced using renewable electricity (such as wind, solar, hydro, or geothermal power), and none of its carbon inputs (if any) may come from biomass. It must also comply with EU rules on additionality, time-matching, and geographic correlation, ensuring the electricity used is genuinely renewable. Finally, it must deliver at least a 70% reduction in lifecycle greenhouse gas emissions compared to fossil fuels.
Producing RFNBOs
Innovative projects are testing how renewable hydrogen can be paired with captured CO₂ to create synthetic fuels. FUELPHORIA, an EU-funded initiative, is one programme exploring various pilot projects that use CO₂ as a sustainable feedstock, alongside green hydrogen. This is “industrial symbiosis”, collecting a waste product from one industry and using it as the resource of another.
Three methods are:
- Capturing CO2 from the fermentation of grapes in wine production and combining it with green hydrogen to create e-methane
- Capturing CO2 from biogas plants and combining it with green hydrogen to create e-methanol or other synthetic hydrocarbons.
- Capturing CO2 from the fermentation of urban biowastes and combining it with green hydrogen to create e-methanol and e-ethanol
Advantages of RFNBOs
RFNBOs support energy security, reducing reliance on imported fossil fuels and enabling Europe to harness its growing renewable electricity base. They create a circular carbon loop – using captured CO2 as an input – they can significantly cut lifecycle emissions. And because they use captured CO2 as a feedstock – a waste product in most industrial processes – they do not compete for land, unlike some biofuels that rely on crop-based feedstocks.
Challenges and constraints
Despite their potential, the development and scaling of RFNBOs face significant hurdles:
- High costs: Today, RFNBOs are several times more expensive than fossil fuels and often more costly than biofuels, mainly due to the machinery (electrolysers) and electricity costs for green hydrogen production.
- Low energy conversion: Currently, the technology uses more energy than direct electrification, meaning more electricity is used to produce the same amount of energy in fuel.
- Infrastructure and logistics: Transporting, storing, and blending synthetic fuels requires new or upgraded systems.
- Policy framework: Rules around how emissions are counted, and fuel certification is inconsistent, which creates uncertainty for investors.
Looking forward
The next decade will be critical for RFNBO development. Costs may fall as electrolysers scale, renewable electricity becomes cheaper, and synthesis technologies mature. EU mandates for aviation and maritime will create guaranteed demand, encouraging investment and industrial build-out.
Even as innovation continues, in the long term, RFNBOs will not replace all fossil fuels, but they will form an essential part of the energy mix – especially for global transport sectors that must decarbonise but cannot rely solely on batteries or biofuels.
RFNBOs are, in effect, a bridge between renewable power and liquid fuels – turning electrons into molecules, and helping the world move towards a cleaner, more resilient energy future.
