Making synthetic aviation fuel requires two things at once: a steady carbon feedstock and cheap renewable electricity. In practice, neither shows up on schedule.
In a pilot-scale experiment published in the Journal of CO2 Utilization, Topsoe scientists fed two entirely different carbon sources — CO2 and biogas — into the same reactor, sometimes simultaneously, sometimes in sequence. The output was stable syncrude, consistently suited for refining into sustainable aviation fuel.
The Carbon-Sourcing Problem Holding E-Fuels Back
Synthetic fuels are widely viewed as one of the few credible pathways to decarbonizing aviation, where direct electrification isn’t an option. But scaling up production has run into a persistent structural problem: most e-fuel processes are built around a single carbon source, typically CO2, and that dependency creates real vulnerability. Supply disruptions, fluctuating renewable electricity prices, and inconsistent feedstock availability can all stall output at exactly the wrong moment.
The FrontFuel initiative was designed to confront these constraints directly. Sponsored by Denmark’s Energy Technology Development and Demonstration Program (EUDP) and led by researchers from Topsoe, Aarhus University, and Sasol, the project set out to demonstrate whether pilot-scale synthetic fuel production could be made genuinely flexible — not just in theory, but in a working reactor system producing fuel-grade output.
A Reactor That Switches Between Feedstocks on the Fly
The technical centerpiece of the study is Topsoe’s eREACT™ technology, which enabled two chemically distinct processes to run interchangeably inside the same reactor unit. Steam reforming of biogas (CH4) and reverse water-gas shift of CO2 and hydrogen aren’t the same reaction. Yet the system handled both — and transitions between them — without requiring a separate apparatus for each.
What made this possible was dynamic control of the feed gas composition using hydrogen and steam. As the ratio of CO2 to CH4 at the reactor inlet varied, operators adjusted these inputs to keep the syngas output at a constant composition, producing stable syncrude throughout the experiment even as the feedstock mix changed. Flexibility, in other words, didn’t come at the cost of consistency.
That stability matters more than it might first appear. Downstream fuel synthesis processes are sensitive to syngas quality, so any instability at the reforming stage propagates through the entire production chain. The pilot maintaining steady output across different feedstock conditions is a meaningful proof of concept — not an incremental refinement.
Turning Grid Volatility Into a Production Advantage
One of the less obvious implications of this dual-feedstock capability is what it means for how a facility interacts with the electrical grid. Converting CO2 is more energy-intensive than converting biogas — a difference that might look like a complication but is actually a lever.
When renewable electricity is cheap and abundant, during peak wind or solar generation, a plant can lean heavily on CO2 conversion, consuming more power and helping absorb grid surplus. When electricity is scarce and expensive, the same facility can shift toward the less energy-intensive biogas pathway, reducing its draw on the grid without halting production. The switching happens within the same system, with no retooling required.
This built-in flexibility means a synthetic fuel plant isn’t just a passive electricity consumer. It can act as a flexible load, actively supporting grid balance. The same logic applies to natural fluctuations in feedstock availability: if CO2 supply tightens or biogas delivery is interrupted, the system compensates rather than shuts down.
From Syncrude to Sustainable Aviation Fuel
The pilot didn’t stop at syngas. Syncrude produced by the eREACT system was routed through Sasol’s Fischer-Tropsch technology, and the output was confirmed to be of a quality suitable for upgrading into sustainable aviation fuel. That full-chain result — from mixed carbon feedstocks through to SAF-grade syncrude — is what gives the study its weight.
The setup also allows byproducts from downstream fuel synthesis to be recycled back into the eREACT system, improving overall yield and cutting waste. At commercial scale, where efficiency losses compound quickly, that kind of integration isn’t a nice-to-have.
Publication in the Journal of CO2 Utilization represents a documented, peer-reviewed milestone for flexible synthetic fuel production. Pilot scale is not commercial scale, and the path from one to the other involves substantial engineering, financing, and regulatory work. But the FrontFuel results give producers and policymakers something concrete to build on: a demonstrated system that handles variable carbon inputs, supports grid stability, and still delivers aviation-grade output. The next question is how quickly that architecture can be replicated at the scale aviation actually needs.
