TAKE-OFF project: From CO2 and hydrogen to sustainable aviation fuels

The challenge: making aviation sustainable

While alternative propulsion methods like electric or hydrogen-powered flight are being developed, these are not expected to be viable options for long-haul flights. "Aviation fuel consumption is approximately 400 billion liters and growing 2% to 3% yearly", explains Lawien Zubeir, senior scientist and technical lead of synthetic fuels and chemicals at TNO. "When you consider these volumes, optimizing these processes, even by small margins, can create significant benefits."

Current alternatives to fossil jet fuel each face limitations. Biofuels depend on finite resources like cooking oils and animal fats. Meanwhile, established synthetic fuel processes like Fischer-Tropsch produce a wide range of products that require extensive processing to isolate jet fuel. These challenges highlight the need for more targeted, efficient approaches.

The breakthrough: precision targeting for efficiency

The TAKE-OFF project took a fundamentally different approach by designing a process specifically for jet fuel production. By using captured CO2 and renewable hydrogen as raw materials, the technology sidesteps the limitations of biological feedstocks. This is an important advantage as synthetic SAF is expected to grow to 35% of all sustainable aviation fuels by 2050.

"Unlike conventional methods such as Fischer-Tropsch synthesis, our process is specifically engineered to yield hydrocarbon chains in the jet fuel range", Lawien explains. "In contrast to conventional methods that generate a wide array of hydrocarbons, requiring substantial downstream processing, the TAKE-OFF project's strategy is uniquely tailored to streamline production." This precision targeting sets the stage for big efficiency improvements.

40% yield increase because of the SIENNA reactor

At the heart of the indirect route's success lies TNO's SIENNA reactor. Traditional methanol synthesis hits a wall at 20% conversion due to thermodynamic equilibrium limitations. The SIENNA reactor breaks through this barrier.

The innovation is elegantly simple in concept: continuously remove water as it forms during the reaction. Unlike reactors using sorption materials or sweep gas, SIENNA uses a selective membrane to extract steam directly from the catalyst bed, condensing it on a cooling element at the reactor's center - all within a single, continuous process.

"With conventional technology, you'd convert only 20% of the CO2, with 80% needing to be recycled", Lawien explains. "With SIENNA, we achieve 37% conversion. That 40% improvement in methanol yield changes everything. It means smaller facilities, less energy use, better economics."

From lab to runway: proving the concept

After four years of intensive research, the TAKE-OFF team produced their proof of concept: one liter of actual jet fuel made from CO2 and hydrogen. While a single liter might seem modest, it represents a major milestone.

"The fuel meets physical property requirements for certification", says Georgiana Stan, TNO's project coordinator for TAKE-OFF. Lawien adds: "The sample underwent rigorous testing. Its physical, chemical and combustion properties were examined to verify it meets the requirements for commercial aviation use."

While this validation program represents a major milestone toward certification, it's not the only notable achievement. "Beyond the technical success, what excites us is the environmental performance. Our fuel produces four times less soot than conventional jet fuel", says Georgiana.

The environmental advantages extend beyond reduced soot. With negligible aromatic hydrocarbons and no sulfur compounds, TAKE-OFF fuel promises lower NOx, SOx and particulate emissions. These improvements matter not just for air quality but for climate impact. Because soot particles create contrails, which research suggests may have an even bigger warming effect than CO2 emissions.

"We've advanced the technology from proof of concept at TRL 3 to validation in relevant environments at TRL 5", Georgiana notes. "That's a huge leap in just four years."

Impact beyond aviation

While these results mark significant progress toward sustainable aviation, the project's innovations and insights reach far beyond the skies. "The knowledge gained also has potential benefits for other technologies in the chemical sector", Georgiana explains.

“While the path to industrial-scale production of SAF using the Take-off method, may take 10 to 15 years, the insights gained in catalyst development, CO2 conversion, and process optimization are already valuable for other chemical processes.”

Some partners are already working on the next phase. "Integration is key", Lawien explains. “In the follow-up project we will be exploring the integration of multiple process steps within a single reactor, an approach that has the potential to substantially lower both capital and operating expenditures.”

The regulatory landscape is pushing hard for change. The EU's ReFuelEU directive mandates increasing SAF percentages: 6% by 2030, rising to 70% by 2050, with 35% required to be synthetic. "With sufficient funding and the right expertise, we could compress the timeline to industrial implementation", Lawien says. "The urgency is there, the technology is proven, now it's about scaling up."