Fuelling the future: Closing the loop in sustainable aviation
Mika Järvinen, Associate Professor at Aalto University, explains how Circular Fuels is working to close the loop in sustainable aviation.
As the climate crisis reaches higher altitudes and the pressure to decarbonise soars, the aviation industry faces a choice: innovate or risk a turbulent future.
Responsible for 14.4% of the EU’s transport-related emissions, air travel remains one of the most carbon-intensive sectors and one of the hardest to decarbonise.
While electric vehicles are becoming increasingly mainstream for road transport, the dream of battery-powered long-haul flights remains distant.
The aviation sector remains dependant almost entirely on fossil fuels, contributing greatly to our current climate crisis. We must cut these carbon emissions in order to reduce our impact on the planet.
In Europe, there has been some movement towards a fossil free future in recent years. In 2021, the EU presented the Fit for 55 plan aiming to cut greenhouse gas emissions by a 55% reduction by 2030 in comparison to 1990 levels.
To help reach this target, they also introduced initiatives aiming to boost the use of cleaner aviation fuels and reduce the environmental impact.
After discussions throughout 2022 and 2023, EU leaders and the European Parliament finally reached an agreement, and the ReFuelEU Aviation regulation was officially adopted in October 2023.
The solution is clear. To advance aviation and reach these ambitious targets set by the EU, we must take a more radical approach rooted in the circular economy principles.
Closing the loop in sustainable aviation
Launched in 2023, with the backing of the EU’s Green New Deal and CORDIS initiatives, the Circular Fuels project is redefining how sustainable aviation fuels (SAF) can be developed, scaled, and integrated into our global energy system.
Not only does this project present technological upgrades, it also offers a systems-level rethinking, bringing circularity to the skies by integrating renewable energy, waste-based inputs, and zero-emission processes into a closed-loop model.
At its core, Circular Fuels is built on the foundation of circularity. Rather than relying on extractive, linear production chains that take, make, and waste, this project takes a regenerative approach.
Waste materials, including agricultural residues and forestry byproducts, are transformed into valuable bio-oils, which are then refined into high-quality, drop-in aviation fuels.
But the innovation doesn’t stop at feedstock. The process is powered entirely by solar energy, both through photovoltaic (PV) electricity and concentrated solar thermal systems.
Parabolic mirrors harness solar heat to generate temperatures over 3000°C, which are then funnelled into pyrolysis reactors that convert biomass into bio-oil. This heat production involves no combustion, meaning no carbon emissions. It’s a major leap forward in sustainable energy practices.
Meanwhile, solar PV powers PEM (Proton Exchange Membrane) electrolysers are used to produce green hydrogen from water. This hydrogen is essential for the hydrotreatment of bio-oil, removing oxygen and refining the product to meet the strict quality requirements of aviation fuels.
Every step in the process is deliberately designed with circularity in mind to eliminate waste, close energy loops, and minimise environmental impact.
The implications of this model extend far beyond fuel production. From agriculture to energy, this initiative is setting a precedent for how entire sectors can integrate circularity into their operations.
For farmers and biomass producers, this means new revenue streams from agricultural waste that would otherwise be discarded or burned, as well as offering municipalities an opportunity to reduce local biomass waste whilst contributing to EU-wide climate targets.
In sectors, such as solar and hydrogen, the project creates synergy, turning intermittent renewable energy into stable, high-value products. For aviation companies and passengers, it paves the way towards low-emission air travel without sacrificing performance.
Alongside this list of benefits, the project provides policy recommendations and economic models to ensure that these technologies are not only environmentally sound, but commercially viable.
It’s a powerful reminder that circular solutions must be scalable and sustainable across social, economic, and environmental dimensions.
Circular Fuels is tightly aligned with the EU’s Fit for 55 package and RefuelEU Aviation regulation, aiming to ensure 2% SAF usage in EU airports by 2025, scaling up to 70% by 2050.
Crucially, the project focuses on advanced biofuels made from waste, as opposed to crop based biofuels which often compete with food production and degrade land quality.
Not all renewables are created equal
This is important to distinguish as not all renewables are created equal.
Crop-based biofuels can reproduce some of the extractive dynamics of fossil fuels. In contrast, Circular Fuels taps into truly regenerative resources, turning what was once waste into a product that displaces fossil kerosene, one of the aviation sector’s most polluting fuels.
It’s a blueprint for how circular economy principles can drive deep decarbonisation in even the most emissions-heavy industries.
By integrating clean energy, waste valorisation, cross-sector partnerships, and policy alignment, this initiative demonstrates how circularity can become a powerful engine for innovation and sustainability.
In a world that urgently needs scalable climate solutions, we need more than hope – we need action. With solar-powered, waste-based jet fuel on the horizon, the skies may soon be a lot cleaner thanks to the on-going hard work taking place here on the ground.
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