Food Waste Could Become Aircraft Fuel for Commercial Aviation

Could an airliner be powered by organic waste? Researchers in the United States have just shown that it is theoretically achievable, and that their fuel meets the sector’s standards.

Civil aviation is far from exemplary on environmental matters. Globally, the industry accounts for a meaningful share of greenhouse-gas emissions - “around 2%” of CO₂, according to the Air Transport Action Group. Over recent years, many initiatives have emerged to make commercial aviation greener: hydrogen propulsion, altered flight paths to avoid contrails, and synthetic fuels (HEFA).

So far, none of these options has managed to combine profitability with energy performance, and the industry is still searching for the right answer. It may come from the work of engineers at the University of Illinois Urbana–Champaign, who found a way to turn food waste into genuine aircraft fuel. Their study, published in Nature Communications on 30 October, proposes something entirely unprecedented in the history of commercial aviation.

Could our bins provide the jet fuel of the future?

For Yuanhui Zhang, an engineer at the University of Illinois and lead author of the study, the aim was less about producing a “miracle fuel” than proving that organic material could compete chemically with fossil kerosene. “In a linear economy, we produce, consume and then throw things away. In this project, we recover energy and materials to create a useful product,” he explains.

This “missing link in the circular paradigm”, as he calls it, draws on a well-established and widely used principle, particularly in geochemistry: hydrothermal liquefaction (HTL). The process replicates within hours what the Earth takes millions of years to do: convert organic matter into crude oil.

The team collected food-production residues from food-processing plants, then exposed them to extremely high temperatures and pressure. This produced a biological oil made up of a mixture of oils, water and carbon compounds, which then still requires refining.

Once obtained, the oil underwent catalytic refining - known as hydrotreating - using cobalt and molybdenum, two metals employed by the petroleum industry to remove impurities. This stage eliminates water, salts and ash, as well as unwanted atoms such as sulphur, nitrogen and oxygen, which would impair combustion. The end product is bio-based kerosene indistinguishable from conventional kerosene used in aviation.

Is aviation ready to move beyond oil?

This kerosene also complies with every standard set by the sector’s two watchdogs: the American Society for Testing and Materials (ASTM) and the Federal Aviation Administration (FAA). The achievement should not be understated: few bio-based fuels immediately satisfy the joint requirements of these two bodies, which apply some of the world’s most rigorous assessment protocols.

The next, particularly difficult question is industrial feasibility. Producing a few dozen litres of biofuel in a laboratory is one thing; supplying fleets of airliners is another. Although the kerosene developed by these engineers works, incorporating it into such a tightly regulated industry will not be straightforward. Aviation operates under strict certification and reliability requirements, and is probably the least suitable field for experimentation.

“Our job is to solve the scientific and engineering problems. It is up to industry to take over,” Zhang rightly states. Scientific advances alone cannot keep aircraft engines running; they must be matched by sufficient capital and at least some willingness from industry.

Sustainable aviation fuels and the challenge of scaling up

It will therefore take time, investment and industrial commitment before the work of Zhang and his team finds a real-world application. It would be a great shame if their kerosene remained a prototype, given that sustainable aviation fuels (SAF) of this kind have already demonstrated their potential. If deployed widely, they could cut the carbon footprint of flights by up to 80%, while remaining compatible with existing engines and supply chains. If airlines want to keep their aircraft flying in the decades ahead, they will ultimately have no alternative but to learn to do without oil, whether they want to or not.