The start of electric aviation is upon us, but it’s going to take many more years before the average environmentalist can fly guilt free on a fully electric long haul jet.
In the meantime, scientists are trying to make the commercial planes we already have more sustainable, and one of the best ways to do that is to change the fuel they consume.
Instead of spitting carbon dioxide (CO2) out into the atmosphere, researchers at the University of Oxford and the University of Cambridge in the UK have now come up with a way for airplanes to capture this gas from the air and burn it for fuel.
Instead of creating a whole new fleet of electric planes, which would require huge leaps in battery storage technology, this new approach would allow the world to reduce its carbon footprint from flying much sooner. That is, if it proves to work on a larger scale.
In the lab, researchers were able to capture and convert gaseous CO2 directly into jet fuel using an inexpensive iron-based catalyst.
The amount of liquid fuel produced is still far too small to power an actual airplane, but if the carbon can be captured from the air in high-enough volume, converted into energy at great enough efficiency and then re-emitted, a plane could theoretically fly ‘carbon neutral’.
“This catalytic process provides an attractive route not only to mitigate carbon dioxide emissions but also to produce renewable and sustainable jet fuel,” the authors write.
“The recycling of carbon dioxide as a carbon source for both fuels and high-value chemicals offers considerable potential for both the aviation and petrochemical industries.”
Normally, when fossil fuels burn, the hydrocarbons they contain are turned into carbon dioxide and water, releasing energy. The new system essentially reverses this natural process.
By adding heat to the system, engineers were able to combine carbon dioxide with hydrogen, split from water, to produce a few grams of liquid fuel that the authors say could work in a jet engine.
The catalyst responsible for this impressive chemical reaction is composed of iron, manganese and potassium, which are abundant Earth elements, easier and cheaper to prepare than many similar candidates. The catalyst also interacts easily with hydrogen and shows high selectivity for a range of jet-fuel hydrocarbons.
The outcome is a little bit of fuel, as well as several petrochemicals that can only be obtained from fossil fuels.
The new system isn’t the first, nor will it be the last that converts our carbon emissions into desirable biofuel. In Canada, scientists have been developing a huge industrial complex to capture CO2 like the trees of a forest would, using it to form hydrocarbon fuel.
But while a handful of studies have shown it’s possible to convert atmospheric CO2 into liquid fuel, it’s extremely challenging and expensive to produce more than a tiny amount.
The new system looks promising, but whether or not its practical is another matter.
“This does look different, and it looks like it could work,” Joshua Heyne, an independent engineer who was not involved in the study, told Wired.
“Scale-up is always an issue, and there are new surprises when you go to larger scales. But in terms of a longer-term solution, the idea of a circular carbon economy is definitely something that could be the future.”
Some, like Heyne, are hopeful, while others see ‘flying on air’ as mere hype. Last year, when a company in Europe announced they were working on a way to capture CO2 from the air to power future airplanes, critics pointed out the fuel produced each day would only allow for five minutes of flying.
Such tiny yields are not a solution to the climate crisis, and some environmentalists argue our only feasible option is to fly less. Especially because the reality of a circular carbon economy is still far off and the crisis of climate change is already upon us.
In the end, it all depends on how quickly we can scale up this promising technology, and the fact is, it might not happen fast enough.
Engineers want to ultimately hook up their new system to established carbon emitters, such as coal-burning power plants, and that would, of course, require continued fossil fuel production. It’s also really expensive, and might not be appealing to businesses even if it did work.
Still, with climate change accelerating and aviation only set to increase in coming years, the team of engineers argues CO2 conversion and utilisation as “an integral and important part of greenhouse gas control and sustainable development.”
Other sustainable biofuels which rely on plants require vast amounts of cropland and don’t tackle our emissions at the same time.
“This, then, is the vision for the route to achieving net-zero carbon emissions from aviation,” they conclude, “a fulcrum of a future global zero-carbon aviation sector.”
We shall see.
The study was published in Nature Communications.