The start of electric aviation is coming, but it will be many more years before the average environmentalist can fly blamelessly in a fully electric long-haul jet.
In the meantime, scientists are trying to make commercial airplanes that we already have more sustainable, and one of the best ways to do that is to change the fuel they consume.
Instead of spitting out carbon dioxide (COtwo) into the atmosphere, researchers at the University of Oxford and the University of Cambridge, UK, found a way for airplanes to capture this gas from the air and burn it as fuel.
Rather than 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 earlier. That is, if it proves to work on a larger scale.
In the laboratory, the researchers were able to capture and convert CO gastwo directly into jet fuel using a cheap iron-based catalyst.
The amount of liquid fuel produced is still too small to power a real plane, but if fossil fuels could be captured from the air at a high enough volume, converted to energy with sufficiently large efficiency and then reissued, an airplane 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 aviation fuel,” write the authors.
“Recycling carbon dioxide as a carbon source for high-value fuels and chemicals offers considerable potential for the aviation and petrochemical industries.”
Normally, when fossil fuels burn, the hydrocarbons they contain are transformed into carbon dioxide and water, releasing energy. The new system basically reverses this natural process.
By adding heat to the system, engineers were able to combine carbon dioxide with hydrogen, separated from water, to produce a few grams of liquid fuel that, according to the authors, could work in a jet engine.
The catalyst responsible for this impressive chemical reaction is composed of iron, manganese and potassium, abundant elements of the Earth, easier and cheaper to prepare than many similar candidates. The catalyst also combines easily with hydrogen and shows high selectivity for a variety of jet fuel hydrocarbons.
The result is a little fuel, in addition to several petrochemicals that can only be obtained from fossil fuels.
The new system is not the first, nor will it be the last to convert our carbon emissions into a desirable biofuel. In Canada, scientists have developed a huge industrial complex to capture COtwo as trees in a forest would, using it to form hydrocarbon fuel.
But although a handful of studies have shown that it is possible to convert atmospheric COtwo in liquid fuel, it is extremely challenging and expensive to produce more than a small amount.
The new system looks promising, but whether it is practical or not is another matter.
“It looks different and it can work,” said Joshua Heyne, an independent engineer who was not involved in the study. Wired.
“Scaling up is always a problem, and there are new surprises when you go to larger scales. But in terms of a long-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 in the air’ as mere exaggeration. Last year, when a company in Europe announced that it was working on a way to capture COtwo from the air to power the planes of the future, critics pointed out that the fuel produced each day would allow only five minutes of flight.
Such small productions are not a solution to the climate crisis, and some environmentalists argue that our only viable option is to fly less. Mainly because the reality of a circular carbon economy is still far away and the climate change crisis is already upon us.
In the end, it all depends on how quickly we can expand this promising technology, and the fact is that it may not happen fast enough.
Engineers ultimately want to connect their new system to established carbon emitters, such as coal-fired power plants, and that, of course, would require the continued production of fossil fuel. It is also very expensive and may not be attractive to companies, even if it works.
Still, with climate change accelerating and aviation only increasing in the coming years, the team of engineers argues that COtwo conversion and use as “an integral and important part of greenhouse gas control and sustainable development”.
Other sustainable biofuels that depend on plants require vast areas of cultivation and do not solve 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 cornerstone of a future global zero carbon aviation sector.”
We’ll see.
The study was published in Nature Communications.