No solution for heating stripes at the moment | NOW

Schiphol is in the news all the time. Then there are the long queues that make many people miss out on holiday flights. But the half-filled planes are problematic for another reason: they consume a lot of oil and cause climate change. There is in theory a (partial) solution to this.

Flying is the most climate-damaging way to travel. This is not only due to the high emissions per kilometers, but also the sharply increasing distances: If you make a few intercontinental flights, you quickly emit more CO2 than the rest of the year from heat and electricity.

Furthermore, CO2 is only half the story when flying. The other half are ‘flight stripes’, the condensation traces that often remain in the air where jets have flown.

These thin clouds at high altitude retain a relatively large amount of heat radiation. And it makes the heating effect more than double, says cloud expert Pier Siebesma from TU Delft and KNMI.

“Surprisingly, the stripes of air have a warming effect that is at least as strong as the CO2 emissions from the combustion of petroleum.”

Less soot means fewer streaks

Is there anything you can think of? In theory yes, says Siebesma: biokerosen. This is aviation fuel that is not made from (fossil) petroleum, but from vegetable material. Or synthetically based on hydrogen and pure CO2.

“Air streaks are created because water vapor is released during combustion, but also because soot particles are emitted from jet engines,” says Siebesma. Water or ice condenses around these soot particles, making the streaks much thicker and the clouds also last longer.

Biopetroleum can more than halve the climate impact

But that is much less the case with biokeros. Siebesma points to recent research from, among others, NASA. “This shows that the combustion of biopetroleum produces far fewer soot particles and therefore fewer ice particles than with fossil petroleum.”

This is because the chemical composition is different. Fossil petroleum contains many so-called aromatics, which burn incompletely and thus form soot.

“If aviation were to switch completely to biokeros, the heating effect could be reduced by more than half, because not only CO2 emissions but also the amount of air streaks would then decrease. So that is good news,” says Siebesma.

Petroleum from hydrogen and CO2 does not yet exist

The extent to which CO2 emissions can be reduced depends to a large extent on the production process and the raw materials used. For example, if the biokerosene is produced from (food) crops such as corn or sunflower, it competes with food production.

In addition, a lot of extra agricultural land is needed, which in turn can be at the expense of the forests. The CO2 gain in such cases is very small.

Theoretically, it is also possible to produce CO2-neutral biopetroleum, for example based on green hydrogen (produced using electricity from the sun or wind) and pure CO2, says Siebesma. This is often referred to as synthetic petroleum.

The price will rise rapidly: Producing biokeros from food crops is already more than twice as expensive as petroleum. Synthetic petroleum is not produced on a large scale, and is therefore several times more expensive.

Aviation growth reverses climate gains

And there is another catch: growth in aviation. Based on the current growth rate, the number of passenger flights doubles every twenty years. Such a doubling would therefore greatly offset the potential climate benefits of biokeros, while it is highly uncertain whether aviation can completely stop using fossil fuels in such a short term.

Conclusion: So far, climate-neutral flight is in the future and is the most effective climate solution to try to slow down growth. For especially now that we are looking for ways to save as much oil as possible due to the war in Ukraine and the impending boycott of Russian oil, the long queues may not yet be the real problem.

Leave a Comment