Having recently revealed in Learmount.com that air travel could easily be rendered less of a global-warmer than it is (see previous article Airline climate harm can be halved), another significant discovery enabling further advances on that front has just been chalked up.

Sustainable aviation fuel (SAF), if used at 100% concentration rather than a mix of about 50% with fossil-derived aviation fuel, appears to be able to reduce – by more than half – the global warming effects of high level cirrus cloud formed from persistent aircraft contrails.

Use of SAF is, at present, the most tangible action airlines can take to reduce their global warming effect, although its production is nowhere near sufficient to power the entire world fleet. Deriving from waste vegetable oil and production processes that consume global warming gases, its sustainability is its most obvious benefit. It is turning out, however, also to have unpredicted advantages, like a higher energy output per unit weight as well as a much cleaner burn.

This clean-burn effect has come to light as a result of trials conducted by Airbus, using one of its A350-900s, fueled with 100% SAF and cruising at 35,000ft over the Mediterranean Sea, trailed by a Dassault Falcon 20 chase aircraft carrying out contrail sampling. The trial has found that burning 100% SAF produces 35% fewer soot particles per unit burned than normal aviation kerosene, and an even higher reduction in ice particle formation, at 56% less. Visible contrails result from the water produced by fuel combustion condensing on soot or other particles in the atmosphere, and it is when high level aircraft contrails consist of ice particles that they persist longest in the upper atmosphere, creating cirrus cloud that would otherwise not exist.

Air travel has recovered vigorously from the dip experienced as a result of the Covid 19 pandemic. Indeed the pandemic lock-downs seem to have heightened travellers’ desire to fly, so any progress the industry can make toward reducing its climate change effects is more than just desirable, it is essential.

For greater detail on the Airbus trials, and more on the science of contrails, see David Kaminsky Morrow’s article on FlightGlobal.com and the Learmount.com article immediately preceding this one.