Part of our series Securing Global Net Zero, featuring innovation, research and technology from the University sector which could help reach targets for net zero carbon by 2050.

Determining the impact of aircraft emissions on climate is not a simple problem, as it does not rest solely with carbon dioxide. Other greenhouse active gases are emitted including oxides of nitrogen (NOx), which can react to form ozone. And then there are carbon particles (soot) and water vapour emissions that can form contrails, which act like transient high cloud, absorbing and reflecting radiation from above and below.

Alex and his team have been comparing contemporary kerosene-based fuel with the two of the main contenders for powering future aircraft, liquid hydrogen and fuel cells. Their preliminary findings show that while hydrogen and electric propulsion produce neither soot nor carbon dioxide (and no NOx in the case of electric), they can potentially form more contrails than kerosene. But these contrails will behave differently because the particles comprising them will be larger.

That’s not the only issue. If you are going to introduce new fuels, they will need to be as safe as kerosene, and manufactured, stored and moved without increasing carbon in the atmosphere.

Even so, Alex is relatively confident that the problems are solvable. “I think zero-carbon-emission flight is possible, and not too far off. Perhaps even by the end of the decade.”

Find out more from our member, the University of Leeds: https://environment.leeds.ac.uk/see/staff/1492/dr-alex-rap