Seeding jet exhaust with ice-nucleating particles could reduce aviation's climate impact
Renaud de RICHTER
Seeding jet exhaust with ice-nucleating particles could reduce aviation's climate impact
Credit: ACS ES&T Air (2025). DOI: 10.1021/acsestair.5c00241 If you look up at the sky on a clear day, chances are you'll notice thin, white clouds—also known as contrails—following behind airplanes.
The formation of these wispy ice clouds is a complex process that involves the mixing of hot exhaust gases with cold air. Depending on the atmospheric conditions, contrail ice particles can last for a short time or persist for several hours or longer. Before dissipating, they trap heat that would otherwise be released into space, contributing to climate change.
A study that looked at aviation's contribution to climate change between 2000 and 2018 concluded that contrails create 57% of the industry's warming impact, significantly more than the CO2 emissions from burning fuel.
Fangqun Yu, a senior research faculty at the University at Albany's Atmospheric Sciences Research Center, has developed an advanced model for simulating contrail formation and published several papers on the formation and properties of contrail ice particles.
In a new study, published this week in the journal ACS ES&T Air, Yu suggests that adding a tiny amount of ice-nucleating particles into aircraft engine exhaust could make contrails far less harmful by shortening their lifespan.
The innovative method helps create fewer but larger ice crystals in the contrail, causing it to fade more quickly and trap less heat.
"Ice-nucleating particles are tiny specks that act as seeds for ice crystals to form," said Yu. "Because they can trigger ice formation at warmer temperatures, they take up water vapor in the plane exhaust earlier and grow crystals large enough for gravity to draw them out of the atmosphere. That means shorter-lived contrails, ultimately reducing their warming effect to a very small level."
Curbing contrails in the sky
Yu's technique proposes adding ice-nucleating materials, such as silver iodide, bismuth triiodide, or other suitable materials that can freeze efficiently and have low environmental impacts, into the aircraft exhaust during the flight.
To test the method under real-world conditions, Yu and his research team used the Aerosol and Contrail Microphysics model, a simulation tool that tracks what happens inside an aircraft exhaust plume in the seconds after it leaves the engine.
The results of their method showed as much as a 50-fold reduction in the number of contrail ice crystals formed.
"The amount of ice-nucleating material needed is very small, comparable to, or even less than, the lubrication oil planes typically consume," Yu said. "Also because the application would happen high in the atmosphere during flights, and in tiny amounts, our early modeling shows that the material reaching the ground would be negligible. Still, we need to further examine how these added particles might influence natural ice-nucleating particles, cloud formation and precipitation."
More sustainable aviation
Yu has studied the microphysics of particles in the atmosphere (including contrail formation) and their impact on the environment for more than two decades.
While more research and testing are needed before Yu's technique can be tested on airplanes, he believes the early results are promising.
"In the future, we hope to test and refine our proposed method through controlled laboratory experiments and field measurements," Yu said. "We will also carry out more simulations to further assess its efficacy and potential environmental impacts."
In addition to this work, Yu is also currently partnering with a team at GE Research to help better understand the impact of clean aviation fuels and new engine technologies on contrail formation.
More information: Fangqun Yu, Toward Sustainable Aviation: Minimizing Aircraft Contrail Ice Particle Formation and Climate Effects by Controlled Seeding of Ice Nuclei Particles, ACS ES&T Air (2025). DOI: 10.1021/acsestair.5c00241