Your car’s antifreeze may have started as deicing fluid for airplanes

SALT LAKE CITY — The Salt Lake City International Airport is the only one in the country that recycles deicing fluid, or propylene glycol, from start to finish.

Deicing Fluid Reclamation Plant Manager Kelly Clark said there are three parts to recycling the glycol: pretreatment, evaporation, and distillation.

“Other airports like Pittsburgh, Minneapolis/St. Paul and Detroit do one or two of the steps and then have to ship the partially recycled glycol to Romulus, Michigan to complete the process.”

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Getting the glycol from where planes are deiced on the tarmac to the plant requires a lot of infrastructure underneath the airport.

“[There are] six underground pump stations, and five miles of HDPE pipe leading from the deicing pads to the recycling plant north of the airport,” said Clark. “All the fluid ends up in 3-storage lagoons, each of which can hold 3.4 million gallons of water and used deicing fluid.”

The process starts near the runways at the airport

During cold and stormy weather, airlines need to make sure snow and ice don’t inhibit planes’ ability to take off.

Planes are directed to one of three deicing pads located around the runways. Each pad can hold either six or eight airplanes. A fourth deicing pad has been built but is not open for use yet.

Randy Hubbell, the general manager for Integrated Deicing Services, said four deicing trucks will surround an aircraft and spray it down.

“We have two different types of propylene glycol,” Hubbell said. “The orange-colored glycol is called Type 1. It is used to melt snow and ice. Then we can also spray Type 4, which is green, on top of the Type 1. This prevents snow or ice adhering to the plane for about 30 minutes while the plane taxis and then climbs through possible icing conditions in clouds.”

“Most of the glycol does stick to the aircraft,” said Clark. “But some of it will fall to the ground, which is why there are drains and pipes to carry the fluid away.”

Keeping Utah’s waterways clean

The Reclamation Plant began operating in 2001. Before then, all the excess deicing fluid was collected and then slowly released to the water treatment plant in Salt Lake City.

“They couldn’t send the entire amount of glycol into the system all at once because it would kill the microbes designed to filter the water,” said Clark. “That’s why the underground infrastructure was installed starting in 1998. The city knew the airport was growing, and they planned to have the recycling plant as part of their operations so more and more glycol wouldn’t be sent into the Jordan River or Great Salt Lake.”

“Any moisture, like snow or rain, collected with the deicing fluid is separated from the glycol and used in the recycling process so they don’t need to pull more water from the system,” Clark said.

A lot of glycol is used each winter

Hubbell said that, on average, an aircraft needs 50 gallons of deicing fluid.

“But during the inversion earlier this month, we used 13,000 gallons of fluid in one day.”

Hubbell said the inversion creates ice crystals that coat the plane and are hard to see.

“That’s really, really hard on us. We went through a lot of fluid during that stretch of the inversion.”

“The winter of 2022-2023 was the worst,” said Hubbell. “I had to order over a million gallons of deicing fluid.”

He said, on average, he orders 600,000 gallons each year.

All that glycol is stored in temperature-controlled storage tanks at the airport. The deicing trucks can pull up to pumps to fill up. They need to do this multiple times a day during winter weather.

Hubbell said he has more storage facilities across the Wasatch Front, which can be delivered to the airport within eight hours if they are using a lot of glycol on a snowy day.

However, they are not temperature-controlled.

Hubbell said it isn’t good for glycol to bake in hot temperatures. So he starts reducing the amount of glycol he orders starting in February.

Recycling starts each January until the overflow is gone

While orders for new glycol are reduced starting the first of each year, Clark said that’s when his work begins.

“We start pulling the used glycol out of our storage lagoons in January. The process runs 24/7 until all the glycol has been recycled — usually in September or October,” said Clark.

“Once all the water and impurities have been pulled out of the used glycol, we resell it to third parties. It is then put in anti-freeze, all types of paint, and sprayed on aggregate to keep it from freezing during winter months,” Clark said.

The used propylene glycol has not been approved to be sprayed back on airplanes.

“There are a lot of tests that still have to be done on the recycled fluid and then the FAA would have to approve it,” said Hubbell.

Both Clark and Hubbell said they would like to have the used glycol make it back for use on airplanes. That is, if it is safe and effective. It would also be less expensive in the long run.

“New glycol costs $8.00 a gallon, while the recycled glycol sells for $4.00 a gallon,” said Clark.

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