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Keeping Airports Operational in Inclement Weather: A Case for Glycol Recycling

Airports depend on fuel, people and planes to remain functional, but once the temperature drops and a winter storm moves in, glycol becomes a key component for reliable operations. Glycol, used as deicing fluid, is sprayed on aircraft to remove frost, snow and ice from the wings and protect against refreezing before takeoff. Airlines have tried numerous different methods for handling deicing of aircraft over the years, from drive-through induction heaters to fixed boom operations. The solution settled upon almost always sends with a person in a vehicle spraying aircraft with a glycol/water mixture.


While it’s a bit of a nuisance and managerial headache for the airlines to deal with staffing and application of the fluids, the real problem happens when deicing fluid hits the ground. Whether it’s at a deicing pad or next to the gate, the ability to capture and control spent glycol is a huge issue that airports and airlines have been dealing with for decades. Propylene glycol, the main chemical in deicing fluid used in the U.S., is generally considered safe for human consumption — but that’s not the case for wildlife.

U.S. Environmental Protection Agency regulations have specific requirements for the capture and treatment of deicing fluids used at airports, including more stringent guidelines for larger airports. While most airports have focused attention on capture and pretreatment of glycol effluent, there might be a better solution that often gets overlooked: Technology advances have allowed glycol effluent to be recycled where it is typically treated as a waste, turning it back into a readily available deicing fluid that can be resprayed on aircraft.

 

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While it’s a bit of a nuisance and managerial headache for the airlines to deal with staffing and application of the fluids, the real problem happens when deicing fluid hits the ground. Whether it’s at a deicing pad or next to the gate, the ability to capture and control spent glycol is a huge issue that airports and airlines have been dealing with for decades. Propylene glycol, the main chemical in deicing fluid used in the U.S., is generally considered safe for human consumption — but that’s not the case for wildlife.

U.S. Environmental Protection Agency regulations have specific requirements for the capture and treatment of deicing fluids used at airports, including more stringent guidelines for larger airports. While most airports have focused attention on capture and pretreatment of glycol effluent, there might be a better solution that often gets overlooked: Technology advances have allowed glycol effluent to be recycled where it is typically treated as a waste, turning it back into a readily available deicing fluid that can be resprayed on aircraft.

Hidden Costs and Opportunities

Deicing consortiums are not commonplace across the U.S.; instead, the burden of dealing with spent deicing fluid often falls upon an airport’s environmental staff. The easiest path of management often leads to the construction of deicing pads and dedicated pond systems to limit glycol effluent from being mixed with the remaining airport stormwater.

The process largely works, but it comes at a great cost. The impact isn’t just in the capital costs to build deicing pads and ponds or the tower and personnel to control access to the pads. It can impact flight operations, when many aircraft are being funneled into a small set of pads that are quickly overwhelmed when a heavy precipitation event moves in.

Even if glycol-laden stormwater could effectively be captured, how quickly can it be discharged away from the airport? Aging infrastructure is not merely a roads and bridge problem; it also propagates downstream of the airports into the wastewater treatment facilities. At these facilities, bacteria are used to treat the glycol, but due to the unpredictable nature of deicing events treatment facilities have turned to limiting discharge rates as a method to minimize overrun and production of bacteria at facilities. This has resulted in the need for larger holding systems at airports, which generally have space constraints, or the need for some sort of airport pretreatment facility. So not only does the airport have to pay to send winter stormwater to a wastewater treatment plant, but also for costly pretreatment and on-airport storage.

Then there’s the actual cost of the raw deicing fluids the airlines use. Like almost everything related to the U.S. supply chain, the ability of airlines to source and purchase deicing fluids has been impacted by the pandemic. This is due to the lack of truckers available to transport the fluid from manufacturers to the airport and even shutdowns at production facilities. All of this has caused glycol costs to more than double in the last five years.

As you start to add up all these costs, the payback on building out a glycol recycling facility with the ability to treat glycol on-site at an airport starts to become increasingly appealing. The potential for both airports and airlines to recognize significant savings in a short period of time becomes apparent.

A More Sustainable Solution

With most airlines and airports driving toward carbon neutrality, glycol recycling benefits are becoming more attractive. When glycol-laden stormwater is sent to a wastewater treatment plant for biological degradation, there’s a substantial amount of carbon dioxide created as part of the process. Then, production of new glycol, along with the distribution network needed for delivery to airports, creates a carbon footprint that also must be accounted for.

The overall carbon cost of new glycol is estimated to be more than 1,350 metric tons per 100,000 gallons of glycol used. This quickly adds up across an airline’s entire network and at larger hub airports across the northern part of the U.S. and throughout Canada. By contrast, on-site glycol recycling, especially if any necessary energy is sourced from renewable sources like solar or wind, can be under 2 metric tons of carbon for the same quantity of glycol. A reduction of up to 99.9% of carbon dioxide can be made by recycling glycol on-site at an airport.

With all of the benefits, from a more viable supply chain to lower costs to minimized environmental impact, now is the time for airlines and airports to take a serious look at glycol recycling.

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2022 Special Report


Author

Skye Coleman, PE

Aviation Ramp Services Project Manager