Deicing and anti-icing fluids play a critical role in providing safe, uninterrupted and timely air travel during inclement winter weather.
All aircraft must comply with the Federal Aviation Administration (“FAA”) “Clean Aircraft Concept,” which prohibits takeoff with frost, ice, or snow (contamination) adhering to the critical surfaces of an airplane. The buildup of ice and snow on critical surfaces of an aircraft decreases lift and can lead to disastrous results.
Therefore, deicing and anti-icing fluids are regulated and monitored on a global basis, and have to undergo stringent testing and long approval processes to ensure product safety
Typically, an aircraft is sprayed with Type I deicing fluid, which provides for immediate and temporary removal of any accumulated snow or ice. After Type I is applied, the aircraft can then be sprayed with a Type IV anti-icing fluid to prevent re-accumulation of precipitation before takeoff.
History of Deicing/Anti-icing Fluid
Changing demands in the industry have spurred the evolution of deicing fluid and introduction of new products.
Starting in the 1950s, deicing fluids were made using ethylene glycol (EG), the same chemical used in early versions of automotive antifreezes. In the 1980s, the toxicity of EG led fluid suppliers to look for a safer alternative to replace EG in deicing fluids. Propylene Glycol (PG) was chosen since it is very similar to EG, but PG is considered GRAS (Generally Recognized As Safe) by the FDA, where as EG is toxic to mammals.
Then came the introduction of PG-based type IV fluid, designed to have longer holdover times over the Type II fluids being used at the time. Holdover time is the estimated time anti-icing fluid will prevent the formation of frozen contamination on the protected surfaces of an aircraft. The use of type IV fluids led to significant environmental benefits and cost reductions for airlines since fewer aircraft had to return to the gate to be re-deiced, and therefore less deicing fluid was used.
Type I deicing fluids remained relatively unchanged for a decade until their aquatic toxicity (adverse effects on marine life) became a concern in the late 1990s. This led to the re-formulation of the additive packages for deicing fluids, and the removal of environmentally unfriendly chemicals, such as triazoles.
In 2008, the EPA proposed technology-based effluent limitation guidelines (ELG’s) and new source performance standards under the Clean Water Act for discharges from airport deicing operations. These requirements would apply to wastewater associated with the deicing of aircraft and airfield pavement at primary commercial airports, and will likely focus on COD limitation. COD, or chemical oxygen demand, can be described as the amount of oxygen required for the total chemical breakdown of organic substances in water. Although many airports recover spent deicing fluid, some is discharged into waterways where it breaks down and pulls oxygen from the water. Even though these proposed ELGs are still in the commentary phase, placing stricter standards on deicing related discharges will be a significant challenge to the entire airline industry.
EcoFlo Enters the Deicing Market
To assist airlines and airports in meeting more stringent regulation, Octagon Process has produced a reduced COD fluid called, EcoFlo. EcoFlo is a hybrid PG and glycerin based Type I deicing fluid that lowers biological oxygen demand (BOD5) by 35 percent and COD by 25 percent over other commercially available PG-based fluids. EcoFlo is ideal for airports that will be forced to comply with strict wastewater discharge permits as it will reduce municipal wastewater costs by decreasing BOD5 & COD.
There are many challenges to overcome when introducing a new fluid into the deicer market. After a fluid passes all of the certification tests and appears on the FAA qualified fluids list, each airline must go through its process of approving the fluid for use. In many cases, this includes a spray test where the new fluid is applied to an aircraft or test surface, and its tendency to foam, surface wetting and slipperiness are evaluated. There are also operational disruptions and costs that must be considered when switching to a new fluid.