The objective of this project was to demonstrate the field application and environmental benefits of non-toxic, biodegradable, low biochemical oxygen demand (BOD) alternatives to the current aircraft deicers (i.e., propylene glycols[PG]) used extensively by the Department of Defense (DoD). Qualification testing was conducted by independent laboratories prior to the field demonstration to verify that the new fluids were compatible for use on aircraft. The field demonstration measured the operational performance of the deicing fluid and quantified their environmental benefits. Environmental monitoring was conducted, and computer-based modeling of the runoff water quality was employed to allow further analysis, including predictions of environmental impact during a variety of weather conditions and side-by-side comparisons with other deicing fluid formulations.

Technology Description

The low BOD fluids contain a combination of non-toxic, biodegradable, water soluble, organic freezing point depressants and surfactants to meet all deicing fluid performance requirements and provide a tailorable biodegradation rate. By allowing a slow, complete degradation of the ingredients, the fluid will not dangerously deplete dissolved oxygen levels in receiving waters. In addition, fluids ingredients have reduced aquatic toxicities and are lower in cost as compared to current propylene glycol-based fluid formulations.

Demonstration Results

Significant results from this technology demonstration include:

  1. One deicing fluid manufacturer’s LBOD fluid foamed when applied to the aircraft and was considered unacceptable for Air Force use. The ground crew and the pilot were concerned they could not visually conclude the aircraft to be free of frozen contamination when inspecting through the foam. The manufacturer was given the opportunity to correct this problem by reformulation, but failed to do so within the allotted time.
  2. Another manufacturer’s deicing fluid was tested twice. The fluid foamed significantly during the first demonstration and also was deemed unsatisfactory for Air Force use. The fluid was reformulated for a second demonstration during which the fluid was observed to produce little foam and compared favorably with PG-based fluids, though the manufacturer has added a small amount of PG as part of this new formulation. The manufacturer claimed that the reformulated fluid still met the project’s objective of producing a lower cost and lower BOD fluid. In addition, this fluid contained no corrosion inhibitor that typically has been the source of hazardous chemicals in PG-based fluids. 
  3. LimnoTech performed the Niagara Falls Air Reserve Station (NFARS) local characterization of the fluid and concluded that NFARS had no serious environmental problems resulting from deicing fluid runoff. Moreover, they concluded that NFARS has significant room to increase future deicing events without falling out of environmental compliance. From their fluid comparison study, LimnoTech concluded that a lower BOD reduces disposal cost and reduces the risk of exceeding environmental permitting constraints. LimnoTech also developed and tested their Decision Support Tool which helps determine how best to remain in environmental compliance and estimate potential cost savings against one commercial airport and two Air Force bases.

Implementation Issues

The second manufacturer’s deicing fluid formulation left a slippery residue on the aircraft that did not evaporate or shear off in flight and reduced visual acuity on various aircraft transparencies. This residue prevented ground crews from performing their normal wing walk inspections following the flight without posing significant personal injury risk. As a result, both fluids failed to meet acceptable performance criteria.

The ultimate benefits to DoD for using low BOD deicing fluids include: (1) introduction of a low toxicity, low BOD alternative to current military deicing fluids and (2) elimination of the need to capture, contain, and treat deicing fluid runoff using expensive and operationally disruptive centralized deicing facilities. If all DoD operations switched to low BOD fluids (once acceptable formulations have been commercialized), savings could be realized. Moreover, the use of low BOD fluids would reduce the risk of Notices of Violation for non-compliance with existing storm water discharge permits.