Aircraft anti- and de-icing

Owing to the cold and humid winter conditions of Finland, it is common that snow and ice builds up on the surface of the aircraft. For flight-safety reasons, they must be removed, as they can disrupt the performance and controllability of the aircraft.

Moreover, pieces of ice separating from the aircraft surface may be ingested into the engine and cause a failure. De-icing treatment prevents snow build-ups on the aircraft surface and the formation of an ice layer on it during the take-off run and take-off. At cruising altitude, the humidity and air pressure are low enough that the ice-formation is negligible. Aircrafts are equipped with electronic or mechanical de-icing mechanisms in case of ice-formation during the flight.

Glycol consumes oxygen

In Finland propylene glycol based fluids are used for both de- and anti-icing. During their preparation, 20-50% water and 1-2% additives are added to the de-icing fluids. Propylene glycol (C3H6(OH)2) is a highly water soluble and quickly biodegradable substance also used widely is the cosmetics industry. Its greatest hazards are the depletion of oxygen in waters, caused by its degradation and the unpleasant odour of the degradation products. Propylene glycol solution requires a relatively large amount of oxygen (0.8-1.3 g O2/ 1 gram of solution), depending on the consistency. In conditions, where only a little oxygen is dissolved in water, the degradation slows down.

Mitigating the impacts

There is currently no environmentally friendlier alternative for using propylene glycol. The environmental impacts caused by glycol can, however, be mitigated through improved working methods requiring less chemicals and through introducing alternative methods or purifying glycol-contaminated runoffs. The glycol-contaminated runoffs collected at Helsinki-Vantaa airport are processed by the municipal water treatment works. Glycol fluids can also be recycled, a practice that some airports abroad have adopted. The wider introduction of recycling glycol fluids has been hindered by the costs and the fact that certification criteria for de-icing fluids are not applicable for recycled fluids.