The reason that we don’t often see many aircraft condensation trails over Mauritius is that the great majority of aircraft movements around and over our island are “arrivals” or “departures”, that is to say the aircraft are at a fairly low altitude. Contrails, on the other hand, occur typically at aircraft cruising altitudes several miles above the earth’s surface, and It is the combination of the low temperatures that exist between 25,000 and 40,000 feet , and the presence of water droplets and mainly carbon-dioxide based impurities in engine exhausts, that allows ice particles to form and show us visible contrails. Depending on temperature changes and the action of the upper winds these lines in the sky can disappear quite quickly or “hang around” for several hours. They may also spread out, in effect making the sky more cloudy. The point is however that, whether visible contrails form or not, the exhaust from current aircraft engines is contaminating our atmosphere and contributing to the global warming situation that we all (with the exception of one would-be ostrich in America) recognize as a recipe for a future disaster.
At this point we need to see Contrails not just as pretty geometrical patterns over our heads, but as indicators of an unwanted contributor to worldwide greenhouse gas emission.
It is of course well-known that Aviation, responsible for 2% of the world’s CO2 emissions, is a minor contributor compared with the 27% due to all other forms of transportation. The other main sources are Electricity Generation (due to use of mainly fossil fuels), Industry, Commercial & Residential and Agriculture, together responsible for 71% of our problem. But Aviation’s 2% contribution, expected to grow with the development of the industry to 3% by 2050 if we do nothing about it, stands as too high: It is as much as the emission contribution of a whole country the size of Canada and must therefore be reduced.
Aviation is therefore very much included in the considerations of the Paris Climate Change Agreement of 2015. In meeting this challenge the major aircraft manufacturers such as Boeing and Airbus,together with jet engine makers like Rolls Royce, have already invested heavily in aircraft and engine design improvements, and it is well known that the resultant fuel efficiency of state-of-the-art airliners such as the Boeing B787 or the Airbus A350 ( the choice of Air Mauritius) is a step-change away from that of the designs of the past. Older MK customers may recall the fuel-guzzling “B747 SP”, the mainstay of the airline’s longhaul fleet in the late ‘80s /early ‘90 s, which consumed up to 10 tonnes of kerosene per hour!
But in an expanding industry a reduction in fuel required per flight is not a sufficient solution. Transport on the ground is slowly being transformed by the arrival of hybrid and all-electric cars, and it is well known that both the French and British governments intend that there shall be no petrol or diesel cars on their roads by 2040. The aviation industry will try to match this eventually, although not immediately, by going all-electric. (More battery development is needed). The feasible first step is to reduce the amount of fossil-based kerosene by using mixtures with bio-fuels, and this process has already started. With the support and approval of the International Air Transport Association (IATA), and observing stringent safety norms, several Airlines including KLM, Lufthansa and Finnair started making biofuelled commercial flights in 2011. In the Finnair case it is reported that both engines (of a twin-engined aircraft) used a 50% bio (waste vegetable oil) /.50% kerosene mixture . Since then and to date several others have followed, most using waste vegetable oil or oil from the Jatropha or Camelina plants. NASA has determined meanwhile that a 50% aviation biofuel mixture can cut air pollution caused by air traffic by 50-70%. While we progress to an eventual zero fossil fuel aviation industry in an all-electric sky, Contrail-watchers and photographers will soon be out of job!
Of course there are still hurdles, the first being cost: With oil barrel prices as low as they are now environmental considerations may be deliberately overlooked by airline managers in pursuit of that all-important profitable bottom line. The efficiency of Kerosene-type fuels is of a high order. Second and also important is agricultural productivity and the preservation of CO2-swallowing forests… if land is used more extensively to grow Camelina and Jatropha for example, the balance with alternative land use must be maintained.
”You can’t win” ?
Yes we can! But nothing worthwhile is easy to achieve, is it?
Dick Twomey, in Mauritius’ WEEKLY magazine, 05-11 October 2017