There are 15,000 commercial airplanes in the world. “But in 20 years’ time there are forecast to be 15,000 more,” says Professor Ian Poll, director of the Cranfield School of Aeronautics. “Aviation in volume terms accounts for less than 5% of carbon dioxide emissions, but of all modes of transport it has the highest growth potential as a source of emissions.”
Poll is a member of Greener by Design, a forum set up by the aircraft industry to address the problem. Progress is being made but it is slow, he says. “Planes are expensive. Once a company buys one, it works it hard and keeps it in service for as long as possible. Some aircraft could be in service for 40 or 50 years.”
New aircraft, he points out, are more fuel-efficient than their predecessors, and aircraft engineers are constantly working on airframe and engine designs that will perform even more efficiently. This is not just out of concern for the environment; it makes sound economic sense. Fuel has to be lifted off the ground and carried, which means that improved fuel efficiency not only saves on the cost of the fuel, but also enables a greater payload to be carried.
“There’s a misconception that aviation exists to take people on exotic holidays,” Poll says. “The global view, though, is that it underpins wealth creation by moving cargo. Countries in the developing world, for example, depend on it for the transportation of goods to markets that would otherwise be unavailable to them.” According to the Air Transport Action Group, 40% of cargo is transported by air.
For Poll, the greatest challenge is to quantify exactly what is happening. “You have to distinguish between local emissions on the ground and high-altitude emissions. It’s possible that in the stratosphere, emissions of water vapour may be more serious than carbon dioxide in the way they affect the climate.”
If that were to prove to be the case, a switch to hydrogen-fuelled aircraft would be disastrous because they would produce more rather than less water vapour. “It’s a fiendishly complex problem, involving engineers, atmospheric physicists and climatologists,” Poll says.
One innovation that could reduce emissions is already in place. Most new planes are equipped with advanced communication, navigation and surveillance (CNS) systems that use satellite technology to allow planes to fly on the best possible route at the best possible altitude.
Manufacturers say CNS could improve overall fuel efficiency by between 8% and 18% and potentially reduce carbon dioxide emissions by 6% to 12%. The problem is that air traffic management is organised on national not global lines. The EU is working on a unified air traffic management system for its members, the Single European Sky, but it is not expected to be in place before 2020.
