Why the Aviation Industry Can Be Sustainable
Leafing through a few articles on climate change, it is incredible how many of them quote Kermit the Frog.
It isn’t easy being green.
While that may be true, it is getting easier.
There has often been a lack of economic benefit or financial incentive to adopt sustainable technology. Alas, ‘going green’ has usually meant spending some as well.
Aviation, on the other hand, presents a compelling economic case for sustainability. As a former director of the International Air Transport Association (IATA) said in 2008, the 186 billion dollar fuel bill is an incentive to improve environmental performance.
Aviation comprises merely 2 percent of human-made greenhouse gases. Nonetheless, the industry needs to do better.
In 2017, civil aviation, emitted around 859 million tonnes of CO2. IATA has called for a cap on net aviation CO2 emissions from 2020 (carbon-neutral growth)
Here is how to make that happen.
The science of greenhouse gases, though highly politicized, is reasonably established. Carbon dioxide, methane and ozone (emitted from aircraft engines) are contributors to climate change.
Unlike vehicles on the road, aircraft engines deposit gases and particles into the upper atmosphere where they have a direct impact on atmospheric composition.
Since 1960, airline passenger traffic has grown by roughly 9% per year. Boeing has predicted air traffic will double every fifteen to twenty years, but there is a reason to believe that the growth curve will steepen.
While the trajectory of North American and European air traffic remains steady, commercial air travel in India and China is accelerating and will continue to do so in the coming years.
By introducing more fuel-efficient aircraft, developing sustainable fuel sources, and upgrading air traffic management systems, the industry is reducing its carbon footprint.
Aircraft today are quieter and more efficient than they were 30 or 40 years ago. The reasons are threefold: engines, aerodynamics and weight.
Engine technology forms the backbone of aircraft efficiency improvements. Through 3D printing of lighter components, the CFM LEAP-1A engines are approximately 15% more efficient than the CFM56 engines used on today’s Airbus 320 fleet. As many A320neo aircraft will harness the LEAP-1A, this will mean significant fuel savings on the refreshed design.
While the general shape of passenger aircraft has not changed in decades, a notable improvement to aerodynamics has been the addition of winglets.
Drag is an unavoidable by-product of lift. This aerodynamic trade-off impedes the forward motion of the aircraft meaning the engines must produce more thrust, and therefore, higher emissions.
Winglets reduce the induced drag produced during flight, which improves efficiency. Boeing’s new Split Scimitar winglets tack on an additional 2% of fuel savings over previous winglet designs.
The more an aircraft weighs, the higher the lift and thrust required to keep the airplane aloft. Carbon-fiber and composite materials feature extensively in the design of the Boeing 787 and Airbus A350 which reduces their weight considerably while preserving structural integrity.
On June 5, United Airlines launched its so-called Flight for the Planet. One objective was to demonstrate the use of sustainable aviation biofuel.
Biofuels are typically produced from plant oils and yield a lower carbon footprint. Mixing in biofuels means burning less petroleum-based jet fuel without sacrificing engine performance.
However, some of the most promising approaches to biofuel production leave considerable carbon footprints of their own. The process of cultivating crops to make fuel is not necessarily sustainable. Also, a substantial amount of land is required to grow the raw materials.
An alternative could be the refinement in the production of biofuels born from algae.
Algae is renewable, has a high oil yield per weight, and has a high crop yield per hectare. Unfortunately, the production cost is still much higher than petroleum-based fuel.
Improving Air Traffic Control
At peak efficiency, all aircraft would follow the most direct routes, point to point, with uninterrupted climbs and descents and no delay. However, the concept of free-flight will become increasingly challenging as traffic continues to grow.
The main barrier to flight efficiency is airspace capacity. One of the most effective ways to increase capacity is to build more runways, but this creates other environmental challenges. Apart from runway throughput rates, the reduction of in-trail spacing requirements through time-based separation and more integrative flow management practices can provide some benefit.
Oceanic and remote regions will see significant gains in efficiency. Satellite-based surveillance provided by Aireon will improve efficiency by a considerable margin. With air traffic controllers able to ‘see’ aircraft which are not visible to ground-based radar, separation on oceanic tracks can be reduced, allowing aircraft to climb to optimum altitudes as they cruise to the destination.
A 2016 study at Purdue University predicted that global adoption of space-based ADS-B surveillance would save airlines more than 110 million gallons of fuel by 2020.
As air navigation moves from ground-based to performance-based navigation (PBN), there is the potential to reduce the industry’s impact on the environment. By enabling the aircraft flight management system to fly an optimized descent profile, GPS approaches allow aircraft to burn less fuel, produce fewer emissions, and make less noise during descent.
These are just a few of the ways that flying is becoming greener and more efficient. The aviation industry can be sustainable, and this will happen as stakeholders come to accept that reducing greenhouse gas emissions makes sense not only for environmental reasons but for economic ones too.