The expression “flight shame” (from the Swedish flygskam) has become a popular term since the young activist Greta Thunberg pushed for the option of renouncing air travel as a way to fight against climate change. The movement against air travel seems to have already left a tangible mark: published reports speak of a decline in the number of short-haul flight passengers in Europe, along with an increase in train travel. But given that it is difficult to imagine the survival of our globalised world without air transport, would it be possible to substantially reduce its environmental impact?
In 2018, commercial aviation was responsible for 2.4% of CO2 emissions from fossil fuels, according to the International Council for Clean Transport. But its growth rate is rapid: in the previous five years these emissions increased by 32%, and if this trend continues, they could triple by 2050.
Despite this, technology is trying to ensure that the volume of emissions does not increase in parallel with the growth of air traffic. Today’s aircraft emit 80% less CO2 than their predecessors, and even half as much as in 1990, and new aircraft models have increased fuel efficiency by 15% over their predecessors. However, this is not enough, which is why so many technological efforts are now being made to take these emissions cuts much further.
Reduce fuel consumption
More efficient engines or lighter materials are the targets of current research, as are improvements in aircraft design that aim to save fuel. These innovations can be seen today in so-called winglet devices, such as the bent ends of wings, which decrease air resistance. But perhaps in the future we will see much more radical alterations in the shapes of aircraft. An example of this is the Flying-V, a project being developed by the Delft University of Technology (Netherlands) whose blended wing/body design integrates the fuselage and wings in such a way that there is no clear delimitation between the two.
The Flying-V, which is supported by the Dutch airline KLM, has the potential to reduce fuel consumption by 20%. But as to whether or when we will see these devices traversing our skies, engineer Roelof Vos, the project manager, explains to OpenMind that there is a long runway from the laboratory to take-off. “Together with industry partners we are currently working on a roadmap of research that needs to be performed on this new configuration.” As Vos points out, not only must the 20% savings be demonstrated, but also that the aircraft complies with the certification regulations for large passenger aircraft, or what modifications must be made to the design to obtain compliance. And finally, he concludes, “it is up to the management of large airplane manufacturers to decide whether to produce and sell this aircraft.”
However, Vos admits, “if we are serious about reducing aviation’s contribution to global warming, reducing the energy consumption of these vehicles is only part of the solution.” The engineer points out that another potential area for development is that of alternative fuels to the current ones, such as liquefied natural gas, hydrogen or synthetic kerosene. “However, we have some steep challenges with respect to weight, volume and cost of these alternative fuels, let alone the impact they have on global warming when combusted at high altitudes.” Another current proposal is the use of biofuels, but these are not without their problems either: some experts have warned that the carbon footprint due to the use of land for the production of crops intended for these green fuels cancels out the benefit obtained from their lower CO2 generation.
The condensation trails
To make matters worse, the climate impact of aviation is not just limited to CO2 either. Scientists have drawn attention to the condensation trails (contrails), the white stripes that we can sometimes see behind aircraft and which are due to the formation of ice crystals around the particles in the exhaust. These trails and the cirrus clouds they form act like natural clouds, retaining the infrared light from the sun that contributes to global warming. This effect is less persistent than that of CO2 emissions —lasting for decades rather than centuries— but in the short term it has a greater impact on the climate. Solutions have been proposed: a recent study suggests that if just 1.7% of aircraft were to fly at 2,000 feet below normal altitude, the impact of contrails would be reduced by 59% without a significant increase in fuel consumption.
Despite all this, some experts are sceptical about what these efforts can achieve. In 2016, the UN’s International Civil Aviation Organization promoted the Carbon Offset and Reduction Scheme for International Aviation (CORSIA), which encourages the purchase of carbon offsets and the use of alternative fuels, so that from 2020 CO2 emissions from aviation will not grow. But the opinion of sustainable transport and tourism expert Stefan Gössling of Sweden’s Linnaeus University is clear: “I believe everyone should have understood that the CORSIA scheme will not work. It only covers a share of CO2 emissions, ignores non-CO2 emissions, is voluntary and focuses on cheap offsets,” he tells OpenMind.
The only way forward, suggests Gössling, is to enact climate policies for aviation: “We need a significant tax on carbon, in the form of an emission levy that air travellers have to pay.” To this, he says, should be added other measures concerning subsidies and the establishment of mandatory quotas for the use of sustainable alternative fuels, preferably synthetic ones. “Without governance at the national level, we will never see a climatically sustainable aviation regime,” he concludes.
The only way forward, suggests Gössling, is to enact climate policies for aviation: “We need a significant tax on carbon, in the form of an emission levy that air travellers have to pay.” To this, he says, should be added other measures concerning subsidies and the establishment of mandatory quotas for the use of sustainable alternative fuels, preferably synthetic ones. “Without governance at the national level, we will never see a climatically sustainable aviation regime,” he concludes.
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