A commercial aircraft takes off from Geneva Airport in Switzerland after sunset.


From the historic flight of the Wright brothers in 1903 to the development of supersonic aircraft, the history of aviation has been driven by technology and ambition.

Even now, as the 21st century advances, the industry continues to show its appetite for innovation and radical design.

Last September, for example, a hydrogen fuel cell aircraft capable of carrying passengers made its maiden flight over England.

That same month, Airbus also released details of three hydrogen-powered concept aircraft, with the European aerospace giant claiming they could enter service by 2035.

United Airlines recently announced that it had signed a commercial agreement to purchase aircraft from a company called Boom Supersonic.

In a statement, United said the Overture aircraft – which has yet to be built – will be “optimized to run on 100% sustainable aviation fuel.”

All of this is linked by a focus on technologies to reduce the environmental footprint of aviation. This is a huge task, even if the number of flights has plummeted over the past year due to the coronavirus pandemic.

According to the International Energy Agency, carbon dioxide emissions from aviation have “increased rapidly over the past two decades,” reaching almost 1 gigaton in 2019. This corresponds to “around 2.8% of global CO2 emissions from burning fossil fuels”. “

Elsewhere, the World Wildlife Fund describes aviation as “one of the fastest growing sources of greenhouse gas emissions that are driving global climate change”. It adds that air travel “is currently the most carbon-intensive activity a human can do”.

A variety of solutions

Iain Gray is the Director of Aerospace at Cranfield University, UK. In a phone interview with CNBC, he described zero carbon emissions as “the top priority” for the industry and tried to highlight the importance of developing a range of solutions to address this challenge.

“The really big technology driver is the drive system,” he explained, “but that doesn’t change the importance of new technologies around … new lightweight materials, improved carbon composites and the systems themselves.”

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Gray took his point further and provided an example of why innovations in aircraft flying overhead should not be viewed in isolation.

“There is a lot of effort going into reducing the weight of an aircraft so that it only has to spend half an hour circumnavigating an airport,” he said.

“The entire interaction of air traffic management with the aircraft itself is a … very important development and new technologies for airspace management are constantly emerging.”

The power of the drive

In addition to the development of hydrogen fuel cell aircraft, there has also been a lot of discussion in recent years about electric propulsion, with companies such as Volocopter and Lilium eVTOL developing or electrically vertical take-off and landing aircraft.

The key to such technologies are the types of trips to which they can be applied.

“If you look at hydrogen fuel cells and batteries, it really is very geared towards the smaller planes, that is the range of less than 1,000 kilometers,” said Iain Gray of Cranfield.

“You have to do this in a carbon-free way, no question about it,” he added. “Will that have a major impact on the total CO2 contribution made by aviation? No.”

“We have to focus on long-haul flights, especially flights over 1,000 kilometers, flights over 3,000 kilometers.”

Fuel change

This focus on long-haul travel will be important in the years to come, even if they only make up a small proportion of flights.

According to a sustainability briefing published by Eurocontrol at the beginning of the year, “around 6% of flights from European airports in 2020 were long-haul flights” with a length of over 4,000 kilometers.

The intergovernmental organization went on to say that “more than half of the CO2 emissions from European aviation come from this tiny fraction of the total number of flights”.

This point of view was shared by Jo Dardenne, Aviation Manager at Transport & Environment, a campaign group based in Brussels.

“We shouldn’t forget that most of the air traffic emissions are associated with long-haul flights because you fly longer and fly higher,” she told CNBC.

“All in all, you are producing more CO2 … these long-haul flights can only be decarbonised by replacing the kerosene used.”

Sustainable aviation fuel could play an important role in the future, especially on these longer journeys.

Although the European Aviation Safety Agency says that there is “no single internationally agreed definition” for sustainable aviation fuel, the overarching idea is that it can be used to reduce emissions from an aircraft.

For its part, Airbus describes SAF as “made from renewable raw materials”. She adds that the most common raw materials are based on crops or used cooking oil and animal fat.

“Right now, the big challenges for sustainable aviation fuel are getting it in the right quantities, at the right cost,” said Cranfield’s Gray.

The origin of the raw materials used for SAF is also important, he explained. “If you … transport fuel with raw materials from the other side of the planet around the world to produce sustainable aviation fuel, is that really sustainable?”

“The biggest effort right now is how to produce sustainable aviation fuels the … green way.” This could be fuel from waste or local resources, Gray added.

An interesting type of fuel is e-kerosene, which is also known as synthetic kerosene. According to a briefing published by T&E in February, e-kerosene is made by combining carbon dioxide and hydrogen.

“The great thing about it is that it can fall into these jets without modifying the aircraft’s engine and technology,” Dardenne said.

“It’s a carbon neutral fuel that is easy to fill,” she added. “The only problem is that it’s very expensive.”

Cutting costs will indeed be crucial in the years to come, but organizations like T&E are keen to highlight the potential environmental benefits of using them.

If the CO2 is “extracted from the atmosphere” and hydrogen is produced with renewable energies, says T&E, “the combustion of e-kerosene, apart from some residual emissions, will be almost CO2-neutral.”

The future

As technology advances, the world must also enact rules and regulations that focus on the environmental footprint of air travel.

Examples of these efforts are the Carbon Offsetting and Reduction Scheme for International Aviation and the European Union, which has included carbon dioxide emissions from aviation in its emissions trading system since 2012.

In her interview with CNBC, Dardenne from T&E stressed the importance of “proper regulation”.

She said, “If you effectively price emissions and pollution and then mandate the use of clean technology, you are sending the right signals to private and public investors to invest in them.”

“The clearer the regulatory framework, the more certainty you can give the market that these technologies have a future,” she added.

“And that will actually bring added value, financial added value and ecological added value.”

Looking at the bigger picture, she went on to explain that “proper regulation” would be through effective carbon pricing and fuel legislation, describing the latter as an obligation to use cleaner fuels. These are, she argued, “the cornerstone of an effective decarbonisation strategy for aviation”.