Can sustainable aviation become a reality by 2050?

Can green aviation become a reality by the year 2050?

Air transportation significantly contributes to the global climate crisis. A report by the German Bundestag's Office of Technology Assessment (TAB) indicates that achieving a climate-friendly aviation industry through technical solutions could take a long time. A professor in sustainable tourism suggests that the industry itself holds more responsibility than politics.

The report suggests that a single technology is not enough to make aviation more environmentally friendly. Instead, a combination of technologies to explore various aspects is necessary. These include electric motors, sustainable fuels derived from wastes or biomass, green hydrogen, improved fuel efficiency, and more efficient aircraft designs.

In response to the report, Linnaeus University professor Stefan Gössling argues that the long-term goal of a nearly carbon-neutral aviation industry by 2050 is unattainable without drastic measures such as taxes or quotas. Research and development support could contribute, but the government and aviation industry share some accountability.

Researchers and analysts do not foresee quick solutions for either engines or alternative fuels. The report warns that development and approval times for new technology in aviation can be lengthy, with some technologies potentially requiring up to 15 years before going to market and another 30 years for widespread adoption.

Gössling identifies a weakness in the report's starting point, because aviation is set to have a less ambitious climate target than other industries, despite being one of the fastest growing sectors. He points out that people typically ignore that roughly one-third of the population, primarily frequent flyers, account for a large share of aviation-related emissions.

Globally, flight emissions could increase by 60% by 2050, according to the report. The aviation sector has already seen a surge in passenger numbers: from about 136 million in 2004 to around 227 million in 2019.

The report highlights the importance of reducing demands for flights. Possible measures include taxing long-distance flights, which generate the most emissions. "25 percent of the longest flights make up 70 percent of the emissions," Gössling explains.

According to the TAB, international aviation contributes somewhere between 3.5% and 5% to anthropogenic warming. In Europe, aviation accounts for approximately 4% of annual greenhouse gas emissions.

Apart from CO2 emissions, the report mentions non-CO2 effects such as soot particles, water vapor, sulfur and nitrogen oxide, which are produced by kerosene combustion and lead to the formation of contrails and cirrus clouds. While their overall climate impact remains difficult to assess due to limitations in current scientific understanding, they seem to play a significant role.

The TAB is also investigating alternatives to fossil fuel-based airplane fuels, such as sustainable aviation fuels (SAFs). These include both biofuels and e-fuels. E-fuels are chemically similar to fossil fuels like kerosene and are produced by converting water into hydrogen and then creating synthetic fuels using the power-to-liquid (PtL) process. However, the TAB highlights the need for an expansion of renewable energy resources to meet the energy demands of e-fuels.

While hydrogen fuel cells have been explored for a while, challenges remain, as hydrogen must be stored in large, insulated, heavy tanks at sub-253-degree temperatures onboard aircraft. Potential application in the short-term is therefore unlikely.

The TAB also emphasizes the need for a unified energy supply system at all airports to avoid costly parallel infrastructures. This is another reason why a fundamental shift to a new energy supply system is not expected within the next few years.

Gossling thinks that the TAB report still has too much optimism, even with the restrictions that have been put in place. There aren't even any operational e-fuel pilot plants yet - the report makes it seem like only needing enough electricity is the problem. "The technology is hard and difficult to scale up; if it works, it will require massive amounts of electricity that will be lacking in other electrification areas." On top of that, the cost of e-fuels would be so high that no airline would voluntarily use them.

The TAB sees a crucial role in optimizing flight operations initially. Improvements in aerodynamics, including smooth surfaces or curved wingtips, can cut down on fuel usage. Flight planning at the airline and air traffic management level can also reduce emissions. This would entail better airspace management to reduce detours, efficient flight procedures such as a slower descent, speed and flight profile optimization, and increased aircraft usage. A targeted taxation system could speed up these developments.

"A greater focus could be placed on the private aircraft sector, which is predominantly used for short-haul flights," suggests the Office of Technology Assessment. "In Germany, there has been a significant increase in flights, leading to a disproportionate share of harmful emissions."

Gossling also believes it's important to consider who contributes the most to emissions - a tiny group of frequent flyers who take more than ten flights per year. These individuals often fly in premium class, which creates emissions three to five times greater than in economy class.

"Restricting this group or making them fly more in economy would have a huge potential for reducing emissions," says Gossling. "Banning frequent flyer bonus programs that promote additional travel and upgrades would also be beneficial in this context."