Is Sustainable, Guilt-Free Air Travel on the Horizon?

The aviation industry is facing a significant challenge in transitioning to a more environmentally friendly future. Despite committing to reducing its planet-warming emissions by 2050, it is currently not on track to meet this goal due to the lack of clear solutions. While aviation currently only accounts for about 2.5% of global carbon emissions, its overall climate impact is greater due to the release of other greenhouse gases and the creation of heat-trapping condensation trails from jet engines. Additionally, the demand for air travel is expected to continue to grow, with the global commercial airplane fleet projected to double in size by 2042 according to Boeing.

"According to Gary Crichlow, head of commercial analysts at AviationValues, the problem with air travel is that it's not only growing, but also very difficult to decarbonize. This means it's expected to account for a larger share of emissions as other industries reduce their emissions faster. The heart of the decarbonization problem is the lack of a non-carbon energy source that can match the energy density of jet fuel at the scale, cost, safety, and reliability required for global aviation.

Medium- and long-haul flights are the main contributors, responsible for 73% of aviation's carbon emissions. The Aviation Environment Federation, a UK nonprofit group that monitors aviation's environmental impact, states that a return flight from London to Bangkok can produce more emissions than you'd save by following a vegan diet for a year."

Searching for SAF

With the ongoing climate crisis, more and more people are rethinking their travel plans, opting for less harmful journeys closer to their homes. However, the question remains: when will we have access to a truly sustainable, "guilt-free" long-haul flight?

The Airbus ZEROe fuel cell engine demonstrator has been used to test a hydrogen-powered engine.

Airbus aims to achieve net zero by 2050 by significantly reducing its planet-warming pollution and implementing strategies to remove any remaining emissions from the atmosphere. So, how does the company intend to accomplish this goal?

Professor Gökçin Çınar of the University of Michigan states that the technologies under consideration are primarily sustainable aviation fuels, which are currently being used at a minimal level, as well as two more advanced options: electrification and hydrogen.

Sustainable aviation fuel, or SAF, is an alternative jet fuel that can reduce carbon emissions by up to 80%. It has a low carbon footprint as it is typically made from plants that have absorbed carbon dioxide (CO2) during their lifetime. When burned, the CO2 is released back into the atmosphere, whereas traditional jet fuel kerosene made from fossil fuels releases CO2 that had previously been stored.

SAF can originate from various sources, such as algae, hydrogen, and directly capturing CO2 from the air. However, in the near future, the most potential SAF comes from waste, particularly used cooking oils, according to Çınar.

A Virgin Atlantic Boeing 787-9 Dreamliner, with registration G-VWHO, is photographed landing at London Heathrow Airport in the United Kingdom. The photo credit goes to Markus Mainka/imageBROKER/Shutterstock.

A plane will be flying from London to New York using 100% Sustainable Aviation Fuel. Experts warn that this isn't a permanent solution. Only a small fraction, about 0.1%, of current jet fuel is SAF. The International Air Transport Association (IATA) hopes to reduce aviation's climate impact by 65% by 2050, but the slow adoption of SAF is due to its higher cost, which is 1.5 to 6 times more expensive than regular jet fuel. Lowering the price will require increased production and political pressure, both of which could take years.

Ryan Faucett, director of environmental sustainability at Boeing, explains that while they are forming partnerships and trying to influence policy, the current regulations limit sustainable aviation fuel (SAF) to a maximum blend of 50%. He highlights that using SAF up to 50% has been proven to be a drop-in fuel with no required changes. The focus now is on exploring higher SAF blends, with the potential outcomes being minimal changes needed or updates to certain components.

Hoping for hydrogen

Boeing and Airbus, the dominant players in the commercial airplane market with a combined market share of over 90%, have confirmed to CNN that all their new aircraft will be compatible with 100% SAF by 2030. In the meantime, testing of the available technology is ongoing. The first transatlantic flight powered by 100% SAF was successfully operated by Virgin Atlantic on November 28, flying from London to New York.

The world's largest passenger plane, the A380, has been used to test SAF.

Alexandre Doumenjou from Master Films, courtesy of Airbus, explains that while Sustainable Aviation Fuel (SAF) is used to power aircraft, it still produces CO2 emissions similar to regular jet fuel. The most promising technology for emissions-free flights appears to be hydrogen, a clean-burning fuel that would reduce pollution from jet exhaust, though it is not completely climate-friendly at this point.

Andreas Schäfer, a professor at University College London specializing in energy and transport, predicts that smaller hydrogen aircraft could be operational by the 2030s. Larger aircraft, however, may not be introduced until 2040 or later.

Meanwhile, companies such as Cranfield Aerospace are already working on retrofitting existing aircraft with hydrogen fuel cell technology. For example, Cranfield Aerospace plans to conduct test flights on its converted Britten-Norman Islander monoplane as early as 2024.

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Redesigning planes for long-haul journeys will require significant progress in tank technology. Most jet fuel is currently stored in the wings, but with liquid hydrogen being stored at extremely cold temperatures, a new storage tank with a small surface area is needed to minimize heat loss and evaporation. Otherwise, the pressure build-up could cause the entire wing to explode.

This entails that tanks will need to be placed in the fuselage, posing technical challenges. However, experts say that once this problem is solved, hydrogen will yield significant benefits.

Airbus has been heavily involved in the advancement and experimentation of hydrogen propulsion. According to a spokesperson from Airbus speaking to CNN, "Our goal is to introduce a hydrogen-powered aircraft by 2035." In the near future, we anticipate that hydrogen could significantly decrease the environmental impact of air travel.

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Airbus revealed multiple hydrogen-powered concept aircraft in 2020, including a traditional "tube and wing" shaped plane capable of carrying up to 200 passengers, and a more radical "blended wing" type of similar size, in which the wings merge with the main body of the aircraft. This design is also being developed by other companies, such as California-based JetZero, with the goal of putting a blended-wing aircraft into service by 2030. Engineers anticipate that it will deliver a 50% reduction in fuel burn and emissions due to its innovative shape.

Electric and beyond

When hydrogen planes take off, they will be emissions-free, but that's only part of the story. "It's important to remember that while hydrogen is technically zero emissions at the point of use from a carbon perspective, its production's environmental impact matters from a planetary perspective," says aviation analyst Critchlow. He notes that most hydrogen currently comes from fossil fuels and that the infrastructure to store and transport hydrogen for hydrogen-powered aircraft is yet to be developed and operational.

ZeroAvia has completed short test flights of a small battery-powered electric airplane.

Courtesy of ZeroAvia

An Easyjet plane is pictured coming in to land in Manchester, England, in November 2013

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Cinar predicts that by 2040, fully electric planes will be introduced for regional aircraft, accommodating up to 100 passengers. Looking further into the future, she anticipates that widebody aircraft may incorporate mild electrification, but that the greater impact will come from hydrogen and sustainable aviation fuels.

Schäfer shares a similar perspective, noting that any electric aircraft introduced in the coming decades will be for niche market applications and shorter distances. He emphasizes the need for a significant advancement in battery chemistry for larger planes and acknowledges the volatility of the current market. While he believes that progress can be made, he cautions that the development of lithium-air batteries with energy levels comparable to jet fuel is a long-term endeavor, unlikely to be achieved by 2050.

Prior to that time, you will need to search in other places. Before 2050, the effort to make aviation more sustainable will probably involve a mix of factors, according to Faucett: "More fuel-efficient engines, more fuel-efficient aircraft, and operational efficiency."

"We are collaborating with regulators and developing technologies that enable us to have more efficient flight paths," he says, noting that the latter should reduce fuel consumption - and thus emissions - by 5-10%. For long-haul flights, he highlights SAF as "the major factor."

He believes that the industry has a chance to promote these multi-solution, more sustainable flights, especially once aircraft are ready to run on 100% SAF. "I expect the transition to happen in the next five years - first with demonstration long-haul flights using 100% SAF, and then followed by regular service," he predicts.