Hydrogen-powered planes could handle a third of passenger air travel, study finds

Major aviation companies are increasingly eyeing hydrogen as a potential long-term solution for decarbonizing their oil-dependent industry. Airbus, the world’s largest aircraft manufacturer, unveiled plans last fall for hydrogen-powered commercial planes that it claims could hit the skies by 2035. The British airline easyJet is partnering with Airbus to develop the aircraft, while U.S. firms like United Airlines and Alaska Airlines are backing hydrogen aviation startup ZeroAvia.

The recent spate of announcements made one team of aviation researchers curious: How viable could hydrogen-powered passenger flight be in the not-so-distant future?

“We really wanted to drill down on what kind of aircraft is possible in a 2035 timeframe,” said Jayant Mukhopadhaya, an aerospace engineer and Berlin-based researcher at the International Council on Clean Transportation (ICCT).

“We were pleasantly surprised” by the findings, he told Canary Media.

About one-third of total passenger traffic worldwide could be carried by planes burning liquid hydrogen, based on 2019 route data, Mukhopadhaya and his ICCT colleagues reported in a white paper released on Wednesday. In the most optimistic scenario, aircraft powered by ​“green hydrogen” — produced using renewable electricity — could reduce total emissions from passenger flights by 31 percent compared to projected emissions levels in 2050.

The study arrives as the global aviation industry and government regulators are starting to more seriously confront the climate toll of air travel. Aviation contributes about 2.5 percent of global greenhouse gas emissions every year, primarily from burning petroleum-based jet fuel, or kerosene, during tens of millions of flights worldwide. Those emissions are projected to soar in the coming decades as passenger travel continues to grow.

Some airlines are already chipping away at their emissions by blending their kerosene with small amounts of ​“sustainable aviation fuels,” or SAFs, which are primarily made today from used cooking oils and discarded animal fats. Producers and policymakers are pushing to drastically boost adoption of SAFs for commercial flights starting this decade, from about 26 million gallons every year to several billion gallons a year by 2030.

Yet while plant- and waste-based alternatives can be cleaner to produce than jet fuel, they still emit carbon dioxide when burned in engines. Hydrogen does not — hence the industry’s intensifying efforts to develop H₂-powered aircraft.

Hydrogen planes could capture a huge share of shorter flights, but not long trips

For the paper, the ICCT researchers evaluated the performance, fuel cost and market potential of two concept planes proposed by Airbus in September 2021.

The first model is a smaller turboprop aircraft with propellers, which is typically used for regional flights, and the second is a narrow-body turbofan aircraft, which carries passengers on short- and medium-haul flights. Both models have a conventional tube-and-wing design and use combustion engines, making them more like a retrofit of existing aircraft than a complete reimagining of the passenger jet. (The team did not evaluate a third concept plane, which has a triangular ​“blended-wing body” shape.)

The researchers’ analysis suggests that liquid hydrogen-powered aircraft would be less energy-efficient and have a shorter range than their kerosene-powered counterparts — making them impractical for long-haul flights without more technology innovations. However, the zero-emission planes could still service a sizable share of passenger air travel.

A turboprop burning liquid hydrogen could transport 70 passengers up to 1,400 kilometers (870 miles), or nearly the flight distance between New York and St. Louis. A narrow-body aircraft could carry 165 passengers up to 3,400 kilometers (2,113 miles), roughly the flight distance between New York City and Mexico City.

Hydrogen planes could service about 97 percent of the turboprop market and 71 percent of the narrow-body market, the researchers found.

“That was bigger than we expected,” Mukhopadhaya said. He initially thought the challenge of storing liquid hydrogen would hinder the planes’ performance more than it actually did, at least on paper.

Liquid hydrogen packs much less energy on a volume basis than kerosene does, so planes would have to store more of it to travel the same distance. The zero-carbon fuel must also be kept at around -250 degrees Celsius (-420 degrees Fahrenheit) in heavy cryogenic tanks, further weighing down the plane. In the two Airbus designs, the main bodies of the planes are elongated to accommodate the extra fuel storage.

If these planes are actually ready by 2035, airlines would probably gradually work them into their fleets as they retire older fossil-fuel-burning aircraft, Mukhopadhaya said. In that case, the hydrogen models could reduce aviation emissions by 6 to 12 percent compared to projected emissions in 2050. The more optimistic outlook, with a 31 percent emissions cut, envisions airlines swiftly replacing their kerosene-burning planes with hydrogen aircraft on every feasible route.

EasyJet, the airline partnering with Airbus, said it welcomes the findings. The report ​“shows that carbon-free flight is possible over shorter ranges, something we have long argued,” Johan Lundgren, CEO of easyJet, said in a statement.

Despite hydrogen hopes, some companies doubling down on ​“drop-in” fuels instead

Other aviation companies are more skeptical about the prospects of hydrogen-powered air travel, at least within the next 15 years or so.

Boeing, the world’s other top aircraft manufacturer, has flown five different airplanes on hydrogen since 2008, including four demonstration projects that used fuel cells to produce electrical power and one that burned liquid hydrogen in a combustion engine. But the company has said it doesn’t expect hydrogen aircraft to enter service before 2050.

Significant challenges remain when it comes to using hydrogen in aircraft, beyond just technical performance. To start, the world will need to build gigatons’ worth of additional wind, solar and other renewable energy capacity to produce enough green hydrogen to supply a zero-emission aircraft fleet — as well as to power the energy-intensive process of liquifying that hydrogen. Significant investments will be required to build the infrastructure to make, move and store hydrogen and resupply airports worldwide.

Meanwhile, industry standard-setters are still developing protocols for using the potentially explosive fuel both on the ground and in the air. According to the International Air Transport Association, ​“Certain characteristics of hydrogen make it safer as a fuel than kerosene, while other characteristics make it more dangerous.”

For these reasons and others, Boeing is putting its ​“near-term emphasis” on sustainable aviation fuels as ​“the most direct way to make substantial reductions in net carbon emissions from aviation today,” the company said in its 2021 sustainability report. Last year, Boeing set a goal to have all of its commercial airplanes capable of using 100 percent SAFs by 2030.

Today, these ​“drop-in” fuels made of used cooking oil or forest residues represent less than 1 percent of total jet fuel demand. In Europe, aviation officials are pushing to accelerate the production and use of such fuels. The ReFuelEU Aviation proposal introduced last year would require that fuels delivered to European Union airports contain at least 2 percent SAF by 2025, ratcheting up to 63 percent by midcentury.

Mukhopadhaya said the new report suggests that industry regulators should consider hydrogen as one of the possible alternative fuels when setting policies and providing incentives to slash emissions associated with air travel.

“There’s a real merit in considering hydrogen as a sustainable aviation fuel as well,” he said. ​“Because these aircraft can fly.”