Airliners worldwide are looking down the runway at a fossil-free future. Innovative technologies ranging from battery power to sustainable aviation fuel to green hydrogen promise to help meet a global goal of reaching net-zero emissions by 2050.
Since the Wright brothers successfully flew a motor-operated airplane on the shores of North Carolina in 19031, people have looked up to the skies to open the world and push the boundaries of progress. Aviation has come a long way from the early days. Every day, about 100,000 commercial flights take off and land around the globe. Add in private jets, military planes, and other forms of flight—including space flight—and the total picture is staggering.
The airplane is undoubtedly one of humanity’s greatest innovations. Nonetheless, aviation is at an inflection point. As global economic growth spurs greater demand for air travel, it remains one of the dirtiest parts of the global economy. Safely and reliably, flying hundreds of people is hard and expensive no matter what, and fossil fuels are the easiest way to put planes in the sky.
About 20-40% of the cost of a typical flight2 is reserved for fuel. Most commercial planes burn several thousand gallons of fuel while flying. Today’s jets are much more fuel-efficient than their predecessors, but the bottom line is that it takes a lot of energy to lift a commercial airplane and keep it in the sky for hours on end. Up until now, with very few exceptions, all of that fuel has been some sort of fossil fuel. The result? Aviation contributes 4% to human-induced global warming3 and is projected to cause about 0.1 degrees Celsius (0.2 degrees Fahrenheit) of warming by 2050 if the industry keeps growing at pre-pandemic rates. If aviation were a country, it would be the world’s sixth-biggest emitter.
For many of the world’s major economic activities, replacing fossil fuels with cleaner alternatives is technically simple. Consumer technologies like electric vehicles and heat pumps perform similarly or better to their conventional (and dirty) counterparts while being either comparably intricate or simpler in terms of fundamental technology. As such, they’re also becoming cheaper and more popular. Electrification and other forms of innovation can make decarbonization fairly easy for the vast majority of the global economy. But many activities aren’t so easy to decarbonize. Aviation is one of them.
Why is that? Above all, flying a typical commercial plane—let alone a smaller plane—thousands of miles requires a lot of energy. Fossil fuels are energy-dense, so even though fuel adds weight to the plane, it’s still economical. Nonetheless, airliners worldwide are looking down the runway at a fossil-free future that will hinder their current business models. If they want to remain profitable without excessively polluting the skies, they must innovate.
The most promising vision for aviation’s future is battery power. This would eliminate the need for any sort of fuel to power a plane and would represent an astonishing level of innovation in an industry that hasn’t innovated much at all for a long time. Like electric cars, electric planes rely on battery-generated electricity rather than jet fuel for power. These planes can save airlines money by lowering fuel costs and maintenance costs. The major obstacle is that today’s batteries aren’t nearly energy-dense enough to power a plane for thousands of miles.
It’s hard to envision using batteries to power every single commercial plane anytime soon. But for shorter flights, battery power is coming into view. Luckily, about half of all commercial flight routes go less than 500 miles, so batteries can power a substantial piece of the aviation industry in the not-too-distant future.
In July 2021, United Airlines agreed to buy4 100 19-seat ES-19 electric planes from Swedish startup Heart Aerospace. Heart’s ES-19 planes can fly up to 250 miles, and United expects them to enter service as soon as 2026. Another electric aviation startup, Wright Electric, plans to roll out an electric 100-seat plane by 20265 and an electric 186-seat plane with an 800-mile range by 2030.
Perhaps the most exciting development to date7 in the electric aviation space occurred just a few months ago. In late September 2022, Eviation Aircraft, based in Washington state, completed the first all-electric test flight of its uniquely named airplane, Alice. This plane, named after Alice in Wonderland, is the world’s first all-electric passenger commuter aircraft, built entirely for electric propulsion. Alice can carry nine passengers and two crew members, with a targeted range of 150 to 250 nautical miles.
The runway between a test flight and commercial viability is long. Even if everything goes according to plan, Eviation doesn’t expect Alice to hit the skies with paying passengers onboard until at least 2027. But with hundreds of startups working on electric planes just like Alice, it’s only a matter of time before battery-powered flight makes a name for itself on the global stage.
With an eye on both the need to decarbonize the global economy and these promising developments in the private sector, governments are also paving the runway for electric flights. Countries like Denmark and Sweden8 have promised to make all domestic flights fossil-free by 2030. These proclamations, combined with funding and regulatory influence from sustainability-oriented policies like the Inflation Reduction Act, might force the hands of airlines and aircraft makers who might not be as fully onboard for sustainable aviation as the global need to lower emissions would imply.
For flights longer than a few hundred miles, relying on battery power will likely be infeasible for a long time. Sustainable aviation fuel (SAF) has been touted as a cleaner solution for long-range aviation. SAF is a biofuel with similar properties to conventional jet fuel but with a smaller carbon footprint. Instead of fossil fuels, SAF is made from a range of renewable starting materials or feedstocks. These include biological waste products (including used cooking oils), corn stover (what’s left after the cob is harvested), food scraps, or municipal solid waste.
Airlines like SAF because it can essentially be used without any technical modifications to existing aircraft, engines, or airport fuel systems. Here’s the problem (well, two problems, really): SAF isn’t truly sustainable. First, the raw materials needed to make it can exacerbate deforestation, and using them for SAF can often divert resources (like food) from needy areas or promote environmentally destructive industries like factory farming. Second, the emissions benefits of SAF are uncertain and highly contingent on the raw material used to make it.
So is SAF better than conventional jet fuel? It’s hard to say. That uncertainty in and of itself should dissuade airlines from betting the skies on SAF. The bottom line is that using SAF at scale would be like trying to lose weight solely by replacing white bread with whole wheat bread. Sure, you might make some improvements at the margins, but you’re not addressing the root of the problem.
That doesn’t mean SAF has no place in aviation’s future. If airlines use it as a secondary or tertiary fuel source rather than a primary one and ensure that their SAF consumption does not conflict with the need to provide essentials to a growing human population, SAF might have a role to play. Otherwise, SAF should remain on the sidelines. Keep in mind that most flights will be able to harness electric battery power fully. For longer flights, airlines would be better served to turn to a different fuel source: hydrogen.
When people think of hydrogen and aviation, the Hindenburg disaster is usually what comes to mind—and for good reason. An official cause has not been determined, but a report from the U.S. Department of Commerce and the U.S. Navy pointed the finger at the most obvious cause9: a mixture of free hydrogen and air. At least one of the sealed hydrogen cells powering the Hindenburg airship was likely punctured, leaking free hydrogen that ended up burning the whole structure. The disaster, which killed dozens of people, contributed to the end of the airship era and marked a turning point in the history of aviation.
Today, however, hydrogen presents an exciting opportunity for a safe, abundant, and carbon-free fuel that airlines can rely on indefinitely. Hydrogen planes would look a lot like today’s planes. Smaller hydrogen planes would likely use propellers, while bigger planes would use jet engines. Flying a plane with hydrogen requires a storage system to safely store liquid hydrogen, fuel cells to convert it to electricity, and a device to control those cells. All of those major components must be developed.
Thus, for those ambitions to become realistic, a few key technological developments must occur. Hydrogen storage must advance enough to carry liquid hydrogen over long distances. Hydrogen will need to be moved from one airport to another, and airports must develop hydrogen refueling infrastructure. The planes themselves will need some modifications to adapt to being powered by hydrogen.
But the biggest barrier by far between today’s hydrogen ambitions and tomorrow’s hydrogen reality is the cost of the hydrogen fuel itself. That’s where government policy will come in, and recent legislation passed by the U.S. Congress will play a pivotal role in leveling the aviation playing field. The Bipartisan Infrastructure Law passed in 2021 includes up to $7 billion10 to establish between six and ten regional hydrogen hubs across the country. These hubs are intended to link producers and consumers while providing the infrastructure needed to grow and maintain the hydrogen economy.
The U.S. Department of Energy launched another program in 2021 to cut the cost of clean hydrogen by 80%11 to $1 per kilogram within a decade. The Inflation Reduction Act contains major incentives for hydrogen production, most notably a nifty tax credit for hydrogen production that maxes out at $3 per kilogram for hydrogen produced without releasing any carbon emissions. It scales down proportionally as more emissions are generated to produce hydrogen.
The European Union is similarly focused on advancing the hydrogen economy, with a stated aim of having 40 GW of renewable hydrogen electrolyzers12 installed across the bloc by 2030. China’s getting in on the action, too, as evidenced by its construction of the world’s largest green hydrogen factory13. With this level of investment and policy-making aimed at green hydrogen, it’s only a matter of time before airlines look to hydrogen to decarbonize without disrupting their core operating strategy. A July 2022 report14 by the World Economic Forum and the University of Cambridge’s Aviation Impact Accelerator predicts that by 2035, hydrogen fuel cells could be used to electrify mid-range flights of up to about 4,000 kilometers (~2,400 miles), roughly equivalent to the route between New York and San Francisco.
You probably won’t board a hydrogen-powered long-range flight for at least another decade, if not two or three decades. The technology isn’t commercially viable yet, and once it is, it will take many years for both airlines and airplane makers to shift their business models. Nonetheless, hydrogen presents the most buoyant pathway toward fully decarbonized aviation for longer flights.
Airlines don’t just move people; they also move cargo. Despite the differences between moving cargo and moving people, most of the cargo that’s transported through the air moves more or less the same way that a typical airline passenger will. But in the not-too-distant future, your online shopping packages might be whisked through the skies differently.
While studying materials science at Harvard, Kyle Clark wrote a thesis on a plane piloted like a motorcycle and powered by clean energy. His paper was named the engineering department’s paper of the year, reflecting a passion for aviation that has now manifested itself in Beta Technologies15, a startup Clark founded that is focused on innovating electric cargo planes that take off and land vertically.
Beta, which is based in Vermont, envisions these electric cargo planes replacing the fleets of short-haul trucks that currently deliver cargo across the country. Unlike those trucks, Beta’s planes wouldn’t congest the roads and, more importantly, wouldn’t emit greenhouse gasses.
Here’s the catch: instead of flying from one airport to another, they would fly from one solar-powered charging station (made out of a shipping container) to another across the country. This could drastically decentralize supply chains by reducing the conventional dependence on massive distribution centers. For less dense urban areas or even rural areas like Vermont, this concept could be a game changer.
Beta has sold its vision to some big names. Amazon – which has been steadily working on autonomous cargo delivery via Amazon Prime Air since 2013 – has invested heavily in Beta through its Climate Pledge Fund. Both the Air Force and the Army have signed contracts with the company. UPS has ordered 10 of its flagship product—the Alia aircraft, which is essentially an unmanned flying battery that can be recharged in 50 minutes and fly 250 nautical miles on one charge—by 2024 and has signaled its intent to buy 140 more. And Blade, a commuter helicopter service, has reserved the right to buy five Alias for $4 to $5 million each.
In the not-too-distant future, your packages might arrive at your doorstep via a drone-like Amazon’s Prime Air or a helicopter-like Beta’s Alia aircraft. No longer would you fear the din of noisy trucks delivering packages all day or the noxious clouds of exhaust fumes they emit.
In October 2022, the International Civil Aviation Organization agreed to achieve net-zero carbon dioxide emissions by 2050.16 This agency, which has 193 member countries, adopted the long-term aspirational target after nearly a decade of negotiations. It remains to be seen exactly how aviation will achieve net-zero emissions by 2050. Aviation is notoriously slow to innovate and difficult to disrupt. Change typically occurs on decade-long scales rather than month-long or year-long scales. And despite periodic hiccups (like recessions and the COVID-19 pandemic), the status quo has worked for aviation’s big players for many decades, resulting in little appetite for change unless it’s absolutely necessary.
But drastic changes are on the horizon for aviation, compelled largely by the climate crisis. For shorter flights, battery power is poised to shuttle both people and goods sooner than you might think. For longer flights, hydrogen presents a simple opportunity to replace jet fuel with a much cleaner alternative. Sustainable aviation fuel is one of many technologies that might help on the margins, along with continued efficiency improvements.
Given aviation’s hefty contribution to the climate crisis (not to mention the high fares and frequently unpleasant consumer experience, both of which might be alleviated in a fossil-free aviation landscape), these improvements will come not a moment too soon. Aviation has come a long way since the Wright brothers brought their ambitious dream to live on the beaches of North Carolina in 1903. It’s about making some big leaps toward a cleaner future.
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