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Next time you get on a plane, consider this: A nonstop flight from Los Angeles to New York spews about 1,300 pounds of planet-warming carbon into the air — per passenger.
Aviation is one of the fastest-growing sources of pollution on the planet and one of the hardest industries to clean up. Entrepreneurs and scientists around the globe are working on the problem, offering up new technology that could slow the pace of emissions.
A future with electric planes
Now that electric cars are common, why not electric airplanes? There are limitations to the power that electric batteries can produce, but experts say there is a role for small electric planes in the future.
At a farm in California’s Central Valley, a company called Pyka runs test flights of its electric crop duster.
“People usually when they see it fly — the first few passes — it’s riveting,” says CEO Michael Norcia, as an autonomous, battery-powered plane swoops down to spray a crop of winter wheat.
A crew from the California-based company Pyka stands in front of an autonomous electric aircraft after a demonstration flight. (Peter O’Dowd/Here & Now)
The aircraft is essentially a drone with a 38-foot wingspan. A crew assigns the plane a mission inside a small control center then monitors it from the ground.
“My heart rate is slightly elevated no matter what,” says Norcia. “It’s just the margin for error. Right now, it’s nine feet above the crop canopy going 70 miles per hour — so nothing can go wrong.”
Autonomous aviation is in its early days.
Pyka’s crop dusters are flying in Brazil and Honduras. Last year, the Federal Aviation Administrationpermitted it to operate in the United States.
At the company’s headquarters in Oakland, workers are busy on the newest project: an electric cargo plane that looks just like a traditional aircraft without the cockpit and the emissions.
Replacing one agricultural aircraft with an autonomous Pelican crop duster is roughly equivalent to removing 100 internal combustion cars from service, Norcia estimates.
The cargo plane can take off on a short runway and carry a 400-pound payload about 200 miles. Some day, Norcia believes planes like this will carry people.
“What motivates me is I want to build a technology that’s going to have an enormous impact when I die. I want to leave this Earth having done something really meaningful,” he says “It has to be electric to do that.”
Around the world, piloted carbon-free flights are already taking off.
In 2022, a nine-seat electric plane flew over Washington state. Another small aircraft has flown training missions in Europe.
In November 2023, a pilot flew an eVTOL over the Tampa International Airport. The battery-powered “air taxi” is designed for short flights and can take off and land vertically, like a helicopter. The aircraft was built by Volocopter, a company based in Germany. (Courtesy of Dalton Hoch)
And last November, a crowd was mesmerized at the Tampa International Airport when a pilot waved the rotors of a battery-powered helicopter at people on the ground. That type of aircraft — which can take off and land vertically — is known as an eVTOL or air taxi. In Tampa, it hovered above the tarmac like a futuristic, mechanical insect.
Airlines like Delta and United have invested in the technology, and air taxis could be available in Chicago as soon as next year.
“It’s new mobility,” Tampa airport CEO Joe Lopano said after the demonstration. “We need mobility around here, right? Well, this aircraft will go above all the traffic and take you where you need to go, within the city.”
Air taxis will not reduce aviation emissions because they are not designed to replace airplanes, says Jayant Mukhopadhaya, a senior researcher at the International Council on Clean Transportation.
“They’re marvels of engineering. I would love to fly in one,” he says. “It’s just not a climate solution.”
He adds that EVTOLs would take some cars off the road, but flying an air taxi cannot compete with the efficiency of electric cars. However, Mukhopadhaya does see a niche role for small electric passenger planes where the road system is not fully developed.
“Norway has an extensive system of regional airports where very small aircraft operate because you have to drive around all of these huge fjords to get from one village to another,” he says. “That’s where electric aircraft would shine.”
That shine quickly wears off because today’s plane batteries are only powerful enough to carry nine passengers about 100 miles, and the vast majority of aviation emissions come from longer flights in big jetliners, Mukhopadhaya says.
So could you go from an electric crop duster to battery-powered Boeing 737s?
“No,” says United Airlines CEO Scott Kirby. “There’s not even a theoretical physics that allows batteries to have enough energy density to fly even medium-sized airplanes medium distances.”
Instead, Kirby says the future of clean aviation rests squarely on the fuels that airlines put inside big planes.
Sustainable aviation fuel
While battery-electric and hydrogen-powered planes are still getting off the ground, the aviation industry’s main focus for reducing emissions is on sustainable aviation fuel or SAF.
“More than likely if you’ve flown this year, there’s been a small percentage [of SAF] already on your flight,” Andrew Chen of the Rocky Mountain Institute told Here & Now in December. “So we’re seeing them now, but it is a long hill in front of us to climb.”
SAF is jet fuel made from waste, not fossil fuels, and it burns about 80% cleaner than the traditional blend of gasoline and kerosene in most plane engines. As a “drop-in” fuel, it can be used by any commercial plane or airport in the world, Chen says.
So far only a few are. That includes San Francisco International Airport, where United flights guzzle a blend of SAF and traditional jet fuel, says Lori Augustine, United’s local vice president of operations.
Lori Augustine, vice president of the San Francisco International Airport Hub for United Airlines, with a refueling truck pumping sustainable aviation fuel at SFO. (Chris Bentley/Here & Now)
“Operationally, it has not changed anything,” Augustine says. “No difference.”
SAF is how United says it plans to reach net-zero greenhouse gas emissions by 2050 without buying carbon offsets. It has agreed to buy more than a billion gallons, the most of any airline.
While United and other airlines have inked deals to buy billions of gallons of SAF in the coming years, relatively little has actually been produced. In 2023, United burned 7.14 million gallons of SAF, and only 1.54 million gallons of that at SFO.
Airlines pay a premium: Green jet fuel is at least twice as expensive as fossil fuels, but Augustine says it’s worth it.
“I think it’s important to our customers, I think it’s important to our company, especially for our community here,” she says, standing in an emerald green blazer under the wing of a refueling 737 Max 9. “When people want to pick an airline I think they’re going to look to somebody who’s going to be climate sensitive.”
A worker at San Francisco International Airport refuels a 737 Max 9 plane with a blend of sustainable aviation fuel. (Chris Bentley/Here & Now)
Some passengers are willing to pay more for cleaner fuel. Last year United asked customers to pitch in to a “Sustainable Flight Fund,” adding $1, $3.50 or $7 to the cost of their ticket during check-out. The company says more than 137,000 people have so far.
‘Demand is strong’
World Energy used to refine crude oil and make asphalt at its plant in Paramount, California. It still looks like an oil refinery: several city blocks worth of huge round tanks, labyrinths of steel pipes and trucks pulling in to fill up and haul fuel.
Now, World Energy’s Joe Ran says they’re cooking with different ingredients.
“We use animal waste,” says Ran, VP of business development at World Energy. “Tallow is essentially unused animal parts: fat, cartilages, tendons.”
To a chemical engineer like Ran, oil from animal fat is not all that different from petroleum on a molecular level. And as far as its climate impact, burning waste is a lot better than burning fossil fuels.
But getting it into a form that can be pumped into jet engines is difficult, and expensive.
Joe Ran, vice president of business development at World Energy. (Chris Bentley/Here & Now)
“It costs more. It takes a lot more work to produce a product that is 80% less carbon-intense,” says Ran. “I think scaling is absolutely necessary and it will bring efficiency and reduce that [cost], but decarbonization work will always have a value, and it needs to have a value to create that marketplace.”
That marketplace includes airlines like United, but also companies that want to clean up their corporate travel and are willing to pay money to do it. Last year, Microsoft agreed to co-fund the purchase of nearly 44 million gallons of sustainable aviation fuel from World Energy over the next decade. Last week, a group of corporations called the Sustainable Aviation Buyers Alliance announced it will invest nearly $200 million in companies that produce SAF.
Ran says that’s part of a “virtuous cycle” of investment that companies like World Energy need if they’re going to ramp up their supply and bring down costs.
“Demand is strong. Our marketing group keeps coming to me and saying, ‘Joe, can you get this facility to make more?’” Ran says. “And we are. But it takes time.”
One person’s trash is another one’s treasure
There’s only so much you can do with animal fat.
The National Renewable Energy Laboratory’s Zia Abdullah says there are about 3 billion gallons worth of SAF that the U.S. can make from animal fat – about the amount of fuel U.S. airlines burn in two months.
There are also competing uses for tallow, from making soap to refining biodiesel for trucks, further complicating the supply issues and economics for SAF producers.
Abdullah says there is more than enough raw material for SAF to someday replace fossil jet fuel: from animal manure and farm waste to advanced biofuel crops, and even carbon dioxide captured from coal plants or pulled directly from the atmosphere.
Those new ingredients require new recipes, and Abdullah expects more oil refineries to make the switch to biofuels like World Energy did.
“It’s a whole new industry,” he says, “but we do believe that the existing petroleum industry will have a big role in this.”
The Finnish oil refiner Neste recently announced plans to convert a crude oil refinery in Porvoo, Finland, into a biofuels plant, part of a pledge to get out of fossil fuels by the mid-2030s. Its facility in Singapore is already the world’s biggest producer of sustainable aviation fuel, and it is retrofitting another refinery in Rotterdam, Netherlands.
LanzaJet is about to open what it calls the world’s first alcohol-to-jet-fuel production pathway in Soperton, Georgia. And Southwest Airlines recently invested in a company making renewable ethanol from corn stover.
Today, however, SAF makes up less than 0.5% of the global jet fuel supply. The Biden administration set a goal of getting that to 100% in the next 25 years and pledged $4.3 billion in federal backing.
By then, some passengers might be taking short trips in electric air taxis or even long-haul flights running on hydrogen.
United and Virgin Atlantic have flown demonstration flights on 100% SAF, but federal regulations limit commercial flights to a blend of 50% SAF. That’s because, ironically, while SAF burns cleaner than jet fuel, plane engines are designed to work with the chemical impurities in fossil fuels.
For now, SAF remains just a proverbial drop in the global fuel tank.
This article was originally published on WBUR.org.
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