IT’S THE TIME of year to set goals, and United Airlines recently announced a lofty one. The carrier plans to reach net-zero carbon emissions by 2050. How? In part by backing a technology called direct air capture, which sucks carbon dioxide from the atmosphere.

Humans spew more than 44 billion tons of CO₂ into the atmosphere every year. Tourism contributes up to 8 percent of those emissions, with flying making up the largest share, according to a 2018 study published in Nature Climate Change.

During the pandemic, we’ve witnessed how ecosystems benefited from the slowing of a frenetic global economy powered largely by fossil fuels. It was a reckoning for many travelers, who are rethinking how and why they fly—and seeking ways to reduce their carbon footprint when they do take to the skies.

Purchasing traditional carbon offsets can be helpful, but their impact is hard to quantify. By removing carbon from the atmosphere and storing it in the earth, direct air capture (DAC) may offer a more concrete solution.

Until now, this negative-emissions technology has been limited to scientific circles, but new initiatives aim to get the travel industry—and travelers—involved.

How direct air capture works

A specific type of carbon capture, DAC is the focus of companies such as Swiss-based Climeworks. Its modular machines use a fan to draw air into a collector, which catches the carbon with a filter made of organic compounds. Once the filter is full, the collector is closed and heated to 100°C (212°F), releasing pure carbon dioxide.

At Climeworks’ Hellisheidi, Iceland, facility, which sits like a space camp in a lunar landscape, the carbon is then combined with water and piped underground. Natural basalt formations in the earth react with the carbon, turning it into stone over the course of a couple years.

The key to making these plants viable is powering them with renewable energy. In Hellisheidi, Climeworks partnered with CarbFix, an expert in rapid underground mineralization of carbon dioxide centered around a geothermal power plant, which fuels the air capture machines.

In the case of Climeworks’ Hinwil, Switzerland, project, a waste incineration plant powers the process. Other DAC projects around the world—including Carbon Engineering in Canada and Global Thermostat, based in the United States—use similar renewable energy sources.

‘A synthetic forest’

One way to think of a direct air capture facility is as a super-forest. While real forests remove carbon naturally, most experts acknowledge that the process is too slow to make the dramatic impact our planet needs.

“The terrestrial biosphere and the ocean only collectively uptake half of what we dump into the atmosphere every year,” says Jennifer Wilcox, an energy policy expert at the University of Pennsylvania, who was just appointed to a leadership position at the U.S. Department of Energy. “We’re out of time.”

A new study shows that ice is melting at a faster rate, putting the planet on track for the worst-case climate change scenario outlined by the Intergovernmental Panel on Climate Change in 2018. Not only do we need to accelerate carbon removal, but we also need to consider ocean health (absorption of carbon dioxide by the ocean causes acidification) and land use when looking at different removal methods.

“A direct air capture plant can be up to a hundred times more efficient than a forest per given land area,” says Wilcox. “Land is a limited resource … the benefit of direct air capture is you don’t need arable land, so that’s why I think of the direct air capture plants as a synthetic forest.”

At Climeworks, each collector captures the equivalent of what 2,000 trees would, and because the carbon concentration is the same everywhere in the world, these facilities are location independent.

What airlines are doing

To get its carbon capture plan off the ground, United has invested in 1PointFive. The firm plans to build a large-scale DAC plant in Texas that would permanently sequester one million tons of the gas every year. Delta is also integrating carbon removal into its sustainability strategies.

In DAC projects where the captured carbon is not stored in the ground, it can be recycled and used as a raw material. At Climeworks’ Hinwil plant, for instance, the carbon is used to fertilize greenhouses and add fizz to Valser, a Swiss mineral water.

“Having a business model where they can sell CO₂ as a product helps, because it develops technologies,” says David Goldberg, a research professor at Columbia University’s Earth Institute. “One of those products can be fuel.”

When mixed with hydrogen made from a renewable energy source, captured carbon can be used to create a sustainable aviation fuel, like the one Norsk e-Fuel is making. “You burn the fuel and the carbon goes back into the atmosphere, but you never touched petroleum in doing that,” says Wilcox.

While this application doesn’t permanently remove carbon from the air, it is creating a circular economy, as well as a market for carbon removal that might allow the technology to scale up to a level that has real impact.

How travelers can help

Tomorrow’s Air, a collective of globe-trotters that has partnered with Climeworks, aims to get travelers involved in these efforts. Airline passengers can offset their emissions by donating to carbon capture on a monthly basis while receiving perks from affiliated tour companies, such as Tierra Del Volcan and Natural Habitat Adventures.

Through initiatives including its Artists for Air series and Airbnb Climeworks tours, the collective also educates people on how the technology helps combat climate change.

“There’s a lot of potential for individual travelers being able to take climate action into their own hands,” says Christina Beckmann, founder of Tomorrow’s Air. “We need to do all we can to reduce our emissions, but nobody is talking about permanent storage,” she says.

Travelers have noticed the visible effects of climate change and are looking for concrete ways to offset emissions. “You can see the glaciers melting in Greenland,” says Lykke Geisler-Yakaboylu, a travel enthusiast and founder of destination marketing company Sila Greenland. “We’ve had our warmest summers ever the past two years.”

Geisler-Yakaboylu recently joined Tomorrow’s Air and plans to integrate a DAC offset into the cost of her trips. “It makes it feel like you can actually do something.”

While traditional offsets—such as tree planting—have value, DAC has a more immediate impact. “If we say, I’ll offset something for you in 50 years when the tree grows but I’m emitting today, it doesn’t really feel like an offset,” Goldberg says.

Reforestation offsets also are complicated by the wildfires surging around the world, which can release sequestered carbon back into the atmosphere. “Drawing down CO₂ and putting it away—that is a real offset, real storage,” Goldberg adds.

Realizing the potential

Encouraging travelers to see the value in carbon removal could help create more meaningful journeys. “For all of our trips, we offset CO₂ emissions by 1.25 times through various projects, one of them being Climeworks,” says Jeff Bonaldi, founder of The Explorer’s Passage.

“Travelers know where their money is going, and it does change things for them when they’re connecting to something that’s more than just an adventure,” says Bonaldi. “They’re connecting to try to help the planet.”

Demand for captured carbon offsets from consumers and corporations might also help to drive down the cost of the technology—which is still incredibly high. Microsoft, for instance, recently made a pledge to be carbon negative by 2030 through the use of various capture and storage technologies.

“Government and policy have to play a role as well; the technology alone will not save us,” says Wilcox. In December, the U.S. Congress reserved $447 million to research and develop large-scale carbon removal. President Joe Biden’s goal to have a net-zero-emissions economy by 2050 includes upping federal investments and tax incentives for carbon capture technology.

The potential of DAC to combat climate change, and make travel more sustainable, is promising. But it’s in no way a panacea. Experts hope it will work in tandem with other forms of carbon reduction.

“We’re going to have to do all of it,” says Goldberg. “Scaling up this direct air capture technology as fast as possible and reducing emissions; we don’t get to choose.”