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.