Deceptively Simple Plan to Seal Away Carbon Could Alter Global Warming’s Trajectory
Illustration by Lauren Biagini
A University of Maryland team today moved a major step closer to the finish line in a multiyear global competition to develop technology to filter carbon from the atmosphere—making a cut that shrank the field in the XPrize Carbon Removal challenge from 1,133 to 60.
On Earth Day this Friday, the XPrize organization in collaboration with the Elon Musk Foundation will narrow the field again, to 15 winners of $1 million prizes to further develop their carbon-fighting ideas. The Musk-funded competition features a grand prize of $50 million, with three runner-up teams splitting $30 million; winners will be announced in 2025.
While many teams are focused on high-tech machinery to mechanically remove greenhouse gases from the air, UMD’s team, Wood Vault, is working with a highly efficient carbon-removal “device” that has been cleaning the air and soaking up climate-changing gas naturally for hundreds of millions of years: trees.
Here’s where the counterintuitive part comes in: Team Wood Vault is less focused on living trees than dead ones. That’s because whether they’re bulldozed and burned, or lie behind the back fence and slowly rot, any carbon that trees pull from the environment—up to several tons in many full-grown species—escapes right back into it when they’re dead.
Atmospheric and oceanic science Professor Ning Zeng was on a nearly 20-hour flight back from a conference in Australia more than a decade ago when, through back-of-the-napkin calculations, he realized dead wood offers an opportunity to buy time for the planet while human societies struggle to develop less destructive ways to live.
“It didn’t take long on that terrible flight to assemble the conceptual pieces,” says Zeng, who now leads the Wood Vault team. “The math works. This can keep a very significant effect on the atmosphere.”
As Zeng’s studies and tests since that initial epiphany confirmed, it requires gathering millions of trees that fall or are cut in backyards, city streets, forests and farms, and burying them deep—deep enough that the process of decomposition does not set in. In another potential approach, growers could rapidly suck carbon dioxide from the air with a vigorous species like poplar, then harvest and bury the trees, and plant anew.
Instituting a system of what amounts to wood dumps around the world—perhaps in quarries or abandoned mines—could yearly put away a billion or more metric tons of carbon dioxide. It’s about one-tenth of humanity’s total carbon production, says one of Zeng’s students, Henry Hausmann Ph.D. ’24, who’s helping to oversee the multidisciplinary team of more than a dozen, including other faculty members and students from atmospheric and oceanic science, environmental science and technology, mathematics, mechanical engineering and public policy.
While not a small effort, it would be technically simple and inexpensive compared to carbon-removal schemes like direct capture from the air. The team’s research has shown that builders and others are already willing to travel long distances to landfills and pay tipping fees to get rid of dead wood; their plan for wood dumps would be free of charge to users, funded by societal environmental spending, he said.
Municipal dead wood collection might be politically easier to sell than some other approaches based on the idea people can be convinced or coerced to change their everyday behavior.
“People can bristle at the idea of some more individual requirements to address climate change, but a top-down approach that takes a large amount of wood out of the carbon cycle can have big effects,” Hausmann says.
To make sure the "vault" is really working, Hausmann helped Zeng’s students design a monitor for buried wood to ensure it’s not decomposing underground.
Zeng believes the method could quickly become a popular route for companies looking to reduce their carbon footprints through investments in carbon removal because of the ease of verifying the method is working.
“All the wood is right there—you just have to watch it,” Zeng said.
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