Another Kind of Tree Planting

Researcher Asks: Could Burying Enough Dead Wood Alter the Globe’s Climate Trajectory?

In a world grappling with climate change, a living tree is a treasure—cleaning the air and soaking up carbon dioxide that causes global warming.

But a dead tree? Not so much.

Whether a tree is bulldozed and burned or lies behind the back fence and slowly rots, carbon it gathered from the environment—up to several tons in many full-grown species—then escapes.

As a natural part of the global carbon cycle, that’s hardly a cause for alarm. But returning from a conference in Australia more than a decade ago, a UMD scientist doing back-of-the-napkin calculations realized dead trees offer 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 Ning Zeng, professor of atmospheric and oceanic science. “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. Or, growers could rapidly suck carbon dioxide from the air with a vigorous species like poplar, then harvest and bury it, 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 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. While not a small effort, it would be technically simple and inexpensive compared to carbon-removal schemes like direct capture from the air. Municipal dead wood collection might also be politically easier to sell than some other approaches.

“People can bristle at the idea of some more individual requirements to address climate change, but a top-down approach that takes large amount of wood out of the carbon cycle can have big effects,” he says.

To help wood burial scale up to have an effect, Hausmann and other students of Zeng’s are designing a monitor for buried wood to ensure it’s not decomposing underground; they’re scheduled to compete in February in the XPRIZE student competition for carbon removal, which could fund deployment of the devices at test sites around the country if they win funding.

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.”