This 3,775-Year-Old Log May Hold the Secret to a Low-Cost Climate Solution

In 2013, a team of experts traveled to Quebec to bury roughly 35 metric tons of wood underground for an innovative proof-of-concept. They were hoping to demonstrate that the technique, called wood vaulting, would prevent the wood from decomposing and releasing the carbon dioxide it had accumulated throughout its lifetime back into the atmosphere.

While digging the trench, however, the team discovered an old wooden log that would prove pivotal to their study. The team carbon-dated the log and found that the Eastern red cedar wasn’t just old—at approximately 3,775 years old, it was ancient. Further testing revealed that it had lost less than 5 percent of its carbon dioxide, based on a comparison to a freshly cut Eastern red cedar log. The result confirmed their proof-of-concept years before they otherwise could have. The team's findings were published on Thursday in the journal Science.

“I remember standing there just staring at it,” Ning Zeng, a climate scientist at the University of Maryland and lead author of the study, tells Science News’ Jonathan Lambert. He remembers thinking, “Wow, do we really need to continue our experiment? The evidence is already here, and better than we could do.” The team had planned on revisiting their buried wood nine years later.

Every year, forests absorb more than six times the amount of carbon dioxide that humans release into the atmosphere by burning fossil fuel, Dino Grandoni reports for The Washington Post. Most of that carbon dioxide, however, is returned to the atmosphere within a few decades of a tree’s death thanks to decomposition, where the gas joins other human-caused greenhouse gasses driving climate change.

This didn’t happen to the ancient Eastern red cedar log, however, because it was buried more thean six feet deep into a layer of low-permeability clay soil that sealed it off from oxygen and critters that would aid its decomposition.

Wood vaulting is an emerging low-cost climate solution that aims to mimic that process, burying nonviable wood—like diseased trees and wood scraps—to keep carbon trapped in the ground rather than allowing it to release into the air. The team estimates that wood vaulting could sequester up to ten metric gigatons of carbon dioxide a year and cost only about $30 to $100 per metric ton when the process is optimized.

In fact, the concept has recently gained more attention, Stephen Pacala, an ecologist at Princeton University who was not involved in the study, tells Science’s Saima Sidik. The question now, however, is whether scientists can recreate the right conditions on a large scale

“People tend to think, ‘Who doesn’t know how to dig a hole and bury some wood?’” Zeng says in another statement. “But think about how many wooden coffins were buried in human history. How many of them survived? For a timescale of hundreds or thousands of years, we need the right conditions.” After the discovery of the ancient log in Quebec, the team continued their proof of concept in the hopes of pinpointing the best approach for wood vaulting moving forward.

The good news is that clay soil is common around the world. However, the specific clay the log was found in was deposited by an ancient sea that no longer exists, per Science. Kate Moran, an ocean engineer at Ocean Networks Canada who was not involved in the study, tells Science that marine clay is “not ubiquitous,” and thus she would like to see evidence that wood vaulting can be equally successful in other soils.

Ultimately, Zeng specifies that wood vaulting as a climate solution would work best in conjunction with other climate actions, like reducing greenhouse gas emissions.

Margherita Bassi | READ MORE

Margherita Bassi is a freelance journalist and trilingual storyteller. Her work has appeared in publications including BBC Travel, Discover magazine, Live Science, Atlas Obscura and Hidden Compass.