Ancient logs reveal the climate benefits of burying wood

In 2013, Ning Zeng discovered a very old and very important log.

At the time, he and a colleague were digging ditches in Quebec, Canada. They planned to fill it with 35 metric tons (39 US tons) of wood. The wood is then covered with clay soil and left for nine years. the goal? To prove that wood does not rot.

If successful, the experiment could prove that burying plants is an inexpensive way to store carbon. Preventing such carbon from entering the atmosphere could help fight climate change.

But while digging a trench, Zeng’s team unearthed an untouched twisted log. It was very old, older than anything that could have been produced in an experiment.

“I remember standing there and just looking at it,” Zeng said. He is a climate scientist at the University of Maryland in College Park. He recalls thinking, “Wow, do I really need to keep experimenting?” The evidence is already here and better than we can.

The exposed logs were once part of the Eastern Red Cedar. About 3,775 years ago, the tree sucked out carbon dioxide (CO)₂took carbon molecules from the air and used them to create wood. When the tree died, it was buried under just 2 meters (6.5 feet) of clay soil.

It turns out that this barrier allows the logs to retain at least 95 percent of their carbon. Zen and his friends We shared our findings. September 24th science.

“Scientists and entrepreneurs have long considered burying trees as a solution to climate change, and this new study shows it’s possible,” says Daniel Sanchez. An environmental scientist at the University of California, Berkeley, he was not involved in the study.

“Durable, low-cost climate solutions like this hold great promise in combating climate change,” he says.

Burial: a realistic proposal

New solutions to climate change are desperately needed. Reducing greenhouse gas emissions is not enough to achieve atmospheric CO₂ A level that slows down global warming. And by 2060, about 10 billion more tonnes of carbon will need to be extracted from the atmosphere and stored every year.

Plants store approximately 220 billion tons of carbon dioxide just by growing.₂ Every year. But when plants die and decompose, much of that carbon is released into the air. By burying the tree, you may be able to stop just some of that breakdown. However, this strategy relies on finding conditions that prevent air, water, and microorganisms from decomposing buried carbon for long periods of time.

Newly discovered ancient logs give researchers clues.

Zeng now suspects that the clay blanket may have prevented oxygen from reaching the logs, even if they were not buried very deep. “This type of soil is relatively widespread. You can save it by simply digging a hole a few meters down and burying the tree,” he says.

The cost of burying wood can range from $30 to $100 per tonne of carbon dioxide.₂researchers estimate. Its simplicity and low cost make wood storage more practical than other carbon capture technologies, Zeng added. For example, technologies designed to extract carbon directly from the atmosphere cost between $100 and $300 per ton of carbon dioxide.₂.

underground wooden safe

This diagram shows the structure of the proposed wooden safe. In this setup, the buried wood is placed under a layer of clayey soil. That soil prevents oxygen from reaching the tree and helps retain stored carbon.

It’s not yet clear whether scientists will be able to recreate the conditions in which the Canadian logs were preserved. But if so, this method could store up to 10 billion tons of carbon per year.

Despite discovering the ancient log, Zeng’s team carried out the experiment they had planned. They are currently finishing their analysis. What they learned should help inform best practices for storing carbon in buried wood.

But the log itself shows the potential for a wooden safe, Zeng said. “We now have the evidence to say, ‘Yes, we’re ready to implement.'”