Researchers from the University of Maryland, led by Professor Ning Zeng of the Atmospheric and Oceanic Science department, analyzed the ancient log and the clay soil from which it was excavated. The analysis showed that the log had lost less than 5% of its carbon dioxide, thanks to the protective properties of the clay soil. "The wood is nice and solid - you could probably make a piece of furniture out of it," Zeng commented.
This discovery could be key to advancing the practice of "wood vaulting," a technique that involves burying wood that is not commercially useful, such as dead trees, old furniture, or construction waste, to prevent decomposition and carbon release. Trees naturally sequester carbon during their lifetime, but when they decompose, that carbon is released, contributing to global warming.
Zeng explained, "People tend to think, 'Who doesn't know how to dig a hole and bury some wood?' 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."
The preserved log was discovered by Zeng and his team in Quebec in 2013 during a pilot wood vaulting project. "When the excavator pulled a log out of the ground and threw it over to us, the three ecologists that I had invited from McGill University immediately identified it as Eastern red cedar," Zeng recalled. "You could tell how well it was preserved. I remember standing there thinking, 'Wow, here's the evidence that we need!'"
In past research, preserved wood samples were studied without much focus on the soil conditions surrounding them. Zeng's team, however, concentrated on understanding how the clay soil's low permeability helped prevent oxygen, fungi, and insects from reaching the log, which contributed to its exceptional preservation.
Further analysis by UMD's Department of Materials Science and Engineering in 2021 revealed that the ancient log had retained much of its carbon dioxide, confirming its potential to inform wood vaulting practices. The study shows that wood vaulting, especially in clay-rich soil, could be a low-cost and effective method of carbon sequestration in many parts of the world.
Zeng emphasized that wood vaulting should be combined with other strategies to reduce greenhouse gas emissions to combat climate change effectively. "It's quite an exciting discovery," he said. "The urgency of climate change has become such a prominent issue, so there was even more motivation to get this analysis going."
Research Report:3775-year-old wood burial supports "wood vaulting" as a durable carbon removal method
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