A remarkably well-preserved log, buried nearly 4,000 years ago, has emerged as a powerful testament to a simple and effective way of locking away carbon to combat climate change – burying dead trees in giant graveyards. This discovery, detailed in a study published in the journal *Science*, provides strong evidence for a method known as ‘wood vaulting,’ which could significantly reduce greenhouse gas emissions.
The ancient log, unearthed in Saint-Pie, Quebec, Canada, was found during a 2013 project aimed at identifying sites for these so-called ‘wood vaults.’ The project involved burying woody biomass under a layer of clay soil, effectively sealing it off from the atmosphere and preventing the release of carbon dioxide. This process, known as biological carbon sequestration, utilizes the natural ability of living things to capture carbon.
Lead author Ning Zeng, a climate scientist at the University of Maryland and founder of a company focused on commercializing this technology, emphasizes the significance of this discovery. He explains, “This log, a single data point, tells us that if you bury wood under these conditions, it will work. It’s a critical piece of evidence, and it’s immediately implementable.”
The log, identified as an Eastern red cedar, was discovered beneath 6.5 feet of blue clay near a creek bed. The clay sediment played a crucial role in its remarkable preservation. It acted as a barrier, effectively suppressing the growth of microorganisms that would have otherwise broken down the wood. The dense, water-saturated clay particles also limited oxygen penetration, creating an environment where decay was virtually impossible.
The wood’s composition – lignin and holocellulose – naturally resists decomposition. However, if the log had remained exposed to the elements, fungi and other organisms would have quickly broken it down.
In the oxygen-deprived environment of the buried log, only anaerobic bacteria could survive. These bacteria, however, were only able to digest the outer layers of holocellulose, a carbohydrate found in plants. They couldn’t break down lignin, the polymer responsible for a plant’s rigidity, and were unable to penetrate the log’s inner layers.
Carbon dating confirmed the log’s age at nearly four millennia. Analysis using infrared spectroscopy and scanning electron microscopy revealed that it had retained the majority of the carbon it absorbed from the atmosphere during its lifetime. The log contains only about 5% less carbon than a modern log of the same species, suggesting that wood vaulting could effectively sequester carbon for extended periods.
These findings serve as proof of concept for wood vaulting. While plants naturally capture carbon from the atmosphere, much of it is released back into the atmosphere when they decay or are burned. The researchers believe that large-scale burial of trees could significantly alter this cycle, potentially offsetting nearly a third of our annual fossil fuel emissions.
The authors advocate for diverting waste wood from urban trees and managed forests to wood vaults. Clay soils, they emphasize, are abundant, and sites could be repurposed for agriculture or solar farming once the wood is buried.
Zeng has already spearheaded several pilot projects through his company, Carbon Lockdown. Other companies, including one partially funded by Bill Gates, are also exploring this technology. Research is also underway to investigate the potential of burying fast-growing plants, like grasses, for carbon sequestration.
The discovery of the ancient log provides a compelling case for wood vaulting as a practical and sustainable solution for mitigating climate change. By effectively sequestering carbon for millennia, this innovative approach holds immense promise for a greener future.
