In 2013, a group of researchers wanted to see if they could keep wood from breaking down by burying it underground. They thought it might help keep carbon dioxide out of the atmosphere. As they started to dig, they discovered a 3,775-year-old log that proved their idea was a good one.
Carbon Dioxide
Carbon dioxide is a greenhouse gas that traps heat in Earth’s atmosphere. Carbon dioxide and other pollution from the burning of fossil fuels has helped create the climate crisis. Scientists have been looking for ways to remove carbon dioxide from the atmosphere and store it for hundreds of years.
Trees naturally pull carbon dioxide out of the air. They store this carbon in their wood. This is one reason people suggest planting trees as a way of fighting climate change. But when trees die, the wood rots and the stored carbon dioxide is released back into the air.
“Wood vaulting” is being studied as a method of locking away the carbon collected in wood. The idea is simple: take wood and bury it in a “vault” – a hole in the ground. But to keep wood from breaking down, the conditions must be just right.
In 2013, scientists, led by Dr. Ning Zeng, designed an experiment to test wood vaulting in Quebec, Canada. Their plan was to bury a massive amount of wood (about 77,000 pounds, or 35,000 kilograms) underground. They planned to leave the wood there for 9 years, and then dig it up to see how much it had rotted.
But as they were digging the hole to bury the wood, the scientists discovered an old log. They could tell that the log was old, but they didn’t know how old until they tested it. It turned out to be an Eastern red cedar tree that was 3,775 years old. And it hadn’t rotted.
Dr. Zeng says that he remembers staring at the log, and thinking, “Do we really need to continue this experiment?” The ancient log seemed to have already proved that wood vaulting could work.
When the team tested the log, they discovered that it had only lost about 5% of its carbon. It had held onto more than 95% of its carbon for almost 4,000 years.
The ancient log was buried about 6 feet (2 meters) deep, and was covered with a layer of clay. The scientists think the clay protected the log, keeping water and air from getting through. The clay also kept out insects and other creatures that might have helped break the log down.
The discovery is important because it shows that wood vaulting can keep carbon out of the atmosphere for a long time. Wood vaulting is simple, and is a much cheaper way to store carbon than many other methods.
The researchers believe that if it’s done the right way, wood vaulting could keep as much as 10 billion tons of carbon out of the air every year. That’s about 20% of the greenhouse gases that are released into the atmosphere each year.
Clay soil is common around the world, but some scientists wonder if there might have been something special in the clay in Quebec. Experts say it’s important to discover exactly what conditions are required to make wood vaulting successful.
The researchers say wood vaulting can’t solve climate change by itself. But it can be part of the solution.