Does Burying Dead Trees After a Wildfire Trap Carbon Emissions?

In 2021, underground coal seams ignited,
sparking a wildfire in Poverty Flats, Montana, that scorched 267 square kilometers and decimated about 50,000 trees, primarily ponderosa pines. This devastation impacted ranching operations at Gentry Ranch, where cattle found shade.

Scorched remnants remained scattered across the barren landscape. These “widows” pose risks, as they can drop unexpectedly, causing harm to livestock and potentially fueling future wildfires. Traditional methods would involve burning the downed trees, releasing approximately 7,000 tonnes of CO2 into the atmosphere.

However, innovative excavating tactics were employed. A bulldozer and specialized felling machinery relocated the trees into a 5,000 square meter pit, which was subsequently covered with six meters of earth, gravel, and polypropylene cloth. Mast Reforestation, the organization behind this initiative, asserts that this process will inhibit decay for centuries, thus curbing greenhouse gas emissions and mitigating future wildfire risks. They also have the opportunity to generate carbon credits to finance the planting of new trees.

“This is not a one-size-fits-all solution, but for forest management, it’s a significant advancement,” declares Grant Canary from Mast Reforestation.

The United Nations Climate Change Agency states that offsetting hard-to-reduce emissions will require CO2 extraction techniques, including tree planting and air filtration systems. Plants, including trees, absorb CO2 as they grow, but they also release it upon decay. To combat this paradox, startups are converting forestry and agricultural residues into biochar, which can be applied to fields, formed into bricks, or stored underground.

Mast has expanded its focus to include wildfire-damaged timber. Historically, the West has experienced wildfires that have grown exponentially larger, with current conditions potentially leading to another severe wildfire season following this spring’s extreme heat.

Approximately half of wood mass remains after a wildfire, with carbon content remaining substantial. For the Gentry project, Mast meticulously calculated the CO2-equivalent mass of logged trees, estimating around 7,000 tons using nitrogen and moisture levels, eventually selling 4,277 verified carbon credits through the Puro.Earth registry.

For bulk buyers, these carbon credits are available for less than $200 each—more expensive than traditional tree-planting credits but competitive with biochar credits.

Mast has allocated a portion of its profits to cultivate seedlings, planting them on ranch areas which saves owners from the hefty costs associated with land clearing. In Montana, around 6.5 million tons of trees destroyed by fire remains available for recovery, according to Canary. The company is now preparing to expand its operations with a goal of processing 150,000 tons of timber annually by 2030.

The Puro.Earth guideline indicates that sequestration through buried biomass can last beyond a century. Research in 2022 found that a cedar log buried near Montreal retained 95% of its carbon after 3,775 years. However, exposed wood can begin to decompose in just a few months under unfavorable conditions.

Wood-decaying fungi and bacteria thrive on oxygen, moisture, and warmth. By isolating wood from air, these microorganisms can be neutralized. Ning Zeng from the University of Maryland discovered that burying logs under at least one meter of clay-rich soil is effective in preventing air infiltration.

Although soils in the western U.S. are predominantly stony, impermeable deposits like glacial fields can still be available near burn zones. Further research is crucial to understand optimal conditions for wood preservation, Zeng suggests.

“While we support these commercial initiatives, the primary concern remains proper execution,” says Zeng. “It’s essential for implementers to be well-informed, as precise scientific guidance is still evolving.”

If buried wood were to decompose, emissions could soar as machinery operates for removal or relocation. Excavation can also disrupt vegetation and release soil carbon; however, maintaining the integrity of the topsoil and applying it back over can mitigate this impact, according to Zeng.

A former employee’s wrongful dismissal claim alleged that the company inflated the values of carbon credits sold through reforestation efforts that excluded dead tree burial. Mast has since resolved the lawsuit, assuring that its operations remain unaffected.