Trees Are Climate Change, Carbon Storage Heroes

Mature trees like this Elm can sequester more than 48 pounds of carbon dioxide in a single year. Photo by USDA Forest Service

J.R.R. Tolkien, author of The Lord of the Rings, once wrote, “I longed to devise a setting in which the trees might really march to war.”

If climate change is a battle for Earth’s survival, then trees will be a vital army holding the line. When Tolkien imagined trees marching to war, he couldn’t have foreseen how relevant those words would one day be.

Trees are a bastion against climate change.

They sequester carbon as they’re growing from the soil and store it when their lumber is used to build our homes.

To grow, a tree needs water, sunlight, minerals, and carbon dioxide. During photosynthesis, a tree converts these ingredients to sugars that feed the tree and fuel its growth. The carbon dioxide used by the tree is permanently stored in its fibers.

In one year, a mature live tree can absorb more than 48 pounds of carbon dioxide.

Life Cycle Assessment diagram. LCA is an international standard that captures the environmental impact of a given product from birth to death. USDA Forest Service image.

So, whether the tree is still growing or used to make a wood product, carbon is sequestered until the tree or wood experiences another physical event—like fire or decomposition—that releases its carbon.

But it’s hard to talk about how wood products store carbon without talking about how to assess the impact of a product’s carbon storage capacity versus the carbon cost of its fabrication.

In a 2019 journal article, “Life Cycle Assessment of Forest-based Products: A Review,” Forest Products Laboratory (FPL) researchers explain the use of an internationally accepted standard method called Life Cycle Assessment (LCA). It maps the life of a product holistically from birth to death, or cradle-to-grave, and analyzes how much environmental impact a product will have on the planet. LCA compares how much carbon is stored versus how much was produced during a product’s manufacture.  

The 25-story Ascent Building under construction with mass timber products in Milwaukee, WI. Photo by Thornton Tomasetti and Korb + Associates

Using LCA, researchers found that with sustainable forest management, forests and wood products sequestering carbon have great potential to reduce climate change impacts.

Dr. Hongmei Gu – Statistics, Life Cycle Analysis, and Economics Research Research Forest Products Technologist

LCA studies found that cross-laminated timber buildings environmentally performed better overall (such as lower global warming effects and greater carbon storage) than other buildings constructed from non-timber materials.

Cross-laminated timber. Photo by Darryl Byle, stock.adobe.com

FPL researcher Hongmei Gu, explained, “With the mass timber building’s carbon storage benefit, I always like to envision it as a medium to move trees from the forest to the city and open more spaces to grow next generation trees—mass timber is a perfect example of renewable and sustainable.”

Furthermore, Gu said, “With the immediate carbon emission reduction benefit from replacing fossil-based non-renewable concrete and steel with renewable mass timber products, the urgent climate change crisis can be mitigated now to help save our future.”

The tiny fibers of nanocellulose under a microscope. USDA Forest Service.

Regardless of wood product size, trees will store carbon. That’s the case for nanocellulose. It is made by breaking wood (or plant) fibers down to nano-scale rods and filaments.

Nanocellulose can be produced sustainably, has low environmental impact, and is biodegradable. Adding nanocellulose to existing products, such as concrete or plastic, can reduce carbon emissions because nanocellulose can make materials and products perform better, so less of the material is needed to do the same job.

Precasting of cellulose-nanocrystal-infused concrete bridge planks. Photo by Michael Goergen, U.S. Endowment.

For example, cement, an ingredient of concrete, is the third largest industrial source of pollution. Adding trees as a concrete additive can significantly reduce CO2 emissions and create a stronger, longer lasting product, all while storing carbon.

From being a microscopic additive to constructing tall buildings, wood products of any size can have big, positive environmental impacts in the fight against climate change.

Dr. Richard (Rick) Bergman – Statistics, Life Cycle Analysis, and Economics Research Supervisory Research Forest Products Technologist
A bridge in California being constructed from cellulose-nanocrystal-infused concrete. Photo by Michael Goergen, U.S. Endowment.

In the journal article, “The Carbon Impacts of Wood Products,” FPL researcher Rick Bergman explained that they found a significant two pounds of carbon savings per pound of wood when using wood products to construct buildings versus buildings constructed with non-wood alternatives. During their thorough analysis of various wood types and products (from cradle to grave), they found that if the trees were harvested sustainably, all wood products resulted in a net emission savings compared with non-wood alternatives.  

Sustainable forestry can create a sustainable wood products economy for a sustainable planet.

Tolkien’s heroic tree character Treebeard said, “The world is changing: I feel it in the water, I feel it in the earth, and I smell it in the air.”

Climate change is the greatest challenge of our generation. But trees are here to fight with us—to build a greener future together.  

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To find out more about the extraordinary contributions our researchers are making to the world of wood science, please visit the Forest Products Laboratory at https://www.fpl.fs.fed.us/ 

Contact us about this research or any of our other incredible projects at https://www.fpl.fs.fed.us/news/mediacontacts/index.php