How does mass timber help capture carbon?

MADISON, Wis. -- Can sustainable harvests for timber construction of commercial buildings help with carbon retention? How does that actually work?

Mark Wishnie, executive director of the Timberland Investment Group for BTG Pactual responded to these questions in a presentation at Michigan State University’s Department of Forestry earlier this month.

Wishnie pointed out the massive size of the worldwide construction industry -- $10 trillion annually -- and its corresponding global impact on CO2 emissions -- 11% of total world wide emissions and growing. This means CO2 reductions from savings in this industry can be at a massive scale.

But how does the use of wood construction technology or “mass timber” actually lead to lower emissions? Wishnie explained that this happens through a three-part process that involves sequestration, storage and substitution.

Here’s how he explained this process:

Sequestration is storage of carbon in living trees that are part of diverse-aged forests. As one group is harvested, its volume is being replaced by other growing conifers leading to no net loss of volume. (He noted that this is hard to model on properties that are too small to have multiple stands.)

Storage After harvest the carbon in the trees is stored permanently or long-term in the products or structures that the timber was used to build (like buildings and furniture).

Substitution A key factor in wood (or “mass timber”) commercial construction is its use in place of carbon-intensive products like steel and concrete.

Wishnie also adds Circularity as a factor --- the likelihood that wood products will be reused or recycled. He asserted that the combination of these factors can mean a climate benefit that is more than double the benefit of a simple standing forest.

Mass timber is production of stronger wood products created by layering softwood lumber in a cross-hatch pattern. The layers are bonded. Mass timber products include cross-laminated timber (CLT), glued laminated timber (Glulam) and mass plywood.

Mass timber use and enthusiasm is growing throughout the world, with recently approved revision of the International Building Code standard allowing construction of wood buildings up to 19 stories next year. France has mandated that wood content of all public buildings must be at least 50% after 2022. This is modelled after a comparable requirement for all buildings for the 2024 Olympics in Paris.