Look around your yard or local park, and you’ll find what could become the next big eco-friendly construction material: wood. In a new study, scientists report that a switch to wooden buildings could house a rising world population while keeping billions of tons of carbon out of the atmosphere—provided that the construction industry takes heed.
“It’s just a really well put together argument for why we need more carbon storage,” said Joseph Gutierrez, a geoscience educator at California State University, Fullerton, who was not involved in the study. “We need to change how we’re doing…construction and building management.”
Building Toward Sustainability
Steel and concrete remain go-to materials for constructing new homes and commercial buildings. But although these materials are sturdy and durable, their manufacture and transport spew carbon into the atmosphere.
“Both of these materials will basically never become zero carbon,” said Galina Churkina, the study’s lead author and an environmental scientist at Germany’s Potsdam Institute for Climate Impact Research.
Instead, Churkina turned to one of the world’s oldest construction materials: wood. Carbon sequestration has only recently become a hot topic in climate change discussions, but microbes mastered carbon capture—photosynthesis—more than 3 billion years ago, with the first woody plants developing more than 300 million years ago.
Churkina worked with a team of architects and scientists to calculate the benefits of using wood to build urban mid-rise buildings from 2020 to 2050. The team forecast four different scenarios. In the first, dubbed “business as usual,” 99.5% of new buildings would be built with steel and concrete. In the other three scenarios, 10%, 50%, or 90% of new buildings would be made from wood.
The researchers estimate that the 90% scenario would keep up to 20 billion tons of carbon out of the atmosphere over the next 30 years. That value decreases to a maximum of 11 billion tons in the 50% scenario and 2.3 billion tons in the 10% scenario. By comparison, scientists estimate that global carbon emissions reached around 37 billion tons in 2018.
These savings stem from the fact that carbon makes up half the dry weight of wood. In contrast, steel contains only about 0.4% carbon, and concrete takes hundreds of years to store carbon.
Getting on Board
The future carbon savings of wooden buildings look promising but raise important questions. For one, wouldn’t wooden buildings burn? Researchers point out that although small wooden planks are flammable, large sections can be remarkably fire resistant, withstanding temperatures of over 982℃. When a large wooden panel catches fire, its outer layer chars; this charred surface protects the core by blocking heat and oxygen.
Another potential issue is whether a shift to wooden buildings would deplete the world’s forests. To assess this, the researchers evaluated both future projections and past data. Models forecasting future levels of forest growth showed that forests should be able to support even the 90% wooden building scenario. And when the scientists reviewed wood harvest data from 65 countries between 1990 and 2010, they found that two thirds of the countries were harvesting less wood than their forests were growing back.
“It actually looks pretty good. It’s a bit of a surprise in a way,” Churkina said. “There was much more forest regrowth than was removed.”
For Churkina and colleagues, the next big challenge will be convincing the construction industry and regulators that a wooden future is as economical as it is environmentally friendly. That will require changing building codes and retraining an industry that has long favored concrete and steel—no easy task, says Gutierrez.
“I think it’s going to be a tough sell and a tough transition to make, but hopefully [we can] at least get close to the 10% or 50% [scenarios],” Gutierrez said. “If you can’t convince administrations and construction companies to buy into these things, they’re hard to get going.”
The new study was published in Nature Sustainability in January 2020.