It’s not as visibly bad as the belching smokestacks of the coal industry or the gas-chugging backups on suburban highways, but the building industry is a major contributor to climate change. From their materials to their construction to their energy needs over time, buildings generate nearly 40% of global greenhouse gas emissions. Of that, around a quarter is embodied carbon, or the sum of emissions that resulted in the production, transportation, and use of building materials. What a building is made of can have a huge climate impact.
One simple solution is to switch to wood, which sequesters carbon, as a primary building material. According to a new meta-study, switching to wood on a wide scale could bring emissions down by using a material that naturally absorbs and sequesters carbon from the atmosphere. Over just the next 20 years, 420 million tons of carbon dioxide could be sequestered within wooden buildings in Europe—the equivalent of a year’s worth of emissions from 71 million homes or 108 coal plants.
Spread out to a global scale, there is massive potential for wooden buildings to become long-lasting carbon sinks, according to Ali Amiri of Aalto University in Finland, one of the authors of the study. As forests are planted to meet a potentially growing demand for wood, Amiri says, “we can store and store and store.”
Wood represents a much greener alternative to the materials often used in construction: concrete and steel. The production of these two materials adds up to roughly 15% of global CO2 emissions. Shifting more construction to wood would help bring those numbers down.
Amiri’s study looked at the carbon storage of 50 wooden buildings, comparing structures with different sizes, uses, and locations. Amiri and his coauthors used this data to develop three levels of carbon storage, depending on the amount of wood used for both the buildings’ structures as well as their internal furnishings, like counters and chairs.
At the low end, buildings using only some wood could store 20.5 pounds of carbon dioxide per square foot. At the high end, in buildings made almost entirely of wood, that figure could be about 61 kilograms (134 pounds) per square foot. Estimating a gradual increase of wood in new buildings over the course of two decades, and looking specifically at the average amount of new housing built annually in Europe, the researchers found that stored carbon could hit a total of 420 million tons by 2040.
The source of this wood is another question. Though Amiri says forestry practices in places like Europe and North America are generally sustainable, illegally logged wood is a major problem globally, and one that would have to be reckoned with.
For builders and designers, making the transition will require shifting away from materials like concrete and steel. And though small buildings have long relied on timber for construction, wood is becoming a more viable alternative to concrete and steel. The development of structural mass timber products like compressed laminated timber have allowed wood to be used in much taller buildings than in the past, including mid-rise towers that can reach more than a dozen stories using wood alone.
For all but the tallest buildings, Amiri says, wood can be a practical material. And the industry is catching up, with mid-rise mass timber buildings being developed from Portland, Oregon, to Toronto to Norway.
Before becoming a researcher, Amiri worked in the building industry, designing and building apartment buildings. They mostly used concrete and steel. “Because I have been in building construction, I have seen what is happening and what we need in the future,” Amiri says, noting that he sees a lot of potential in using wood in construction, and is planning to continue his research to explore how wood construction can become more of a standard practice internationally. “We can do something for the world.”