Traditional methods of scraping lumber such as converting it into yard mulch or fire chips unfortunately release carbon into the air. According to the Institution of Structural Engineers, lumber also provides a natural type of carbon absorption. The information comes at a time when demand for low-carbon construction and building materials is increasing as the construction sector becomes more conscious about climate change.

According to an MIT media release, odd-shaped tree pieces like knots and forks are normally scraped or converted into mulch, but MIT experts are looking at how to harness the unique qualities of these "waste pieces" as construction components.

In construction, the "Y" sections where branches join the trunk can be used as load-bearing members, and they could be capable of supporting load demands. Caitlin Mueller, an associate professor at MIT and her team are trying to figure out how to use this old timber to make new parts for buildings instead of steel or concrete.

Industrial interest in unconventional wood

"I had the sense, and others have had this too, I think that there's this amazing internal fiber structure that achieves what's essentially a rigid moment connection in a tree branch," Mueller stated. "Each tree branch is a cantilever, through a really complex, intertwined, three-dimensionally curved alignment of internal woodTree forks are often considered waste and used for mulch. Source: Felix Amtsberg fibers. We don't have the capabilities to make that today with 3D printing or other manmade manufacturing processes."

While Mueller believes that this research would not instantly result in builders utilizing tree knots in building, she believes it will motivate them to find alternate applications for materials rather than discarding them.

According to a study from MIT in 2019, the concrete sector is responsible for 8% of the world's carbon dioxide emissions. The steel industry is accountable for another 7%, according to the International Energy Agency. As climate change gets worse, more and more contractors are looking for ways to build more sustainably.

Help from a tree database

Mueller sought the assistance of the city of Somerville's Urban Forestry Division, which maintains a digital database of more than 2,000 street trees, including their position, diameter and condition.

Robotics help guide tree forks through a band saw. Source: Felix AmtsbergWorkers brought the discarded wood to MIT, where researchers cut, scanned and cataloged the forks after they were cut down to make space for a new school. According to the announcement, they then scanned the components in 3D and displayed them in the system as three straight bars joining at a single point. The team was able to link the pieces with architectural nodes using this approach.

Mueller believes that the work done so far has already generated new momentum for the architectural design process. Architects may now easily calculate the embedded carbon or projected energy consumption of a design choice using digital resources. The study was supported by MIT’s School of Architecture and Planning by the HASS Award.

“Now we have a new metric of performance: How well am I using available resources?” Mueller said “With the Hungarian algorithm, we can compute that metric basically in real time, so we can work rapidly and creatively with that as another input to the design process.”