Turning wood waste into ultra strong material

Backed by a $2 million award from the Defense Advanced Research Projects Agency (DARPA), the Waste Upcycling for Defense (WUD) project seeks to develop cost-effective and sustainable alternatives to metal. UT spearheads the program, working alongside the University of California, Riverside, and Georgia Tech.

Wood offers a naturally abundant and eco-friendly alternative to metals and alloys, but its mechanical properties have traditionally limited its use in load-bearing structures. Prior studies have demonstrated that densified wood-achieved by extracting lignin and compressing the cellulose fibers-can deliver exceptional strength.

"Lignin forms a very stiff matrix with hemicellulose to protect the cellulose. It basically supports the plant, so once we remove that, that leaves a lot of space in the wood or in the cell wall," said Yunxuan Wang, a UT postdoctoral researcher collaborating with Ragauskas. "At that point, the cell wall is basically composed of cellulose and can be densified when compressed. The fibers form hydrogens bond that will provide additional strength to the material."

However, applying this technique to mixed-source wood waste poses unique challenges due to its inconsistent composition, which can include sawdust, cardboard, and paper.

"You don't always have large chunks of wood available. You usually have a lot of waste wood during the manufacturing of wood, like the sawdust or those waste materials," Wang explained. "So, the goal of the project is to utilize this material, but to achieve the same goal to make this densified board with very high strength."

As demand grows for environmentally friendly materials, the team believes densified wood products could serve as sustainable alternatives in automotive, aerospace, and construction sectors. Metal production is notoriously energy-intensive, adding urgency to the search for greener substitutes.

Densified wood is not a new concept. As early as the 1930s, it served as a metal replacement in military aircraft manufactured in the United States and Germany.

"The conversion of waste wood to a high-performance board provides a unique opportunity to turn 'trash to cash,' minimize landfill needs, and reduce the logistics of building materials, especially in remote areas," Ragauskas noted.