Turning wood waste into metal alternative
Imagine if all the wood waste left over from home construction zones, furniture manufacturing, landscaping projects, or lumber mills could be turned into a substance as strong as steel.
That is the goal of a research project at the University of Tennessee led by Art Ragauskas, UT-ORNL governor's chair for biorefining and acting department head of the Department of Chemical and Biomolecular Engineering.
The project—Waste Upcycling for Defense (WUD)—received a $2 million contract from the Defense Advanced Research Projects Agency (DARPA), which is a government agency that develops new technologies for national security. UT, the lead university on the project, is collaborating with the University of California, Riverside, and Georgia Tech.
Wood is a low-cost, environmentally friendly alternative to metal and alloys. Natural wood, however, lacks the strength and toughness for wider use a structural material. Past research has proven that wood exhibits exceptional strength properties when it is densified by removing the lignin, which is the glue that holds wood cells together, and compressing the wood.
"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, the UT post-doctoral researcher assisting Ragauskas on the project. "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."
This approach becomes more challenging for mixed waste wood material due to the diverse nature of the starting biosources like scrap wood, 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 said. "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."
There has been a need to develop more sustainable materials to replace metal because metal processing and fabrication are energy intensive. Producing wood with an increased strength could potentially be used in cars, airplanes, or buildings.
As early as the 1930s, densified wood was used to replace metal materials in military aircraft 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," Raguaskas said.
Provided by University of Tennessee at Knoxville