Transforming scrap wood into lightweight and strong building materials could help divert staggering amounts of waste from landfills, says University of British Columbia chemical engineer Orlando Rojas.

According to the US Environmental Protection Agency, recycled municipal waste wood accounted for 3.1 million tons in 2018, representing just 17 per cent of the that country’s total wood waste.

“Canada has almost 10 per cent of the world’s forests. We should be at the forefront of achieving circularity in wood materials,” says Rojas. “The goal of our research is a marriage of wood recycling and the creation of a long-lived building material.”

He and his team have come up with a process to turn wood scraps, decayed wood and even sawdust into a material that is five times stronger than natural wood. In a paper published in May in Nature, they describe using a solvent called dimethylacetamide in the presence of lithium chloride to dissolve lignin, a glue-like substance in plant cell walls. The chemical pairing also exposes tiny fibres called cellulose fibrils in the plant cell wall.

When regenerated with water, the wood’s fibrils align to create what the researchers describe as “healed “wood. This alignment, along with the resulting hydrogen bonding in the nanoscale pores of the cellulose fibrils, creates a densely packed material with vastly improved mechanical strength. The wood is stronger than commercial laminated wood and some metals, plus it’s resistant to organic solvents.

The material, however, does have its limits. If submerged in water, it will hold its shape but lose some of its strength, making it suitable for indoor uses only.  It could also be used in composite materials, insulation and packaging.

Part of the beauty of the team’s process is that it doesn’t require high temperatures or pressure, reducing its energy footprint. “We use chemical energy,” says Rojas. “And we can, in principle, recover the solvent and use it over and over again.”

Steve Eichhorn, a materials scientist with the University of Bristol in the UK calls it an elegant way to heal wood, using a well-known cellulose solvent to recover and enhance wood’s mechanical properties.

“The approach is potentially scalable and in doing so this should take this technology to the next level,” says Eichhorn.

Rojas says next steps include analyzing the process’s economic feasibility and conducting a life cycle study of its carbon footprint.