A material made from recycled wood is five times stronger than natural wood and can be made from any timber by-product, including shavings and sawdust. Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic material – a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere, such as in the roots of trees or shrubs.[citation needed] In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or wood chips or fiber. Wood has been used for thousands of years for fuel, as a construction material, for making tools and weapons, furniture and paper. More recently, it emerged as a feedstock for the production of purified cellulose and its derivatives, such as cellophane and cellulose acetate.
As of 2005, the growing stock of forests worldwide was about 434 billion cubic meters, 47% of which was commercial.[2] As an abundant, carbon-neutral[citation needed] renewable resource, woody materials have been of intense interest as a source of renewable energy. In 1991 approximately 3.5 billion cubic meters of wood were harvested. Dominant uses were for furniture and building construction.[3]
Wood is a hugely versatile material, but millions of tonnes go into landfill each year. To build a truly circular economy, wood will need to be re-used on a grander scale.
Orlando Rojas at the University of British Columbia, Canada, and his colleagues have invented a process that dissolves lignin, a glue-like component inside plant cell walls, and exposes cellulose myofibrils, which are tiny fibers also found in the plant cell wall.
When two pieces of wood treated in this way are brought together, the myofibrils bind to create what the researchers call a “healed” piece of wood. Although this no longer looks like natural wood, it has better mechanical properties. Tests show it is more resistant to breaking than stainless steel or titanium alloys.
“We get a mechanical strength that supersedes the strength of the original material,” says Rojas. “It works because we use the inherent properties of cellulose, which is a material that binds together very strongly by something called hydrogen bonding.”
Not only can wood treated this way be re-used to create new objects, but the treatment process can be performed repeatedly on the same pieces of wood to extend their working lifetime. “This is a really elegant way to heal wood, using a common cellulose solvent, recovering and enhancing the mechanical properties of nature’s wonder material,” says Steve Eichhorn at the University of Bristol, UK. “The approach is evidently scalable, and therein lies the challenge to take this technology to the next level.”
Rojas and his team didn’t examine how much their method would cost if scaled up to an industrial level, but all the techniques used are well-established. “The processes that we use here are very typical in wood processing,” says Rojas. “So scalability is not an issue.
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