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A second life for old treated wood

February 14, 2018 | Gisèle Bolduc

Update : November 10, 2020

Every year, several thousand tons of treated wood waste is buried, incinerated, or mixed with untreated wood waste. The management of this waste is problematic because treated wood contains preservatives such as arsenic, chromium, and copper to slow its deterioration. To remedy this, INRS researchers have found a simple, effective, and environmentally friendly solution.

They have developed a process that successfully removed more than 90% of the contaminants present in treated wood waste in experiments conducted on a small scale in the laboratory. Thanks to an Idea to Innovation Grant from the National Science and Engineering Research Council (NSERC), professors Jean-François Blais and Guy Mercier and their team will be able to assess the performance of this process on a larger scale in order to determine its technical and economic feasibility.  

“The hydrometallurgical process allows for the simultaneous solubilization of contaminants present in wood waste,” said Professor Blais. “It stands out from existing technologies for its ease of operation, its metal solubilization capacity, and its low greenhouse gas emissions.” 

Once decontaminated, the wood waste can be reused as a raw material for the manufacture of value-added products such as particleboard or heating pellets. In addition, recovered metals could potentially be used to manufacture by-products, such as chromium oxide and copper sulphate.

In short, this hydrometallurgical process outperforms the biological and thermal processes currently used to decontaminate treated wood waste. It is low cost and offers several advantages: 

  • It improves the management of treated waste wood by diverting it from landfill or incineration.
  • It allows the wood fibre to be recycled.
  • It reduces contamination in the recycled wood industry.
  • It ensures a regular and constant supply of quality wood fibre.