Words by Thomas Musson
“Why, given the pressing need to reduce and stabilize atmospheric CO2 levels, are we content to design these durable, highly engineered elements to be single-use?”
Wood is becoming a popular solution for many buildings where steel or concrete used to be the only options. This has been made possible by the development of engineered timber, a relatively modern collection of products made by binding timber laminations, strands, particles or fibres using adhesives or mechanical means to create composite elements that are far stronger and more robust than traditional wooden components.
Timber’s appeal lies in its low embodied carbon. Well designed and executed engineered timber structures, using wood from sustainable sources, are inherently sustainable due to the natural process of sequestration. As trees grow, they absorb carbon dioxide from the environment and lock it away in the structure of the wood. Depending on its density, 1m3 of wood may store more than 1 tonne. This remains locked in during the production of engineered timber elements and over the life of the building.
But when the structure is burned or sent to landfill, this carbon is released back into the environment. The way that most timber buildings are currently designed, with no thought for how the components might be recovered and reused, makes this a certainty. This means that we are missing a major opportunity to keep it locked away for longer, and to avoid the emissions associated with producing new building materials. Why, given the pressing need to reduce and stabilize atmospheric levels of greenhouse gases, are we content to design these durable, highly engineered elements to be single-use?
Accurate figures are hard to come by, but some estimates put the volume of recycled wood products as low as 30%. In comparison, over 95% of steel recovered from demolition waste in Europe is reused and recycled into new steel products, and a similar proportion of concrete waste is crushed and repurposed for other uses such as recycled aggregate. To maximize the long-term sustainability of engineered timber buildings, the timber recovery and reuse market must reach the same level of maturity.
This is partly a question of policy and economics, but it’s also an engineering challenge that we need to start solving now. The potential stock of timber components increases with every new timber building — but only if we design them so that they can be dismantled and reused.