Neel Strøbæk, Devapriyo Das

July 3, 2022

Is recycled timber the answer to our carbon woes?

Timber is becoming a popular sustainable alternative to building materials such as concrete and steel. Yet an ever more sustainable solution is to build with waste timber. Colin Rose, inventor of upcycled climate-friendly timber, explains in this video.

By reclaiming the wood that gets discarded from London’s building sites, we would have enough material to build 1,000 new homes per year entirely from waste wood.
That is the ballpark estimate of Dr. Colin Rose, a researcher at University College London, who in 2020 won the Flemming Bligaard award for his research into upcycled timber as a climate-friendly building material.
Also known as cross-laminated secondary timber, this material can replace steel and concrete, and could reduce embodied carbon in the built environment. It is an urgently needed solution in the fight against climate change, as the building and construction industry accounts for 40% of global energy-related greenhouse gas emissions.
We caught up with Colin to discuss what his research can tell us about the future of circularity in the buildings industry.
Watch the full interview (above). A transcript is provided below, edited lightly for clarity.
How can cross-laminated secondary timber reduce the embodied carbon of buildings?
“The embodied carbon in the built environment is going to become increasingly critical, and there are lots of ways that you can focus on reducing embodied carbon. The way cross-laminated secondary timber can contribute is, firstly, by capturing carbon. As long as we keep timber in use as a solid material, then it continues to store atmospheric carbon.
“So the longer that we can keep timber in use, and structural use is a really good example of long-term use, the more the built environment acts as a store for carbon
“Second, there's a potential for it to displace the use of more carbon intensive materials. So by getting waste wood back into use as a structural material, there's the potential for it to replace structural steel and concrete, which are two of the biggest producers of embodied carbon. Weighed against that is the impacts of production of cross laminated secondary timber. So there's the whole carbon accounting question.”
The Flemming Bligaard Award is given annually to an early career academic, whose work has made an outstanding contribution to sustainable development. Colin Rose’s current research, which is funded in part by the €65,000 Bligaard award, focuses on the ‘technical core’ of CLST: the engineering properties and performance of secondary wood.
Do you think the building sector, which tends to be conservative, has recognised the potential of CLST?
“I think we're still in the lab phase. So we haven't gone far in exposing ideas to industry. But the fact that Ramboll is willing to award give me the Flemming Bligaard award to progress this research is a good marker of confidence in the idea.”
Since recording the interview, Colin notes there has been progress in exposing ideas to industry. He says more is being done with UK EPSRC Impact Acceleration funding - and there is demand in the UK market for CLT that doesn't have to be shipped a long distance. At the same time, there is growing interest in the circular economy. Colin has since helped establish UK CLT with a view to commercialising the research into cross-laminated timber.
“And there are other research projects I'm following on from our initial scientific paper on cross-laminated secondary timber. As part of the Horizon 2020 CIRCuIT project, Grimshaw [an architecture firm, with engineers Simple Works, ed.] and a developer in London are looking at the idea of making glulam from secondary timber. There's also been some work on this topic in Ireland, Spain and Norway. So it's gaining traction.”
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“The CLT producers themselves, arguably should be looking at this, but their business model is very much focused on new wood from forestry. And the forests are plentiful. They possibly should be considering the longer-term challenges that will come about from increasing competition for the use of land as global population rises. We get materials like wood from land, but we also need to increasingly grow food.

"Industry does not take kindly to reuse at the moment. There's no consistency, and it doesn't fit with the way that buildings are typically procured."

Senior Research Fellow, UCL

So the idea of something like cross laminated, secondary timber and the way that I like to think about circular economy reuse, is that you try to move towards a product which can be specified as easily as a new material. So it's much more aligned with current procurement methods. I think that way, reuse can become a mainstream activity rather than something that operates in niches.
You mentioned the competing use of these resources and the pressure on land. Now we know that about two thirds of the world's population will be living in cities by 2040. Most of the growth will be spurred by developments in developing countries. Can CLST help build more sustainably in developing countries?
“It's a question we're really interested in. I think it's challenging. At the moment, a CLT plant is a multimillion-pound investment. So it's a case of how we get the technology to produce the material down from that sort of levels being something that's much more able to be rolled out.
“One idea I'm particularly interested in at the moment is a ‘flying factory’. Instead of having a factory that's in one established place, you design all of the equipment required to do the process, so that it fits onto a shipping container. So it can go on a truck, arrive at a site, carry out the process and deliver new materials for that particular site.
“These kinds of ideas are really relevant when you're working with sources of waste because they arise in all sorts of different places.
“And if we can get to the point where you can design and build that factory so that fits in a shipping container, maybe that's also getting to the point where costs are low enough to make use of local labour and use it in all sorts of parts of the world.
“Timber is ubiquitous. So it seems to make sense.”
To contact the editor of this story, email: Devapriyo Das

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