Timber in the circular economy
As a natural resource, timber is set to play a significant role in the future of our built environment, offering enormous potential within a new circular approach to construction sector resources and best practices.
According to the Ellen MacArthur Foundation,1 the circular economy offers environmental, business and social resilience by decoupling economic activity from the consumption of finite resources. The circular framework relies on the principles of designing out waste and pollution, keeping products and materials in use, and regenerating natural systems. This is in stark contrast to the current built environment model, which is highly linear, traditionally relying on the manufacture and use of new materials and producing vast amounts of construction, demolition and excavation waste.
While timber distributors will always want to sell new timber, reclamation has always had an accepted role within the marketplace. However, despite these good foundations, we are still at the beginning of true transformation, with many challenges yet to be faced and a great deal still open for discussion. Here, BM TRADA looks at some current research and poses a few key questions to industry experts, asking how we might begin to tackle the challenges faced when attempting to maximise the service life of timber.
What are the challenges of timber waste reduction and reuse?
Alastair Kerr, Director General of the Wood Panel Industries Federation2 said:
“There is a very well-established system for the collection and processing of waste wood from construction, household waste and industrial waste wood. Waste wood from these sources provides an invaluable raw material input for the manufacture of chipboard. At the end of life, chipboard can also be recycled. Wood-based panels grew out of a need to use smaller dimension forestry wood and residues from the sawmilling sector. By reconstituting wood fibre/chips etc into standardised panels, they help to reduce waste.
“Reducing timber waste in construction is more problematic. Off-site construction helps to optimise material use and in doing so reduces waste. Reuse is probably the most challenging aspect because the majority of timber and wood-based products are installed as a component of larger systems and in order to meet the technical demands of the application, materials within these systems tend to be rigidly fixed, making disassembly without damage to the components nearly impossible.
“Prefabricated system components could potentially be reused but if they have been in for the life of the building, it’s unlikely that anyone would want to pay the costs necessary to segregate out materials undamaged.”
Reusable design and construction
Project InFutUReWood was led by RISE (Research Institutes of Sweden) under the umbrella of ERANET Cofund ForestValue. According to the project report, its mission was to answer the question: ‘How should we build today to be able to circulate tomorrow?’. The scope of the project was the reuse of structural timber from current buildings and how current and past experience of demolition might help the design of timber buildings (1–3 storey) to facilitate future deconstruction and new products out of recovered wood. The primary focus for new products was sawn and laminated structural timber.3 >>
Here we look at current research and open discussion around how we might tackle problems faced when maximising the service life of timbers as the construction industry learns to embrace a more circular economy.An automated auger for loading processed wood chip heating fuel into a biomass boiler. Photo: georgeclerk
Now, RISE is leading the Design for the Future - Reuse of Timber Buildings in a Circular Economy study which aims to develop demountable and reusable wooden buildings based on environmental impact calculations and collaboration across players throughout the construction and demolition supply chain.4 Researchers and industrial partners are currently developing two demonstrators with design for deconstruction and reuse in mind. One is a modular building and the second is a flexible timber building. The project principals look forward to publishing their results later this year.
The secondary timber value chain
In their paper, A Shed Resource: A look at wood recycling in the UK,5 Marlene Cramer and Daniel Ridley-Ellis of Edinburgh Napier University explored the secondary timber value chain and the future of timber in the circular economy by interviewing community wood recyclers, chip producers and board making companies.
For their report, Cramer and Ridley-Ellis spoke with seven UK wood recycling companies, whom they believe represent a good cross-section of the sector. These companies collect and process a mix of waste wood that includes used and unused solid timber and board products rejected or reclaimed from sawmills and construction sites and pre-used products like furniture and whisky barrels.
“On our way to a more circular, bio-based economy, we will need to start treating recycled timber as a more valuable
resource,” explain the authors. “In a perfect world, your garden shed might serve as a dinner table, before it gets chipped and lives again as a kitchen top, possibly again as a flooring board, and finally provides heat for your grandchildren’s home, when it is incinerated at the end of its life. But what happens in reality?” they ask.
Cramer and Ridley-Ellis conclude: “None of the companies sees particular problems in processing recovered material, since existing contaminations are manageable. For these companies it is business as usual to remove all the nails, paint and concrete that is adjacent to the parts of your garden shed and most of these processes are automated. On the other hand, none of the companies sees a potential for higher value products made from the material they receive. The timber is mostly damaged and mixed with other materials from the demolition process or earlier use.”
However, the report also notes that; “The big companies for wood recycling are not receiving any government support for their circular material use.” And that, “The varying prices for the recovery notes are therefore problematic.”
What is the current level of timber recycling in the UK?
Despite these challenges, Julia Turner, Executive Director at the Wood Recyclers’ Association, said:
“The level of wood that is recycled and recovered in the UK has gone up considerably over the last two decades, with the industry now an exemplar of best practice in the UK circular economy. Our annual waste wood statistics show that in 2021, of the 4.5 million tonnes of waste wood collected in the UK, over 4 million tonnes were processed. Of this, roughly a third (34%) was sent for reuse or recycling, to markets such as panel board, equine surfaces and animal bedding, while around two-thirds (66%), was sent to small-scale biomass, exported, or used in large-scale biomass plants to generate baseload domestic renewable energy.
“With regards to recycling, the panel board sector – the largest user of recycled wood in the UK – increased its usage of >>
waste wood by 10% on the previous year, reaching a record high of 1.08 million tonnes.
“We expect that even more waste wood will be processed this year, as we now have valuable end markets for all waste wood. This shows how far the waste wood industry has come since 2008 when the majority of waste wood was sent to landfill.”
Cross-laminated secondary timber
Dr Colin Rose is a Senior Research Fellow at University College London (UCL), Strategic Advisor for the Built Environment at ReLondon, where he contributes to the CIRCuIT project, and founding partner of UK CLT LLP. Having won Ramboll’s Flemming Bligaard Award 2020, he leads circular economy research at UCL investigating the use of secondary timber.
“Reuse is a challenging aspect of circularity; with timber, it’s far easier to chip it and incinerate or downcycle. What we mean by downcycling is that the qualities of, say, 19th-Century floor joists are lost when you turn them into panel boards or animal bedding. Many demolished buildings contain large quantities of joists, studs and rafters that could be reused, but are typically skipped. We refer to these materials as secondary timber,” Rose continues, “because they don’t need to be thought of as waste. They often retain structural as well as aesthetic qualities, so the challenge is to put that to use in a practical and valuable way.”
“With cross-laminated secondary timber (CLST), we’re aiming to upcycle wood into a standardised and recertified product that meets the requirements of the mainstream construction industry. As a low-carbon alternative to concrete and steel, CLST achieves long-term carbon capture and storage beyond timber’s first use. Furthermore, it can be designed for future deconstruction and reuse, before eventually becoming chipboard and biomass.”
“We share the wood recyclers’ goal of creating a more circular timber industry. There’s a lot of work to do before we’ve optimised our use of secondary timber, but it’s fantastic to see growing interest from academia and industry in its potential for production of engineered wood products.”
Transforming the timber industry
Transformation of an industry is no mean feat. It begins with discussion. If you have expert input you wish to share on this matter, BM TRADA would be interested to hear from you. If you wish to find out more about how you can safely assess the service life of your timber, please do contact our technical helpline on 01494 569601. n
About the contributors
Alastair Kerr
Director General Wood Panel Industries Federation
References
Colin Rose
Senior Research Fellow at the Department of Civil, Environmental & Geomatic Engineering, University College London
Julia Turner Executive Director Wood Recyclers’ Association
Karin Sandberg
Senior Forskare Research Institutes of Sweden
1. Ellen MacArthur Foundation, www.ellenmacarthurfoundation.org
2. Wood Panel Industries Federation, www.wpif.org.uk
3. InFutUReWood, www.infuturewood.info
4. RISE/News, ‘Design for the Future – Reuse of Timber Buildings in a Circular Economy’, https://www.ri.se/en/ what-we-do/projects/design-for-the-future-reuse-of-timberbuildings-in-a-circular-economy accessed 9 December 2022
5. Cramer, M., & Ridley-Ellis, D., ‘A Shed Resource: A look at Wood Recycling in the UK’, September 2020, paper presented at Timber 2020, online
Further reading
• WIS 2/3-58 Sustainable timber sourcing, BM TRADA, 2019
• WIS 2/3-59 Recovering wood waste, BM TRADA, 2020
• Rose, C. M., & Stegemann, J. A., ‘Feasibility of crosslaminated secondary timber’, Fifth International Conference on Sustainable Construction Materials and Technologies (SCMT5): Vol 1, 1, 2019
• Rose, C. M., Bergsagel, D., Dufresne, T., Unubreme, E., Lyu, T., Duffour, P., & Stegemann, J. A., ‘Cross-laminated secondary timber: Experimental testing and modelling the effect of defects and reduced feedstock properties’, Sustainability (Switzerland), 10 (11), 2018, doi:10.3390/su10114118