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will be a need to optimise material flows to deliver a balance of benefits to society and the environment. The service life of wood-based panels (i.e., residence time in the built environment) is a strong benefit when recycling wood into the wood panel product group. Storage durations for some panel products are as long as the structural timber, especially in the case of timber frame housing systems. The same information can also support a case for recycling wood fibre within MDF panels or into insulation products to achieve further extension of the residence times, and an increased environmental benefit. Traditional wood and timber recycling methods are often considered to lead to down- cycling, producing materials of lower quality than the original. The common applications include energy generation, particleboard production, and animal bedding. Yet the hierarchy contains surprises, as the wood-based panels that use material from Categories A, B, and C can have considerable value as forms of carbon storage and offer further recycling cycles. The emerging option of MDF recycling, now demonstrated at scale, is a clear example of how even previously hard-to-recycle panels can enter the recycling chain. In future, it may be necessary to consider much more complex models of the different cascading routes within a network of recycled wood using options. To transition to a better integrated circular economy in the timber industry, greater awareness of the suite of panel products and their range of qualities and service lives will enhance decision making. In addition, there is scope for new innovation, either into advanced recycling and cleaning methods or for the creation of higher-value products from recovered wood. If a price premium becomes associated with certain applications, this could assist the economics of novel cleaning methods, thereby improving recycling rates. Chemical systems to remove preservative treatments have been demonstrated but require effort to scale up or a pull through from the market to utilise the cleaned wood. One option that could take cleaned wood and generate a premium is cellulose nanocrystals. A different option is pyrolysis oils as a feedstock for adhesives and wood treatments. Author Contributions: Conceptualisation, M.J.S. and G.A.O.; investigation, M.J.S., A.D. and G.A.O.; resources, G.A.O.; writing—original draft preparation, M.J.S., G.A.O., A.D. and S.F.C.; writing—review and editing, M.J.S., G.A.O. and S.F.C. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by Welsh Government under grant number: SFIS 081. Conflicts of Interest: The authors declare no conflicts of interest.
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