BLOG – Jessica Tuck, National Technical Director
Industry owes it to society to conserve materials in every possible way. Not only for the element of cost in the manufactured article but mostly for the conservation of those materials whose production and transportation are laying an increasing burden on society.
Sound familiar? You could well hear it at an industry event today, however, it was actually said by Henry Ford, the American inventor and industrialist, in 1926.
Transitioning from a ‘take-make-waste’ linear economy to a circular economy, where waste is designed out and materials kept in use and reused across their lifecycle, is not a new concept. But the opportunity to drive material circularity across our infrastructure and road assets is not being fully captured.
During a recent event, I asked a group of senior clients how many had a plan to work with their full supply chains to drive material circularity. Those who did were a small minority. If I had asked the question about carbon reduction across the supply chain, it would have been a very different answer.
Delivering circularity will help our commitment to net zero. Circular economists believe that 45% of the world’s greenhouse gas emissions are embodied in everyday products such as our cars, clothes, buildings, infrastructure and food. Radically changing how we use resources and keeping materials in service for as long as possible is therefore key to carbon reduction and net zero delivery.
We have to plan for circularity.
At an operational and project level we need to understand what is in the asset and how the materials can be recycled. However, there is an important step before this. Infrastructure clients need to ensure that their supply chains prioritise circularity and align industry effort. A change of mindset will require our sector to better design road schemes for circularity and for us all to share knowledge. The opportunities for recycling and reuse are significant. Asphalt is one of the most recycled materials in the world but there are still a lot of opportunities to increase the use of recycled asphalt planings (RAP) in both the surface course and lower layers of roads. The surface course continues to represent both a challenge and an opportunity. At the moment, surface course asphalt materials are recycled into new asphalt products and placed back in our roads. However, it is common practice to use only the finer recycled material in new surface course materials.
The industry is not getting the benefit of recycling precious nominal size high polished stone value (PSV) aggregates that are finite and key to delivering skid resistance on our roads. It is technically viable to recycle high PSV aggregates back into surface courses. To do so we need to understand the PSV of the coarse aggregates in the planings. We do not currently have an industry system for tracking the PSV of the aggregate in the asphalt planings.
Data on the PSV composition of the existing asset does not always exist and is not commonly shared as standard practice within the supply chain. In the absence of available data to enable the recycling of high PSV aggregates in surface course asphalt, contractors need to plane off the surface layer and store the planings separately from the lower layers so that the PSV of the coarse aggregate can be confirmed before recycling into a new surface course. Once the RAP aggregate has been quarantined, the next steps are to recover the binder and take PSV samples. This can be a time-consuming process and requires a lot of space to store materials, which is another reason why the high PSV aggregate is not being recovered and reused.
National Highways is exploring a digital approach within its pavement community which, if developed, would unlock opportunities for increased circularity of high PSV stone: the asset owner would provide data relating to the area from where the asphalt is removed to enable its reuse without the need for PSV testing. There are no similar plans when it comes to binder testing so these protocols would remain unchanged.
Across the industry, a number of potential avenues for boosting circularity are being explored. Although there are no plans to allow the reuse of PMB binders, it is an option being explored in conjunction with PMB suppliers to understand whether PMB properties could be assumed or verified for such reuse.
Materials circularity remains a significant priority for Tarmac. We already reuse more waste generated by other people than the volume of waste we produce. In 2022, we recycled 99% of the waste generated across our operations and our goal is zero waste by 2030. Each year we recycle over one million tonnes of recycled asphalt planings in new asphalt – translating to 15% of our asphalt production. We also recycle over seven million tonnes of waste and secondary materials as raw materials or fuels from other sectors. Materials mattered to Henry Ford in the 1920s. In a world transitioning to net zero, they need to matter to all of us today.
