In last month’s column, I provided an overview of the concept of circularity in terms of both product and building design. This included an introduction to Arup’s Circular Buildings Toolkit focused on the architect’s role in rethinking the way we design and construct buildings, and a brief discussion of steps that building material manufacturers could take to move toward a circular economy. This second part deserves deeper exploration for two key reasons.
Rounding up Carbon Emissions and Waste in Building Materials
Firstly, life cycle assessment of individual materials and whole buildings covers three stages: material extraction and manufacturing, and building construction (Stage A), building use (Stage B), and end-of-life (Stage C), typically viewed as a linear process with a beginning and end, cradle to grave. We put more emphasis on Stage A because this is where most of the embodied carbon emissions and other environmental impacts occur. However, maintenance and replacement practices in Stage B influence the longevity of the materials. And while the Stage C impacts are small compared to Stage A, effectively recovering and recycling materials as feedstock for new building materials can significantly reduce environmental impacts in Stage A of the next life cycle when we close the loop. In other words, one direct way to reduce embodied carbon in Stage A is to optimize closed-loop recycling potential in Stages B and C.
Secondly, much of the focus on embodied carbon reduction in buildings has been on structural systems. This makes sense, as the foundation and superstructure of a typical building represents approximately 50% of the initial embodied carbon, with the enclosure being roughly 30% and the interior finishes the remaining 20%. However, the structure of a well-designed and sited building can be expected to last 100 years or more, while exterior enclosure elements have a 20- to 30-year life due to weathering, and interior materials will typically be replaced every five to ten years, due to aesthetic obsolescence or changes in use. This means that these building elements will be replaced three to 15 times or more over the life of a building, eclipsing several times over the initial embodied carbon of the structure.
Therefore, achieving circularity with non-structural building elements is critical to reducing the lifetime embodied carbon and environmental impacts of buildings. This is especially true for materials such as roofing, insulation, cladding systems, glazing, carpet, gypsum board, acoustic ceiling tile and carpentry. Unfortunately, even materials that currently have recycled content are downcycled into lower value products or landfilled at the end of their lives, either because recovery and recycling systems do not support closed-loop recycling or because composite materials are difficult to separate for recycling of their various constituents. For example, recovered gypsum board to typically ground up and used as a soil amendment and old carpet is often used to create lower-quality plastic resins for automotive parts and other short-lived products destined for disposal. This may be slightly better than a trip straight to the landfill, but it still means a waste of valuable resources and that new materials must rely on carbon-intensive, virgin raw materials.
The solution to creating a circular economy for building materials will require three primary initiatives that must co-evolve to completely close the loop: material science innovation, recovery logistics and designing for deconstruction.
Traditional priorities for building materials include high performance, low cost and compliance with standards. These remain important of course, but government “buy clean” mandates, private sector carbon emission reduction initiatives, and the imperative to address the climate crisis require that manufacturers invest in material science innovations to increase closed-loop recycling of their products at the end of their useful lives. Using old products as feedstock for the same product anew presents an opportunity to gain first-mover competitive advantage and positive brand image by leading the movement toward circularity.
The logistics of recovering and transporting recyclable materials back to manufacturers is a barrier to cost-effective, closed-loop recycling. The use of building materials is obviously very dispersed, and the quantity of recoverable material from any given region could vary widely over time. Of course, current raw material supply chains and finished product distribution networks are also complex and variable. There is an opportunity to reimagine value chains and find efficient ways to integrate the collection and transport of recovered materials for recycling into existing networks. The European Union has pioneered extended producer responsibility (EPR) laws, requiring manufacturers to take partial responsibility for the recovery and recycling of the products they make, including packaging, electronics and batteries, and vehicles. Following this lead, four U.S. states (California, Colorado, Maine, and Oregon) have adopted EPR requirements for packaging and foodservice ware. These EPR mandates will expand both geographically and in scope, eventually including building materials. It would be prudent to stay ahead of regulatory trends and find business advantage in maximizing the use of recovered feedstocks.
Another barrier to optimizing closed-loop recycling is the current economic advantage demolition has over deconstruction, because construction details and methods make disassembly of building systems time consuming, labor intensive, and/or physically impractical, and due to the lack of information at end-of-life of what went into the building years before and how it was assembled. Architects can help by considering the varying life cycles of building elements and designing for disassembly and replacement with minimal disruption to adjacent elements. More importantly, the emerging concept of materials passports, first introduced in Europe, could be game-changing. A material passport is a catalog of the composition and recyclability of materials and assemblies in a building. It provides information to guide the future deconstruction of assemblies, making it easier to estimate effort and plan processes for successful deconstruction and optimized material recovery.
Government mandates and carbon emission reduction imperatives in the building industry will be pushing the transition to circularity in the built environment. The transition will take time and will require collaboration of multiple stakeholders, so there is no time like to present to get started with material science innovations, new material handling and transport logistics, and design and documentation to optimize deconstruction and material recovery potential. Each of these steps will get the building industry closer to closing the loop.
Alan Scott, FAIA, LEED Fellow, LEED AP BD+C, O+M, WELL AP, CEM, is an architect and consultant with over 35 years of experience in sustainable building design. He is director of sustainability with Intertek Building Science Solutions in Portland, Ore. To learn more, follow Scott on LinkedIn at www.linkedin.com/in/alanscottfaia/.