Infrastructure Is Promising Use for Recycled Plastics, But Needs Study

Government report cites benefits and concerns of using recycled materials in high-volume market

The U.S. needs to reduce the amount of plastics waste generated every year that ends up in landfills or as litter. Improved collection and recycling could increase the volume of post-consumer recyclable (PCR) plastics that find new life in products. At the same time innovative uses for PCR plastics in the high-volume infrastructure market could also significantly boost recycling rates. 

This is one finding of a pre-publication report from the National Academy of Sciences, released July 18, that analyzes the potential for use of waste plastics as additives, fillers or recycled content in infrastructure (Plastics Engineering, July 25). The diversion of PCR plastics to this market could go a long way toward reversing the low U.S. recycling rate, while creating a sizeable market opportunity for recyclers and entrepreneurs.  

In the report, “Recycled Plastics in Infrastructure: Current Practices, Understanding and Opportunities,” the National Academy examines the feasibility of diverting PCR plastics into such end-uses as asphalt, roads and pipes.  

The volume of recycled plastics specified for infrastructure hasn’t been sufficient to disrupt the supply of PCR in the U.S., much less narrow the gap that exists between capacity and supply. A considerable amount of performance testing and examination of the merits of PCR plastics in infrastructure is also necessary, the report advises.  

Recycling capacity in the U.S., according to a 2022 report by the Association of Plastic Recyclers (APR), is at least twice as much for major plastics as what’s utilized. The APR report stated that 80 percent of recycled plastics comprise just three polymer types—PET, high-density polyethylene and polypropylene. The average recycling rate for these resins is 21 percent, while the processing capacity for them is 42 percent.  

“The imbalance in supply and demand will continue into at least the near future,” forecasts the National Academy report.  

At the same time, expanding the use of PCR in infrastructure will likely affect the economics and supply of recycled materials to conventional markets. As the National Academy notes: “To achieve real-world benefits from the recycling of plastics into infrastructure, a holistic assessment is needed to avoid overlooking important burdens or benefits within either the plastics system or the infrastructure system. … It is possible for well-intentioned changes in one part of a product system to have significant negative indirect impacts that completely wipe out or reverse the imagined benefit …”  

The report’s authors write that replacing “common construction materials and virgin plastics in infrastructure with recycled plastics requires the consideration of the life-cycle implications of these material substitutions.” Specifically, they note that “using plastics waste as feedstock to manufacture infrastructure components involves different supply chains, processing methods and material properties compared to manufacturing with primary feedstocks. These differences have qualitative and quantitative implications for material flows, transportation, product performance and durability, product end-of-life management, product environmental footprint, costs and other aspects of the plastic product life cycle.”  

Moreover, recycling PCR plastics into infrastructure “will only reduce the impacts of primary production of plastic if it reduces the demand for virgin plastics,” the report’s authors write. “If used to replace other infrastructure materials (e.g., binder in asphalt), downward pressure on plastic production would not be expected and the question becomes, ‘What is the relative impact of using recycled plastic compared to the other material it would displace?’” 

We’ll consider further observations and report recommendations in a future post.