Despite the fact that waste plastic can be recycled, in the U.S. less than 10% of it actually is. Part of the problem is a lack of demand for the plastic coming out of recycling facilities. But according to researchers from Stanford University, viable ways to reuse waste plastics are hiding in plain sight. From roads to building facades to drainage pipes, many common infrastructure and construction projects could easily be made using recycled plastic.
“We were trying to find a solution that will create a large amount of demand for recycled plastics, and we were also trying to find a solution that has a long-use life,” says Zhiye Li, a postdoctoral scholar in civil and environmental engineering, and lead author of a white paper showing that under the right conditions, recycled plastic could be reused at a vast scale in the form of building materials.
The white paper is an appendix to the National Academies of Sciences, Engineering, and Medicine’s annual report to Congress, the U.S. Department of Transportation, and the U.S. Environmental Protection Agency. Like a guidebook of best practices, the report lays out achievable ways the waste streams of today can become the building blocks of tomorrow.
“When we try to think about what is a viable solution for reusing some of these materials, we need to identify parts of our economy that consume huge amounts of material. And the industry that consumes much more by mass than anything else is construction,” says Michael Lepech, a professor of civil and environmental engineering at Stanford, and coauthor of the white paper.
Li and Lepech interviewed dozens of construction industry experts and practitioners, and explored several case studies of experimental uses of recycled plastics, and found that recycled glass fiber reinforced polymer composites are viable alternatives to the virgin materials used in common materials like roads, drainage pipes, railroad ties, and the exterior panels on buildings.
Li says using single polymer materials would make the recycling process easier. By using these materials in projects that have a long life, there will be less material degradation. “When we recycle [plastic], the chemical and mechanical properties and the performance will decrease,” says Li. “If we recycle them too many times, the performance will be very bad.”
Using recycled plastic in a road that will last for decades or in a building that will stand for more than a century, Li says, puts these waste streams to work for much longer than simply recycling one plastic bottle into another. And at the end of their useful lives, these materials could be deconstructed and recycled again. “You know what this is and how it was managed, which of course makes it easier to use the next time around, in a more circular fashion,” Lepech says.
Further research is still needed on various elements of this type of recycling, according to the researchers, including more study on the safety of the materials and potential health impacts related to microplastics.
“This really should be investigated and studied,” Lepech says. “The best science we have says that this can possibly work, and with appropriate levels of investigation and funding it can be made both good and safe.”
Though recycled plastics could become a new material of choice for the construction industry, the researchers aren’t suggesting that they replace all other common building blocks. “It’s not quite right to say it’s concrete or steel or polymers or something else,” Lepech says. “Climate change will require a cadre of many technologies that come together because of the magnitude of the problem and the global nature of it.”