Jie Li, PhD, an engineering professor at RMIT and leader of the study, estimates that around 6.88 billion disposable face masks are being produced daily around the world. These single-use masks are not recyclable (they can clog recycling machines and pose a health risk to the people who run them), meaning billions of masks are destined for the trash.

“Since they are mainly made of non-biodegradable plastics, these single-use masks will take as long as 450 years to break down in the environment,” Li tells mbg via email. “Therefore urgent action at every possible level is needed to address this serious environmental threat.”

His team, which specializes in recycling and reusing waste materials for civil construction, set out to find a second-life application for PPE. They had a hunch that surgical masks could be repurposed into a sturdy but pliable road material. To form the base of a stretch of road, they combined masks with processed rubble from construction—another abundant waste product.

They found that a mix of 1% shredded face masks to 99% recycled building material would be strong enough to do the job. Even at this relatively low percentage, the material would use 3 million masks per kilometer (0.62 miles) of two-lane road. So if it was used to build all of, say, Highway 1—Australia’s longest highway at 9,010 miles—it would spare at least 43 billion masks.