Repurposing used plastic into road infrastructure could take all waste PET of U.S.
The founder of a company that worked for years to research ways to repurpose plastic waste into roads and develop a product said that if its composite asphalt pavement use were to extend beyond parts of Los Angeles across the U.S., it could eventually use up all the waste PET in the country.
The product is an asphalt mix technology already put to use in California that may not just cut plastic waste in the U.S., a pressing need after China banned such imports in 2018, but also yield strong, flexible pavement while improving roads and helping cut carbon emissions in the process.
The product has already proved viable, and there are several projects ahead, said Sean Weaver, TechniSoil Industrial president.
“Big picture, a city like Los Angeles is able to gather their plastic waste and give that to us, we convert it using the glycolysis to react it into our polymer, and then we recycle their roads with it,” he said.
“If we fully adapted our system throughout all 50 states we can potentially take all the waste PET from the U.S.,” he added.
The plastic composite pavement has the flexibility of plastic but also the compressive strength of concrete.
“Plastic has incredible tensile and elongation properties which create a strength and flexibility far superior to bitumen,” he said. The result are flatter roads with less potholes, he added.
Eight years of research
The American Chemistry Council (ACC) on Oct. 1 celebrated legislation approved in the Fall 2020 that supports “studying innovative ways to repurpose used plastics.”
The studies are to find “ways to repurpose plastics in infrastructure projects, such as roads and bridges” as part of the Save Our Seas Act, it added.
Weaver said the research that led to TechniSoil’s product goes back to 2012.
“We came up with a polymer substitute for bitumen that performed really well with 100% recycled asphalt, so in 2015 we started a five-year program with the University of Nevada, Reno to evaluate the pavement,” he added.
“We recycled a road in 2015 using this material, and we evaluated and studied that road through 2019, and everything looked very good. The road performed better than new asphalt,” Weaver said.
China’s ban on waste imports
China’s January 2018 ban on the import of eight types of plastic waste turned into an opportunity.
“In 2019 the Department of Energy (DOE) reached out to me about the study and said hey, since China stopped taking our plastic in 2018, the DOE is looking for ways that businesses or industries could incorporate large amounts of the U.S. waste plastic back to some valuable end use,” Weaver said.
Then “the City of Los Angeles heard about our technology and were very keen to be the first city to run trial and testing,” Weaver said.
“They conducted 1,400 tests over the course of three months in 2018. They got very good findings in the labs and that resulted in three test sections, with the last test section on a public road,” he said.
That test section “turned out really well and much stronger than their best traditional asphalt roads,” he said.
“They are now looking at utilizing our technology to recycle their bus lanes initially, and moving to other lanes after that,” he added.
Rescuing degraded PET
“Traditionally, you re-melt the plastic into another bottle, but every time you re-melt, you degrade the quality” so a plastic bottle can only be recycled a maximum of 10 times, he said.
“So what do you do with the plastic once it’s distressed past the point of recyclability?“ he added. Chemical recycling can then turn the degraded plastic back into its original elements, he added.
“So we’re able to capture 100% of the monomers out of plastic and incorporate that into our new binder,” he said.
Currently the U.S. recycles 26% to 30% of PET that it produces, he said.
“We see our road system in the U.S. as one of the few applications that is big enough to make long-term, productive use of recycled PET,” Weaver said.
“Polyester and PET are the same thing,” he added. There is potential to eventually also use other PET sources including that in other packaging, and perhaps other plastic.
“We know the technology can accommodate other types of plastic in pelletized form. This is a priority for us to explore as the technology continues to develop,” Weaver added.
Stronger roads
“When used to produce pavement in the laboratory it creates life cycle gains 6 to 13 times longer than traditional asphalt. In the field we’re conservatively claiming two to three times the cycle of traditional hot mix asphalt,” Weaver said.
The composite “has the flexibility of asphalt but the compressive strength of concrete,” he added. This is because of plastic’s tensile and elongation properties, he added.
The road system would improve, he said.
“These roads will have less potholes, they’ll be flatter, which creates better gas mileage, and they’ll need far less maintenance, he said.
Reducing carbon emissions
Under the current road repair process across the country, “when a road reaches the end of its useful life, it is milled out to a depth of 3 - 4 inches, waste asphalt is removed from site, and new asphalt is laid down,” Weaver said.
“So for every lane mile, (one mile long by one lane wide) they have to remove 42 trucks of waste asphalt and bring 42 trucks of new asphalt in,” he said.
This system is not only a waste of existing asphalt and unnecessary use of virgin aggregate, but it also damages surrounding roads that endure the traffic, he added.
“Utilizing our binder we can recycle the asphalt, the whole asphalt, 100%,” he said. This also eliminates the need for truck fuel.
“We also use approximately six times less energy because we perform the treatment at ambient temperature, without heat involved,” Weaver said.
By Renzo Pipoli
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