It’s no secret that the world has a plastic problem. Close to 300 million metric tons of plastic are produced each year, with the majority of products discarded as waste at the ends of a short lifespan.
One of the most concerning contributions comes from disposable plastic bottles—1 million of which are purchased each minute around the globe.
But according to a study published today in the journal Joule, a new recycling method developed by the National Renewable Energy Laboratory (NREL) could someday change the fates of the hundreds of billions of plastic bottles that end up in oceans or landfills every year.
By combining the polyester found in disposable bottles, known as polyethylene terephthalate (PET), with plant-based materials, the method converts cheap plastic into longer-lived polymers sturdy enough to be used for car parts, snowboards, wind turbine blades, and more. Unlike typical PET recycling, which creates lower caliber plastics with each cycle, this process generates higher quality end products with bigger price tags—which means the process could have the potential to jumpstart new markets in recycling.
“This is really promising work,” says Jenna Jambeck, an environmental engineer studying plastic pollution at the University of Georgia who was not involved in the study. “It’s really cool to think about taking a current recycled material and turning it into something more valuable. This could be a lesson learned for other plastics.”
Single-use bottles are typically pretty easy to recycle, but during the recycling process, polyesters like PET are crushed, shredded, and remixed, often mingling with contaminants—and by the time it comes out the other end, the plastic is less pure, and often takes on a cloudy appearance.
This dip in quality and aesthetics makes bottle manufacturers hesitant to use recycled PET. Instead, the polyester ends up in other products like carpets or clothing, which are much harder to reclaim. Ultimately, less than 15 percent of PET bottles find a second life.
Tackling the behemoth of plastic pollution has no single solution. But finding a more sustainable second home for this problematic polyester could be one way to make a difference, says study author Gregg Beckham, a chemical engineer at NREL.
So rather than “downcycling,” or repurposing plastic into a product of lower quality, Beckham and his team came up with a way to “upcycle” PET into a superior substance by blending it with sustainably sourced, plant-derived compounds. Their end products were two types of fiber-reinforced plastics with over double the value of the starting PET material.
“The use of chemical recycling methods for PET isn’t new, but this is a novel and creative approach,” says Margaret Sobkowicz-Kline, a plastics engineer at the University of Massachusetts, Lowell who was not involved in the study. “They’re seeking to make the whole process green.”
While these aren’t the first fiber-reinforced plastics to come out of recycled PET, previous iterations have relied on petroleum that needs to be drilled out of the ground. By comparison, the new, plant-based fiber-reinforced plastics is estimated to require almost 60 percent less energy to manufacture and produce about half as much greenhouse gas. “From this point of view, we can persuade investors that they can save a lot of energy by adopting this method, which, to some extent, might mean saving money,” says Wan-Ting (Grace) Chen, a plastics engineer at the University of Massachusetts, Lowell who was not involved in the study.
And, because the end products are durable, they could serve as high-quality building blocks for products both recreational and industrial, some of which could last for decades.
“A lot of times, there’s not much value in recycled material,” Jambeck says. “That’s why, in many cases, recycling doesn’t work. But the [plant-based] component adds value, and could be a game-changer.”
That said, the technology has yet to leave the lab, and it remains to be seen if it will fare well in mass manufacture settings, or be cost-effective on a larger scale. And there’s still one big drawback: Unlike PET, these new fiber-reinforced plastics aren’t themselves recyclable—which means when they eventually do reach the end of their lifespans, they will still end up in landfills (but, then again, so would any run-of-the-mill snowboard or car part).
The researchers’ next goal is to tinker with their product until it, too, can be repurposed. “The dream is to go in, reclaim the starting materials and refabricate it anew,” says study author Nicholas Rorrer, a polymer engineer at NREL.
That’s probably a long way off. In the meantime, it’s important to keep in mind that upcycling—no matter how effective—isn’t a silver bullet for plastic pollution as a whole, Beckham says. While new technologies like these will hopefully play an increasingly large role in recycling, this form of upcycling is tailored specifically to PET, which accounts for only about 20 percent of all plastic. And there’s still a need for more alternatives to single-use plastics to keep them out of the waste stream in the first place.
Rorrer points out that this specific technology won’t necessarily help reduce plastic consumption. But even so, he says, “if we can reclaim plastics, and there is an economic incentive to do so, it will keep them out of the ocean.”