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Australian Scientists Might Have Found a Way to Turn the World’s Plastic into Oil

If it works, the technology could be used to make all plastics recyclable.

by Gavin Butler
22 November 2019, 12:58am

Images supplied

A pair of Australian scientists claims to have come up with a circular solution to the world’s plastic waste problem: by developing a technology that effectively melts polymers down into reusable oil. For the past 12 years, Len Humphreys and Sydney University professor Thomas Maschmeyer have been working on the creation of the Catalytic Hydrothermal Reactor (Cat-HTR), which uses a chemical process to recycle plastic by turning it back into the oil from which it originally came. It’s thought that such technology could be used to make all plastics recyclable.

“Basically, it's a technology which breaks down plastics through heat,” Maschmeyer told VICE over the phone. “And we do that in a way that is more controlled than other technologies.”

The most well-known of these other technologies is currently something called pyrolysis, which essentially dissolves materials by exposing them to extreme temperatures. But Maschmeyer pointed out that this process has limitations. There are many types of plastic that can’t be recycled with pyrolysis, for one, and those that are, often don’t get completely broken down. Then there’s mechanical recycling, which relies on extremely well sorted, high purity streams of plastic and can only recycle a small fraction of the plastics around the world.

According to Maschmeyer and Humphreys, Cat-HTR is different.

Polyethylene terephthalate
Polytrimethylene terephthalate (PTT) is a type of polyester commonly used to make carpet fibres.

“Unlike other techniques such as pyrolysis, the Cat-HTR can recycle a mix of plastics including PET, polypropylene, polystyrene, soft plastics, and multilayer flexible plastic packaging,” Humphreys explained over email. “This increases the total quantity of plastic that can be recycled and, therefore, the process economics. The Cat-HTR also produces a high yield of oil from plastic (around 85 percent oil... that can be recycled back through the process).”

The Cat-HTR’s “hydrothermal” mechanism more or less works by exposing the plastics to supercritical water (that is, water at extremely high temperature and pressure) and breaking them down through thermal decomposition: turning otherwise unrecyclable materials into oil. That oil can then be turned back into plastic or used to produce solvents, lubricants, fuels—even roads. More significantly, though, Humphreys suggests that such technology could “fill the gap by recycling plastic that can’t be recycled mechanically.”

Regardless of whether or not you put it in the right bin, the inconvenient truth is that the majority of post-consumer plastic doesn’t get recycled. Instead, they end up in landfills. Humphreys hopes that the combination of physical recycling with chemical processes such as those performed by the Cat-HTR “will allow us to become plastic neutral.”

There are currently plans to build two plants that use Cat-HTR technology: the first in the UK, which is set to undergo construction in 2020, and the second on the central coast of New South Wales, Australia, where a pilot plant is already in operation. Further to those, Maschmeyer revealed that he and Humphreys are in negotiations to grant licenses to a number of companies around the globe.

Cat-HTR reactors
Cat-HTR reactors

Demand for efficient and effective plastic recycling technology is high, he explains, since China stopped importing and burning much of the world’s plastic in 2018. “They’ve now stopped that practice, so this material stream is available and it allows us to really kickstart that circular economy and have this plastic, those molecules, going round and round and being reused over and over again,” he said.

The implications of this “circular economy” are huge—not just in the way we approach recycling processes in the future, but also the way we think about plastics in general.

“We believe [this technology will lead to] a paradigm shift for the world,” Machmeyer declared. “This will change the discussion from plastic as a problem to plastic as a valuable resource. It'll change the way people approach collecting it, and it will lead to a dramatic reduction in environmental pollution.”

"The result is that we can use plastic," he continued, "and plastic is fantastic—it's cheap, it's durable, it's safe, it's hygienic, it helps food not going off, it helps in hospitals. Plastic has huge applications everywhere. But once we have used it, what do we do with it at the end of its life? That was a big problem: disposing of it. Our technology allows us to basically have our cake and eat it too. So we can use it, and then we can reuse it.

“That technology was missing. Now it’s available.”

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