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The world produces 460 million metric tons of plastic each and every year. But only about 9 percent of it gets recycled, leading to a ballooning plastic waste issue impacting every part of our planet, from the bottom of the Mariana Trench to the inside of your own skull. The issue of plastic waste polluting our ecosystems and bodies is growing greater all the time, as is the need to reduce production and increase recycling of plastics.
For years, scientists around the globe have been trying to find ways to convert the petroleum products in plastics back into oils that are usable for energy production. The leading technology for achieving this is called pyrolysis, a process that involves heating the plastic to extremely high temperatures (approximately 900 degrees Celsius, or 1,652 degrees Fahrenheit) in a setting without oxygen. This breaks down the polymer chains of the plastic into reusable hydrocarbon molecules.
“These are organic compounds made mainly of carbon and hydrogen atoms and are the basic molecule required for creating fuel energy,” reports Popular Mechanics. “Results vary, but pyrolysis usually turns about 60 percent of plastic into bio-oil.”
The problem is that pyrolysis requires a lot of energy – rendering the process rather pointless – and usually involves costly catalysts that make the process commercially non-viable. But a new breakthrough from a team of scientists at Yale has just brought pyrolysis one big step closer to commercial scalability. The scientists created a device capable of creating fuel from plastics at a relatively high level of efficiency – extracting 66 percent of fuel chemicals from polyethylene – without any catalyst whatsoever.
The device is a “3D-printed electrically heated carbon column reactor made of three sections of decreasing pore size,” according to a report from Yale Engineering. The varying pore sizes control the reactions of the chemicals, providing a major optimization breakthrough. The device also allows for greater control over temperatures throughout the process. All of this serves to create a pyrolysis system that is more efficient and scalable than ever before.
“The selectivity and yield of traditional plastic pyrolysis are poor, with products featuring broad molar mass distributions,” states the abstract for the paper reporting the scientists’ findings. “Here we report a highly selective, energy-efficient, and catalyst-free pyrolysis method that can upcycle plastic into value-added chemicals via pore-modulated pyrolysis,” the paper continues. The study was published this July in the esteemed science journal Nature Chemical Engineering.
To further test the scalability of their breakthrough, the scientists also tested a model of their device made using carbon felt instead of 3D printing. While this model was slightly less efficient, it still achieved a 56 percent yield of useful chemicals, putting it ahead of most traditional pyrolysis methods.
“These results are very promising and show a great potential for putting this system into real-world applications and offering a practical strategy for converting plastic waste into valuable materials,” Shu Hu, assistant professor of chemical and environmental engineering, was quoted by Yale Engineering.
While this is a promising step forward in a world choked with single-use plastics, critics doubt whether pyrolysis will ever provide a real solution. The history of the plastics industry includes no shortage of tall tales about recycling and other ways to offset the sector’s impact. Like plastics recycling more generally, critics believe that pyrolysis is just one more example of a petroleum-industry greenwashing campaign, rather than a disruptive innovation. Last year, the nonprofit investigative journalism outlet ProPublica published a takedown of pyrolysis, writing that “the industry uses mathematical acrobatics to make pyrolysis look like a success,” concluding that commercial pyrolysis is more than likely a “fairy tale”.
As Popular Mechanics concludes, “it’s clear that—at least for now—the best kind of plastic is still one that’s never made in the first place.
By Haley Zaremba for Oilprice.com
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