Scientists, who are part of Bio-Optimised Technologies to keep Thermoplastics out of Landfills and the Environment (BOTTLE) Consortium, have found that enzyme-based plastics recycling is more energy efficient, and better for environment. They used enzymes for recycling PET, a common plastic in single-use beverage bottles, clothing, and food packaging.
BOTTLE Consortium included scientists from the US Department of Energy’s (DOE’s) National Renewable Energy Laboratory (NREL) and the University of Portsmouth. They found that using enzymes was more sustainable approach for recycling polyethylene terephthalate (PET).Scientists, who are part of Bio-Optimised Technologies to keep Thermoplastics out of Landfills and the Environment (BOTTLE) Consortium, have found that enzyme-based plastics recycling is more energy efficient, and better for environment. They used enzymes for recycling PET, a common plastic in single-use beverage bottles, clothing, and food packaging.#
An analysis shows enzyme-recycled PET has potential improvement over conventional, fossil-based methods of PET production across a broad spectrum of energy, carbon, and socioeconomic impacts.
The concept, if further developed and implemented at scale, could lead to new opportunities for PET recycling and create a mechanism for recycling textiles and other materials also made from PET that are traditionally not recycled. PET ranks among the most abundantly produced synthetic polymers in the world, with 82 million metric tons produced annually; roughly 54 per cent of PET is used in the manufacture of textiles for clothing and fibres for carpet.
“From all the plastics that were produced since the 1950s, less than 10 per cent of it has ever been recycled,” said Avantika Singh, a chemical engineer at NREL and first author of a new paper outlining the path toward enzyme-based recycling. “Most waste plastics end up in landfills.”
The paper is published in the journal Joule.
BOTTLE is striving to address the problem of plastic pollution with two innovative approaches - develop energy-efficient, cost-effective, and scalable recycling and upcycling technologies, and design modern plastics to be recyclable by design.
The new research addresses the challenge of plastic recyclability. While images of discarded bottles floating in oceans and other waterways provide a visual reminder of the problems posed by plastic waste, the lesser-seen issue remains of what to do with the PET used to manufacture textiles for clothing and fibres for carpet.
The researchers modeled a conceptual recycling facility that would take in a fraction of the 3 million metric tons of PET consumed annually in the United States. The enzymatic recycling process breaks down PET into its two building blocks, terephthalic acid (TPA) and ethylene glycol. Compared to conventional fossil-based production routes, the research team determined the enzymatic recycling process can reduce total supply-chain energy use by 69–83 per cent and greenhouse gas emissions by 17-43 per cent per kilogram of TPA. Additionally, an economy-wide comparison of virgin TPA and recycled TPA in the United States shows that the environmental and socioeconomic effects of the two processes are not distributed equally across their supply chain. The proposed recycling process can reduce environmental impacts by up to 95 per cent, while generating up to 45 per cent more socioeconomic benefits, including local jobs at the material recovery facilities.
The study also predicts that enzymatic PET recycling can achieve cost parity with the production of virgin PET, thus highlighting the potential for this enzyme technology to decarbonise PET manufacturing, in addition to enabling the recycling of waste PET-rich feedstocks, such as clothing and carpets.
“That’s one of the biggest opportunities,” Singh said. “If we can capture that space—textiles, carpet fibres, and other PET waste plastics that are not currently recycled—that could be a true game-changer.”
The research was funded by DOE’s Advanced Manufacturing Office and the Bioenergy Technologies Office. The work was done as part of the Bio-Optimised Technologies to keep Thermoplastics out of Landfills and the Environment (BOTTLE) Consortium.
NREL is the US Department of Energy's primary national laboratory for renewable energy and energy efficiency research and development.
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