Scientists have developed a recycling process that transforms single-use plastic bottles, and fabrics made from a common polyester material into more valuable products with a longer lifespan.
Their research, published in the journal Joule, could help protect oceans from plastic waste by boosting the recycled plastics market.
Polyethylene terephthalate (PET) is strong but lightweight, resistant to water, and shatterproof—properties that make it extremely popular among manufacturers.
Although PET is recyclable, most of the 26 million tonnes produced every year ends up in landfills or elsewhere in the environment, where it takes hundreds of years to biodegrade.
However, even when it is recycled, the process is far from perfect. Reclaimed PET has a lower value than the original and can only be repurposed once or twice.
"Standard PET recycling today is essentially 'downcycling'," said Gregg Beckham, a Senior Research Fellow at US Department of Energy's National Renewable Energy Laboratory (NREL).
"The process we came up with is a way to 'upcycle' PET into long-lifetime, high-value composite materials like those that would be used in car parts, wind turbine blades, surfboards, or snowboards," said Beckham.
The team combined reclaimed PET with building blocks derived from renewable sources such as waste plant biomass.
This resulted in a new material that combines reclaimed PET and sustainably sourced, bio-based molecules to produce two types of fibre-reinforced plastics (FRPs), which are 2-3 times more valuable than the original PET, meaning that future plastic bottles could live lucrative second lives.
Through their collaboration with analysts at NREL, the team also predicts that the composite product would require 57 per cent less energy to produce than reclaimed PET using the current recycling process and would emit 40 per cent fewer greenhouse gases than standard petroleum-based FRPs—a significant improvement over business as usual.
"The idea is to develop technologies that would incentivise the economics of PET reclamation," said Beckham.
"That's the real hope—to develop 'second-life' upcycling technologies that make single-use waste plastic valuable to reclaim. This, in turn, could help keep waste plastic out of the world's oceans and out of landfills," he said.
However, there is still work to be done before this recycling process can be implemented beyond the laboratory bench.
The team plans to further analyse the properties of the composite materials that result when PET is combined with the plant-based monomers and to test the process for scalability to determine how well it might fare in a manufacturing setting.
They also hope to develop composites that can themselves be recycled; the current composites can last years and even decades but are not necessarily recyclable in the end. In addition, the NREL team plans to develop similar technologies for recycling other types of materials.
"The scale of PET production dwarfs that of composites manufacturing, so we need many more upcycling solutions to truly make a global impact on plastics reclamation through technologies like the one proposed in the current study," said Nicholas Rorrer, an engineer at NREL.