L'étude, qui a été dirigée par le National Renewable Energy Laboratory (NREL) du Département américain de l'énergie et comprend un membre du corps professoral du Collège d'ingénierie de l'Oregon State University (OSU), publiée aujourd'hui dans la revue Les sciences.
Scientists have taken a key step to significantly expand the range of plastics that can be recycled. This breakthrough is important because plastic waste is a huge problem both globally and in the United States. In fact, only about 5% of used plastic is recycled in the United States, according to NREL.
Packaging materials, containers and other discarded items are filling up landfills and polluting the environment at an incredibly fast rate. According to NREL, scientists estimate that by 2050 the ocean will contain more plastic by weight than fish.
A collaboration led by NREL’s Gregg Beckham and including Lucas Ellis, an OSU researcher who was an NREL postdoctoral fellow during the project, combined chemical and biological processes in a proof-of-concept to “upgrade” mixed plastic waste. To enhance means to increase the value of something.
The research relies on the use of chemical oxidation to break down a variety of plastic types, a method pioneered a decade ago by chemical industry giant DuPont.
“We have developed a technology that uses oxygen and catalysts to break down plastics into smaller, biologically friendly chemical building blocks,” said Ellis, assistant professor of chemical engineering. “From there, we used a biologically modified soil microbe that could consume and ‘channel’ these building blocks into a biopolymer or component for advanced nylon production.
Beckham, principal investigator at NREL and lead of the Bio-Optimized Technologies to keep Thermoplastics out of Landfills and the Environment Consortium – known as BOTTLE – said the work provides a “potential entry point into plastics processing that cannot be recycled at all today.”
Current recycling technologies can only work effectively if the plastic inputs are clean and separated by type, says Beckham.
Plastics can be made from different polymers, each with their own unique chemical building blocks. When polymer chemicals are mixed in a collection bin or formulated together into certain products like multi-layer packaging, recycling becomes expensive and nearly impossible as the polymers often have to be separated before they can be recycled.
“Our work has resulted in a process that can convert mixed plastics into a single chemical,” Ellis said. “In other words, this is a technology that recyclers could use without having to sort plastics by type.”
The scientists applied the process to a mixture of three common plastics: polystyrene, used in disposable coffee cups; polyethylene terephthalate, the base of carpets, polyester clothing and single-use beverage bottles; and high-density polyethylene, used in milk jugs and many other consumer plastics.
The oxidation process broke down the plastics into a mixture of compounds including benzoic acid, terephthalic acid and dicarboxylic acids which, in the absence of the modified soil microbe, would require advanced and expensive separations to yield pure products.
The researchers engineered the microbe, Pseudomonas putidato biologically channel the mixture into one of two products – polyhydroxyalkanoates, an emerging form of biodegradable bioplastics, and beta-ketoadipate, which can be used in the manufacture of performance-enhanced nylon.
Trying the process with other types of plastics, including polypropylene and polyvinyl chloride, will be the focus of future work, the researchers said.
“The chemical catalysis process we used is just a way to speed up a process that occurs naturally, so instead of degrading over hundreds of years, you can break down these plastics in hours or minutes. “said co-author Kevin Sullivan, a postdoctoral researcher. researcher at NREL.
Reference: “Recovery of mixed plastic waste by chemical oxidation in tandem and biological funnel” October 13, 2022, Sciences.
Funding was provided by the U.S. Department of Energy’s Office of Advanced Manufacturing and Office of Bioenergy Technologies, and the work was carried out as part of the BOTTLE Consortium.
Scientists from the Massachusetts Institute of Technology (MIT), University of Wisconsin-Madison and Oak Ridge National Laboratory also participated in the study.
NREL is the US Department of Energy’s primary national laboratory for renewable energy and energy efficiency research and development. It is operated for the department by the Alliance for Sustainable Energy, LLC.