BOTTLE Project Outlines New Two-Step Process for Turning Mixed Plastic Waste into Valuable Bioproducts

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October 21, 2022

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(U.S. Department of Energy) Combining chemical and biological processes is a promising new strategy for the valorization of mixed plastic waste, according to researchers from the Bio-Optimized Technologies to keep Thermoplastics out of Landfills and the Environment (BOTTLE) Consortium. BOTTLE is a collaboration between scientists from the National Renewable Energy Laboratory (NREL) and peers from Oak Ridge National Laboratory (ORNL), the Massachusetts Institute of Technology, and the University of Wisconsin-Madison.

Different plastics are composed of different polymers, each with their own unique chemical building blocks. When polymer chemistries are mixed—either in a collection bin or formulated together in materials such as multi-layer packaging—recycling becomes expensive and difficult because each polymer often must be separated prior to chemical deconstruction. The BOTTLE team developed a process that can convert mixed plastics to a single chemical product, working toward a solution that would allow recyclers to skip sorting plastic by type.

The process builds upon work pioneered a decade ago by a scientist from DuPont that used chemical oxidation to break down a variety of plastic types. The NREL researchers expanded upon this chemistry, which uses oxygen and catalysts to break down the large polymer molecules into smaller chemical building blocks. The project also draws on synthetic biology expertise from ORNL researchers to engineer a microbe that converts deconstructed plastic waste into building blocks for next-generation materials.

Read more in the journal Science about this plastic recycling research, which was funded in part by the U.S. Department of Energy (DOE) Bioenergy Technologies Office (BETO) and Advanced Manufacturing Office.

Mixed plastics waste valorization through tandem chemical oxidation and biological funneling (Science Magazine)

Excerpt from Science Magazine: Mixed plastics waste represents an abundant and largely untapped feedstock for the production of valuable products. The chemical diversity and complexity of these materials, however, present major barriers to realizing this opportunity. In this work, we show that metal-catalyzed autoxidation depolymerizes comingled polymers into a mixture of oxygenated small molecules that are advantaged substrates for biological conversion. We engineer a robust soil bacterium, Pseudomonas putida, to funnel these oxygenated compounds into a single exemplary chemical product, either β-ketoadipate or polyhydroxyalkanoates. This hybrid process establishes a strategy for the selective conversion of mixed plastics waste into useful chemical products. READ MORE

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