Generating value from waste polyolefin plastics through depolymerization and biological conversion to valuable fuels, chemicals, or intermediates has great promise but is limited by several factors including lack of cost-effective depolymerization methods, low yield of low molecular weight products due to polymerization or loss of carbon as CO2, toxicity and/or low bioconversion of the breakdown products. Depolymerization of polyolefins requires carbon–carbon bond cleavage. To address that need, we developed a catalytic Fenton reaction that efficiently cleaves C–C bonds in sulfonated polymers at or near room temperature while minimizing unwanted repolymerization. This is especially advantageous for bioconversion since reactions occur in aqueous solution and the catalyst (Fe) is biocompatible. This method was used to depolymerize commercial LDPE films (Mp = 154,000 g/mol) into small molecular weight fragments (Mp = 220 g/mol). Various conditions were explored with the goal of minimizing loss of carbon as CO2, maximizing yield of low molecular weight acids and alcohols, and avoiding repolymerization. The breakdown products were characterized by various analytical methods and evaluated for bioavailability. These products are rich in acid and alcohol functionalities and include sulfur as a result of sulfonation. A panel of organisms were tested for the ability to grow on the breakdown products. Growth was observed in several monocultures with breakdown products as the sole carbon source. The results suggest that chelator-mediated Fenton depolymerization is a promising method for biological conversion of waste polyolefin plastics into higher value chemicals or intermediates. Opportunities and challenges for this approach will be presented.

Depolymerization of low density polyethylene (LDPE) and lignin for biological conversion through sulfonation followed by Fenton reaction

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