Futile to Utile: Pyrolysis of Single-Use Plastics to Promote Circularity

Single-use plastic waste is a significant problem today. Found in all industries, very little single-use plastic waste is recycled classically via mechanical recycling—grinding and re-forming into new plastic products—due to differences in design and composition. Chemical recycling via pyrolysis offers a way to introduce circularity to the single-use plastic industry. In pyrolysis, plastics are decomposed in the absence of oxygen at very high temperatures (>420°C) into diesel that can be used as fuel or further processed into monomers for plastic production. At Oregon State University, a 1-kg research kiln reactor has been used to successfully convert polypropylene (PP) syringes, polypropylene (PP) Dutch Brothers coffee cups, and mixed ocean plastics (typically a mixture of HDPE, LDPE, PP with some PVC and PS) into diesel. Each run, the reactor is loaded with up to one kilogram of shredded plastic waste and attached to a counter-current double pipe condenser. Electricity is used to power heating coils within the kiln. The polymer feedstock melts, then vaporizes, and is forced through a packed bed before exiting to the condenser.

A partnership with the Benton County Needle Exchange program provided used syringes, eliminating a portion of red bag waste the community must process. The Dutch Brothers Coffee shop on the OSU Corvallis campus donated used drink cups, keeping them out of the landfill. Ocean plastics were obtained from beach clean-ups in Kodiak, Alaska attended by OSU students in collaboration with the Ocean Plastics Recovery Project. Results will be presented on kiln reactor operation and complete characterization of input plastics (DSC, TGA, FTIR) and diesel characterization (GC, NMR).

Long term, the project goal is to produce larger versions of the OSU reactor (5-kg, 10-kg) for communities that lack recycling systems to promote circularity of plastic products and increase residents’ access to diesel in their community.