J.B. Curley
National Renewable Energy Laboratory, Colorado, United States
Keywords: Plastics recycling, energy efficiency, renewable materials, polyesters, circularity
The loss of petroleum-based plastics to landfills and the environment represents a significant pollution crisis and a massive waste of carbon, energy, and investment. Biodegradable polyesters offer an attractive solution to the plastic pollution problem, as they can be sourced from biogenic carbon and naturally break down into water, biomass, and carbon dioxide in composting facilities and some natural environments. However, these valuable materials should ideally be kept in circulation rather than permitted to degrade. Herein we present EsterCycle™, an integrated depolymerization (based on methanolysis), monomer recovery, and repolymerization platform for recycling a mixture of biodegradable and non-biodegradable polyesters including polyethylene terephthalate (PET), polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), and polybutylene succinate (PBS). The process is also compatible with novel polyesters currently being studied as recyclable-by-design and biodegradable replacements for polyolefins. We have successfully demonstrated EsterCycle at the 1 kilogram scale and developed a downstream separation process for monomer recovery and purification. Monomers can be repolymerized to virgin-like polyester products with high yield and purity. Comprehensive techno-economic analysis (TEA) and life cycle assessment (LCA) validated by experiments show that this recycling process reduces associated environmental impacts compared to virgin polyester production while remaining economically competitive.