Reducing the carbon footprint of polyurethanes by chemical and biological depolymerization: Fact or fiction?

Abstract

Polyurethanes (PUs) are one of the most widely employed classes of polymers, with a continuously increasing production demand that is expected to reach around 21 million tons in 2022. Due to the simple polymerization process by which they are produced, the versatility in PU chemistry, and the strong inter/intramolecular interactions present between urethane moieties, these robust materials can be used in diverse applications ranging from elastomers to foams. However, this high versatility, combined with the high stability of the urethane bond and the chemically cross-linked nature of most commercial PUs, leads to long-lasting, potentially contaminating, PU waste in landfill sites. While many strategies are under investigation to improve the end-of-life options for polyurethanes, in this review we focus primarily on the latest advances in the chemical and biological routes for PU recycling. These two routes can potentially allow for monomer recovery and reuse for further synthesis of PUs, achieving materials with identical properties to the virgin materials. Aside from reviewing the latest advances in the field, we will highlight the importance of using life cycle assessment (LCA) to find a truly sustainable solution to landfilling and to incentivize the implementation of chemical and biological recycling approaches at the industrial scale.