RePURpose: Danish consortium develops new technologies for the recycling of polyurethane products

Danish researchers have developed a chemical recycling method for polyurethane (PU) targeted at handling end-of-life products. This new technology is considered an important new step towards a circular plastic economy for polyurethane. The method breaks down polyurethane into chemical building blocks that serve as feedstock for new PU products. Importantly, the chemical recycling process is robust and will, for the first time, be able to convert a wide variety of different PU materials, said the researchers.

A Danish consortium has developed a chemical recycling method for polyurethane end-of-life products. (Source: Danish Technological Institute)

Irreplaceable and hard to recycle

Polyurethanes can be found in everyday objects like refrigerators, mattresses, and shoes, but also in more sophisticated materials used in the automotive and aviation industries. PU currently accounts for at least 5 % of the global plastic production and the demand is expected to grow in the decade to come.

PU is a versatile and irreplaceable type of plastic used in countless industries. However, its chemical structure makes polyurethane hard to recycle. As a result, end-of-life products end up in landfills or are sent for energy recovery through incineration. The promising results in this project are an important step towards recycling of these materials, said Anders Lindhardt (PhD), Senior Specialist at the Danish Technological Institute.

The project, called RePURpose (2019 – 2021), is led by a consortium consisting of leading Danish companies within the polyurethane industry, including Ecco Sko, Dan-Foam, Logstor, Tinby, Plixxent, H. J. Hansen, and researchers from the Danish Technological Institute and Aarhus University. Innovation Fund Denmark has invested EUR 1.5 million in the project that has a total budget of EUR 2.5 million.

Waste is turned into new building blocks

The results were recently published in the Journal of the American Chemical Society – Au (JACS Au), an open access journal. Here, the researchers show that through innovative chemical recycling, it is possible to deconstruct commercial and end-of-life PU materials into its monomeric building blocks. In practice, the researchers have deconstructed a range of different PU materials, including examples of insulation foams, pillows, mattresses, and shoe soles back into two chemical fractions. These fractions can be used for construction of new virgin PU materials. Very importantly, by using a catalyst in the combination with a green solvent and dihydrogen the developed methodology has proven to work on all four major classes of PU, i.e. flexible solid, flexible foamed, rigid solid, and rigid foamed. This result is ground-breaking because for a plastic like PU, the chemical structure makes recycling very difficult. The method provides a novel entry to the original building blocks of this plastic material, that in turn can be applied in new PU products, said Steffan Kristensen (PhD) from Aarhus University.

Growing demand for polyurethane

Technologies for partial PU recycling are available today. These comprise mechanical recycling and glycolysis. While these methodologies do offer some recyclability of PU, most end-of-life and post-consumer products are currently being landfilled or incinerated. Global annual production of PU is estimated to be above 16 million t, a number set to increase in the years to come. Therefore, with a focus on circular economy, RePURpose is working towards developing technologies that move both production spill and end-of-life products towards a circular economy where polyurethane is recycled at its highest possible value.

Towards a circular economy for polyurethane

RePURpose started in 2019 with the purpose of making polyurethane recyclable. Only a few plastics like high density polyethylene, polypropylene, polystyrene, and polyethylene terephthalate are recycled. These materials belong to the class of thermoplastics, where the molecular structure of the plastic makes it possible to perform mechanical recycling, like remoulding.

The presented technology in the manuscript is still in its early face, but it demonstrates that a potential circular plastic economy is possible for PU, where PU-waste ends up being landfilled or send for energy recovery. Future work within the RePURpose consortium will focus on scaling the process to ensure a cost-efficient methodology.

The open-access article “Catalytic Hydrogenation of Polyurethanes to Base Chemicals: From Model Systems to Commercial and End-of-Life Polyurethane Materials” can be found here (no subscription needed): https://pubs.acs.org/doi/10.1021/jacsau.1c00050

www.repurpose.nu

Contact: Anders T. Lindhardt Senior Specialist, PhD, Environmental Technology Tel. +45 72201143 Danish Technological Institute Aarhus, Denmark www.dti.dk Steffan K. Kristensen Assistant Professor, PhD Tel. +45 28154100 Aarhus University Aarhus, Denmark https://international.au.dk/