Sustainable recycling of PET trays

Research project

André Heeres en Erik Keller bij ZAP Groningen.jpg

Start date 16 November 2021

Plastic containers have become part of our daily lives. We often use these containers when we buy or want to preserve food. However, this also means that we use these containers only once and for a short period of time. After opening, we throw the containers away and they end up on a landfill site. This is harmful to our environment and a waste of resources. Therefore, this project aims to find alternative routes to recycle these materials.

Background

Plastic is most often made of petroleum or crude oil, a fossil resource. The global supply of crude oil is large, but also exhaustive. It is estimated that the easily-reached oil supply lasts for only fifty years. At the same time, the demand for plastics increases. Plastics currently in use can be recycled and reused, if they are reprocessed properly.

Plastics consist of polymers. These are long chains of the same building blocks, similar to a chain link necklace. These links or building blocks are called monomers. Theoretically, polymers can be degraded into monomers or oligomers. The latter are a smaller group of monomers. After degradation, the monomers or oligomers can in turn be reused as building blocks for new polymers. This can be a similar kind of polymer, or a different kind by adding new monomers or other substances, thereby creating a new plastic.

The recycling of plastics is a vital method to meet the growing demand for plastics in the future.

Currently, 1 million tons of PET film is stored in Europe, waiting for a suitable recycling technology. Every year this quantity grows by 150 - 250 kilotons. In the meantime, petroleum is used as a raw material for the production of new PET trays. Petroleum is an exhaustible resource and therefore not sustainable. Both problems can be solved by proper recycling of PET.

Packaging materials are difficult to recycle because they consist of multiple types of polymers. They are also often contaminated, for example by food scraps. Mechanical recycling of these plastics is therefore not possible. With mechanical recycling, the chemical compounds in the product are not broken down, but the product itself is transformed by grinding or melting it into smaller parts, such as granules. This is used for plastic that is relatively clean and consists of one type of polymer, such as deposit bottles. Other plastics require chemical recycling, which breaks down the polymers in the material into monomers or oligomers.

This research project investigates the combination of chemical recycling and thermochemical recyling. The company CuRe Technology, situated in Emmen, is specialised in the different routes of chemical recycling. With this method, plastic is degraded into monomers or oligomers through chemical reactions. The company BioBTX, situated on the Zernike Campus (Groningen), uses thermochemical recycling to reprocess waste streams, such as biomass and plastics, into aromatics.

By combining these technologies, multi-layered PET trays can be fully recycled. The first step in this process is the extraction and purification of different polymers, so these can be partly broken down into oligomers. Some polymers can neither be recycled mechanically nor chemically. These can be converted into aromatics by thermochemical recycling. Within the scope of this project, the focus is on innovative routes for the reprocessing of waste streams to facilitate the sustainable production of polyesters.

This project results in new routes for the recycling of packaging materials and food containers. Specifically, it develops methods to fully recycle complex packaging materials, made of different polymers, into new monomers and polyesters. This contributes to the closing of the material cycle. Moreover, it generates new knowledge about the several applications of the obtained monomers. This facilitates the production of circular plastics.

This project contributes to the closing of the material cycle. By developing new methods for the recyling of plastic, current plastic containers and packaging materials can be recycled. This leads to a lower need for fossil resources and less waste pollution.

By cooperating with companies, this research matches the needs and opportunities of the industry. The acquired knowledge is immediately used in practice. Likewise, practice will show which methods are useful at a larger scale.