Quality of recycled plastic too poor

Researchers at DTU Environment have conducted several studies to gain more knowledge on plastic recycling. In Denmark, the primary focus has so far been on collecting as large amounts of plastic as possible, whereas the quality of the collected plastic has not been examined.

“Our ability to close the plastic loop and thus contribute to a circular plastic economy depends on the quality of the plastic we reuse. Our studies show that the quality of the recycled plastic we produce today is so poor that it has very limited usability. This means that we are not doing nearly enough to close the plastic loop,” says Marie Kampmann Eriksen.

Marie Kampmann Eriksen and her colleagues have conducted both theoretical and practical studies of plastic in our household waste.

The studies have, among other things, included a review of available analyses in this area as well as sorting of about half a tonne of waste from Copenhagen households. Based on their findings, the researchers point to some of the challenges that need to be resolved before plastic recycling can be increased.

Dismantling of plastics

Plastic is a very complex material. It consists of different types of plastics which cannot be recycled together, and of many different types of products with individual product designs. It is a challenge for the recycling, particularly when it comes to quality and usability of the recycled plastic.

“Today, consumers only have a single container for plastic waste, but if the plastic from food packaging is to be reused for new foods, it should not be mixed with plastic that has been used for other purposes—empty shampoo bottles, for example,” Marie Kampmann Eriksen explains.

In addition, the different types of plastics such as PET and PP must be separated. It can be difficult, as packaging for meat, for example, may consist of a plastic tray made of one type of plastic—and plastic film made of a different type.

“If the plastics are not separated, the quality of the recycled material degrades. Similarly, paper residues from e.g., labels, which are often glued to the plastic packaging contribute to ‘contamination’ of the plastic,” says Marie Kampmann Eriksen.

The researchers stress that good sorting of plastic waste from our households is essential in order to achieve better recycling, but that it is necessary to supplement with other measures if we want to take the vision of circular economy in the plastic area to the next step.

“As early as when the plastic products are designed, we must consider recycling. It may, for example, be considered in the preparation of plastic packaging, where all parts, e.g., both container and lid are made of the same type of plastic,” says Professor Thomas Fruergaard Astrup. “In addition, the product design should in any case be aligned with the layout of the waste handling and plastic waste sorting.”

DTU Environment is currently working on a couple of new projects that will contribute to generating more knowledge about plastic recycling.

(Anne Kirsten Frederiksen)