Credit: PantherMedia

(Semi)-circular economy: “We cannot achieve a 100 per cent closed plastic loop”

Monday 23 Sep 19


Thomas Fruergaard Astrup
DTU Environment
+45 45 25 15 58


• For many years, DTU Environment has worked with life cycle assessments of waste and resource management.

• The research has led to one of the world’s most advanced LCA models (LCA: Life Cycle Assessment) for waste and resources.

• The model is called EASETECH, which stands for the Environmental Assessment System for Environmental Technologies.

• Among other things, the model makes it possible to calculate the environmental impact or benefits as well as the socio-economic consequences of recycling a resource like plastic.

• EASETECH can also be used to calculate environmental impacts within bioenergy.

• EASETECH is constantly evolving, and DTU Environment’s research is continually contributing new data that is included in the model. And new algorithms for more advanced modelling are added to EASETECH in collaboration with DTU Compute.

• You can access EASETECH by completing an EASETECH course at DTU Environment.

The challenges of plastic recycling

The quality of plastics is threatened through recycling because of contamination by:

• Mixing of different types of plastics.

• Remnants of the packaging’s original contents.

• The consumer’s use of the packaging (e.g., if you have stored chemicals in a Coca-Cola bottle).

• Other parts of the packaging, such as labels, glue, paper, etc.

• The various additives found in the original plastic products in order to achieve, for example, a certain colour, hardness, or softness.

• Heavy metals – a study conducted by DTU Environment found that recycled plastics contain more heavy metals than newly produced plastics.

Plastic recycling will not cover our need for new plastics. We will have a continued need to produce pure plastics for products such as food, explains a waste and environmental researcher at DTU.

Perhaps you have recently opened a package of minced meat to use in meat balls or a meat sauce by pulling the clear plastic foil off the plastic tray and tipping out the meat.  And maybe you have waste sorting where you live, which is why you have disposed of the packaging with the rest of the plastic waste.

Minced meat packaging is particularly interesting, because it illustrates one of the biggest challenges in achieving a closed plastic loop, namely contamination. Contamination reduces the quality of the recycled plastic. Even if we were perfect at sorting plastic from other waste—the first prerequisite for a closed plastic loop—the plastic packaging can be contaminated in several ways: it may consist of several kinds of plastics, like the minced meat packaging, as well as of other materials, such as the glue that fixes the foil.

In addition, remnants of paper labels (stating weight, price, etc.) will also be included in the plastic fraction, and it is likely that there is also a bit of meat juice left on the packaging.

Quality deteriorates
When plastic waste is processed for recycling, the packaging is rinsed and washed, but remnants of glue, paper labels, and food can be difficult to get rid of. When the plastic is chopped into smaller pieces and melted down, the resulting plastic is then of an inferior quality to that of the original, says Professor Thomas Fruergaard Astrup of DTU Environment.

“In most cases, when recycling plastics, we don’t get the same quality as the plastic of the original packaging. It turns into a kind of average, and for every recycling, the quality deteriorates further,” says Professor Fruergaard Astrup, who elaborates:

“Low quality recycled plastics can easily be used for products such as traffic cones and garden furniture, but not for food, because of its very stringent material requirements. Therefore, we cannot avoid the production of new plastics. It’s naive to think that we can achieve a fully closed plastic loop without any loss of either quantity or quality. Otherwise, we would’ve invented a perpetual motion machine.”

"It’s naive to think that we can achieve a fully closed plastic loop without any loss of either quantity or quality."

Thomas Fruergaard Astrup and his colleagues at DTU Environment have been dealing with plastic waste for many years and have literally had their hands in tonnes of the Danes’ waste, in order to study what people actually throw out. With their detailed knowledge of the plastic waste in Denmark, the researchers discovered that, unfortunately, the potential for recycling today is limited.

“The problem is that some plastics can be recycled, and some cannot. Our research shows that we can probably collect, reprocess, and recycle large proportions of plastic waste, but that we also lose quality when recycling. In other words, with today’s technologies, we can at most achieve a closed plastic loop for households, equivalent to about 40 per cent of the need for new plastics. The rest of the plastic is lost,” says Thomas Fruergaard Astrup.

Ambitious EU targets
The EU has made demands on the member countries to recycle at least 55 per cent of their plastic packaging by 2030. Professor Fruergaard Astrup calls this demand ‘ambitious’. Today, 57 per cent of plastic waste in Denmark is sent for incineration, according to the report ‘The new plastics economy’ by Innovation Fund Denmark and McKinsey & Company.

If Denmark is to comply with this EU target, it will require more than just dedicated sorting by consumers. It also makes demands on manufacturers’ packaging design—demands that require political action, believes Fruergaard Astrup.

“Many product designs use different plastic types that can’t be separated. But we should be able to separate them in order to get a plastic quality that will allow us to recycle the material for products similar to the original ones. The ideal solution would be to create a separate recycling loop for food packaging and other separate loops for other plastic packaging and so on,” says Thomas Fruergaard Astrup.

Recycling plastics can easily serve a good purpose, but the waste researcher points out that there is no guarantee that it will reduce our total plastic consumption.

“One of the points of circular economy is to provide cheaper raw materials through recycling. What happens to our plastic consumption when the raw material becomes cheaper? We risk creating new markets and increasing consumption, and as a result we don’t reduce the pressure on the environment or on natural resources. We should also consider whether recycled plastics actually replace newly produced plastics, or whether they replace completely different materials such as wood instead. We need to be much clearer about the type of recycling we want to support and ensure that the maximum environmental benefit is actually achieved through recycling,” says Thomas Fruergaard Astrup.

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