Fewer fragrances, better recycled materials -- interpack

Efficient recycling processes are essential to a functioning circular economy. It will only be possible to gradually reduce the amount of new plastic required and sustainably cut the industry’s CO2 emissions when it also becomes possible to return sufficient quantities of recycled materials to the production cycle.

But good intentions by themselves are not enough. All types of plastic are different. Packaging manufacturers, however, must be able to rely on the consistent quality of raw materials during production. A process developed and recently presented by the Fraunhofer Institute for Structural Durability and System Reliability (LBF) constitutes another important step in the right direction.

The process takes one hour

Scientists at the institute have succeeded in removing problematic fragrances from recycled plastic. They have been able to do so by developing a pressurised water-extraction process that removes the limonene tracer fragrance from commercial HDPE packaging. The process does not require any organic solvents and therefore is not harmful to the environment. The entire process to improve the recycled material takes just one hour in the lab.

Three lemons placed next to a spray bottle of detergent on a kitchen counter.

It’s true that citrus oils are natural substances. However, during the process of recycling, they can have a negative effect on the quality of the recycled materials being produced. (Image: preciousplasticmelbourne/unsplash)

Such citrus oils as limonene or citral are often used in cleaning products. They are also frequently found in detergents marketed as natural products because they are themselves natural substances. The Umweltbundesamt (German Federal Environment Agency), however, has stated that they should be treated as sensitising and environmentally hazardous as they may trigger allergies and be harmful to aquatic organisms.

An application scenario is emerging

The scientists in Darmstadt were able to use infra-red and mass spectrometry to determine the chemical composition of samples extracted in different conditions. It was found that the processes also reduced other impurities and short-chain HDPEs in the recycled material besides the amount of limonenes in it. “The project results demonstrate the benefits of a systemic approach to solving current issues within the field of plastics technology that are highly relevant to society,” says Dr.-Ing. Guru Geertz, who is supervising the project at the Fraunhofer LBF.

Theory is all well and good … but how can the method be usefully applied in the real world, i.e. in industry? The Darmstadt team has come up with an answer to that question as well. It employed machine-learning methods to optimise the efficiency of how the process is controlled. One application scenario is already emerging. “The extraction process we’ve developed is showing how it may be possible to recycle single-use plastics with an increased range of applications and so help protect the environment,” says Dr Geertz. The institute says that the process is suitable for industrialised, emerging and developing countries alike.