Fraunhofer Institute for High Frequency Physics and Radar Techniques FHRWaste4Future
Polyamide is expected to be recycled to a large extent in the future. However, it is difficult to separate polyamides from other plastics in black plastics. A new sorting demonstrator can now achieve this.
12 million tons of plastic are consumed in Germany alone – per year, mind you. Their production releases 33 million tons of CO2 annually. The recycling rate still leaves much to be desired: only 47 percent of plastics are recycled material-wise, while 53 percent await thermal recovery, meaning incineration. In the Fraunhofer flagship project "Waste4Future," researchers from eight Fraunhofer institutes – including Fraunhofer FHR – have developed a way to close the plastics loop. "Our sorting demonstrator is equipped with various sensors that can differentiate between different plastics," explains Sven Leuchs, a scientist at Fraunhofer FHR. "At the same time, we map the recycling process through a digital twin, and an evaluation model enables meaningful decisions about the type of recycling." The project ran for a total of four years and was successfully completed at the end of 2024.
Recycling Black Plastics
Sorting black plastics, such as those used in car dashboards, is more challenging. In the last project year, the focus was on sorting black plastics based on terahertz technology. Optical and near-infrared sensors quickly reach their limits with black plastics, so the research team relied on a terahertz sensor developed at Fraunhofer FHR. "The measurement signal of our sensor is influenced differently by the dielectric properties of the various plastics and is thus suitable for black plastics – the signal from polyamide clearly differs from that of other plastics," says Leuchs. If a plastic fragment is characterized as polyamide by an AI model, it is sorted out using a controlled airflow and shot into a different container than the remaining parts.
The researchers started with samples measuring eight by eight centimeters with the same thickness; they can now also recognize two by two centimeter small fragments – at a belt speed of 1.3 meters per second. "In the next step, we will sort black real fractions," specifies Leuchs, "whose particles may be similar in size but are significantly more irregular than the previous samples."