Sorting of black plastics for recycling

The recycling of plastic waste is a key factor for resource-friendly production. Techniques that are capable of sorting black plastics according to type play an important role here.

Black plastics cannot be recycled satisfactorily with the technology that is available today. The soot that is used to blacken plastics absorbs most of the electromagnetic radiation in the visible as well as in the infrared wavelength range. As a result, black plastics can hardly be distinguished and separated according to type with conventional sensor technology. This not only reduces the quality of products made from recycled material but also lowers the per ton value of the recyclate. The separation of black plastics according to type therefore opens up new earnings potential for companies.

We want to overcome this technical problem by using terahertz technology. The absorption behavior in the terahertz range allows the separation of recyclate and, in particular, black plastics according to type. To date, the high expenditure associated with the development of a full spectroscopic, imaging terahertz sensor system has hindered its application in the industrial sector.

Fraunhofer FHR and Fraunhofer IOSB decided to tackle these challenges jointly. The combination of a terahertz camera with optical sensors allows complete material characterization using selected frequency bands in the low terahertz range and the acquired data can subsequently be evaluated using new analysis algorithms. Our vision is a cost-effective, realtime-capable multisensor suite with a sorting accuracy of over 90%.  

BlackValue’s targets are:

  • to develop a system with integrated sensors and algorithms
  • upgradeability
  • high separating preciseness
  • applicability on plastic flakes (in particular black flakes)
  • capacities of up to 5 tons per second
  • cost-effective, economic implementation

The separation into pure grades achievable with this technology, combined with economic efficiency, allows the recycling of black plastics on an industrial scale. The participating Fraunhofer institutes and their industrial customers are therefore opening up new market segments.

The technological approach of the system is currently undergoing validation and in-depth testing. We assume that suitable frequencies and procedures can be found and implemented in the medium term to achieve our ambitious goals.

With you as a pioneer, decision-maker or user of the recycling industry or associated companies, we would be delighted if you could imagine a joint research and development project with us for BlackValue.