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Fraunhofer ILT: laser technology and AI boosting the circular economy

27 Mar 2024

Recycling sector increasingly relying on LIBS to spot reusable raw materials.

The recycling industry is increasingly relying on laser-induced breakdown spectroscopy (LIBS) to identify reusable raw materials in waste streams. The Fraunhofer Institute for Laser Technology (ILT), Aachen, Germany, is developing this precision technology for element analysis and continuously expanding its range of applications.

The transformation to a circular economy is in full swing. Recycling rates for raw materials such as paper or aluminum from packaging are already above 90 percent. In order to close further material cycles, however, the recycling industry needs sensor-based processes that can identify a great deal of different recyclable materials in waste streams not only reliably, but also fully automatically and at high speed.

The ILT has a solution that can significantly improve recycling and minimize high-loss downcycling through highly efficient, reliable and differentiated analyses of the valuable materials contained in waste streams: LIBS is one of the key technologies for an economy based on actual material cycles. This is because the highly accurate, real-time spectroscopic determination of which chemical elements materials contain enables differentiated separation by type.

For spectroscopy, a high-energy laser pulse excites the surface of the material. This creates a plasma in which the chemical bonds between the elements of the material are broken up. The atomic fingerprint is different for each material and can be read spectroscopically at the moment when the atoms return to their stable state: they emit light in specific wavelengths, from which the respective element can be deduced. LIBS, therefore, reveals the exact chemical composition of the laser-excited material in fractions of a second.

Dr. Cord Fricke-Begemann’s materials analysis working group at ILT is driving the development of inline processes based on LIBS technology to pave the way for the unmixed recovery of metals from mountains of waste and scrap. He said, “Using a scanner-based selection of measuring points and around 100 LIBS measurements per second, we can quickly create two-dimensional representations of the element distribution. We can detect technology metals in electronic waste and thus, for example, return valuable tantalum from capacitors to the material cycle.”

Aluminum recycling

Particularly for complex material compositions – as in electronic waste or end-of-life vehicles – one-to-one recycling depends crucially on the accurate, spatially resolved determination and separation of the individual material fractions.

This is what LIBS lays the foundation for: the automated, unmixed separation of a wide range of metal alloys using non-contact, laser-based, quasi-real-time analysis of materials. The process helps users determines how the materials can be used based on product, and, thus, identifies their full value.

However, the differentiated analysis of recyclable materials using LIBS is not only the basis for truly closed material flows without downcycling. It also paves the way for accelerated sorting processes and, in conjunction with automated sorting technology, contributes to their cost-effectiveness. “We can process much more scrap in a shorter time than with traditional manual sorting and also achieve genuine sorting purity,” said Fricke-Begemann.

As part of the PLUS project funded by the Federal Ministry of Education and Research (BMBF), the ILT and Cronimet Ferroleg, based in Karlsruhe, have made LIBS the basis for a new type of process that uses laser-based analysis for a special type of scrap. “These are worn-out drilling, turning and milling tools, which are collected separately in industry. Our project has addressed the special alloys processed in them,” said Fricke-Begemann.

Ultimately, they were able to automate and greatly accelerate the separation process by combining LIBS and robotics. The spectroscopic process identifies more than 20 different alloy elements, even in tiny scrap parts; the robot picks them up and sorts them accordingly. It is the blueprint for fully automated recycling, which can decisively contribute to making recycling processes more efficient.

LIBS can also play a key role in the recycling of batteries, an ability that will soon be essential, says ILT, since the mobility sector is slowly transitioning to electricity and the stationary storage requirements are sharply increasing.

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