Laser Light finds Recyclable Materials - Resources for Our Future

(f.l.t.r) Dipl.-Ing. (FH) Jürgen Bohleber, Prof. Dr.-Ing. Gunther Krieg, Dipl.-Ing. (FH) Dirk Christian Fey

Prof. Dr.-Ing. Gunther Krieg (Spokesperson)
Dipl.-Ing. (FH) Jürgen Bohleber
Dipl.-Ing. (FH) Dirk Christian Fey

UNISENSOR Sensorsysteme GmbH, Karlsruhe

Non-returnable bottles made of PET for beverages have long been notorious for polluting the environment and being harmful for the climate. Yet current studies give evidence that they are no more harmful for the environment and climate than glass bottles. However, the condition for this is that the PET material is reclaimed, recycled and used to produce new bottles. Before this can happen, impurities and contaminants must be removed from the PET. How is it done?

Prof.-Dr. Gunther Krieg, Dipl.-Ing. Dirk Fey and Dipl.-Ing. Jürgen Bohleber have developed a system that separates polyethylene terephthalate (PET) reliably from other materials during recycling so that even minute and virtually undetectable amounts of impurities and contaminants can be sorted out and the recycled plastic used without reservation to produce new bottles in a process that has come to be known as closed-loop or PET bottle-to-bottle recycling. Gunther Krieg heads the Transferzentrum Optoelektronik und Sensorik of the Steinbeis Foundation in Karlsruhe and founded UNISENSOR Sensorsysteme GmbH in 1990. Dirk Fey is chief technical officer at the firm, Jürgen Bohleber is project manager responsible for designing sensor machines for the recycling industry.

“Powersort 200”, the system they have developed, is based on ultra-high-speed laser spectroscopy. In the process used, powerful lasers expose granulate or plastics crushed into flakes to ultraviolet, visible and infrared light. The light excites molecules in the plastic which disperse the light. The wavelengths in the scattered light are a characteristic, physical fingerprint of the material. Sensors that capture the light and analyze it instantaneously are able to differentiate PET reliably from other materials such as PVC or nylon, color residues and impurities such as paper or glue residues. The process even works on minute particles. Supersonic air jets remove the unwanted substances.

More and more beverages around the world are being bottled in non-recyclable PET bottles. Every year manufacturers process around seven million tons of PET. In Germany, almost 70 percent of all light-weight non-recyclable bottles are manufactured for mineral water – and the trend is rising. To reduce demand for petroleum – the starting material in PET bottles – empty bottles are collection and recycled. In conventional methods, however, many impurities and contaminants were unable to be identified and removed. Consequently, in the past, only part of the recycled PET found its way back into food-grade bottles. The rest was used, for example, to manufacture clothing or tarpaulins. The new process, however, achieves such a high grade of purity that the recycled material can be 100% reused to produce in juice, beer, soft drink, or mineral water bottles without any risk to consumers.

Gunther Krieg founded UNISENSOR Sensorsysteme as a spin-off of the Research Center Karlsruhe (now: Karlsruhe Institute of Technology, KIT) and the University of Applied Sciences Karlsruhe. Together with Dirk Fey and Jürgen Bohleber he has been an instrumental force in the development and marketing of the innovative plastic recycling technology. It closes the recycling loop of plastics in foods technology and conserves the use of dwindling resources such as petroleum and energy and significantly reduces CO2 emissions. The economic and ecological potential is enormous. The system is already being used successfully at several recycling centers in Europe and the U.S. – including, for example, the largest European PET recycling company in the Netherlands and in a Coca Cola Company facility in the USA. And: The process will soon also be used to separate and recycle plastics from waste electrical and electronic equipment, such as PC’s or TV’s as well as automobiles. Waste will thus become an exploitable resource.

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