Intelligent sorting with digital watermarks

Elopak is one of the 160+ members of the Digital Watermarks Initiative HolyGrail 2.0, driven by AIM – European Brands Association and powered by the Alliance to End Plastic Waste. Elopak participated in the HolyGrail 2.0 pilot project to prove the technical viability of digital watermarks for accurate sorting of beverage cartons and the economic viability of the business case at a large scale. This technology has been identified by the New Plastics Economy programme of the Ellen MacArthur Foundation as one of the most promising to improve recycling, and can be key to further improve sorting and higher-quality recycling rates for packaging in the EU.

Digital watermarks are imperceptible codes, each the size of a postage stamp. They cover the surface of consumer goods packaging and carry a wide range of attributes, such as packaging type, material, and usage. The aim is that once the packaging has entered a waste sorting facility, the digital watermark can be detected and decoded by a high-resolution camera on the sorting line. The packaging is then sorted into corresponding streams based on specified attributes, including food, non-food, or material types. This leads to more accurate sorting streams and higher quality recyclates, benefiting the complete packaging value chain.

The prototype was developed by the machine vendor Pellenc ST and the digital watermarks technology provider Digimarc. It combined the digital watermarks technology and NIR/VIS infrared for sorting packaging waste and achieved a >95% ejection rate. This sorter was installed in September 2021 at the Amager Resource Centre (ARC) in Copenhagen to start the semi-industrial test phase. Trials and demonstrations with around 125,000 pieces of packaging representing up to 260 different stock-keeping units (SKUs), all prepared by HolyGrail 2.0 members, were held in Copenhagen. Engineers were testing several parameters, including the speed and accuracy of the system, to ensure its ability to withstand the pressures of full-scale industrial operations.