Applying chemical tracers and digital watermarks to ‘tag’ an item with a unique code can improve automated detection and sorting of plastic.
TARGET USERS: Individuals, Businesses, Industry, Government
KEY CONSIDERATIONS: New plastic branding technologies make it possible to separate post-consumer plastics more accurately, generating clean waste streams that can be efficiently recycled.
MORE INFORMATION: See The Holygrail
Today, only a very small fraction of plastic packaging is actually recycled. This is due in part to the complexity of packaging design and the limitations of sorting technologies, which are typically capable of only recognizing a few properties.
The design of packaging disrupts the recycling when an item is ‘invisible’ (e.g. black PET trays cannot be seen by detectors) or in the case of packaging that leads to false positives/negatives, uch as the negative sorting of a full-sleeve PET bottle because the sleeve is typically made of a different material which means the PET is not detected.
Post-consumer plastic packaging can be recycled more effectively when it is labeled by watermarking technology. Postage stamp sized watermarks on packaging, not visible to the naked eye, make it possible to effectively sort material into specific waste streams. With this new technology, it becomes possible to separate materials more accurately and generate clean waste streams, which then can be recycled with enhanced recycling technologies.
Rather than relying only on the ability to distinguish one or several properties of collected items (e.g. shape, density, IR spectrum of the resin, visual identification), detecting and reading the watermark, or code, provides the sorting system with information unique to that item by pointing to a database where that information is stored. The information tells the system in which way to sort the item (e.g. food grade vs. non-foodgrade); such information can be updated and expanded over time to allow for adjustments in sorting preferences if an item’s recyclability improves.
Filigrade utilises watermark technology to apply digital codes in the mould of plastic products during production, giving products their own “DNA”. In the waste separation process, the watermark is read and the watermarked plastic can be sorted automatically. This enables recycling of all types of plastic (white, transparent, coloured, even black, food vs non-food), without chemistry and without residue after shredding. See https://www.filigrade.com/ for more information.
The HolyGrail project was set up to investigate if such chemical tracers and digital watermarks could provide a reliable and efficient tagging system that could eventually be deployed on a large scale, and if so how they might contribute to a circular economy for plastics. Participation in HolyGrail has grown significantly since its initiation and now includes stakeholders from the entire value chain. The project group notably includes leading machine vendors Tomra and Pellenc, digital watermarking pioneer Digimarc and FiliGrade, a Digimarc licensee, as well as material producers, packaging manufacturers, brands, retailers and recyclers. See https://www.newplasticseconomy.org/assets/doc/Holy-Grail.pdf for more information.
PepsiCo participate in the Holy Grail Consortium to trial digital watermarks on packaging as part of efforts to increase recycling across Europe. See
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