Industrial tests for the separate sorting of polyethylene (PE) and polypropylene (PP) films from a mixed packaging stream have been successfully completed, as announced by the HolyGrail 2.0 Initiative. The results show that packaging marked with digital watermarks can be sorted more precisely for recycling with the aim of circular, one-to-one applications. The follow-up phase will use PP packaging films with watermarks collected via the blue bag for testing.
The tests were carried out in Germany between December 2023 and February 2024. The focus was on sorting flexible types of packaging (films and foils) with digital watermarks that had been added to mixed packaging waste. This involved a separate stream of PP films from food packaging and a separate stream of PE films from the packaging of hygiene products.
Pure material streams through extra sorting step
The results show that the combination of NIR (Near-Infrared Technology) and digital watermarks results in the creation of new, higher-quality sorting streams. Sorting centres are already using a combination of technologies, including NIR, but they are unable to achieve the same level of efficiency. The goal is to create highly pure material streams through an extra sorting step, so that they can eventually be recycled into materials that comply with food packaging standards.
Meanwhile, the HolyGrail 2.0 team is preparing for the next steps. This includes a new test to sort digitally watermarked rigid packaging from post-consumer waste streams in Germany. This testing phase goes one step further: this packaging has been actually placed on the market by HolyGrail 2.0 brand owner and retailer member companies, and will be disposed of by real consumers. In other words, the technology will be tested under realistic conditions.
Next phase: films from the blue bag
A follow-up phase will also take place in Belgium, in which Fost Plus will participate. The plan is to apply digital watermarks on PP packaging films from Ferrero, Mondelez, and Pepsico, which will be then placed in Belgian shops so that they can be collected via the blue bag. Initially, this will involve about 150 tonnes of flexibles per month to be sorted into food (packaging items) vs. non-food for the duration of the test.
What are digital watermarks?
Digital watermarks are optical codes that are not visible to the naked eye. They are applied directly to the package label or embossed in the mould. They can contain a wide range of data, such as details concerning the packaging manufacturer, packaging composition and material, application, etc. Digital watermarks are detected and decoded by a high-resolution camera installed on the sorting line, which then sorts the packaging into the appropriate stream (e.g. food vs. non-food). This results in more accurate sorting and consequently higher-quality recyclate.
Why are they important?
One of the most promising applications of digital watermarking is the ability to sort material streams more precisely: not only by material type as is being done today, but also by application – in other words, based on what was contained in the packaging. This increases the circularity of recycling applications. As a result, it will be possible to recycle even more in one-to-one applications. This is important for manufacturers and retailers, so that they can meet the mandatory EU targets for the use of recycled plastic in packaging. Fost Plus is proud to support the HolyGrail 2.0 Initiative and thus contribute to a more sustainable society.