Sorting

Digital Watermarks Initiative HolyGrail 2.0: Use of digital watermarks validated for advanced sorting of flexibles through industrial trials

2024-08-30 2:22 min Sorting and collection

Digital Watermarks Initiative HolyGrail 2.0 Brussels, Belgium

The HolyGrail 2.0 Initiative is pleased to announce the successful validation of digital watermarking technology in combination with NIR for advanced sorting of flexible packaging, with a focus on the separation of hygiene-grade LDPE films and food-grade PP films. The obtained results enable the creation of new higher-quality recycling streams at the efficiency not currently possible with other technologies. Achieving the EU's mandatory 2030 goals for incorporating recycled plastics into packaging will require substantial changes across the entire value chain, notably for manufacturers and retailers that utilise plastic packaging. New technological advancements are poised to fulfil these requirements, presenting opportunities for pioneers in the packaging sector's circular economy.

One step closer to TRL 9

Advanced sortation using digital watermark technology from provider Digimarc and add-on module from machine vendor Pellenc ST has been successfully validated in an industrial setting at Hündgen Entsorgung’s material recovery facility (MRF) for separating flexible packaging. The trial took place between December 2023 and February 2024 under the supervision of the HolyGrail 2.0 technical team. Tests were performed on real streams that were bulked up with additional quantities of digitally watermarked PP films, as well as LDPE films produced by brand owners Essity, Kraft Heinz, PepsiCo and Procter & Gamble. The focus was on sorting flexible packaging to create specific types of output fractions – food-grade PP flexibles and hygiene-grade PE flexibles – from a mixed waste stream. Aggregate sorting results for the trials in December 2023 and February 2024 are shown in the table below.

For the December 2023 assessments, the results demonstrated, on average >95% detection efficiencies, >85% sorting efficiencies, and >70% purity. These results were from single-pass sorting. It is expected that two-pass sorting, typically used in recycling plants, will further improve the purity of the output fractions with around 20%.

(Source: Digital Watermarks Initiative HolyGrail 2.0)

For the further contaminated, baled, and aged streams in the February 2024 assessments, the results for single-pass sorting achieved 89.9% detection efficiency, 75.1% sorting efficiency, while purity was 88.1%. Although the extreme conditions (i.e. multiple baling/unbaling, mix of flexibles and rigids, high throughputs up to 2500 kg/h, dirtier) of the February assessments had a large impact on the marked surface, the impact on the detection efficiency was relatively small for the tested fractions.

The overall sorting results were consistent from run to run, in spite of operating conditions during the trials, which are not reflective of normal industrial settings[1] and were generally harsher than expected for such flexible packaging due to a combination of factors – notably higher and variable throughput, the presence of both flexibles and rigids in the waste stream during sorting, and more baling than usual. Based on these observations, it is estimated that for flexible packaging, the December results are more indicative of the performance of a single sorting step in practice.

At the same site, the team is preparing to commence a three-month trial to sort post-consumer digitally watermarked rigid packaging introduced to the Danish and German markets by various HG2.0 member companies. This will be supported by two fully functional prototypes jointly developed by Pellenc ST and Digimarc, which will be installed on the commercial sorting line of Hündgen Entsorgung. If successful, the test will further validate the detection and sorting capability of the technology in an industrial setting, as well as the robustness of the system, indicating the technology has reached TRL 9 – watermark-based sorting proven in an operational environment.

Recycling trials

Two industrial-sized recycling tests with the sorted material will then complete Phase 3: Testing of the PP films and PE flexible fractions collected at Hündgen Entsorgung is being undertaken by Borealis, whereas testing of the separated non-food PET bottle stream resulting from the rigid trial, will take place at another site.

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[1] characterised by little baling, stable throughput, absence of rigid packaging in the flexible waste sorting stream.

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www.digitalwatermarks.eu

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Digital Watermarks Initiative HolyGrail 2.0: Use of digital watermarks validated for advanced sorting of flexibles through industrial trials

One step closer to TRL 9

Recycling trials

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