HolyGrail 2.0 announces successful semi-industrial test for sorting using digital watermarks


The HolyGrail 2.0 initiative has successfully validated the prototype detection unit for digital watermarks. Semi-industrial tests show a 99% detection rate. The HolyGrail 2.0 initiative thus offers the possibility of developing new, even more precise post-consumer recycling flows.

Digital watermarks are small, imperceptible codes on the outside of packaging. They contain information about the producer, the plastic type, the composition or the use to which the packaging is put, etc.

As part of the validation phase, semi-industrial tests imitating real conditions were set up. So the packaging was soiled, squashed or crumpled – just as it is in the sorting centres today. The tests took place at the Amarger research centre in Copenhagen.

Developing new recycling flows

The technology consists of a software combination of digital watermark detection and NIR detection (near-infrared), to identify packaging both with and without a watermark, as would be found in a sorting centre. This overcomes the limitations of the current NIR sorting technologies.

According to the HolyGrail initiative, the test results show that the digital watermark technology can achieve more granular packaging material sorting on a large scale. This would make it possible to develop individual post-consumer recycling flows that do not exist at the moment. Examples include separate flows for uses such as cosmetics and detergents on the one hand and flows for food-contact packaging on the other. HolyGrail 2.0 thereby supports more circular, one-on-one recycling applications. On average, a detection rate of 99% and a degree of purity of 95% were achieved. The degree of purity for flexible plastic packaging materials was slightly lower (90%) than for the rigid categories.

Via a French recycling partner, Fost Plus supplies PET bottles and PET trays with a digital watermark from the Belgian packaging materials collected via the New Blue Bag.

HolyGrail 2.0, the initiative to test digital watermarks to sort packaging materials, was set up in 2020 and is now coordinated by AIM – the European Brands Association and The Alliance to End Plastic Waste. Industrial pilot projects are to start at various sorting and recycling companies later this year.