How digital watermarks can help raise plastics recycling rates

Sorting and recycling plants are facing the same challenges that we face in front of our bins at home: What is that and how do I sort it properly? In the future, the packaging itself might provide the answer, according to the idea behind the “HolyGrail” project. The goal: Make it easier to sort used plastics and thus increase recycling rates. Gian De Belder and Philip Knapen tell us more about it.

“Unfortunately, less plastic is recycled in practice than would be possible in theory”, says Gian De Belder, packaging technologist at Procter & Gamble (P&G), who is also the initiator of the HolyGrail project, facilitated by the European Brands Association and powered by the Alliance to End Plastic Waste. “The problem is that waste streams are not sorted efficiently”, he says. Different methods are used in sorting plants to distinguish plastic types from each other, for example by size, weight, material, or color. But there is even more to consider, because different packages follow different standards when it comes to recycling. “We could recycle more material if we were able to sort packages that contained food items – such as juice bottles – from those that contained non-food items like detergent or cosmetic bottles”, Gian explains. “To provide that information, our idea was to make packaging more intelligent”, he says.

Digital watermarks make packaging intelligent 

How it works: The watermarks are the size of a postage stamp and ideally cover the entire surface, like a subtle QR code around the packaging. Although the codes cannot be seen by customers, they can be detected by the cameras in the sorting/recycling facility. A database knows what material the packaging is made of and then air streams sort the different materials into separate waste streams. These waste streams can then be recycled, e.g. with mechanical or chemical plastic recycling.   

Digital watermarks make packaging intelligent and provide information for sorting, allowing them to be sorted at product level. And better sorted waste streams lead to higher recycling rates.
Gian De Belder, Packaging Technologist, Procter & Gamble

Next-level sorting

“The digital watermarks work better than a single barcode could too, because they can be identified no matter what position the packaging is in and even at high sorting speed”, tells Gian. “It also enables sorting machines to identify dark colored packaging and multi-layer packaging”, he says. Those have been a challenge for recycling before. With the new technology, it’s also possible to distinguish non-food from food packaging, which is crucial, as the recyclate used for food packages has to fulfill higher standards than non-food packaging, in order to avoid contamination. “In the future, we could also develop new dedicated recycling streams that do not exist at present, for example, separate streams for detergents or cosmetics packaging, making it easier to turn old shampoo bottles into new shampoo bottles”.

How do the codes get on the packaging?

In the first stage of the project (HolyGrail 1.0), the digital watermarks were successfully tested with a variety of enhanced samples, including embossed detergent bottles. They – and several other packaging items – were provided by OMV subsidiary Borealis. “Now the project has reached the second stage, where the digital watermarks will be integrated directly into a mold, or in the design of printed or in-mold labels”, says Gian. That means that the technology is rolled out to more product categories and is right on track to work on an industrial scale. 

Have a look at the following video to find out more: To the end of life. About Project HolyGrail.

On track to a circular economy

While technology is crucial to succeed, it also takes collaboration among many different stakeholders. “To increase recycling rates, every player in the value chain has to contribute – from manufacturing to disposal”, says Philip Knapen from Borealis, which will be supporting the recycling activities in the project. Currently some 170 companies are working together to make this happen.

Plastics recycling is also firmly anchored in our strategy: By 2030, we aim to obtain 40% of the raw material for plastic production from sustainable sources like recycling. That is equivalent to about 2 million tonnes.

To increase recycling rates, every player in the value chain has to contribute –  from manufacturing to disposal.
Philip Knapen, Application Marketing Manager, Borealis

But Borealis is not only a plastics manufacturer, it also operates three sorting plants. In its demo plant in Lahnstein (Germany), the HolyGrail packaging is being tested to find out which camera systems work best in order to introduce them in more sorting facilities. “For us, accurate sorting streams are essential as a prerequisite to achieve higher quality recyclate, which then allow for the production of higher quality plastics”, Philip says. 

Digital Watermarks can also talk to the consumer

Finally, the intelligence of digital watermarks not only helps sorting machines: “The codes can be identified by every camera – even the one on your phone. In the future, this could be used to give consumers recycling instructions, even in combination with augmented reality. So don’t be surprised if one day the cow on the cream cheese package talks to you”, Gian says with a smile.