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The role of printing inks in improving the recyclability of flexible plastic packaging

Olivier Morel explores how, with the right ink choice, brands can ensure that their product labelling will support, and not hinder, recycling efforts

Flexible packaging is used to house 66% of all products sold within the EU and accounts for 44% of post-consumer packaging waste, and yet most EU households do not currently have access to flexible plastic recycling at kerbside, and only 6% of flexible plastics are recycled.

While the lack of infrastructure is undoubtedly a contributing factor, there are other issues which make flexible plastics more challenging to recycle, including the quality of the collected material and its suitability for recycling, which can be affected by the inks and coatings used during production.

Several organisations are now advising that brands should move away from using inks on plastics to improve recyclability – leaving very few options for coding and labelling of products – but such a move is premature and unnecessary.

Recycling rates for flexible plastic packaging

In the Global Commitment progress report for 2022, the Ellen MacArthur Foundation states that the target to completely implement reusable, recyclable, or compostable packaging by 2025 will ‘likely not be met’ by most business signatories, with the use of flexible plastic packaging highlighted as a major contributing factor.

The solution to this issue is anything but simple. For while flexible plastic (e.g. plastic bags, plastic film, and food wrapping) is difficult to recycle, it is highly efficient as a packaging material. It is very low in weight, which minimises carbon emissions from transport, while providing numerous benefits, including product protection, preservation, and quality assurance. Flexible plastic is also 60% more energy efficient to manufacture than other packaging materials such as paper and card – and produces 50% and 70% respectively less water and air pollutants. Moreover, recycling plastics uses just 10% of the energy necessary to recycle paper.

Reducing the amount of flexible plastic used within food packaging would therefore ultimately present other issues around sustainability – but we cannot escape end-of-life challenges when it comes to flexible plastics, as collection and recycling is not carried out at scale. Therefore, as an industry we must redouble efforts to improve the recycling potential of flexible plastics.

One of the key barriers to wide-scale recycling of flexible packaging is the quality of the collected materials, which is typically lower than that of bulkier plastics. The inks used on flexible packaging can be part of this challenge – adding additional materials to plastic packaging can affect the quality of the plastic and harm recyclability.

That said, the inks used on flexible packaging – whether for coding and marking of product data or full printing of flexible films and labels – have a crucial role to play, and so ensuring solutions are suitable for recycling is of significant importance.

The role of inks on product packaging

Product labelling plays a fundamental role in enabling food and beverage manufacturers to communicate essential information to consumers, as well as to retailers, and throughout global food supply chains. From a waste and recycling perspective, product labels are also an effective way of communicating with consumers about how to deal with packaging when it has reached the end of its usable life. This could include information about the packaging composition and its recyclability; guidance on how to dispose of the packaging correctly (e.g., recycle at home, in-store, or specialist recycling); or additional details included in 2D codes, such as websites to locate the nearest recycling point.

Increasingly, we are seeing regulatory requirements and compulsory product labelling introduced to help consumers dispose of packaging correctly. France’s Tri-man logo, Italy’s Legislative Decree 116/2020, and the UK’s Department for Environment, Food & Rural Affairs (DEFRA) Recycle Now mandate have set the scene, and more countries will likely follow suit.

In addition, we are seeing an increase in labelling initiatives aimed at improving the collection and sorting of packaging waste. Digital Watermarks HolyGrail 2.0, for example, aims to use digital watermarking to enable better sorting and higher-quality recycling rates for packaging in the EU. The aim is that once the packaging has entered into a waste sorting facility, the digital watermark (an otherwise imperceptible code) can be detected and decoded by a high-resolution camera and sorted into corresponding recycling streams.

So, how can brands ensure the inks used as part of all these coding requirements will support, and not hinder, the recyclability of a packaging material?

Designing inks for recyclability

Very few regulations specify requirements or restrictions regarding inks on recyclable packaging. However, with the current focus on improving recycling rates, it is likely only a matter of time before these are introduced, particularly given the increase in independent, unaligned guidance documents available for brands. For example, CEFLEX’s D4ACE-Guidelines; Plastic Recyclers Europe’s RecyClass tool; and the Ellen McArthur Pioneer Project Barrier: “Recyclability Guidelines for Plastic-Based Flexible Barrier Packaging”.

There are, however, several best practices regarding ink selection, which brands can follow to maximise their packaging’s suitability for recycling and keep ahead of any future regulations:

Printed packaging should follow the 5% rule: The ink printed should be 5% or less of the total weight of the packaging. This doesn’t present a problem with modern coding and marking solutions, even if the amount printed is increased to print more information, for example, in high-resolution 2D codes or on-pack recycling labels. For full product printing, using digital inkjet printing technologies rather than analogue printing methods will also help ensure the quantity of ink printed stays below the 5% mark.

Inks should be composed of ingredients that are unlikely to create technical problems during recycling: For plastics, where the temperature of reprocessing materials sits between 200°C and 270 °C, it is important to avoid ink ingredients that may thermally decompose and create harmful or problematic materials. Certain ink ingredients can generate corrosive materials that can damage recycling equipment, gases that downgrade the quality of the recyclate, and other chemicals which can cause discolouration. Inks should also be ‘non-bleeding’, i.e., no noticeable discolouration of washing waters during recycling or of recyclate flakes after drying.

Inks should either be of a similar chemical nature to the packaging substrate or able to be separated easily from it: Inks that remain on a recycled material can alter the colour and transparency of the recyclate and make it less valuable. Creating high-quality recyclate from flexible packaging may, therefore, require a de-inking process to remove leftover colourants and return the material to its original state. Analogue printing – where an ink layer for the full decoration of the packaging is embedded between two thin layers of the packaging substrate – can be very difficult to de-ink. Placing the ink on top of the substrate – surface printing – using digital printing technologies, increases the likelihood that the ink can be removed, thereby increasing the value of the recycled material.

Inks should adhere to EuPIA guidelines: When recycling plastics, it is not always possible to remove all contaminants present on the original packaging material, and, over time, this can cause an accumulation of contaminants within the recycling stream. It is therefore important to ensure that inks printed onto recyclable plastics are free from ingredients that could pose a problem for human health if built up in higher concentrations through recycling. To this end, any inks used of recyclable packaging should be designed and manufactured in line with the European Printing Inks Association (EuPIA) Exclusion Policy, avoiding the use of harmful or hazardous substances.

Conclusion

Given the many benefits of flexible packaging and its wide use in global food and beverage markets, it is unlikely that we will see a decrease in the use of flexible plastics in the near future. However, it is undeniable that more must be done collectively to increase the percentage of flexible plastics that are recycled.

While improving recycling infrastructure is one crucial element, it is also vital that we make recycling information more straightforward and accessible for consumers, as well as harnessing technologies to improve sorting and processing within recycling facilities.

Inks play a fundamental role in this communication, so ensuring inks are designed for recyclability is critical. This is where partnering with a reliable ink supplier with experience working in coding and marking, and digital printing, can stand brands in good stead as we strive to meet global objectives to increase the recyclability of flexible plastic packaging.

Olivier Morel is Product Development Manager, Domino Printing Sciences.

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