- Article
Why ”recyclable” cartonboard isn’t always recyclable
All cartonboard packaging products are recyclable, right? Yes, in theory they are. But in reality, things are not quite as straightforward. Many manufacturers use so-called wet-strength additives to compensate for an inherent lack of wet strength in their board. While effective, these additives also make it very difficult to repulp the wood fibers – rendering the product “unrecyclable”. This article highlights a very real problem that you need to keep in mind for the future
What are wet-strength additives?
Wet-strength agents are added to cartonboard to improve its ability to resist water and maintain its mechanical properties and dimensional stability. They do this by crosslinking the cellulose fibers, creating a network that reinforces the paper structurei. Wet-strength additives have been around for almost a century, and they are most commonly used in paper products such as hand towels, hygiene papers and paperboard made for packaging.
Why are they a problem?
In traditional recycling, cartonboard is mixed with water and exposed to mechanical shear forces in so-called hydro-pulpers to create a slurry. This allows the fibers to separate and subsequently be reformed into new paper products. The cross-linked fibers in wet-strength-treated cartonboard resist this process, requiring additional steps and special chemicals to break them apart. Most recycling mills are not equipped to do this, which means that cartonboard containing wet-strength additives is rejected from the process and often end up in landfills or incinerators, breaking the wood-fiber recycling loop.
Are wet-strength additives really necessary?
In applications like tissue, towels and medical paperii, yes. But in many cases, like cartonboard for packaging solutions, wet-strength additives are often used to disguise the fact that the board isn’t strong enough in the first place. In other cases, outdated packaging standards and tests call for excessive wet strength where it isn’t really needed in the real world.
What’s the alternative?
By choosing a high-strength cartonboard that is made from fresh, slowly grown, long and strong fibers, you can often get the wet strength you need without resorting to additives. And if you really need to keep large amounts of moisture at bay, this can be obtained by for example curtain-coating a polymer onto the paper board, or through the use of a thin, laminated plastic film. Somewhat counter-intuitively, these types of barriers are easily separated from the cartonboard in standard recycling mills, leaving the non-treated fibers to be used again – allowing for bio-circularity.
Looking towards the future
The upcoming PPWR legislationiii states that paper packaging with a recyclability rate below 70% will no longer be considered recyclable and may not be brought to market after 2030. In the case of cartonboard, reducing the usage of wet-strength additives are therefore desired. And in the long-run, this will be essential in order to increase circularity rates of fiber-based packaging materials globally. In other words: it is high time to future-proof you packaging by choosing recyclable cartonboard that doesn’t depend on wet-strength additives.
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ii Medical paper gets incinerated in order to kill pathogens and is currently exempt from PPWR
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