The Pitfalls of paperization: Why coatings put paper packaging recycling to the test

Paper packaging is trending and is often seen by consumers as an eco-friendly alternative to plastic. But is paper packaging truly the more sustainable choice? In our three-part blog series, we take a closer look. In this second part, we explain why fiber-based packaging often requires coatings and how these can become a challenge, particularly in terms of recycling and environmental impact.

It’s the prototype of coated paper packaging – and consumers are often unaware of the significant plastic content in this packaging. The challenges of paper packaging are perfectly illustrated by the coffee-to-go cup: since paper is neither water- nor grease-resistant, paper packaging for beverages (like coffee) or moist foods requires an appropriate coating. A plastic coating extends the shelf life of packaged food or even makes paper packaging usable in the first place – but at the same time, it significantly complicates and increases the effort required for recycling.

The environmental challenge for fiber-based packaging:

• Material composition: Paper packaging for food rarely consists of pure paper, but of coated or laminated paper structures that contain plastic or other components. These coatings are necessary to improve the barrier properties and ensure the shelf-life of the products.
• Recyclability: The inseparable combination of paper and plastic makes recycling difficult. While pure paper and pure plastic can be separated and recycled relatively easily, coated paper packaging poses a challenge for the recycling industry.

It turns out that the question of a sustainable packaging solution is often more complex than assumed. After all, there is no single ideal material for all products in terms of protection and ecology: Nuts and chocolate, which go rancid quickly, place different demands on packaging than something like pasta. Liquid or fatty foods also require different packaging than, for example oatmeal. When looking for ecological packaging, it’s therefore important to take a close look at the requirements and then analyze the environmental impact of the packaging in question.

Paper packaging for food often contains a combination of paper and plastic to meet specific requirements. While the paper as the base material of the packaging provides structure and shape, the thin coating of polyethylene or other plastics serves as a barrier against moisture, grease, and other substances that could penetrate the packaging and spoil the food:

• Moisture barrier: Foods such as dairy products, which have a high water content, require a barrier to keep moisture inside and prevent moisture from penetrating from the outside. Pure paper is absorbent and, without a coating, would quickly soak through and lose its structure.
• Fat barrier: A plastic layer prevents fat from penetrating the paper and damaging the packaging for fatty foods, such as butter or cheese.
• Oxygen barrier: Many foods are sensitive to oxygen, which can lead to spoilage or loss of quality. A plastic coating can prevent oxygen penetration and thus extend the shelf-life of the food.
• Microbiological safety: Plastic coatings help to prevent the penetration of microorganisms that could also spoil the food

The barrier therefore ensures a longer shelf life, which often makes preservatives superfluous. However, it is not generally possible to say whether a barrier coating is useful, as foods and their requirements are too varied. Therefore, different packaging is used for food that is stored in a cool place and only has a shelf-life of two or three weeks anyway than for food that is stored at room temperature and needs to keep for months. Better protection is needed here.

The coatings enable the packaging to guarantee the food’s quality and safety. This is particularly important for products with a longer shelf-life and those stored in a humid or variable climate. The issue of barrier thus plays a decisive role in more than just paper packaging. If the right packaging material is to be selected for a product, two parameters in particular need to be considered at the outset: the oxygen transmission rate (OTR) and the water vapor transmission rate (WVTR). Both values guarantee the products’ freshness, quality, and shelf-life.

Dairy products:

• Variety of different products.
• Dairy products are susceptible to oxidation, which can affect their taste, smell, and nutritional value. A low OTR ensures that less oxygen penetrates the packaging, extending the product’s shelf-life and quality.
• Dairy products often have a specific moisture balance, which is essential for their texture and consistency. A low WVTR prevents moisture from escaping from the product or external moisture from penetrating.

Baby food:

• Ethylene vinyl alcohol (EVOH) barrier as an additional protective layer.
• Very low OTR and WVTR.

Coffee:

• Unconditional protection from oxygen to preserve flavor and freshness.
• Very low OTR necessary.

Nuts / chocolate:

• High fat content.
• Low OTR and WVTR values necessary.

Fruit / vegetables:

• High OTR to maintain the breathing process.
• Medium WVTR to avoid moisture loss and absorption and ensure freshness.

Coatings in paper packaging may be necessary to ensure the quality and safety of the food inside, but they pose a challenge for the recycling industry. If only paper packaging coated on one side is added to the paper stream, it can generally be recycled. However, the different materials must first be separated from each other. Double-sided coated packaging (such as that used for wet food) requires cost-intensive, specialized equipment and processes that are not available in all recycling plants. This can lead to many of these packaging types not being recycled. This not only means the loss of valuable resources: If it is incinerated or ends up in landfill sites, this packaging, perceived initially as particularly sustainable, has a much worse impact on the climate and environment than previously thought.