Multi-layer packaging consists of multiple thin layers sandwiched together to form a lightweight package structure that provides barrier properties, strength and storage stability. These desirable properties are great for food packaging to deliver exceptional protection and freshness for the contents inside (e.g., fresh coffee, potato chips/crisps and other snack foods, baby food, pet food) to extend their shelf life—but not so great for recycling. Multiple organizations in the packaging industry are working on ways to improve the recyclability of multi-layer packaging to reduce waste.
Multi-Layer Packaging Overview
Multi-layer packaging can include as many as 11 individual, ultra-thin layers. Even with multiple layers, it is still significantly lighter and thinner than comparable packaging. As an example, moving from glass jars to flexible pouches uses far less material, less gas to transport and less energy to make them, making them more environmentally friendly.
The components typically include PE/PA, PP/PET films together with aluminum, paper and printed layers, with each layer having a specific function. The outer layer might provide abrasion resistance to deliver toughness. The next layer would provide an oxygen or UV barrier (or whatever barrier is needed, moisture, UV, oxygen, etc.). This layer would be followed by a printed layer and then another layer to provide an air-tight seal. Finally, an adhesive layer is used to keep everything held together.
Using fresh coffee as an example, the packaging must provide barrier properties that make it resistant to oxygen. Some food products require moisture or UV resistance while others must be leak proof. Complex structures are needed to build this multi-layer protection with the correct mix of properties to keep the contents safe and healthy.
Multi-layer packaging is a relatively recent invention. The upside is that this type of packaging uses minimal amounts of materials, is very lightweight and excels at protecting the contents inside, which minimizes food waste. As mentioned above, the downside is that multi-layer packaging is very difficult to recycle. That’s because the layers cannot easily be separated. Even if they could be separated, some of the layers might be plastic, paper or aluminum, so they can’t neatly go into one bin without leading to contamination of recycling streams.
The result is that the majority of multi-layer packaging structures are currently landfilled or incinerated. Sometimes, they are “downcycled,” where the layers are mushed together to produce green-gray pellets that can be used for low quality, low volume goods. The benefit is that packaging is not being landfilled, but it’s also wasting valuable resources in low volume products.
The growth in regulations and taxes related to packaging, as well as voluntary plastic pacts where stakeholders in plastic packaging pledge to commit to being more circular in use, mean that packaging needs to be made recyclable (or reusable or compostable). For multi-layer packaging, that is leading to redesigns to make it is easier to recycle while still maintaining the necessary protective performance.
Stakeholders in the industry are exploring multiple approaches to these redesigns, including:
- Mono-component products—this involves making the layered structure out of materials that are all the same chemically. Using the same polymer for all layers will compromise some of the performance, which means a thin, wet coating might be needed on each layer to improve performance.
- Mechanical recycling—the structure stays the same with it easier to separate layers at the end of life. Lubrizol is currently working on ways to separate layers that involve applying a coating between layers. With this method, the layers of materials be captured more cleanly in the right places to avoid recycling contamination. By cleanly separating layers, they can be classified as recyclable (no packaging taxes and adherence to plastics pacts) and valuable materials can be recaptured and fed back into the system.
- Chemical recycling—this approach is in very early stages and involves breaking the polymers down to their basic building blocks. It’s currently very expensive and won’t solve recyclability issues in the short term.
Lubrizol has developed coating solutions that support layer separation and mono-material approaches. By exploring a variety approaches, the future looks much better for improving the recyclability of multi-layer packaging.