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The challenges of PCR in lidding film for high temperatures

Updated 30/10/2020

  • No approved recycling processes for food contact use at high temperatures
  • Barriers to contaminants would lead to more, not less waste
  • Recycled plastic is more expensive than virgin
  • Detection difficulty could lead to fraud

There’s no point in splitting hairs about whether it would be good to have Post-Consumer Recycled content (PCR) in lidding film for food packaging. Any usage of PCR helps the sustainability of plastics and positively contributes to a circular economy. 

Polyethylene terephthalate (PET) is the most suitable material to realise these ambitions. In contrast to other plastics, PET has many approved recycling processes for chilled and room temperature applications, which have been found by the European Food Safety Authority (EFSA) to be safe. 

However, it is worth bearing in mind that a layer of film can literally be as thin as a split hair (possibly 17 microns compared to a 75-micron human hair). And the usage of PCR in thin lidding film for elevated-temperature applications currently presents challenges including:

  • The PCR would need to be obtained from a “super-clean” mechanical recycling process approved by the European Food Safety Authority (EFSA). So far, none of the recycling processes evaluated at EFSA have been approved for food contact use at high temperatures (heating in the pack). This, therefore, prohibits using lidding films with PCR content for products such as ready meals, which require in-pack heating

or;

  • The PCR would need to be kept behind a “functional barrier” of virgin plastic in order to prevent contaminating the food by substances migrating out of the PCR plastic. However, the thickness required for such a “barrier” would be so large that there would be practically no space left for the PCR unless the overall thickness of the film were increased radically. 

Experimental evidence would be required to prove the virgin layer is a sufficient barrier to any kind of contaminant in any amount and for the intended use. The consequence of this would be no significant saving of virgin PET while at the same time at least doubling or tripling the overall thickness of the lid. This would require overall more environmental resources than a virgin lid, and thus be more detrimental to the environment.  

It is the thinness of the lidding film - for example compared to trays - that may prevent the “barrier” from ever being effective enough. Dr. Cynthia Bennett, Director Product Stewardship, Mitsubishi Polyester Film GmbH, told us: 

“Some tray manufacturers may have done challenge tests on trays but those results would not apply to lidding film. 

“The sealable, peelable layer is much thinner than the cover layers commonly used in thermoformed trays; approximately 1/10th the thickness. The characteristic that makes the seal peelable - a lower glass transition temperature - makes this layer far more permeable to contaminants. 

“Based on our experience with migration, we doubt that peelable layers in current thicknesses could meet EFSA’s safety requirements for functional barriers to PCR for elevated temperatures with the appropriate challenge tests and, therefore, rule out the use of PCR material in thin sealable, peelable layers for elevated temperature applications.”

With this in mind, at KM Packaging, we currently can only provide lidding film with PCR content for applications that do not require heating. For example, a lidding film for soft fruits packaged in pulp or clear plastic (APET) trays.

Regarding the wider usage of PCR, there are a number of issues. They include:

  • The cost of recycled content is currently greater than the purchase price of virgin plastic.
  • Recycled plastic in the UK is of poor quality – better material has to be imported.
  • There is low worldwide availability of quality recycled plastic.
  • Flexible “soft” packaging reduces the amount of plastic used – but it’s generally not collected or recycled. It is imperative that the recycling infrastructure is developed in the UK to support a sustainable cradle-to-cradle approach for all materials. This would create a circular model for flexible packaging.
  • It is not possible – even within a laboratory – to accurately measure the proportions of PCR and virgin plastic used within a product. This could open the door to fraudulent claims, especially if importing from unaudited sources.

Fortunately, there is a determination within government and industry to tackle these issues. Already, investments are being made to improve recycling machinery to more easily identify and sort different types of plastic. 

Other technical initiatives are aimed at ”hard-to-recycle” plastics, with the ambition of achieving the same quality as virgin plastic. Chemical recycling by pyrolysis and other methods, is being developed by various companies throughout Europe. Such chemical recycling processes address some of the issues with EFSA approved mechanical recycling processes. Regulations are being developed to ensure that the new chemical processes achieve the same level of safety as with virgin plastic and the existing approvals for mechanical recycling processes.

PET derived from chemical recycling is currently not within the scope of (EC) 282/2008, the regulation on recycled plastic materials and articles intended to come into contact with food. Consequently, in comparison to mechanical recycled material, there is no EFSA assessment of the safety of chemical recycling processes or even guidance on how to do the assessment available. Nevertheless, the general requirement of the framework regulation (EC) 1935/2004 for food contact material to be safe still applies, thus it depends on the manufacturer to assess and prove the safety of this material. Commercially available PET from chemical recycling is usually produced by cutting the polyester chains down to a molecule called BHET (Bis(hydroxyethyl)terephthalate). Such processes have the potential to lead to a polyester which is in general by far cleaner than PET from mechanical recycling, provided adequate, validated process controls to deal with the potential contaminants are employed.

Assessments if existing chemical recycled polyesters are clean enough to be usable in oven applications are currently underway and will also have an influence on an upcoming amendment of the regulation (EC) 282/2008. The amendment bringing chemical recycling in the scope of (EC) 282/2008 is expected for 2022- 2023. Assuming that the UK will not use lower safety standards than the EU, the outcome of that process should be awaited before using chemical recycled polyester in oven applications.

We watch this with interest as well as the importance of the work being undertaken by CEFLEX, a collaborative initiative of a European consortium of companies and associations representing the entire value chain of flexible packaging. The CEFLEX objective is to enhance the performance of flexible packaging within a circular economy. 

These initiatives will be welcome news to manufacturers who, from 2022, will face being taxed on plastic packaging which uses less than 30% recycled content.

The improvement in quality and other developments may also address the challenges we face around PCR in lidding film. Then there will be no splitting hairs over the choice to use virgin plastic or PCR.

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