DOI : https://doi.org/10.47485/2832-9384.1078
Closing the Loop on Food-Contact Polypropylene Design, Decontamination, and the Path to Circularity

Article / Case Study

Edward Kosior1*, Paul Marshall2

1Professor Edward Kosior, Founder and CEO of Nextek Limited.
2Paul Marshall, Food-grade Regulations Manager at NEXTLOOPP.

*Corresponding author :

Professor Edward Kosior,
Founder and CEO of Nextek Limited.
Submitted : 25 August 2025 ; Published : 11 September 2025

Abstract

Polypropylene (PP) constitutes a major fraction of global polymer production and dominates in food-contact applications, where safety and performance requirements are particularly stringent. However, the transition towards circular economy models presents significant challenges for PP packaging due to contamination, design incompatibilities, and inadequate decontamination strategies. This paper critically examines the technical and regulatory barriers to achieving closed-loop recycling of food-contact PP. It appraises recent advances in mutagenicity testing, identifies critical contaminants arising from inks, adhesives, and pigments, and reviews emerging decontamination technologies. We argue that current “design-for-primary-use” paradigms are incompatible with high-purity recycling requirements. A systems-level approach – integrating design for recycling, advanced decontamination and rigorous validation protocols – is required to establish a viable and safe circular pathway for food-contact PP.

Introduction

Polypropylene (PP) is the second most widely produced polymer worldwide, with annual production exceeding 74 million metric tonnes (Plastics Europe, 2023). Its chemical resistance, process ability, and cost-effectiveness have entrenched PP as a dominant material for rigid and flexible food-contact packaging. Regulatory authorities, particularly in the European Union (EU), have introduced ambitious targets for recycled content in packaging, coupled with stringent food safety requirements – Packaging and Packaging Waste Regulation, (PPWR) and (Regulation (EU) 2022/1616) (European Union. Commission Regulation (EU) 2022/1616 of 15 September 2022 on recycled plastic materials and articles intended to come into contact with foods, and repealing Regulation (EC) No 282/2008 (Text with EEA relevance), 2022).

Despite extensive mechanical recycling infrastructure, current recovery yields for PP remain sub-optimal. In the best-case scenario of 75% collection, 95% sorting, and 85% recycling efficiency, material recovery plateaus at approximately 60% (Lange, 2021). Achieving a circular economy for PP therefore requires a paradigm shift in material and product design, decontamination technologies, and safety validation methodologies.

Sources of Contamination in Recycled PP

A principal obstacle to high-purity PP recycling is the migration of contaminants from auxiliary packaging components, such as inks, binders, adhesives, labels, and pigments as well as the formulations held within packaging. While these additives are typically deemed safe under their intended use conditions, thermal and mechanical stress during recycling may trigger degradation pathways that generate by-products that need to be evaluated for their potential to form hazardous materials.

Extrusion of recycled plastics, for instance, may transform nitrocellulose-based binders and organic yellow pigments into mutagenic compounds at typical processing temperatures that are over 200°C. Such transformations require chemical risk assessment and the very low levels of incidence make this challenging, as conventional targeted analyses may overlook ultra-trace contaminants or unidentified degradation products.

Emerging Paradigms in Toxicological Testing

Conventional chemical analyses often fail to detect the presence of low levels of contaminants and may not capture the toxicological relevance of complex mixtures in recycled polymers. The Safe Cycle project (Fraunhofer IVV, OFI, FH Campus Wien) has introduced a complementary bioanalytical framework, utilising modified Ames assays to detect mutagenicity in recycled plastics (Mayrhofer et al., 2023).

This approach has revealed that printed and labelled feed stocks are disproportionately associated with mutagenic responses post-extrusion. Advanced analytical techniques, including high-resolution mass spectrometry and liquid chromatography, were employed to characterise the molecular entities responsible, with nitrocellulose binders and pigment degradation products emerging as critical contributors.
Such bioassay-guided analytical workflows represent a new paradigm for validating food-contact recycled plastics, providing both hazard detection and mechanistic insight.

Advances in Decontamination Technologies

Several novel technologies demonstrate potential for achieving food-grade recycled PP:

  • NEXTLOOPP PPristineTM Process: A two stage, melt- and solid-state decontamination protocol capable of removing volatile and semi-volatile impurities. PPristine resins have repeatedly passed mutagenicity assays, suggesting the feasibility of safe post-consumer PP recycling.
  • COtooCLEAN Technology: Employing supercritical CO₂ (scCO₂) extraction, this process efficiently removes embedded contaminants from polyolefin matrices. The scalability of scCO₂ systems positions them as promising candidates for industrial deployment.
  • HydroDyn HydroCleaner/Separator: A hydrodynamic cleaning system capable of eliminating up to 99.9% of inks, adhesives, and labels from PP feedstocks (HydroDyn GmbH, 2022)
  • Sorema and Siegwerk De-inking Systems: Demonstrated efficacy in caustic wash conditions, achieving ΔE colour differences within 0.5–1.5 units, indicating effective removal of direct-printed inks.

Together, these developments illustrate a multi-pronged technological response to contamination, yet their integration with upstream design practices remains limited.

Redefining Design-for-Recycling (DfR) Principles

Traditional Design-for-Recycling (DfR) guidelines have emphasised material compatibility and mechanical recoverability. However, recent evidence underscores the necessity of expanding DfR to encompass chemical stability and decontamination compatibility.

Essential design principles include:

  • Labels that detach fully in conventional recycling processes.
  • Adhesives that remain with the label and do not migrate to the substrate.
  • Inks and binders engineered to resist leaching and degradation during wash and extrusion.
  • Pigments designed to maintain thermal stability and avoid hazardous degradation pathways.

Industry participants are actively addressing these needs. For example, Bostik has developed next-generation wash-off adhesives for PP, HDPE, and PET, while MCC Verstraete’s NextCycle IML™ technology facilitates label detachment via air classification (Bostik next-generation wash-off adhesives; MCC Verstraete NextCycle IML™ White Paper, 2022).

Regulatory Landscape and Stakeholder Obligations

The EU regulatory framework has intensified requirements for recycled content in food-contact applications. Regulation (EU) 2022/1616 mandates strict decontamination validation, while the PPWR emphasises closed-loop recycling targets (GOV.UK, 2022; TUV Rheinland, 2022; European Environment Agency, 2024). These developments necessitate harmonisation across the packaging supply chain, including resin producers, converters, label manufacturers, and fast-moving consumer goods (FMCG) brand owners.

The regulatory trajectory suggests that compliance with voluntary industry guidelines is no longer sufficient; alignment with bioassay-validated safety standards is emerging as a prerequisite for market access.

The Need for Transparency and Standardisation

A recurring challenge in scaling food-grade recycled PP is the opacity surrounding toxicological testing data. Widespread adoption of recycled PP centres on publicly available datasets demonstrating the absence of mutagenic responses under realistic recycling scenarios. Establishing harmonised testing protocols and open data-sharing frameworks will be essential for building confidence across the value chain.

Conclusion

The transition to a circular economy for food-contact PP requires an integrated approach combining upstream material design, advanced decontamination technologies, and rigorous toxicological validation. Emerging processes such as PPristine and COtooCLEAN demonstrate that technical barriers can be overcome, but their impact will remain limited without parallel innovation in packaging design and transparent industry-wide data practices.

Ultimately, circularity in food-contact PP, and other plastics for that matter, is not merely a technical challenge but a systemic one, requiring co-design between material scientists, toxicologists, regulatory agencies, and brand owners. Only through such collaborative frameworks can PP recycling achieve both sustainability and uncompromised safety as well as high volumes and lower cost economics.

References
  1. Plastics Europe. Plastics – the Fast Facts 2023. https://plasticseurope.org/wp-content/uploads/2023/10/Plasticsthefastfacts2023-1.pdf
  2. European Union. Commission Regulation (EU) 2022/1616 of 15 September 2022 on recycled plastic materials and articles intended to come into contact with foods, and repealing Regulation (EC) No 282/2008 (Text with EEA relevance). http:/data.europa.eu/eli/reg/2022/1616/oj
  3. Lange, J-P. (2021). Managing Plastic Waste─Sorting, Recycling, Disposal, and Product Redesign. ACS Sustainable Chemistry & Engineering, 9(47), 15722–15738. DOI: https://doi.org/10.1021/acssuschemeng.1c05013
  4. Mayrhofer, E., Prielinger, L., Sharp, V., Rainer, B., Kirchnawy, C., Rung, C., Gruner, A., Juric, M., & Springer, A. (2023). Safety Assessment of Recycled Plastics from Post-Consumer Waste with a Combination of a Miniaturized Ames Test and Chromatographic Analysis. Recycling, 8(6), 87.
    DOI: https://doi.org/10.3390/recycling8060087
  5. HydroDyn GmbH. (2022). Hydro Cleaner validation trials. https://www.hydrodyn.de/en/
  6. Bostik next-generation wash-off adhesives; MCC Verstraete NextCycle IML™ White Paper. (2022). https://www.bostik.com/us/en_US/blog/post/durable-goods/construction-materials/bostik-us-post-end-of-life-impact/? And https://www.mcclabel.com/en/news/mcc-verstraete-sets-a-new-standard-for-future-sustainable-iml-packaging-nextcycle-imltm?
  7. Contextual & regulatory sources for broader context: