A New Testing Blueprint to Unlock Food-Grade Polyolefin Recycling

By Prof. Edward Kosior and Paul Marshall, Nextek & NEXTLOOPP

Polyolefins (HDPE and PP) make up the majority of the world’s household plastic packaging. Yet, unlike PET, these materials have been largely absent from food-contact recycling streams –– not because they are inherently unsuitable, but because regulators have lacked solid, contemporary evidence that mechanical and advanced recycling processes can reliably remove contamination to meet toxicological thresholds.

For a circular packaging economy to function, that gap must close. Both the UK Plastics Pact and the EU’s Packaging and Packaging Waste Regulation (PPWR) require average recycled content of 30% across all plastic packaging –– targets impossible to reach without food-grade recycled polyolefins.

This work paves the way for true closed-loop recycling.

To solve this, a three-year collaborative programme led by WRAP and Innovate UK has delivered something the sector has long needed: a practical, science-driven, and reproducible challenge test protocol for HDPE and PP recycling systems. Developed by Nextek’s Food Contact Plastics Specialist, Paul Marshall, the work establishes a new testing paradigm capable of supporting future regulatory submissions for closed-loop applications.

Why Polyolefin recycling has lagged behind

Challenge testing –– deliberately contaminating plastics with specific chemicals and then measuring how well a recycling process removes them –– is not new. But until now, the available guidance mostly described principles rather than actionable methods. At the same time, regulators have been short on data.

The regulatory picture has been fragmented:

• EU Regulation 2022/1616 governs recycled plastics for food contact but contains no validated opinions for HDPE or PP systems.
• EFSA assessments for HDPE have been inconclusive due to inconsistent feedstocks, limited contamination data, and unpredictable migration behaviour.
• FDA guidance, largely unchanged since 2006, is built around PET and does not address the distinct behaviour of polyolefins.

As a result, the industry has been operating without a clear, shared direction for generating reliable evidence. To advance circularity, regulators need robust, process-specific proof that polyolefin recycling systems can achieve adequate decontamination.

Building a modern testing framework

The project began with a deep review of global challenge testing approaches—from Europe, the UK, and US FDA guidance. The goal: determine what worked, what didn’t, and what was missing for polyolefin-specific evaluation.

A central requirement was to design a test that reflected real-world contamination, including:

• Everyday household products such as detergents, bleaches, and personal-care contents.
• Residues from inks, coatings, and labels.
• Additives present in non-food applications (e.g., electrical and automotive plastics).
• Cross-contamination from co-mingled recyclates.
• Higher-risk contamination from residual waste streams.

Understanding these pathways made it possible to develop a structured protocol built around seven defined phases, making it reproducible in both laboratory and commercial settings.

Choosing surrogates that reflect reality

Selecting the right surrogate chemicals –– the stand-ins for actual contaminants –– is fundamental. The team chose a set representing a spectrum of molecular weights, polarities, and volatilities, ensuring that the test captures the actual behaviour of common contaminants without using hazardous or impractically expensive substances.

Two contamination methods were compared:

• Fraunhofer IVV-style conditioning: a heated, concentrated surrogate mixture that reliably absorbs into polymers, especially higher molecular weight compounds.
• FDA-style conditioning: lower absorption, useful for simulating extreme misuse scenarios but costly to prepare large batches for validation of commercial-size processes

The comparative trials confirmed that the Fraunhofer-style method delivers the most consistent, explanatory data for HDPE and PP.

Scaling up: from laboratory to real-world plants

Once validated in the lab, challenge tests were performed at commercial scale across multiple recycling technologies—both mechanical and advanced.

Key outcomes:

• The newly selected surrogate set behaved comparably to the traditional one, confirming its suitability for broad industry adoption.
• Analytical methods and sampling protocols were refined to ensure easy implementation and reliable interpretation.
• Plants processing HDPE, PP, and emerging technologies demonstrated that robust decontamination can be achieved within a controlled recycling workflow.

This alignment between lab and industrial performance was essential to transforming the protocol from a scientific concept into a usable industry tool.

What the final protocol delivers

The completed guidance now provides:

• A unified, validated standard for assessing food-grade recycled polyolefins.
• A solid evidential base for future regulatory approvals in the UK and EU.
• A transparent, non-proprietary testing system, accessible to recyclers of all sizes.
• A framework that supports investment in higher-grade recycling technologies and infrastructure.

Ultimately, this work paves the way for true closed-loop recycling of polyolefins –– turning used milk bottles into new milk bottles, and contact-sensitive shampoo bottles into new packaging, rather than cascading them into lower-value products.

Why this matters for innovation

This project replaces assumption with evidence. It signals that the era of downcycling polyolefins can end.

By providing a rigorous, accessible testing method, it gives:

• Recyclers proof of performance
• Regulators confidence
• Brands a pathway to circular packaging without compromising product safety

The result is a future in which polyolefins –– one of the world’s most used packaging plastics –– can finally participate in high-value circular flows.

Innovation in this context is not theoretical, it is measurable, practical, and now ready to scale.