Food grade recycled polypropylene (rPP) in packaging

Phase 6 - Recycling of food grade packaging using fluorescent markers

The latest phase of the project looked at system optimisation, exploring the use of the technology in PET, HDPE and PP packaging. It also proposed a scope protocol for the use of the markers to be used in combination, to provide different levels of information. For further information please read the project report. Additional information can be found in the appendix report.

Phase 5 - Optimising the use of machine readable inks for food packaging sorting

Since the work with diffraction grating was considered too expensive to be invested at this stage by the technology providers, further work looking at an alternative and economically viable solution was required.

The objectives of this work were to investigate and develop the use of machine readable inks that could be applied to the broadest range of materials and packaging types. This would assist identification of different types of polymers during sorting and recovery for recycling.

Fluorescent ink was identified as a suitable solution as it can be added and applied to existing products by conventional means. The material cost for the additional labelling was estimated as a fraction of a penny (0.003 to 0.108p per label). Required modifications on existing sorting equipment was also considered minimal. The sorted material achieved over 99% purity. Further tests will be required to identify what happens with the ink after reprocessing (e.g. if remains visible or is removed). For further information please read the project report.

Phase 4 – further analysis of decontaminated rPP, and diffraction gratings

WRAP carried out further research and development work, which involved carrying out additional testing of decontaminated rPP to further assess its suitability to produce a food grade material, and researching sorting techniques identified in Phase 3.

Key findings

Further analysis of the decontaminated rPP was undertaken to establish whether there were any substances of concern remaining in the material produced in Phase 3. This has answered remaining questions around its suitability for use in food contact applications. The research found that the two resins analysed (clear and white) are compliant for food use according to regulations used in the EU and USA.

It is hoped that these results will provide confidence to the packaging and recycling industry to continue to develop and commercialise a food grade recycling process for post-consumer PP packaging, using the testing methodology presented in the report.

Research has also shown that diffraction gratings could be an effective and economical way to identify food contact packaging. Recommendations for further work are provided in the report. WRAP will continue to work with the sector on identifying packaging that has been in contact with food as the technology investigated needs further research and development, and it has wider application to food grade plastics recycling in general (i.e. could also apply to PET and HDPE as well as PP). This therefore has the potential to be used by a range of food grade plastics reprocessors.

Phase 3 – further development and testing of the recycling process

The work we carried out in this phase had three strands.

A) Polypropylene packaging market data

WRAP carried out an assessment of the UK market for PP packaging and estimated the amount of PP packaging waste that could be available for a food grade PP recycling process in the UK. The report provides a breakdown of the PP packaging market by type and discusses key aspects of PP packaging and their impact on food grade recyclability.

B) Decontamination of UK PP packaging waste

WRAP carried out decontamination trials on the process identified in Phase 2, using real PP packaging waste from UK households. Sample packaging was manufactured using rPP from this process and food grade testing was carried out. This work indicated that rPP could be used in a range of food packaging.

C) Sorting plastic that has previously been used with food

In order for food grade rPP to be produced in the UK, a technically and commercially viable automated solution is required to sort packaging that has been used with food from that which has not, because food grade recycled plastics must be made from >99% food contact raw material. This project determined that a marking and detection technique could be developed to identify food contact plastic packaging in recycling plants. This work included an investigation into whether the use of lasers to identify diffraction gratings in packaging could potentially be used to sort packaging that has been used for food. This technique is also discussed in a 'diffraction grating – proof of concept’ report.

Phase 2 – development of a food grade recycling process for post-consumer PP

The aim of this phase of work was to develop a food grade recycling process that could decontaminate post-consumer PP packaging waste to the standards required by EU regulations for food contact and cope with the wider range of materials encountered in the post-consumer PP packaging stream.

A range of high performance processing and decontamination techniques were evaluated and a process consisting of two technologies combined was found to produce material that could be suitable for use in a wide range of food packaging applications.

Phase 1 – scoping study

WRAP tested whether a recycling process already used to produce food grade rHDPE in the UK could be adapted to recycle PP to meet food grade approval. The key findings were:

• an automated process needs to be developed to sort food contact from non-food contact as hand sorting of food contact is not cost effective; 
• the food grade recycled PP can be both thermoformed and injection moulded and therefore is suitable for use in the common PP conversion processes; and 
• it has been possible to clean the PP in certain applications but an improved cleaning of heavier contaminants is required.

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