Solving the Polypropylene waste issue

16 January 2020

As policy makers, governments and organisations around the world continue to explore ways to reduce or eliminate the amount of plastic packaging sent to landfills, recyclers have been hampered by their limited capacity to sort plastic by polymer type. Professor Edward Kosior of Nextek discusses the latest developments that support Polypropylene waste sorting.

It is not widely known that despite Polypropylene (PP) being one of the main materials to be used in consumer goods packaging it is the least recycled material in the packaging recycling stream. In fact it is virtually non-existent as a food-grade recycled material. Yet it also happens to be one of the easiest polymers to recycle, if recyclers could only identify its past history during the sorting process. The reason PP is not available as a food grade recycled material is due to the inability to separate food grade from non-food grade PP.

As a consequence, whilst the more readily decontaminated PET bottles can be recycled back into PET bottles, PP is recycled into non packaging applications like crates and bins or still ends up in landfills or incinerators. To date identifying what the pack once contained has been a near impossible task. With no effective way to differentiate between a bleach bottle and a milk bottle of the same polymer type, the plastic waste sector has suffered from a severe lack of value creation and therefore investment.

Food grade plastic has been the most complex to obtain due to the risks of using second-hand plastics potentially containing toxic chemicals that could be dangerous to human health. Up until now recyclers have not been able to differentiate and capture specific materials and separate food from non food packaging, however, a new technology is poised to change this. An innovative identification technology, which can separate plastic to food grade quality in one single step, is set to radically transform the sorting process in recycling facilities.

A world class British consortium has developed a technology that can rapidly and efficiently distinguish between food-grade and non food-grade polymers, identify black plastics and tag full-length shrink-sleeves. Plastic Packaging Recycling using Intelligent Separation technologies for Materials (PRISM) applies high performing luminescent materials to labels on plastic packaging, creating what is best described as an invisible barcode for plastics recycling.

The process is simple. Fluorescent markers - produced from materials recovered from fluorescent lamp recycling and non-rare earth based compounds - are printed on labels or plastic packaging sleeves. As the mixed plastic waste runs along the conveyor belt the high speed sorting system is illuminated by an ultraviolet (UV) light source that identifies the coded PRISM label, reads its code and air-jets propel it into the appropriate recycling category.

Following extensive trials PRISM is now well proven in MRF (Materials Recovery Facility) setups and is plug & play ready. It is complementary to existing NIR (Near Infrared) technology and can easily be adapted to most sorting facilities around the world to target specific recycling streams such as food contact plastic packaging.

This innovative technology uses traditional labelling and branding methods that can be coded to specify the status of the pack. The PRISM labels can be flattened, crumpled and soiled and will still be easily detected and the markers can be removed during recycling leaving no traces for the next cycle of use.

Even the most challenging plastic waste can now be sorted in a single step at full speed of 3m/s and 2 tonnes per hour to over 96% purity with a yield in excess of 95%. This meets the EU’s stipulated 95% purity for PET food grade plastic in a single sorting step at full sorting speed.

This is a significant step forward in the categorisation of plastics which are sorted automatically at high speed, and it opens up a wealth of new opportunities for brand-owners wishing to recover their packaging as part of the circular economy.

PRISM’s unique ‘marker’ technology is set to finally launch the recycling of food grade PP packaging (as well as all other plastics), allowing recyclers to effectively sort and recycle used plastics such as PP into both food and non food applications.

This technology promises to harness the untapped potential of post-consumer PP, revitalise the recycling sector and reduce our current dependence on virgin plastics in food packaging.

The first commercial trials have been completed and included beverage bottles for a large international drinks company and a European recycling company that aims to utilise PRISM’s unique sorting capacity to select specific products in the waste stream that require special treatment.

The technology offers a reliable refined sorting solution which will be of benefit across the whole plastics packaging supply chain and Nextek welcomes all packaging companies and retailers to test the sorting system for themselves.

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