Fluorescent markers printed on labels permit high-value food packaging made of polypropylene to be sorted and recycled.

PET bottles have hogged the recycling limelight and for good reason: They are available and can be collected then decontaminated and recycled back into food-grade PET bottles.

What is less known, however, is that an additional 77,000 tonnes/84,878 tons of food-grade plastic could be reused if it were properly sorted. Alas, most of it still goes to down-cycling applications, ending up in energy recovery or landfill.

The biggest missing-in-action plastic is polypropylene (PP). It is not only one of the most popular plastic packaging materials in the world due to its versatile nature, it is also the least recycled [of the recyclable rigid packaging polymers?  What about PVC?] rigid packaging polymer. Because PP is heat- and chemical-resistant as well as flexible and tough, it is widely used in a range of packaging applications. In fact, the PP market is projected to reach $133 billion by 2023.

Currently, PP is recycled into nonfood-grade applications such as crates and bins, automotive components and industrial storage products. One of the key reasons PP is virtually non-existent as a food-grade recycled material is due to the inability to separate food grade from non-food grade PP.

Being able to identify what a recycle-ready PP container had previously contained led a British consortium to combine their expertise and resources to find a solution.

Up until recently there has been no effective way to differentiate between a food tray, soup pot or a fertilizer tub of the same polymer type, but after six years of research and trials, the consortium’s innovative tech is about to change all that.

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

The process is simple. Fluorescent markers are printed on conventional labels or shrink-sleeve sleeves. As the mixed plastic waste runs along the conveyor belt of a recycling facility, a high-speed sorting system is illuminated by an ultraviolet (UV) light source paired with a reader. It identifies the PRISM label, reads the UV-printed code and air-jet propels it into the appropriate recycling category.

Until now, the commonly used Near Infrared Radiation (NIR) techniques used to identify different polymers were unable to detect dark-colored plastics as they absorb the radiation. PRISM allows recyclers to efficiently distinguish between food-grade and nonfood-grade polymers including black plastics and full-length shrink-sleeves.

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

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

 

What it means and what’s next

Even the most challenging plastic waste can now be sorted in a single step at full speed of 3 meters per second and 2 tonnes/4,409 pounds per hour to more than 96% purity with a yield in excess of 95%. This meets the EU’s stipulated 95% food-grade packaging for PET grade plastic in a single sorting step at full sorting speed and can achieve greater than 99.5% purity in two passes as required for PP and high-density PP.

This is a significant step forward in the categorization of plastics that 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 nonfood applications.

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

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

 

British Consortium of PRISM Partners

Nextek (London), PRISM project manager and recycling R&D consultancy;

Brunel University London-Wolfson, material Processing Luminicescent expertise;

CCL Labels (Castleford, UK), multinational label maker;

Enlightened Lamp Recycling (Redhill, UK), fluorescent lamp recyclers;

Johnson Matthey (London), specialty chemicals, catalysis and process technology;

Mirage Inks (Frome, UK), manufacturer of printing inks for packaging applications;

Tomra R&D (Karlich, Germany), provider of automatic detection systems;

WRAP UK (Banbury, UK), leading waste and resources charity.

 

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