A high-level consortium has received funding from government innovations agency, Innovate UK, for its project to identify new luminescent materials which can be applied, invisibly, to labels on plastic packaging, offering a low-cost sorting technology for the performance-boosting sub-categorisation and purity of recyclables.
The project, Plastic Packaging Recycling using Intelligent Separation technologies for Materials (PRISM), has secured £772,000 of funding over two years.
As well as Innovate UK, part of the funding is contributed by the Engineering and Physical Sciences Research Council (EPSRC) and by matching funding from the commercial partners.
The PRISM project will develop new fluorescent materials from novel metal oxides as well as converting reprocessed powders from recycled fluorescent lamps into suitable fluorescent materials.
Fluorescent Marking Technology
The fluorescent marking technology is one of the most important developments in sorting in decades, according to recycling consultancy and lead partner in the project, Nextek.
“This could be the equivalent of an invisible barcode for plastics recycling,” said Prof Edward Kosior, MD of Nextek. “It is a significant step forward in the sub-categorisation of plastics which are sorted automatically at high speed. It enables new initiatives from brand-owners eager to recover their packaging as part of the circular economy. Of course, it also provides a massive impetus for new businesses in the recycling sector.”
The technology has already shown excellent initial results thanks to research projects led by waste and resources charity, WRAP.
“It is a significant step forward in the sub-categorisation of plastics which are sorted automatically at high speed. It enables new initiatives from brand-owners eager to recover their packaging as part of the circular economy”
WRAP worked with Nextek to carry out the first phase that focused on the identification and separation trials, achieving 98% yield and 95% purity. The second phase is on-going and is looking at further optimisation of the system, including new fluorescent compounds, how they react through the supply chain and if the markers get completely destroyed after reprocessing.
The fluorescent label sorting system is designed to be integrated with the current near infra-red (NIR)-based sorting systems used in materials recovery facilities (MRFs). While NIR retains its important role in identifying the different polymers, this system would be triggered by an ultraviolet (UV) light source that is detected in the visible spectrum. This is within the capacity of many modern automatic sorting units.
The UV light adds an additional, high-value layer of sorting. PRISM technology captures the unique code created by the normally invisible application-specific luminescent compounds in the label.
This will allow, for instance, food-grade polymers to be distinguished from non-food-grade, black plastics to be identified and full-length shrink-sleeves to be tagged according to the underlying plastic. Brand-owners could even establish closed-loop collection of specific packaging formats.
At Brunel University London, Prof Jack Silver, Dr George Fern and Prof Karnik Tarverdi are working on the PRISM project. Prof Silver said: “We have been working with phosphorescence since the 1990s. More recently, it became clear to me that fluorescence could really make a difference in waste reclamation. Using fluorescent materials allows you to sort recyclables at a much higher level than has been done up to now.”
WRAP Packaging Programme Area Manager Claire Shrewsbury said: “The new technology could help boost recycling plant yields, and UK plastics recycling as a whole, with more efficient ways of sorting materials such as polypropylene (PP) packaging, high density polyethylene (HDPE) milk bottles and sleeved polyethylene terephthalate (PET).”
Because the luminescent pigments are applied to a range of labels and sleeves, they are removed before the downstream recycling process, avoiding any risk of contamination in the next cycle of application. Among the PRISM project partners are label and sleeve converter CCL and inks specialist Mirage Inks.
“Our project will help drive the collection of these tubes, some of which are still currently going to landfill, complete with the mercury content”
Johnson Matthey, with its focus on sustainable technologies, is investigating benign, non-rare-earth metal oxides that are safe, plentiful and provide distinctive UV signatures.
ELR’s niche is the collection and recycling of fluorescent lights and tubes and the treatment of industrial, clinical and electrical mercury wastes and they have begun co-operation with the participants of PRISM in the development of new marker materials.
“Our project will help drive the collection of these tubes, some of which are still currently going to landfill, complete with the mercury content,” said Prof Kosior at Nextek.
The automated separation systems can be retrofitted to existing MRF layouts and will run at the same high speeds already achieved by modern plants. In future, NIR and UV-based segregation would be integrated into a single sorting station.
PRISM partners estimate that fluorescent inks would only add a minimal cost to the labels.
The concept of fluorescent markers could also be applied to the different plastics in the Waste Electrical and Electronic Equipment (WEEE) and automotive recycling streams, it says, and that plastics might not be the only recyclable materials to benefit from the technology.
The full list of partners is: Nextek (Project Lead), Brunel University London, Tomra Sorting, CCL Label, Mirage Inks, WRAP, Evolve Polymers, Johnson Matthey and Enlightened Lamp Recycling (ELR).