Invisible marker ‘barcode’ project gets funding boost
The ‘Plastic Packaging Recycling using Intelligent Separation technologies for Materials’ (PRISM) project aims to use invisible inks to develop a more efficient, low cost sorting technology that will increase sorting efficiency and therefore the purity and quality of recycled material.
The project is being funded over the next two years by money from the government innovations agency, Innovate UK, and the Engineering and Physical Sciences Research Council (EPSRC), with funding being matched by commercial partners.
Project partners involved will develop new fluorescent materials from two sources, novel metal oxides and reprocessed powders from recycled fluorescent lamps in order to develop a new fluorescent marking technology.
The full list of partners is: Nextek, Brunel University London, Tomra Sorting, CCL Label, Mirage Inks, the Waste & Resources Action Programme (WRAP), Evolve Polymers, Johnson Matthey and Enlightened Lamp Recycling (ELR).
One of most important developments in sorting
Recycling consultancy and lead partner in the project Nextek says that fluorescent marking technology is ‘one of the most important developments in sorting in decades’. A 2014 WRAP report on ‘Optimising the use of machine readable inks for food packaging sorting’ states that one of the main challenges in plastics recycling is the separation of plastics into single-material streams. The inclusion of as little as 0.1 per cent of ‘non-compatible plastic’ in a particular stream, it says, can reduce the quality of the final recycled product significantly.
Near-Infra Red (NIR) sorting technology is commonly used in many material recovery facilities (MRF) as it can differentiate between different polymers allowing high volumes of plastics to be sorted at low cost.
The new method involving the use of labelling packaging with fluorescent inks would involve the use of ultraviolet (UV) light and when integrated with the current NIR-based method, would add an additional level of sorting.
Nextek says that the PRISM technology, allowing identification of plastics via unique codes printed in fluorescent ink on plastic labelling, has already shown good initial results in research projects.
A first phase of trials, led by WRAP, has already been carried out and focused on identification of individual plastics and trialling separation efficiency. It reported a 98 per cent yield and 95 per cent purity.
The second phase, aimed at further optimisation of the system, is currently in progress. This will test how the fluorescent compounds react throughout the supply chain and investigate the survival of the dyes after reprocessing.
The fluorescent label sorting system is designed to be integrated with the current NIR-based sorting systems used in material recycling facilities (MRFs), meaning there would be no adverse effect on sorting speed. It is thought that in future applications NIR and UV-based methods would be integrated into a single facility.
The project team also asserts that the fluorescent inks, which would be applied to labels removed before the recycling process, would add only minimal costs to the labelling procedure. In addition, removal of tagged labels would ensure the next cycle of application wouldn’t be contaminated with fluorescent inks.
The higher level of sorting made possible by the inks would allow the differentiation between food-grade and non-food-grade polymers, the identification and separation of black plastics and identification of plastics used to make shrink sleeves, commonly used on drinks bottles.
The markers could also be used to identify different plastics utilised in waste electrical and electronic equipment (WEEE) and automotive recycling streams and may at some point be developed to identify and separate non-plastic materials.
When using recycled plastic for food-grade products, it must be ensured that the input plastic has been approved for food applications, and also that the last use of the plastic involved contact with food, order to avoid contamination. PRISM technology is designed to be capable of identifying plastic as ‘prior food use’ and could therefore significantly increase the purity of input materials, the quality of finished products and the degree to which they meet regulations for food contact.
PRISM technology opens up “cost-effective routes to high-grade sorting”
Commenting on the project, Prof Edward Kosior, Managing Director of Nextek, said : “This could be the equivalent of an invisible barcode for plastics recycling.
“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.
“Our project will help drive the collection of these [fluorescent] tubes, some of which are still currently going to landfill, complete with the mercury content”
Professor Jack Silver of Brunel University London, who is working on the project, added: “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).”