Good potential for PTT sorting breakthrough

An innovation that could create good demand for recycled food-grade plastic pots, tubs and trays will be available within years, resource recovery specialist Axion Consulting has claimed.

Currently, it is thought no technology exists which is able to automatically sort polypropylene packaging which has been in contact with food from that which has contained cleaning products or cosmetics. Now, Axion claims to have identified a technology that can do so.

Under European food packaging regulations only PP that has been in prior contact with food can be recycled into new food grade PP. As a result, demand for the material is low with some industry experts arguing that a lack of end markets means it is not economically viable to collect it in large quantities.

However, according to Axion, which has carried out work on behalf of the Waste & Resources Action Programme (WRAP) into the recycling of the material, using a technique known as diffraction grating could make sorting it more commercially viable.

The technique involves marking food contact PP packaging at the production stage with a pattern either stamped on a mould or directly onto the item -that would be detectable by laser. Once this packaging enters the waste stream the detectors would be programmed to recognise which PP packaging has directly been into contact with food.

Innovation

Axion chemical engineer Richard McKinlay, said: This represents an innovative application of existing technology that could revolutionise any food contact plastic recycling in offering a commercially-viable automated solution. Manual sorting is simply too expensive. Diffraction is when one beam of light is split into several, so we are utilising this phenomena to detect a particular type of plastic packaging.

Axion estimates the total capital cost for a single diffraction grating sorting unit, including conveyors and ancillary equipment, at 500,000 with a potential payback within four years. Its report states that this payback period should represent a good investment opportunity for a Plastics Recovery Facility (PRF) operator or a potential food grade reprocessor processing bales of sorted PP packaging.

‘Challenges remain’

But Liz Morrish, Axion senior consultant, acknowledged that there would be challenges in encouraging the use of the technology across the industry, including convincing food packaging producers to adopt diffraction gratings in their products.
She said: Challenges remain, including the need to widen application and markets for this technology. It is also crucial for retailers, manufacturers and machinery suppliers to adopt agreed industry-wide methods that would optimise the identification and subsequent recycling of these waste streams.

Although we focussed heavily on PP for this project, using this technology initially to sort HDPE milk bottles could be advantageous. Once it has been shown to work on this material it may give the industry more confidence to invest further to allow the technology to be used on PP.

Overall it appears that diffraction gratings can potentially be used to identify food contact packaging effectively and economically; however, they are not yet ready for use commercially until a full industry-wide solution has been developed and commercialised.