Within our EU funded project CIRCULAR FoodPack (CFP), one part of our work is to investigate technologies to improve the sorting of flexible packaging waste. There are different aspects of sorting, like categorizing according to materials used, sorting for shape and colour, or separating the packages depending on their intended use in their first life: food or non-food applications. The latter sorting is an important step to ensure material safety in a second life cycle after recycling, because the substances allowed for being in food contact materials are strictly regulated by law.
One approach we are looking at in CFP is the Tracer-Based sorting. These tracers are developed and synthesised by Polysecure and can be integrated into film structures for food packaging during the material production. This allows for a differentiation between food and non-food packaging, which normally do not differ in their intrinsic material properties detectable by NIR sorting.
This summer, we were able to perform our first sorting trials in large scale, as our video shows.
The project partners produced 315kg of packages with tracers and this material was mixed with the same amount French household waste. At the Steinert Technical Center in Pulheim (Germany), the mix was run through the NIR sorting machines and sorted into a traced and a non-traced fraction at industrially relevant parameters: a belt speed of 4.5m/s, a belt coverage of 30% and a throughout of 1.0 tons/hour/m belt width. This way, a purity of 97.4% could be achieved at an efficiency of 90.2% in a two-step sorting process.
This performance shows that the Tracer-concept can work in state-of-the-art sorting machines with minor adjustments and at high speeds – a proof of concept. As a next step, tracer concentrations can be optimized to the necessary amount, which is still detectable reliably, and economically viable. Furthermore, the variety of tracers developed within this project provides the opportunity to tailor tracer combinations to different sorting criteria, food vs. non-food sorting being only one of them.