Quality Leap in Plastic Waste Management by Tracer Based Sorting

Abstract

The research question to be answered in a multi-year R&D project funded by the German Federal Ministry for Education and Research is how tracer based sorting can be applied for plastic packaging waste management in developed countries. Development of enhanced packaging sorting approaches is motivated by a sharp increase of the primary recycling quota for plastic packaging material: Starting at 32% primary recycling required for all plastic packaging used in Germany 2018, a recycling rate of 63% has to be met in 2023. Moreover, the European Union is targeting at higher recycling rates for plastics (50% in 2025, 55% in 2030) with its 2018 European Strategy for Plastics in a Circular Economy, including a more elaborate plastic waste management and a ban of specific plastic products such as EPS containers, or plastic stirrers. With recyclate production expected to double within three years, current recyclate qualities cannot be fully absorbed by the markets. Thus both the recycling rates and the recyclate quality (sorting quality) have to be increased.

State of technology sorting facilities for post consumer lightweight packaging (plastics, metals, paper, composite packaging) in Europe are operating a cascade of more than twenty near infrared (NIR) identification steps, sieves, density separation, magnetic and eddy current separators. Nonetheless a maximum primary (plastic materials) recycling rate of merely 50% is achieved e. g. in Germany. Currently sorting plants are not capable of sorting black plastics or of packages with full-sleeve labels covering the packaging material. Neither identification of food and non-food packaging nor separation of specific polymer types such as thermoforming or injection moulding resin qualities are possible.

Tracer based sorting may overcome these limitations by adding permanent information to the product independently from the packaging materials properties, and thus contribute to high quality identification and sorting. Moreover, complex sorting sequences may be replaced to a large extent by a single, tracer based core separation process step direcly assigning products to the most appropriate recycling route. To this end, the entire plastic packaging value chain has been considered for improved recycling operations, covering technical and economical questions along with innovation diffusion aspects. Research covers packaging design improvement and adaptation to tracer use, tracer material development to provide miscellaneous fluorescence colours, design and operation of a sorting device for bottle sorting, and materials research on plastics recyclate quality and tracer interaction.

The main findings to be presented are covering an optimized tracer material application design on plastic packaging, in order to use minimal marker masses per packaging application. It is proposed to use tracer material on the labels, as this requires minimal tracer use, and tracer separation including tracer substance recycling becomes possible. PET and PE specimen with marker concentrations between 10 and 1000 ppm have been produced. Marker performance in coloured HDPE samples using industrial colour masterbatches was measured. Results show a positive correlation of the marker signal intensity both with wall thickness and the marker concentration. Best marker response was observed with yellow pigments, least signal intensity was found with black pigments.

Waste management research showed that 95 % of all bottles sent to sorting still carry their labels. Moreover, the colours of about 80% of these bottles allow tracer use. If these results are applied to other plastic packaging products, future recycling rates can be met by tracer based sorting. Sorting costs using this tracer approach are estimated at about 200 Euro/ton material sorted. For implementation, multi-stakeholder involvement along the entire value chain is required. A new business model creating appropriate benefits for each stakeholder becomes necessary here, because the maximum value added will be found with the recycler.

Keywords: plastic waste, sorting, recycling, tracer, fluorescence

JEL Classification: Q53, Q5