Recycling Potential of Multilayer Films

Bettina Rutrecht

Research output: ThesisMaster's Thesis

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Abstract

This master thesis is part of the project Multilayer Detection and consists of three parts. Firstly, a material flow analysis (MFA) of a flexible plastic packaging recycling plant was conducted. The findings of the MFA are complemented by expert invterviews of the on-site personnel to display the current challenges, which operators of a plastic recycling plant for flexible waste plastic packaging have to face at present. Secondly, the input material of such kind of plants, the 2D fraction from a lightweight packaging sorting plant, was manually sorted with a special focus on multilayer films. Finally, considerations on a design concept for a sensor-based sorting unit was developed to allow future adjustment of recyclate quality, especially targeting at the detectability of multilayer films. The result of the MFA and the expert interview identified the following areas as the main technical and waste management challenges posed to a flexible plastic packaging waste recycling company: (1) feedstock, (2) plant set-up and process technology, (3) personnel, (4) quality assessment, (5) by-products of the recycling process and the (6) secondary raw material market. Multilayer films pose a particular challenge. Due to their structure, the means to recycle them are very limited. Without technology to detect them, they can have a negative influence on the recycling of the valuable polyethylene monofilm fraction. The hand sorting analysis of a non-representative 39.3~kg random sample of the Austrian yellow bag collection resulted in a sample of 10.4~kg, or n=842 objects, of two-dimensional flexible waste plastic packaging which have been assessed regarding packaging category and product category. Another subtotal of n=143 objects is examined by the means of FTIR-ATR to investigate whether or not multilayer films are present. It turned out that n=45 specimen are identified as multilayer films, which accounts for a share of 24~w-\% in the flexible waste plastic packaging fraction and 6~w-\% in the yellow bag collection. The packaging group in which multilayer films are most frequently found with share of 49~w-\% is food packaging, of which they are most likely present in packaging of bakery products (16~\%), meat (13~\%) and dairy (9~\%) followed by frozen food and convenience products (9~\%). Assuming the ideal recycling potential is equal to the content of multilayer films in the Austrian yellow bag collection, the total ideal recycling potential of multilayer films in the separately collected plastic packaging waste is estimated to be 10,260 tons per year. Recycling these laminated films can ideally increase the Austrian recycling rate of plastic packaging waste by 3~w-\% from 25.7~w-\% to 28.7~w-\% under the premise that specific recycling technologies for multilayer films are available. The use of new advanced NIR sorting technology beyond the detection of multilayer films can additionally uncover previously untapped resource potential of the two dimensional plastic packaging fraction by further separating it into recyclable clean monolayer streams. Therefore, assuming a recycling efficiency of 100~\% and that no more plastic films have to be incinerated, the theoretical recycling rate raises by 14~w-\% from 25.7~w-\% to a hypothetical maximum of 39.7~w-\%. In order to adapt the presented experimental NIR sensor sorting stand two strong levers are identified to improve the spectral quality for the detection of multilayer film: signal intensity and signal density. It is therefore recommended to adjust the illumination intensity, install a diffuser hemisphere or panels next to the conveyor belt or the material chute, changing the NIR measurement mode to transflection, and a change of the chute material to aluminium. A corresponding experimental procedure for their investigation is proposed.
Translated title of the contributionRecyclingpotential von Mehrschichtfolien
Original languageEnglish
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Vollprecht, Daniel, Supervisor (internal)
  • Koinig, Gerald, Co-Supervisor (internal)
Award date17 Dec 2021
Publication statusPublished - 2021

Bibliographical note

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Keywords

  • Recycling
  • flexible waste plastic packaging
  • multilayer films
  • near-infrared spectroscopy
  • NIR
  • plastic
  • yellow bag
  • sorting analysis

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