Quality evaluation and economic assessment of an improved mechanical recycling process for post-consumer flexible plastics

RecyQMeter: Application-specific quality of recycled plastics

Objectively quantifying the quality of recyclates and finding suitable applications for individual products is challenging in plastics recycling. Confronted with ambitious targets for recycled content, industry urgently needs a robust method to understand the quality of recycled plastics. This study describes the RecyQMeter tool, which was developed to address this challenge and help recyclers position their secondary materials in an appropriate market. RecyQMeter contains a first-of-its-kind extensive application-property matrix, a large dataset of application-specific material requirements obtained through data mining, expert interviews, literature searches and modeling. RecyQMeter generates a value between 0 and 1, which refers to the quality of recyclates relative to virgin plastics used in different market applications. Additionally, this tool can be used to automatically estimate substitution ratios in life cycle assessment (LCA) studies. RecyQMeter makes a significant step forward in standardizing plastics recycling and supporting decision makers in achieving higher circularity in the plastics sector with a large database, ease of use, transparent calculations, and a comprehensive approach.

Perceptions and alignment on quality along the circular plastics packaging material chain

In plastics recycling, quality is increasingly important but not unequivocally determined, as there is a wide range of perceptions on what it actually means. This exploratory research offers insights into how different actors perceive quality in the plastics packaging material processing chain. By conducting semi-structured interviews, we gathered data on quality perceptions from polymer producers, converters, brand owners, waste management companies, mechanical recyclers, chemical recyclers, additive producers, and equipment manufacturers. The results show that, depending on the position of the actors in the chain, their perceptions of the concept quality differ. We categorized the quality criteria they use into nine quality categories: purity, uniformity, mechanical properties, physical properties, processability, functionality, regulations & safety, substitutability and circularity. The interviews revealed specific differences in quality perceptions between the actors in the chain, which can complicate the efficiency of the recycling system. Despite these differences, many quality perceptions do match those of the previous and subsequent actors in the value chain but are not necessarily acknowledged as such.

Contaminant detection in flexible polypropylene packaging waste using hyperspectral imaging and machine learning

Flexible plastic packaging (FPP) constitutes one of the largest post-consumer plastic streams processed in recycling facilities. To address the key challenges of its sorting and quality control, this study developed and tested a classification procedure based on hyperspectral imaging (HSI), combined with machine learning. The aim was to automatically detect contaminants (i.e., other polymers and materials) within a polypropylene (PP) stream of FPP waste (FPPW). Hyperspectral images of representative FPPW samples of PP and contaminants were acquired in the short-wave infrared range (SWIR: 1000-2500 nm) and preprocessed using different combinations of algorithms to emphasize their spectral characteristics. Principal component analysis (PCA) was applied as exploratory analysis of the spectral data followed by the application of a hierarchical classification model, based on partial least squares-discriminant analysis (Hi-PLS-DA), to differentiate between PP and other materials considered as contaminants, including polyethylene, polyester, polyethylene terephthalate, polystyrene, cellulose, polyurethane, aluminum and multilayer films. The results showed a classification accuracy of 87.5 %, with 147 out of 168 flakes correctly identified, as verified by Fourier transform-infrared (FT-IR) spectroscopy, demonstrating the model robust performance in distinguishing PP from other materials. Assuming all correctly identified particles are properly sorted, the model is predicted to achieve a Recovery of 98.2 % by weight for PP, indicating minimal material losses, with a Grade of 94.4 % by weight, representing a significant improvement compared to 77.2 % in the initial feed FPPW stream. This work demonstrated the effectiveness of HSI combined with Hi-PLS-DA in developing an automatic and efficient sorting and/or quality control process for FPPW, with minor classification errors occurring in filaments and multilayer flakes.

Beyond the Landfill: A critical review of techniques for End-of-Life Polyvinyl chloride (PVC) valorization

Polyvinyl chloride (PVC) is a polymer comprised of more than 50% chlorine that offers unmatched versatility at low expense. PVC is irreplaceable in several applications, such as construction materials, medical applications, and cables. This versatility and tunable properties come at the cost of complex formulations for the product and challenging end-of-life (EoL) options for PVC waste. Pure collected and sorted PVC is already recycled successfully to some extent, yet, when PVC ends up in a mixed plastic waste stream, it can be detrimental to the recycling process. PVC waste and its effects at various concentrations remain a focal point for both scholars and policymakers. In this review, the narrative begins at the naissance of PVC and continues to investigate the EoL valorization options when the products are inevitably discarded. Strategies for PVC waste recycling and the technical and legal challenges regarding each method are discussed, focusing on the European recycling market. An effective solution to handle EoL PVC requires a combination of policies and schemes for proper collection and sorting of specific waste streams and considering all available technologies to select the right tools. This review can support appropriate policies and the selection of suitable methods of recycling PVC waste.

Exposing the pitfalls of plastics mechanical recycling through cost calculation

The plastic industry needs to match the recycling goals set by the EU. Next to technological hurdles, the cost of plastics mechanical recycling is an important modality in this transition. This paper reveals how business economic cost calculation can expose significant pitfalls in the recycling process, by unravelling limitations and boundary conditions, such as scale. By combining the business economic methodology with a Material Flow Analysis, this paper shows the influence of mass retention of products, the capacity of the processing lines, scaling of input capacity, and waste composition on the recycling process and associated costs. Two cases were investigated: (i) the Initial Sorting in a medium size Material Recovery Facility and (ii) an improved mechanical recycling process for flexibles - known as the Quality Recycling Process - consisting of Additional Sorting and Improved Recycling. Assessing the whole recycling chain gives a more holistic insight into the influences of choices and operating parameters on subsequent costs in other parts of the chain and results in a more accurate cost of recycled plastic products. This research concluded that the cost of Initial Sorting of flexibles is 110,08-122,53 EUR/t, while the cost of subsequent Additional Sorting and Improved Recycling ranges from 566,26 EUR/t for rPE Flex to 735,47 EUR/t for rPP Film, these insights can be used to determine a fair price for plastic products. For the Quality Recycling Process it was shown that rationalisation according to the identified pitfalls can reduce the cost per tonne of product by 15-26%.

Analysis of different polypropylene waste bales: Evaluation of the source material for PP recycling

The use of the polypropylene (PP) recyclates in certain processing methods and applications is still limited by their quality. The high melt flow rate (MFR) and the inconsistent properties of recyclates are common obstacles to their use. Therefore, this work aims to identify possible reasons for the low and inconsistent quality of PP recyclates depending on the source material in PP waste bales. The levels of polymeric and non-polymeric contaminants were assessed. As mixing of different PP grades is an issue for the MFR, the proportions of the different processing grades were also investigated and the potential of sorting by processing method to produce lower MFR recyclates was assessed. The analysis showed that the waste bales, although pre-sorted, still contained high amounts of contaminants. Injection moulding was found to be the predominant processing method in the bales, explaining the high MFR of PP recyclates. However, a sufficiently high amount of low MFR products was found in the bales, which seems promising for the production of low MFR recyclates. Seasonal variations in the composition of the waste bales were identified as one of the reasons for the inconsistent qualities of recyclates. These results highlight the importance of proper sorting and treatment of PP waste bales prior to reprocessing in order to obtain high-quality recycled products.

A comprehensive review of PETW recycling for supercapacitor applications

The rising measure of waste produced from polyethene terephthalate (PET) and the interest in eco-accommodating energy storage arrangements have prompted escalated examination into reusing waste PET into supercapacitors. This review aims to provide a comprehensive overview of the most recent advancements in the recycling of polyethylene terephthalate waste (PETW), as a supercapacitor electrode precursor. The review looks at different methodologies for recovering PET from waste, including mechanical, chemical, enzyme, etc. It further explores the combination strategies for electrode materials produced using PET. Besides, PET-derived materials' electrochemical performance in supercapacitor application is likewise broken down, with an emphasis on key electrochemical boundaries like capacitive behaviour, cyclic stability, and electrochemical impedance spectroscopy. The need for scalable and cost-effective recycling methods, the creation of eco-friendly electrolytes, and the improvement of the electrochemical performance of recycled PET-based supercapacitors are just a few of the issues and opportunities highlighted in this expanding eco-friendly industry. Overall, the goal of this review is to provide a comprehensive understanding of the cutting-edge developments in the use of recycled PETW as a precursor for supercapacitor electrodes, highlighting the eco-friendly energy storage solution's potential and contributing to a sustainable future.

Investigation of the Impact of Single and Double Filtration Systems on Post-Consumer PE Film Waste

Due to the diversity of plastic film waste streams available on the market and the associated variety of contaminants' size and number, the use of melt filtration is necessary. Currently, single and double filtration systems are state of the art in the plastic recycling industry, depending on the application of the produced post-consumer recyclate (PCR). Using PCR for thin films demands small contamination sizes, which are easier to reach using a second filtration step. In the case of relatively clean post-consumer input materials, it must be investigated whether the additional load from the second filter has a counterproductive effect on the material and whether single filtration would be sufficient. For this paper, polyethylene (PE) film waste stemming from a separate post-consumer collection in Austria was processed using an industrial-sized recycling machine with different combinations of filter sizes and systems. Melt flow rate (MFR), ash content, oxidation onset temperature (OOT), and optical contaminant detection were measured to investigate the influence of single and double filtration systems. The investigation showed that, even though the contamination amount and size were reduced, the second filter had a distinct effect on specific properties.

Mechanical recycling of printed flexible plastic packaging: The role of binders and pigments

Low-density polyethylene (LDPE), extensively employed in flexible plastic packaging, often undergoes printing with inks. However, during the mechanical recycling of post-consumer waste, these inks act as contaminants, subsequently compromising the quality and usability of recycled material. To understand better exactly which ink components cause which effects, this study comprehensively assesses the thermal behavior of three organic pigments and two commonly utilised binders, correlated with the impact on the mechanical recycling of LDPE-based flexible plastic packaging. In this regard, the study focuses on four pivotal factors: processability, mechanical properties, aesthetic attributes, and volatile organic compound profiles. The results indicate that nitrocellulose, used as a binder, degrades during reprocessing, resulting in film discoloration and the emission of potentially odorous compounds. Conversely, pigments are found to be dispersed within droplets of polyurethane binder in LDPE recyclates, whilst reprocessing printed samples detrimentally affects film properties, notably dart drop impact resistance, strain at break, and the number of inclusions. Additionally, it is shown that both inks comprise components that emit volatile compounds during reprocessing: non-thermally stable components, nitrocellulose and pigment yellow PY13, as well as low-molecular weight molecules from polyurethane and by-products from wax, plasticisers, and additives.

Depolymerization within a Circular Plastics System

The societal importance of plastics contrasts with the carelessness with which they are disposed. Their superlative properties lead to economic and environmental efficiency, but the linearity of plastics puts the climate, human health, and global ecosystems at risk. Recycling is fundamental to transitioning this linear model into a more sustainable, circular economy. Among recycling technologies, chemical depolymerization offers a route to virgin quality recycled plastics, especially when valorizing complex waste streams poorly served by mechanical methods. However, chemical depolymerization exists in a complex and interlinked system of end-of-life fates, with the complementarity of each approach key to environmental, economic, and societal sustainability. This review explores the recent progress made into the depolymerization of five commercial polymers: poly(ethylene terephthalate), polycarbonates, polyamides, aliphatic polyesters, and polyurethanes. Attention is paid not only to the catalytic technologies used to enhance depolymerization efficiencies but also to the interrelationship with other recycling technologies and to the systemic constraints imposed by a global economy. Novel polymers, designed for chemical depolymerization, are also concisely reviewed in terms of their underlying chemistry and potential for integration with current plastic systems.

Prospects for Recyclable Multilayer Packaging: A Case Study

Food preservation is an essential application for polymers, particularly in packaging. Complex multilayer films, such as those used for modified atmosphere packaging (MAP), extend the shelf life of sensitive foods. These mostly contain various polymers to achieve the necessary combination of mechanic, optic, and barrier properties that limit their recyclability. As the European Union's Circular Economy Action Plan calls for sustainable products and business models, including waste prevention policies and recycling quotas, with plastic packaging being a high priority, solutions towards more sustainable multilayer packaging are urgently needed. This study evaluated and compared the recycling potential of functionally equivalent PET (polyethylene terephthalate) and PP (polypropylene) post-consumer MAP through structure analysis and recycling simulation. The structure analysis revealed that both types of MAP contained functional (stability) and barrier layers (oxygen and moisture). The recycling simulation showed that the PP-based packaging was recyclable 10 times, maintaining its mechanical properties and functionality. At the same time, the PET-based MAP resulted in a highly brittle material that was unsuitable for reprocessing into similar economic value products. The secondary material from the PP-based MAP was successfully manufactured into films, demonstrating the functional possibility of closed-loop recycling. The transition from a linear to a circular economy for MAP is currently still limited by safety concerns due to a lack of sufficient and efficient purification methods, but the proper design of multilayers for recyclability is a first step towards circularity.

Screening the Impact of Surfactants and Reaction Conditions on the De-Inkability of Different Printing Ink Systems for Plastic Packaging

One of the major applications (40% in Europe) of plastic is packaging, which is often printed to display required information and to deliver an attractive aesthetic for marketing purposes. However, printing ink can cause contamination in the mechanical recycling process. To mitigate this issue, the use of surfactants in an alkaline washing process, known as de-inking, has been employed to remove printing ink and improve the quality of recyclates. Despite the existence of this technology, there are currently no data linking the de-inking efficiency with typical printing ink compositions. Additionally, it is necessary to investigate the de-inking process under the process parameters of existing recycling plants, including temperature, NaOH concentration, and retention time. This study aims to evaluate the performance of commonly used printing inks with different compositions under various washing scenarios for plastic recycling in conjunction with different de-inking detergents containing surfactants or mixtures of surfactants. The results indicate that the pigments applied to the ink have no significant effect on the de-inking process, except for carbon black (PBk 7). Nitrocellulose (NC) binder systems exhibit high de-inkability (over 95%) under the condition of 55 °C and 1 wt.% NaOH. However, crosslinked binder systems can impede the de-inking effect, whether used as a binder system or as an overprint varnish (OPV). The de-inking process requires heating to 55 °C with 1 wt.% NaOH to achieve a substantial effect. Based on the findings in this work, breaking the Van der Waals forces, hydrogen bonds, and covalent bonds between the printing ink and plastic film is an essential step to achieve the de-inking effect. Further research is needed to understand the interaction between surfactants and printing inks, enabling the development of de-inkable printing inks and high-performance surfactants that allow for de-inking with less energy consumption. The surfactant and NaOH have a synergistic effect in cleaning the printing ink. NaOH provides a negative surface charge for the adsorption of the cationic head of the surfactant and can hydrolyze the covalent bonds at higher concentrations (>2 wt.%).

WILL WE BE ABLE TO USE RECYCLED PLASTICS OR SHALL WE DECIDE FOR PACKAGING FREE PRODUKCTION?

Recycled plastic and its use are imperative for preserving the environment, including proper plastic wash-out. Will we ever be able to push the Czech population and firms to use recycled material? Or is it happening spontaneously? A questionnaire created on Google Forms involves ten legislative and motivational questions comprising relevant data on the amount of plastic in municipal waste between 2010 and 2020 from the Czech Statistical Office. We found that the population understands the importance of using recycled material and recycled plastic without the government's impulse. Despite the high capital intensity, the state should impose taxes to protect the sustainable environment. We suggest a comprehensive and in-depth survey to acquire more accurate data.

Material flow analysis and recycling performance of an improved mechanical recycling process for post-consumer flexible plastics

Increasing the recycling rates for post-consumer flexible plastics (PCFP) waste is imperative as PCFP is considered a difficult-to-recycle waste with only 17 % of PCFP effectively recycled in Europe. To tackle this pressing issue, improved mechanical recycling processes are being explored to increase the recycling rates of PCFP. One interesting option is the so-called quality recycling process (QRP) proposed by CEFLEX, which supplements more conventional mechanical recycling of PCFP with additional sorting, hot washing, improved extrusion, and deodorization. Material flow analysis (MFA) model is applied to assess the performance of QRP. Four performance indicators related to quantity (process yield and net recovery) and quality (polymer grade and transparency grade) are applied to measure the performance of three PCFP mechanical recycling scenarios. The results are compared against the conventional recycling of PCFP, showing that QRP has a similar process yield (64 % - 66 %) as conventional recycling (66 %). The net recovery indicator shows that in QRP higher recovery rates are achieved for transparent-monolayer PCFP (>90 %) compared to colored-multilayer PCFP (51 % - 91 %). The quality indicators (polymer and transparency grades) demonstrate that the regranulates from QRP have better quality compared to the conventional recycling. To validate the modeling approach, the modeled compositional data is compared with experimental compositional analyses of flakes and regranulates produced by pilot recycling lines. Main conclusions are: (i) although yields do not increase significantly, extra sorting and recycling produces better regranulates' quality (ii) performing a modular MFA gives insights into future recycling scenarios and helps in decision making.