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Recycling and Sustainability of Plastics

A special issue of Sustainability (ISSN 2071-1050). This special issue belongs to the section "Waste and Recycling".

Deadline for manuscript submissions: closed (28 February 2021) | Viewed by 75280

Special Issue Editors


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Guest Editor
CAPTURE—Plastics to Resource, Centre for Polymer and Material Technologies, Ghent University, Ghent, Belgium
Interests: mechanical recycling of thermoplastics; structure–property relationships in polymers; predictive quality modelling of contaminated recycled plastics; design for recycling; design from recycling

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Guest Editor
CAPTURE—Plastics to Resource, Department of Industrial Biological Sciences, Ghent University, Ghent, Belgium
Interests: solid waste management; recycling; sustainability; environmental performance; environmental science; plastics; separation and purification; organic waste; chemical engineering

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Guest Editor
Laboratory for Chemical Technology, Ghent University, 9052 Ghent, Belgium
Interests: reaction kinetics; computational chemistry; chemical reaction engineering; process engineering; chemical processes; energy engineering; modeling and simulation; process simulation; process optimization

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Guest Editor
CAPTURE—Plastics to Resource, Department of Product Development, Antwerp University, Belgium
Interests: design for a circular economy; circular plastics usage; product development; sustainable user experience; product lifetime extension; closing the loop; design from recycling; material identity

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Guest Editor
CAPTURE—Plastics to Resource, Department of Applied Chemical Engineering, University of Antwerp, Antwerp, Belgium
Interests: waste management and recycling; green organic/inorganic and circular polymeric materials; quantitative sustainability assessment

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Guest Editor
1. Sustainable Materials Management, Flemish Institute for Technological Research (VITO), Boeretang 200, 2400 Mol, Belgium
2. Department of Bioengineering, University of Antwerp, 2020 Antwerp, Belgium
Interests: persistent chemicals; sanitation; circular economy; waste management; transition management
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Special Issue Information

Dear Colleagues,

The sustainability of plastics as a material is more than ever a relevant topic for scientists to work upon. Plastics are often misunderstood as an ‘unsustainable’ material because of the very real littering issue in which they feature. Nonetheless, society and environment are rightfully crying out for more and better solutions concerning the collection, sorting, and recycling of plastics. Circular Plastics as a concept requires thinking across the entire value chain as well as in many different fields of science: engineering, chemistry, waste management, consumer behavior, economy, and political sciences. Interdisciplinary problems require interdisciplinary answers. That is why, within the resource recovery platform CAPTURE, over a dozen scientists from different institutes have joined forces in the Plastics to Resource pipeline, working together to bring plastics to true circularity. Six of us are now inviting you to contribute scientific insights from your respective domains to this thematic Special Issue.

This Special Issue “Recycling and Sustainability of Plastics” welcomes papers on the scientific-technical side of the different pathways for recycling (mechanical, thermochemical, solvolysis) as well as logistics and pre-treatment but also material and product design for circularity, sustainability indicators, and holistic policy or macro-economic perspectives.

Prof. Dr. Kim Ragaert
Prof. Dr. Steven De Meester
Prof. Dr. Kevin M. Van Geem
Prof. Dr. Els Du Bois
Prof. Dr. Pieter Billen
Prof. Dr. Karl Vrancken
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sustainability is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • mechanical recycling
  • thermochemical recycling
  • solvolysis
  • sorting and pretreatment
  • plastics value chains
  • sustainability indicators
  • design for/from recycling
  • policy implications for plastics recycling

Published Papers (10 papers)

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17 pages, 2109 KiB  
Article
A Review of Technological Solutions to Prevent or Reduce Marine Plastic Litter in Developing Countries
by Andrea Winterstetter, Marie Grodent, Venkatesh Kini, Kim Ragaert and Karl C. Vrancken
Sustainability 2021, 13(9), 4894; https://doi.org/10.3390/su13094894 - 27 Apr 2021
Cited by 14 | Viewed by 9129
Abstract
Growing global plastic production combined with poor waste collection has led to increasing amounts of plastic debris being found in oceans, rivers and on shores. The goal of this study is to provide an overview on currently available technological solutions to tackle marine [...] Read more.
Growing global plastic production combined with poor waste collection has led to increasing amounts of plastic debris being found in oceans, rivers and on shores. The goal of this study is to provide an overview on currently available technological solutions to tackle marine plastic litter and to assess their potential use in developing countries. To compile an inventory of technological solutions, a dedicated online platform was developed. A total of 51 out of initially 75 submitted solutions along the plastics value chain were assessed by independent experts. Collection systems represent more than half of the shortlisted solutions. A quarter include processing and treatment technologies, either as a stand-alone solution (30%) or, more commonly, in combination with a first litter capturing step. Ten percent offer digital solutions. The rest focuses on integrated waste management solutions. For each stage in the source-to-sea spectrum—land, rivers, sea—two illustrative examples are described in detail. This study concludes that the most cost-effective type of solution tackles land-based sources of marine litter and combines technology with people-oriented practices, runs on own energy sources, connects throughout the plastics value chain with a convincing valorization plan for captured debris, and involves all relevant stakeholders. Full article
(This article belongs to the Special Issue Recycling and Sustainability of Plastics)
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13 pages, 1192 KiB  
Article
Multistage Chemical Recycling of Polyurethanes and Dicarbamates: A Glycolysis–Hydrolysis Demonstration
by Pegah Zahedifar, Lukasz Pazdur, Christophe M. L. Vande Velde and Pieter Billen
Sustainability 2021, 13(6), 3583; https://doi.org/10.3390/su13063583 - 23 Mar 2021
Cited by 38 | Viewed by 5504
Abstract
The use of polyurethanes and, therefore, the quantity of its scrap are increasing. Considering the thermoset characteristic of most polyurethanes, the most circular recycling method is by means of chemical depolymerization, for which glycolysis is finding its way into the industry. The main [...] Read more.
The use of polyurethanes and, therefore, the quantity of its scrap are increasing. Considering the thermoset characteristic of most polyurethanes, the most circular recycling method is by means of chemical depolymerization, for which glycolysis is finding its way into the industry. The main goal of polyurethane glycolysis is to recover the polyols used, but only limited attempts were made toward recovering the aromatic dicarbamate residues and derivates from the used isocyanates. By the split-phase glycolysis method, the recovered polyols form a top-layer phase and the bottom layer contain transreacted carbamates, excess glycol, amines, urea, and other side products. The hydrolysis of carbamates results in amines and CO2 as the main products. Consequently, the carbamates in the bottom layer of polyurethane split-phase glycolysis can also be hydrolyzed in a separate process, generating amines, which can serve as feedstock for isocyanate production to complete the polyurethane material cycle. In this paper, the full recycling of polyurethanes is reviewed and experimentally studied. As a matter of demonstration, combined glycolysis and hydrolysis led to an amine production yield of about 30% for model systems. With this result, we show the high potential for further research by future optimization of reaction conditions and catalysis. Full article
(This article belongs to the Special Issue Recycling and Sustainability of Plastics)
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21 pages, 960 KiB  
Article
Extending Multilevel Statistical Entropy Analysis towards Plastic Recyclability Prediction
by Philippe Nimmegeers, Alexej Parchomenko, Paul De Meulenaere, Dagmar R. D’hooge, Paul H. M. Van Steenberge, Helmut Rechberger and Pieter Billen
Sustainability 2021, 13(6), 3553; https://doi.org/10.3390/su13063553 - 23 Mar 2021
Cited by 19 | Viewed by 3485
Abstract
Multilevel statistical entropy analysis (SEA) is a method that has been recently proposed to evaluate circular economy strategies on the material, component and product levels to identify critical stages of resource and functionality losses. However, the comparison of technological alternatives may be difficult, [...] Read more.
Multilevel statistical entropy analysis (SEA) is a method that has been recently proposed to evaluate circular economy strategies on the material, component and product levels to identify critical stages of resource and functionality losses. However, the comparison of technological alternatives may be difficult, and equal entropies do not necessarily correspond with equal recyclability. A coupling with energy consumption aspects is strongly recommended but largely lacking. The aim of this paper is to improve the multilevel SEA method to reliably assess the recyclability of plastics. Therefore, the multilevel SEA method is first applied to a conceptual case study of a fictitious bag filled with plastics, and the possibilities and limitations of the method are highlighted. Subsequently, it is proposed to extend the method with the computation of the relative decomposition energies of components and products. Finally, two recyclability metrics are proposed. A plastic waste collection bag filled with plastic bottles is used as a case study to illustrate the potential of the developed extended multilevel SEA method. The proposed extension allows us to estimate the recyclability of plastics. In future work, this method will be refined and other potential extensions will be studied together with applications to real-life plastic products and plastic waste streams. Full article
(This article belongs to the Special Issue Recycling and Sustainability of Plastics)
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20 pages, 5091 KiB  
Article
The Feasibility of Using the MFC Concept to Upcycle Mixed Recycled Plastics
by Maja Kuzmanović, Laurens Delva, Ludwig Cardon and Kim Ragaert
Sustainability 2021, 13(2), 689; https://doi.org/10.3390/su13020689 - 12 Jan 2021
Cited by 6 | Viewed by 4791
Abstract
Several mixed recycled plastics, namely, mixed bilayer polypropylene/poly (ethylene terephthalate) (PP/PET) film, mixed polyolefins (MPO) and talc-filled PP were selected for this study and used as matrices for the preparation of microfibrillar composites (MFCs) with PET as reinforcement fibres. MFCs with recycled matrices [...] Read more.
Several mixed recycled plastics, namely, mixed bilayer polypropylene/poly (ethylene terephthalate) (PP/PET) film, mixed polyolefins (MPO) and talc-filled PP were selected for this study and used as matrices for the preparation of microfibrillar composites (MFCs) with PET as reinforcement fibres. MFCs with recycled matrices were successfully prepared by a three-step processing (extrusion—cold drawing—injection moulding), although significant difficulties in processing were observed. Contrary to previous results with virgin PP, no outstanding mechanical properties were achieved; they showed little or almost no improvement compared to the properties of unreinforced recycled plastics. SEM characterisation showed a high level of PET fibre coalescence present in the MFC made from recycled PP/PET film, while in the other MFCs, a large heterogeneity of the microstructure was identified. Despite these disappointing results, the MFC concept remains an interesting approach for the upcycling of mixed polymer waste. However, the current study shows that the approach requires further in-depth investigations which consider various factors such as viscosity, heterogeneity, the presence of different additives and levels of degradation. Full article
(This article belongs to the Special Issue Recycling and Sustainability of Plastics)
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16 pages, 2695 KiB  
Article
Plastics Recycling with Tracer-Based-Sorting: Challenges of a Potential Radical Technology
by Johannes Gasde, Jörg Woidasky, Jochen Moesslein and Claus Lang-Koetz
Sustainability 2021, 13(1), 258; https://doi.org/10.3390/su13010258 - 30 Dec 2020
Cited by 35 | Viewed by 7722
Abstract
To improve the recycling quality of plastics packaging and achieve high recycling rates new identification and sorting technologies are required. Tracer-based-sorting (TBS) is an innovative identification technology based on fluorescent tracers and a corresponding detection unit. TBS can be considered a radical technology [...] Read more.
To improve the recycling quality of plastics packaging and achieve high recycling rates new identification and sorting technologies are required. Tracer-based-sorting (TBS) is an innovative identification technology based on fluorescent tracers and a corresponding detection unit. TBS can be considered a radical technology change towards a circular economy for plastics and to support sustainability as it has the potential to render several established sorting and/or recycling steps obsolete. This article shows which drivers and barriers are perceived by stakeholders with regard to the implementation of TBS in the market and how challenges are addressed responsibly in the early phases of the innovation process. Influencing external factors and framework conditions of TBS are identified and suitable business models for TBS in a circular economy are discussed. Further, practical recommendations on how to optimize technology and market development for TBS are provided. To obtain these results a mixed method approach of integrated innovation and sustainability analysis, external environment analysis (PESTEL analysis), and business model development approaches was chosen. The research results can be understood as a practical contribution towards a responsible and sustainable implementation of a radical technology-based innovation for a circular economy of plastics. Full article
(This article belongs to the Special Issue Recycling and Sustainability of Plastics)
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21 pages, 1796 KiB  
Article
Plastic Bottle Cap Recycling—Characterization of Recyclate Composition and Opportunities for Design for Circularity
by Markus Gall, Andrea Schweighuber, Wolfgang Buchberger and Reinhold W. Lang
Sustainability 2020, 12(24), 10378; https://doi.org/10.3390/su122410378 - 11 Dec 2020
Cited by 22 | Viewed by 21677
Abstract
In line with efforts to create a circular economy of plastics, recent EU legislation is strengthening plastic bottle recycling by ambitious separate collection targets and mandatory recycled content obligations. Furthermore, explicit design requirements on the caps of bottles and composite beverage packaging have [...] Read more.
In line with efforts to create a circular economy of plastics, recent EU legislation is strengthening plastic bottle recycling by ambitious separate collection targets and mandatory recycled content obligations. Furthermore, explicit design requirements on the caps of bottles and composite beverage packaging have been introduced. These caps are typically made of polyethylene or polypropylene and often contain additives such as slip agents and anti-statics. Commercially available bottle cap recyclates (BCRs) as well as specifically formulated model compounds were analyzed in terms of composition by means of infrared spectroscopy, differential scanning calorimetry, and high-performance liquid chromatography. Their composition was found to be heterogeneous due to polyolefin cross-contamination, directly reflecting the diversity of cap materials present in the market. Slip agent legacy additives originating from the initial use phase were found and quantified in both commercial and model cap recyclates. This highlights the opportunity for redesigning plastic bottle caps not only in response to regulatory requirements, but to pursue a more comprehensive strategy of product design for circularity. By including considerations of polymer resin and additive choice in cap manufacturing, more homogeneous waste streams could be derived from plastic bottle cap recycling, enabling recycling into more demanding and valuable applications. Full article
(This article belongs to the Special Issue Recycling and Sustainability of Plastics)
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29 pages, 539 KiB  
Article
Technical Limits in Circularity for Plastic Packages
by Marieke T. Brouwer, Eggo U. Thoden van Velzen, Kim Ragaert and Roland ten Klooster
Sustainability 2020, 12(23), 10021; https://doi.org/10.3390/su122310021 - 30 Nov 2020
Cited by 39 | Viewed by 7443
Abstract
The current Dutch recycling value chain for plastic packaging waste (PPW) has not reached its full circularity potential, as is apparent from two Circular Performance Indicators (CPIs): net packaging recycling rate and average polymer purity of the recycled plastics. The performance of the [...] Read more.
The current Dutch recycling value chain for plastic packaging waste (PPW) has not reached its full circularity potential, as is apparent from two Circular Performance Indicators (CPIs): net packaging recycling rate and average polymer purity of the recycled plastics. The performance of the recycling value chain can be optimised at four stages: packaging design, collection, sorting, and recycling. This study explores the maximally achievable performance of a circular PPW recycling value chain, in case all stakeholders would implement the required radical improvement measures in a concerted action. The effects of the measures were modelled with material flow analysis. For such a utopic scenario, a net plastic packaging recycling rate of 72% can be attained and the produced recycled plastics will have an average polymeric purity of 97%. This is substantially more than the net packaging recycling rate of 37% for 2017 and will exceed the EU target of 50% for 2025. In such an ideal circular value chain more recycled plastics are produced for more demanding applications, such as food packaging, compared to the current recycling value chain. However, all stakeholders would need to implement drastic and coordinated changes, signifying unprecedented investments, to achieve this optimal circular PPW recycling value chain. Full article
(This article belongs to the Special Issue Recycling and Sustainability of Plastics)
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18 pages, 1996 KiB  
Article
Exploring Odor Minimization in Post-Consumer Plastic Packaging Waste through the Use of Probiotic Bacteria
by Bianca Lok, Andrea Buettner, Philipp Denk, Eva Ortner and Tanja Fell
Sustainability 2020, 12(22), 9432; https://doi.org/10.3390/su12229432 - 12 Nov 2020
Cited by 6 | Viewed by 3334
Abstract
Plastic packaging represents a large proportion of the plastic consumption throughout the world. The negative environmental impact associated with plastic packaging waste can be in part abated by recycling plastics, and increasing numbers of regulatory frameworks are being adopted towards this goal. Despite [...] Read more.
Plastic packaging represents a large proportion of the plastic consumption throughout the world. The negative environmental impact associated with plastic packaging waste can be in part abated by recycling plastics, and increasing numbers of regulatory frameworks are being adopted towards this goal. Despite recent advances in modern recycling technologies, the production of high-quality polyolefin recyclates remains a challenge. Among other functional requirements, odor plays a crucial role in the acceptance of recycled packaging. This presents a challenge, as odor contamination in plastic packaging waste can stem from diverse sources, such as spoilage processes, and strongly depends on the quality of the post-consumer input material. The present study addressed this issue by exploring potential odor abatement of malodors in packaging waste through the use of probiotic bacteria. Specifically, probiotics were added to a mixed post-consumer plastic packaging waste fraction, which was subsequently evaluated using human sensory and gas chromatography–olfactometric analyses. A comparison of treated with untreated plastic waste fractions revealed significant sensory differences. Further structural elucidation of the causative odorants confirmed a reduction in malodorous microbial metabolites, although complete odor removal was not achieved. However, this environmentally friendly approach may represent an essential step towards overcoming the odor burden in post-consumer plastic packaging recyclates. Full article
(This article belongs to the Special Issue Recycling and Sustainability of Plastics)
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12 pages, 660 KiB  
Article
Postcollection Separation of Plastic Recycling and Design-For-Recycling as Solutions to Low Cost-Effectiveness and Plastic Debris
by Raymond Gradus
Sustainability 2020, 12(20), 8415; https://doi.org/10.3390/su12208415 - 13 Oct 2020
Cited by 16 | Viewed by 5635
Abstract
In the Netherlands, plastic waste recycling is high on the policy agenda. Much effort is made to recycle, mostly by residents, who separate plastic waste at home. However, much of the separated waste is not recycled into new products. Substantial amounts are burned [...] Read more.
In the Netherlands, plastic waste recycling is high on the policy agenda. Much effort is made to recycle, mostly by residents, who separate plastic waste at home. However, much of the separated waste is not recycled into new products. Substantial amounts are burned or even shipped to Asia. This leads to substantial plastic debris, as recent evidence has shown. Moreover, the cost-effectiveness of plastic recycling versus incineration is very low. Based on evidence from the north of the Netherlands, postcollection or mechanical separation can be a viable alternative as more useful plastics are separated and there are indications that different plastic streams are of higher polymeric purity. Furthermore, there is some circumstantial evidence that cost-effectiveness increases if postseparation is chosen. To avoid large streams of mixed plastics that are barely recyclable, it is important that further agreements with the packaging industry are made to phase out these mixed plastics and further increase the polymeric purity of different plastic waste streams. Full article
(This article belongs to the Special Issue Recycling and Sustainability of Plastics)
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12 pages, 1598 KiB  
Brief Report
Design for Circularity Guidelines for the EEE Sector
by Anton Berwald, Gergana Dimitrova, Thijs Feenstra, Joop Onnekink, Harm Peters, Gianni Vyncke and Kim Ragaert
Sustainability 2021, 13(7), 3923; https://doi.org/10.3390/su13073923 - 1 Apr 2021
Cited by 17 | Viewed by 4098
Abstract
The increased diversity and complexity of plastics used in modern devices, such as electrical and electronic equipment (EEE), can have negative impacts on their recyclability. Today, the main economic driver for waste electrical and electronic equipment (WEEE) recycling stems from metal recovery. WEEE [...] Read more.
The increased diversity and complexity of plastics used in modern devices, such as electrical and electronic equipment (EEE), can have negative impacts on their recyclability. Today, the main economic driver for waste electrical and electronic equipment (WEEE) recycling stems from metal recovery. WEEE plastics recycling, on the other hand, still represents a major challenge. Strategies like design ‘for’, but also the much younger concept of design ‘from’ recycling play a key role in closing the material loops within a circular economy. While these strategies are usually analysed separately, this brief report harmonises them in comprehensive Design for Circularity guidelines, established in a multi-stakeholder collaboration with industry leaders from the entire WEEE value chain. The guidelines were developed at the product and part levels. They are divided in five categories: (1) avoidance of hazardous substances; (2) enabling easy access and removal of hazardous or polluting parts; (3) use of recyclable materials; (4) use of material combinations and connections allowing easy liberation; (5) use of recycled materials. These guidelines are the first harmonised set to be released for the EEE industry. They can readily serve decision-makers from different levels, including product designers and manufacturers as well as policymakers. Full article
(This article belongs to the Special Issue Recycling and Sustainability of Plastics)
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