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Recycling
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Challenges and Opportunities in Plastic Waste Management
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Challenges and Opportunities in Plastic Waste Management

A special issue of Recycling (ISSN 2313-4321).

Deadline for manuscript submissions: 1 July 2025 | Viewed by 20746

Special Issue Editors

Dr. Wan-Ting (Grace) Chen

E-Mail Website
Guest Editor
Department of Plastics Engineering, UMass Lowell Francis College of Engineering, Lowell, MA 01854, USA
Interests: chemical recycling; microplastics; biodegradable materials; ocean plastic waste; hydrothermal processing
Special Issues, Collections and Topics in MDPI journals
Dr. Daniel Lachos-Perez

E-Mail Website
Guest Editor
Department of Plastics Engineering, UMass Lowell Francis College of Engineering, Lowell, MA 01854, USA
Interests: chemical recycling; plastic waste; biomass conversion; supercritical fluids; hydrothermal processing
Dr. Taofeng Lu

E-Mail Website
Guest Editor Assistant
National Renewable Energy Laboratory (NREL), Golden, CO 80401, USA
Interests: physical recycling; chemical recycling; polymer deconstruction; solvent-based recycling; hydrothermal processing

Special Issue Information

Dear Colleagues,

Plastic waste has a significant impact on the environment, affecting ecosystems and human health. Inadequate plastic waste handling practices, such as lack of recycling, incineration, or proper disposal in landfills, result in severe environmental repercussions. Annually, an alarming one to two million tonnes of plastic find their way into the oceans, endangering marine life and ecosystems.

This Special Issue aims to address the challenges and opportunities in plastic waste management. It will cover the latest technologies and methods for plastic waste treatment and recycling and discuss sustainable waste management solutions to reduce environmental degradation. Additionally, this Special Issue will explore the economic and environmental benefits that a plastic circular economy may provide.

Dr. Wan-Ting (Grace) Chen
Dr. Daniel Lachos-Perez
Guest Editors

Dr. Taofeng Lu
Guest Editor Assistant

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. Recycling 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 1800 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

  • physical recycling
  • chemical recycling
  • plastic waste
  • microplastics
  • hydrothermal process
  • pyrolysis

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Published Papers (15 papers)

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Research

19 pages, 2682 KiB  
Article
Life Cycle Assessment of Recycling Polyethylene Terephthalate (PET): A Comparative Case Study in Taiwan
by Allen H. Hu, Chih-Yu Ting, Ali Ouattara, Wei-Tse Chen and Chien-Hung Kuo
Recycling 2025, 10(3), 98; https://doi.org/10.3390/recycling10030098 - 16 May 2025
Viewed by 101
Abstract
Polyethylene terephthalate (PET) is commonly used in beverage container manufacturing; however, its classification as a single-use plastic significantly contributes to environmental pollution. Improper disposal results in enduring contamination of both terrestrial and marine ecosystems, which poses ecological and health risks. Among the disposal [...] Read more.
Polyethylene terephthalate (PET) is commonly used in beverage container manufacturing; however, its classification as a single-use plastic significantly contributes to environmental pollution. Improper disposal results in enduring contamination of both terrestrial and marine ecosystems, which poses ecological and health risks. Among the disposal methods, recycling, incineration, and landfilling, only recycling promotes a circular economy by reducing reliance on landfills, alleviating emissions, and conserving fossil resources. This study employs the life cycle assessment (LCA) method to evaluate the environmental impacts of three PET bottle recycling facilities in Taiwan, considering collection, transportation, and processing in the system boundary. It also assesses the effects of raw material composition, comparing transparent, colored, and mixed PET bottles. The results indicate that facilities processing colorless PET have lower environmental damage values (16.6–18.1 mPt·kg−1 of recycled flakes) than those handling colored and oil-trapped PET (25 mPt·kg−1) due to higher energy demands and poly aluminum chloride usage in wastewater treatment. Granulation was identified as a significant environmental hotspot for recycled PET pellets, with a damage value of 35 mPt·kg−1. Integrating renewable energy and recycled PET into PET bottle manufacturing could significantly reduce their environmental impacts. Policy recommendations include adopting renewable energies as the source energy, calibrating the use of chemicals in recycling facilities, and mandating minimum recycled content in PET products to enhance circularity. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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15 pages, 3312 KiB  
Article
Recycling of Poly(Propylene) Based Car Bumpers in the Perspective of Polyolefin Nanoclay Composite Film Production
by Nemr El Hajj, Sylvain Seif and Nancy Zgheib
Recycling 2025, 10(3), 95; https://doi.org/10.3390/recycling10030095 - 10 May 2025
Viewed by 262
Abstract
This study uses the melt compounding method to recycle polypropylene-based car bumper waste (PP-CBW) in order to produce nanocomposite films for mulch application. The nanocomposite films were compounded by mixing virgin linear low-density polyethylene (LLDPE) with PP-CBW at a constant ratio of 4:1 [...] Read more.
This study uses the melt compounding method to recycle polypropylene-based car bumper waste (PP-CBW) in order to produce nanocomposite films for mulch application. The nanocomposite films were compounded by mixing virgin linear low-density polyethylene (LLDPE) with PP-CBW at a constant ratio of 4:1 in the presence of different percentages of nanofillers. Nanocomposites reinforced with nanoclays were compatibilized with an anhydride grafted polyethylene (PE-g-MAH), at a constant compatibilizer-to-clay ratio equal to 3, to improve the adherence between the nonpolar matrix and the hydrophilic nanoclay and acrylic paint present in the car bumper. An extruder with a corotating twin screw was used to produce blends of different compositions. To create nanocomposite films, the mixtures were further processed in a blown film extruder. The effect of the presence of nanoclays on the barrier, thermal, and mechanical properties of the nanocomposite films was investigated. The dispersion of clay layers in the matrix was examined by atomic force microscopy (AFM). The results indicate that 3 wt% of clay loading maximized the tensile strength in the transverse direction (TD) and machine direction (MD). A 1 wt% clay loading increased the MD tear resistance by 66% and manifested an optimum dart impact strength. Significant improvements in thermal and barrier properties were also achieved in the presence of 3 wt% clay loading. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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21 pages, 4436 KiB  
Article
Sustainability and Innovation: Incorporating Waste from Ophthalmic Lenses into Natural Rubber Composites
by José Afonso Rocha, Carlos Toshiyuki Hiranobe, Dener da Silva Souza, Samara da Silva Araújo, Márcia Ferreira Hiranobe, Guilherme Henrique Barros de Souza, Elmer Mateus Gennaro, Flávio Camargo Cabrera, Guilherme Pina Cardim, Michael Jones da Silva, Erivaldo Antônio da Silva, José Francisco Resende da Silva and Renivaldo José dos Santos
Recycling 2025, 10(3), 90; https://doi.org/10.3390/recycling10030090 - 4 May 2025
Viewed by 303
Abstract
This study investigates the recycling of ophthalmic lens waste (OLW) in the production of vulcanized natural rubber (NR) composites, aiming to promote sustainability and reduce costs. To this end, Vietnamese natural rubber and ophthalmic lens waste were used, varying the filler content from [...] Read more.
This study investigates the recycling of ophthalmic lens waste (OLW) in the production of vulcanized natural rubber (NR) composites, aiming to promote sustainability and reduce costs. To this end, Vietnamese natural rubber and ophthalmic lens waste were used, varying the filler content from 0 to 50 phr. Rheological tests demonstrated that the addition of OLW decreases the cure time. The crosslink density, assessed through the Flory–Rehner and Mooney–Rivlin methods, exhibited an increase with the incorporation of a reinforcement. Thermal and spectroscopic analyses demonstrated the thermal stability of the composites and the absence of chemical interactions between the polymer matrix and the OLW. Mechanical tests showed that the composites exhibit satisfactory tensile and tear resistance, although the filler primarily acts as a filler rather than a structural reinforcement. Thus, the incorporation of OLW in NR composites emerges as a viable alternative for the reuse of industrial waste, fostering more sustainable and efficient practices in the polymer industry. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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17 pages, 11496 KiB  
Article
Secondary Treatment Facilitating the Mechanical Recycling of Film-Coated Waste Automobile Bumpers
by Tetsuo Takayama, Toshiyuki Niiyama, Tadao Tanabe and Jeongsoo Yu
Recycling 2025, 10(2), 74; https://doi.org/10.3390/recycling10020074 - 14 Apr 2025
Viewed by 351
Abstract
Concerns have been raised regarding the mechanical recycling rates of automotive parts, which appear to be low in comparison to those of other sectors. Addressing this issue demands the promotion of the mechanical recycling of waste automobile bumpers. This study investigates primer treatment [...] Read more.
Concerns have been raised regarding the mechanical recycling rates of automotive parts, which appear to be low in comparison to those of other sectors. Addressing this issue demands the promotion of the mechanical recycling of waste automobile bumpers. This study investigates primer treatment effects on the mechanical properties of injection-molded waste bumpers. The primer treatment effects vary depending on the bumper coating. The flexural strength of coated bumpers is greater: 27.6 MPa vs. 29.2 MPa. The flexural modulus is also greater: 1667 MPa vs. 1761 MPa. By contrast, the notched Charpy impact strength is less: 25.4 kJ/m2 vs. 23.4 kJ/m2. The flexural strength and flexural modulus of the bumpers lacking a coating are also lower, respectively, at 25.0 MPa vs. 22.9 MPa and 1523 MPa vs. 1314 MPa. However, the notched Charpy impact strength is greater: 40.0 kJ/m2 vs. 73.6 kJ/m2. These findings suggest that primer treatment can control the mechanical properties of injection-molded parts produced from waste automobile bumpers, which is an important achievement for promoting the mechanical recycling of waste automobile bumpers. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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21 pages, 11384 KiB  
Article
Optimization of the Recycling Process for Aligned Short Carbon Fiber TuFF Composites
by Uday Kiran Balaga, Aydin Gunes, Tekin Ozdemir, Chris Blackwell, Mark Davis, Steven Sauerbrunn, Lukas Fuessel, Joseph M. Deitzel and Dirk Heider
Recycling 2025, 10(2), 55; https://doi.org/10.3390/recycling10020055 - 1 Apr 2025
Viewed by 405
Abstract
Recycling of carbon fibers enables a sustainable feedstock for industrial applications of high-performance composite materials. This allows light weighting with recycled carbon fibers due to their superior mechanical properties while reducing the high embodied energy and cost of virgin carbon fiber composites. This [...] Read more.
Recycling of carbon fibers enables a sustainable feedstock for industrial applications of high-performance composite materials. This allows light weighting with recycled carbon fibers due to their superior mechanical properties while reducing the high embodied energy and cost of virgin carbon fiber composites. This study optimizes a pyrolysis cycle for fiber recovery of an aerospace-grade thermoset prepreg and a cleaning (oxidation) step to minimize fiber degradation and left-over resin residue, enabling dispersion and alignment of the recycled, discontinuous fibers in the Tailorable Universal Feedstock for Forming alignment process. The study balances the influence of the optimized thermal cycle (pyrolysis + oxidation step) on recycled carbon fiber strength retention with the ability to disperse at the filament level to create aligned, recycled carbon fiber composite samples with high fiber volume fraction. The optimized thermal cycle for efficient fiber recovery applied a pyrolysis step at 500 °C for 4 h in an inert gas environment and an additional oxidation step at the same temperature for 100 min. This resulted in ~20% strength degradation of the fiber compared to the virgin fiber. The processed recycled composite achieved 44% fiber volume fraction with full modulus translation (~128 GPa) compared to the virgin continuous composite with strength translation (~870 MPa), reaching ~50%. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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20 pages, 1068 KiB  
Article
FTIR-Based Microplastic Classification: A Comprehensive Study on Normalization and ML Techniques
by Octavio Villegas-Camacho, Iván Francisco-Valencia, Roberto Alejo-Eleuterio, Everardo Efrén Granda-Gutiérrez, Sonia Martínez-Gallegos and Daniel Villanueva-Vásquez
Recycling 2025, 10(2), 46; https://doi.org/10.3390/recycling10020046 - 18 Mar 2025
Viewed by 943
Abstract
This study examines the potential of machine learning (ML) and deep learning (DL) techniques for classifying microplastics using Fourier-transform infrared (FTIR) spectroscopy. Six commonly used industrial plastics (PET, HDPE, PVC, LDPE, PP, and PS) were analyzed. A significant contribution of this research is [...] Read more.
This study examines the potential of machine learning (ML) and deep learning (DL) techniques for classifying microplastics using Fourier-transform infrared (FTIR) spectroscopy. Six commonly used industrial plastics (PET, HDPE, PVC, LDPE, PP, and PS) were analyzed. A significant contribution of this research is the use of broader and more varied spectral ranges than those typically reported in the state of the art. Furthermore, the impact of different normalization techniques (Min-Max, Max-Abs, Sum of Squares, and Z-Score) on classification accuracy was evaluated. The study assessed the performance of ML algorithms, such as k-nearest neighbors (k-NN), support vector machines (SVM), naive Bayes (NB), random forest (RF), and artificial neural networks architectures (including convolutional neural networks (CNNs) and multilayer perceptrons (MLPs)). Models were trained and validated using the FTIR-PLASTIC-c4 dataset with a 10-fold cross-validation approach to ensure robustness. The results showed that Z-score normalization significantly improved stability and generalization across most models, with CNN, MLP, and RF achieving near-perfect values in accuracy, precision, recall, and F1-score. In contrast, the sum of squares normalization was less effective, particularly for CNNs, due to its sensitivity to scale and data distribution. Notably, naive Bayes consistently underperformed because of its limitations in analyzing complex spectral data. The findings highlight the effectiveness of FTIR spectra with broad and variable ranges for the automated classification of microplastics using ML techniques, along with appropriate normalization methods. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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17 pages, 1971 KiB  
Article
Evaluating Plastic Waste Management Strategies: Logistic Regression Insights on Pyrolysis vs. Recycling
by Dimitrios-Aristotelis Koumpakis, Christos Vlachokostas, Apostolos Tsakirakis and Savvas Petridis
Recycling 2025, 10(2), 33; https://doi.org/10.3390/recycling10020033 - 1 Mar 2025
Viewed by 1253
Abstract
The global plastic production total has risen to more than 400 million tons per year; this number is mainly driven by industrial appliances. In the EU, where the annual production is about 30 million tons, only 32% of plastic waste is recycled. Therefore, [...] Read more.
The global plastic production total has risen to more than 400 million tons per year; this number is mainly driven by industrial appliances. In the EU, where the annual production is about 30 million tons, only 32% of plastic waste is recycled. Therefore, a need for a robust and efficient waste management strategy has emerged. This study will introduce a novel logistic regression-based decision-making framework that focuses on the environment and the economy while also considering energy intensity and logistics. These factors reflect the use of Life Cycle Assessment (LCA) in this study, which is an approach that determines the selection of waste management strategies across different European countries. This study introduces a model with 94% sensitivity and 97% overall accuracy in order to compare pyrolysis and plastic waste recycling management methods. One of the main findings is the fact that pyrolysis demonstrated a maximum conversion efficiency of 88%; in comparison, the conversion efficiency for recycling was approximately 58%. Pyrolysis also generates by-products, such as syngas and pyrolytic oil, which are valuable. To conclude, this study is a tool for policymakers and industry leaders, so that they can make sustainable waste management decisions with data-driven and evidence-based reasoning. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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19 pages, 2055 KiB  
Article
Towards a Circular Solution for Healthcare Plastic Waste: Understanding the Legal, Operational, and Technological Landscape
by Bharghav Ganesh, Sayyed Shoaib-ul-Hasan, Iliass Temsamani and Niloufar Salehi
Recycling 2025, 10(1), 27; https://doi.org/10.3390/recycling10010027 - 14 Feb 2025
Viewed by 1035
Abstract
Plastic waste poses a critical challenge in the healthcare sector due to its predominant reliance on a linear “make-use-dispose” model, where plastics are typically incinerated or landfilled. This study examines Swedish healthcare waste management practices, encompassing Swedish and EU regulatory frameworks, hospital protocols, [...] Read more.
Plastic waste poses a critical challenge in the healthcare sector due to its predominant reliance on a linear “make-use-dispose” model, where plastics are typically incinerated or landfilled. This study examines Swedish healthcare waste management practices, encompassing Swedish and EU regulatory frameworks, hospital protocols, disinfection methods, and recycling processes. A key barrier to recycling healthcare plastic waste (HCPW) is the uncertainty surrounding effective decontamination. To overcome this, the paper proposes a circular solution involving on-site microwave-assisted disinfection and shredding, followed by chemical recycling through pyrolysis. This approach considers operational, legal, and technological landscapes and underscores the need for a multidisciplinary solution to enable the transition. This paper also presents a stakeholder collaboration and value capture matrix, identifying the shared value in collaboration among key stakeholders, including hospitals and healthcare service providers, on-site disinfection machine manufacturers, waste management firms, and chemical recycling companies, to advance recycling and foster a circular economy for HCPW. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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16 pages, 1323 KiB  
Article
Recycling of Bulk Polyamide 6 by Dissolution-Precipitation in CaCl2-EtOH-H2O Mixtures
by Ruben Goldhahn, Ann-Joelle Minor, Liisa Rihko-Struckmann, Siew-Wan Ohl, Patricia Pfeiffer, Claus-Dieter Ohl and Kai Sundmacher
Recycling 2025, 10(1), 5; https://doi.org/10.3390/recycling10010005 - 3 Jan 2025
Viewed by 1402
Abstract
To address the problems of virgin plastic production from fossil resources and the growing amount of plastic waste, a rapid transition to a circular economy is being pursued. The separation of mixed plastics into pure fractions is of paramount importance for promoting recycling [...] Read more.
To address the problems of virgin plastic production from fossil resources and the growing amount of plastic waste, a rapid transition to a circular economy is being pursued. The separation of mixed plastics into pure fractions is of paramount importance for promoting recycling and preventing downcycling. In this study, experimental parameters were determined for the selective bulk dissolution of polyamide 6 (PA 6) filaments (1.75 mm diameter, 1 cm length) in CaCl2-EtOH-H2O mixtures (CEW) at 75 °C. These parameters included the energy supply mode, dissolution time, CEW composition and CEW:PA mass ratio. Compared with energy supply by microwaves, energy supply by ultrasound improved the yield of dissolved and recovered PA 6 after 5 h from 31% to 52%. In total, the yield of PA 6 after 3 h of bulk dissolution increased from 18% to 69% when the energy supply mode was changed from microwave to ultrasound and the H2O:EtOH molar ratio of CEW was increased from 0.40 to 1.33 while maintaining an optimal CEW:PA mass ratio of 8.5. Additionally, master plot analysis suggested that dissolution under microwave energy supply followed a contracting cylinder model, whereas dissolution under ultrasonic energy supply aligned with a 2D diffusion or third-order kinetic model. Microscopic observations suggested that, in the case of ultrasonic energy supply, oscillating bubbles on the particle surface enhanced the dissolution rate of PA 6 filaments in CEW. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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31 pages, 4905 KiB  
Article
Multi-Domain Assessment of Thermomechanical Recycling Based on Bio-Based and Petroleum-Based Additively Manufactured Components
by Niko Nagengast, Nicolas Mandel, Christian Bay, Frank Döpper, Christian Neuber, Hans-Werner Schmidt, Clara Usma-Mansfield and Franz Konstantin Fuss
Recycling 2025, 10(1), 3; https://doi.org/10.3390/recycling10010003 - 2 Jan 2025
Viewed by 915
Abstract
The surge in global population growth and the escalating demand for social and economic prosperity present formidable challenges in the 21st century. However, asserting the sustainability of some ecological impact reduction initiatives, such as recycling, requires a comprehensive evaluation within various domains, including [...] Read more.
The surge in global population growth and the escalating demand for social and economic prosperity present formidable challenges in the 21st century. However, asserting the sustainability of some ecological impact reduction initiatives, such as recycling, requires a comprehensive evaluation within various domains, including performance, ecology, and economics, and contemporary advancements in integrating quantitative assessments of material and manufacturing properties, coupled with mathematical decision-making approaches, contribute to mitigating subjectivity in determining the efficiency of recycling. This paper implements a robust multi-criteria decision-making (MCDM) approach to address the complexities of recycling, validating its implementation and effectiveness through a case study. The focus is set on the application of bio-based polylactic acid (PLA) and petroleum-based polypropylene (PP) additively manufactured (AM) parts produced through Fused Filament Fabrication (an approach to ecology/performance domains). The work introduces a cost analysis focusing on calculating thermomechanical recycling within the economic domain. The well-known Analytical Hierarchical Process (AHP) provides a structured framework for decision-making (the ecological impact domain) with the focus being on application. The assessment or recycling viability, encompassing AHP calculations, preprocessing, and supplementary tools, is provided by developing an open-source software tool for practitioners in the field of material science and manufacturing. The results indicate a preference for industrial-scaled recycling over virgin or lab-recycled manufacturing, particularly for petroleum-based polypropylene. The versatility and simple utilization of the software tool allow seamless integration for diverse use cases involving different materials and processes. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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12 pages, 1378 KiB  
Article
Effects of an Inertization System on Waste Plastic Pyrolysis in a Fixed Bed Reactor
by Saša Papuga, Stefano Vecchio Ciprioti, Milica Djurdjevic and Aleksandra Kolundzija
Recycling 2025, 10(1), 2; https://doi.org/10.3390/recycling10010002 - 1 Jan 2025
Viewed by 1024
Abstract
This paper reports the results of a study on the significance of the inertization system configuration of a laboratory-scale fixed bed batch reactor with regard to the yield of pyrolysis oil and reactor conversion. Two typical reactor inertization systems were investigated depending on [...] Read more.
This paper reports the results of a study on the significance of the inertization system configuration of a laboratory-scale fixed bed batch reactor with regard to the yield of pyrolysis oil and reactor conversion. Two typical reactor inertization systems were investigated depending on whether the carrier gas (nitrogen in this study) was added from the top or from the bottom of the reactor. Polypropylene (PP) packaging waste (100 g) was used as a model sample. A factorial experimental design was adopted for one categorical parameter, the arrangement of parts of the reactor inertization system. All experiments were conducted at 475 °C, with a carrier gas flow rate of 0.1 L/min and a reaction time of 90 min. Statistical analysis and processing of the results showed that the configuration of the inertization system had a remarkable impact on the pyrolysis oil and gas yield, while its impact on the overall reactor conversion was negligible. When applying the two observed methods of reactor inertization, the average yields of pyrolysis oil and gas differed by 1.7% and 1.8%, respectively. All of the applied statistical treatments had a significance level of 0.05, i.e., there was only a 5% chance of incorrectly rejecting the hypothesis of equality of arithmetic means of pyrolysis yields when the two different methods of reactor inertization were applied. The explanation of this behavior is attributed to the temperature change inside the reactor, which shows that this particular fixed bed reactor suffers from local overheating in its middle part. Local overheating of the middle part of the reactor is more pronounced in the case of inerting the reactor from the bottom, which leads to greater excessive cracking of volatile products compared to the mode of inerting the reactor from the top part and thus greater formation of non-condensable gases, i.e., a reduction in the yield of pyrolytic oil. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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12 pages, 1684 KiB  
Article
Effect of Joining Mechanism on the Mechanical Recycling of Polymer–Metal Composite Parts
by Sandra Boekhoff, Harald Zetzener and Arno Kwade
Recycling 2024, 9(6), 106; https://doi.org/10.3390/recycling9060106 - 4 Nov 2024
Viewed by 1685
Abstract
In order to be able to recycle composite components made of polymer and metal, which are used in the automotive industry, the joints must be broken. The success of the separation is influenced by the stress and also by the joining mechanism between [...] Read more.
In order to be able to recycle composite components made of polymer and metal, which are used in the automotive industry, the joints must be broken. The success of the separation is influenced by the stress and also by the joining mechanism between the polymer and the metal. Here, force-fit and form-fit connected components are produced and crushed in a rotor impact mill with two different rotors. The results show that the crushing results differ significantly for the different rotors and for the various joining processes. In short, the hammer-type rotor provides much finer and better-separated fragments and the force-fit joints enable a better separation of metal and polymers. The additional cooling of the samples also changes the result in a way, where deep cooling significantly improves the separation of the metal and the polymer. Different types of polymers also led to a different separation result with both rotors. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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18 pages, 5460 KiB  
Article
GC/MS Screening of Substances Released from Post-Consumer Recycled HDPE Pellets into 95% Ethanol: Reproducibility and Variation between Production Batches
by Melanie Brandt, Jens-Peter Vietzke, Dennis Bankmann and Heiner Gers-Barlag
Recycling 2024, 9(5), 101; https://doi.org/10.3390/recycling9050101 - 16 Oct 2024
Viewed by 2337
Abstract
The use of post-consumer recycled (PCR) plastic materials in sensitive packaging applications, such as for cosmetic products and detergents, requires a clear understanding of the identities and quantities of chemical substances, which they may release into packed products. With many potential sources of [...] Read more.
The use of post-consumer recycled (PCR) plastic materials in sensitive packaging applications, such as for cosmetic products and detergents, requires a clear understanding of the identities and quantities of chemical substances, which they may release into packed products. With many potential sources of and thus different types of potentially releasable substances, a reliable non-targeted screening method is required to assess these materials. Such a method should be readily applicable in industrial practice and provide a realistic estimation of substance release. This investigation focused on the use of gas chromatography/coupled mass spectrometry (GC/MS) to analyze substances, which recycled HDPE (rHDPE) plastic pellets release into 95% ethanol under accelerated testing conditions. The results of the repeated testing of reference samples clearly demonstrated the good reproducibility of the described methodology, with standard deviations of repeated determinations of the total released substance amounts of 6.8–8.1%. The application to several production batches of three commercial rHDPE grades additionally demonstrated that the batch-to-batch variation of substances which rHDPE materials release can be confined to less than 10% of variation of the total detectable substance amount. The described methodology is therefore seen as a pragmatic, repeatable assessment of recycled HDPE plastic batches with a view to substance release. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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20 pages, 1980 KiB  
Article
Mechanical Recycling of PET Multi-Layer Post-Consumer Packaging: Effects of Impurity Content
by Giusy Santomasi, Francesco Todaro, Andrea Petrella, Michele Notarnicola and Eggo Ulphard Thoden van Velzen
Recycling 2024, 9(5), 93; https://doi.org/10.3390/recycling9050093 - 8 Oct 2024
Cited by 2 | Viewed by 4000
Abstract
The recycling of PET trays is highly challenging. The aim of this paper was to investigate the issues related to the mechanical recycling process and, the correlation between feedstock composition and the quality of the produced rPET. Four feedstocks with different degrees of [...] Read more.
The recycling of PET trays is highly challenging. The aim of this paper was to investigate the issues related to the mechanical recycling process and, the correlation between feedstock composition and the quality of the produced rPET. Four feedstocks with different degrees of impurity were mechanically recycled at a laboratory pilot scale. The optical and thermal properties of the rPET products were examined to determine the quality and to seek relations with the starting level of impurities. The final products of the PET trays’ mechanical recycling were found to be affected by the presence of impurities (organics) and multi-material (non-PET) elements in the feedstocks. The rPET products crystallised faster for contaminated feedstocks showed lower molecular mass and higher yellow index values due to thermal degradation. Yellowing is a crucial parameter in assessing the thermal degradation of rPET. Injection moulded samples corresponding to higher contamination levels, reported values of Yellow Index equal to 179 and 177 compared to 15 of mono-PET sample. The intrinsic viscosity decreased from 0.60 dL/g to just above 0.30 dL/g, and losses were more significant for soiled or multi-material feedstocks. A method of improving the final quality would involve the purification of the starting feedstock from impurities. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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17 pages, 567 KiB  
Article
Closing the Loop between Plastic Waste Management and Energy Cogeneration: An Innovative Design for a Flexible Pyrolysis Small-Scale Unit
by Dimitrios-Aristotelis Koumpakis, Alexandra V. Michailidou, Christos Vlachokostas and Christos Mertzanakis
Recycling 2024, 9(5), 92; https://doi.org/10.3390/recycling9050092 - 5 Oct 2024
Cited by 1 | Viewed by 3316
Abstract
This study proposes a simplified unit that can be employed in an industrial facility for the utilization of its own abundant plastic waste, primarily from discarded packaging, to achieve full or partial energy autonomy. By converting this waste into synthetic pyrolysis oil equivalent [...] Read more.
This study proposes a simplified unit that can be employed in an industrial facility for the utilization of its own abundant plastic waste, primarily from discarded packaging, to achieve full or partial energy autonomy. By converting this waste into synthetic pyrolysis oil equivalent to 91,500 L, the industry can power a combined heat and power generation unit. The proposed unit was designed with a focus on maintaining high temperatures efficiently while minimizing oxygen exposure to protect the integrity of hydrocarbons until they transform into new compounds. Pyrolysis stands as a foundational procedure, paving the way for subsequent thermochemical transformations such as combustion and gasification. This study delves into the factors affecting pyrolysis and presents analytically the mathematical formulations and relevant calculations in order to effectively design and apply a real-life system. On this basis, fuels from plastic waste can be produced, suitable for utilization in typical equipment meant to produce heat, estimated for six months’ operation and 800 MWh of electricity. This study enhances the transition towards a more circular and resource-efficient economy with technologies that unlock the latent energy contained within the discarded matter. Additionally, it demonstrates the feasibility of a moderate investment in a co-generation system for industries utilizing 568 tonnes of plastic waste per year. The design and accurate calculations of this study highlight the theoretical potential of this technology, promoting environmental sustainability and resource conservation. Full article
(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)
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