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Keywords = PET bottle recycling

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36 pages, 4108 KiB  
Article
Innovative AIoT Solutions for PET Waste Collection in the Circular Economy Towards a Sustainable Future
by Cosmina-Mihaela Rosca and Adrian Stancu
Appl. Sci. 2025, 15(13), 7353; https://doi.org/10.3390/app15137353 - 30 Jun 2025
Viewed by 438
Abstract
Recycling plastic waste has emerged as one of the most pressing environmental challenges of the 21st century. One of the biggest challenges in polyethylene terephthalate (PET) recycling is the requirement to return bottles in their original, undeformed state. This necessitates storing large volumes [...] Read more.
Recycling plastic waste has emerged as one of the most pressing environmental challenges of the 21st century. One of the biggest challenges in polyethylene terephthalate (PET) recycling is the requirement to return bottles in their original, undeformed state. This necessitates storing large volumes of waste and takes up substantial space. Therefore, this paper seeks to address this issue and introduces a novel AIoT-based infrastructure that integrates the PET Bottle Identification Algorithm (PBIA), which can accurately recognize bottles regardless of color or condition and distinguish them from other waste. A detailed study of Azure Custom Vision services for PET bottle identification is conducted, evaluating its object recognition capabilities and overall performance within an intelligent waste management framework. A key contribution of this work is the development of the Algorithm for Citizens’ Trust Level by Recycling (ACTLR), which assigns trust levels to individuals based on their recycling behavior. This paper also details the development of a cost-effective prototype of the AIoT system, demonstrating its low-cost feasibility for real-world implementation, using the Asus Tinker Board as the primary hardware. The software application is designed to monitor the collection process across multiple recycling points, offering Microsoft Azure cloud-hosted data and insights. The experimental results demonstrate the feasibility of integrating this prototype on a large scale at minimal cost. Moreover, the algorithm integrates the allocation points for proper recycling and penalizes fraudulent activities. This innovation has the potential to streamline the recycling process, reduce logistical burdens, and significantly improve public participation by making it more convenient to store and return used plastic bottles. Full article
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25 pages, 2592 KiB  
Article
An Advanced CNN-Based Framework for the Automated Detection of Uncovered PET in Recycling Streams
by Adnan Miski and Omer Bafail
Polymers 2025, 17(13), 1736; https://doi.org/10.3390/polym17131736 - 22 Jun 2025
Viewed by 717
Abstract
Contamination in recycling streams represents one of the most pervasive challenges confronting material recovery facilities (MRFs) globally. Among the various contamination sources in recycling streams, liquid contamination from PET bottles presents particularly severe challenges due to its capacity to spread throughout commingled materials. [...] Read more.
Contamination in recycling streams represents one of the most pervasive challenges confronting material recovery facilities (MRFs) globally. Among the various contamination sources in recycling streams, liquid contamination from PET bottles presents particularly severe challenges due to its capacity to spread throughout commingled materials. Object detection using neural networks enables detection at the collection stage of single or mixed recycling streams, allowing for targeted application in the early stage of the recycling cycle. YOLO (you only look once) models and other object detection models are beneficial due to their speed and accuracy in detecting multiple objects at once. This study aimed to design a model to detect contaminated PET bottles in real time. Several YOLO variations and model sizes were trained on a custom dataset with 7130 images. YOLOv8l achieved the highest performance, with mAP@0.5:0.95, mAP@0.5, precision, recall, and F1 score values of 89.7%, 93%, 89%, 88%, and 88%, respectively. Full article
(This article belongs to the Special Issue Polymer Composites in Municipal Solid Waste Landfills)
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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 3384
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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19 pages, 6562 KiB  
Article
Rethinking PE-HD Bottle Recycling—Impacts of Reducing Design Variety
by Lorenz P. Bichler, Thomas Koch, Nina Krempl and Vasiliki-Maria Archodoulaki
Recycling 2025, 10(3), 93; https://doi.org/10.3390/recycling10030093 - 8 May 2025
Viewed by 1595
Abstract
As the severe environmental impacts of plastic pollution demand determined action, the European Union (EU) has included recycling at the core of its policies. Consequently, evolving jurisdiction now aims to achieve a recycling rate of 65% for non-PET plastic bottles by 2040. However, [...] Read more.
As the severe environmental impacts of plastic pollution demand determined action, the European Union (EU) has included recycling at the core of its policies. Consequently, evolving jurisdiction now aims to achieve a recycling rate of 65% for non-PET plastic bottles by 2040. However, the widespread use of post-consumer high-density polyethylene (rPE-HD) recyclates in household chemical containers is still limited by PP contamination, poor mechanical properties, and low environmental stress cracking resistance (ESCR). Although previous studies have explored the improvement of regranulate properties through additives, few have examined whether reducing the variety of extrusion blow-moulded PE-HD packaging could offer similar benefits. Therefore, two sorted fractions of rPE-HD hollow bodies were processed into regranulates under industrial conditions, including hot washing, extrusion, and deodorisation. Subsequently, both materials underwent comprehensive characterisation regarding their composition and performance. The opaque material, which was sourced from milk bottles in the UK, exhibited greater homogeneity with minor impurities, leading to improved ductility and melt strain hardening at moderate strain rates compared to the mixed material stream, which contained approximately 2.5% PP contamination. However, both rPE-HD recyclates exhibited similar short-term creep behaviour, relatively low strain hardening moduli, and were almost devoid of inorganic particles. Considering the sum of the investigated properties, melt blending with suitable virgin material is likely one of the most effective options to maximise regranulate utilisation in hollow bodies, followed by recycling-oriented packaging design (e.g., for efficient sorting), and the employment of advanced sorting technology. Full article
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19 pages, 3613 KiB  
Article
Ecofriendly Degradation of PET via Neutral Hydrolysis: Degradation Mechanism and Green Chemistry Metrics
by Adhithiya Venkatachalapati Thulasiraman, Arun Krishna Vuppaladadiyam, Ibrahim Gbolahan Hakeem, Kamrun Nahar, Manoj Kumar Jena and Kalpit Shah
Environments 2025, 12(4), 127; https://doi.org/10.3390/environments12040127 - 18 Apr 2025
Viewed by 1450
Abstract
Waste polyethylene terephthalate (PET) bottles represent 12% of global plastic waste; however, only 9% are recycled. Hydrothermal processing presents the opportunity to upcycle waste PET into its monomers, particularly, terephthalic acid (TPA). In this study, post-consumer PET sparkling water bottles were neutrally hydrolysed [...] Read more.
Waste polyethylene terephthalate (PET) bottles represent 12% of global plastic waste; however, only 9% are recycled. Hydrothermal processing presents the opportunity to upcycle waste PET into its monomers, particularly, terephthalic acid (TPA). In this study, post-consumer PET sparkling water bottles were neutrally hydrolysed via a hydrothermal process operating within a temperature range of 220–270 °C, a residence time of 30–90 min, and autogenous pressure of 25–90 bar. Under these conditions, the TPA yield varied between 7.34 and 81.05%, and the maximum TPA yield was obtained at 250 °C, 90 min, and 40 bar. The process temperature had a more profound impact on the PET conversion and TPA yield than the residence time. The values of the environmental factor (EF) were found to be 0.017–0.106, which were comparable to those of bulk chemicals (EF < 1). With the chosen operating conditions, the environmental energy impact (EEI) of TPA production was estimated to be 5.29 × 104 °C min. The findings demonstrate that neutral hydrolysis is a feasible approach for converting PET polymers into monomers under mild environmental conditions. In addition, a GCMS analysis of the aqueous-phase product revealed a notable increase in the secondary degradation products of TPA, such as benzoic acid, rising from 66.4% to 75.7% as the process temperature increased from 220 °C to 270 °C. The degradation mechanisms of PET were found to be decarboxylation, dehydration, and oxidation. The dominant mechanism was found to be a decarboxylation reaction. Full article
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20 pages, 1750 KiB  
Review
Post-Consumer Recycled PET: A Comprehensive Review of Food and Beverage Packaging Safety in Brazil
by Carolina Soares Marcelino, Vitor Emanuel de Souza Gomes and Luís Marangoni Júnior
Polymers 2025, 17(5), 594; https://doi.org/10.3390/polym17050594 - 24 Feb 2025
Cited by 2 | Viewed by 2846
Abstract
Polyethylene terephthalate (PET) is widely used in the food and beverage packaging sector due to its chemical and mechanical properties. Although PET is a fossil-based polymer, its recyclability significantly contributes to reducing the environmental impacts caused by excessive plastic consumption. However, the growing [...] Read more.
Polyethylene terephthalate (PET) is widely used in the food and beverage packaging sector due to its chemical and mechanical properties. Although PET is a fossil-based polymer, its recyclability significantly contributes to reducing the environmental impacts caused by excessive plastic consumption. However, the growing demand for post-consumer recycled PET (PET-PCR) food packaging has raised concerns about the efficiency of decontamination processes involved in recycling this material. This review initially addresses PET synthesis processes, highlighting injection stretch blow molding as the predominant technique for packaging production. It then discusses reverse logistics as a strategy to promote sustainability through the recovery of post-consumer packaging, such as plastic bottles. This review examines mechanical and chemical recycling methods used in PET-PCR production, food safety requirements including positive lists of permitted substances, contaminant migration limits, non-intentionally added substances (NIASs), and updated criteria for the National Health Surveillance Agency (ANVISA) of food-grade PET-PCR resins. Finally, the review explores future prospects for using PET-PCR in the food and beverage packaging sector, assessing its environmental impacts and potential technological advancements to enhance its sustainability and safety. Full article
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11 pages, 2395 KiB  
Proceeding Paper
Re-Engineering and Initial Computational Study on Non-Organic Waste and Hazardous Waste Incinerators
by Muhammad Iqsal Oktavani, Sarjito and Agus Yulianto
Eng. Proc. 2025, 84(1), 54; https://doi.org/10.3390/engproc2025084054 - 11 Feb 2025
Viewed by 493
Abstract
Unmanaged waste can cause environmental pollution, as well as hygiene and health problems. Sitimulyo Piyungan Bantul at the coordinates of −7.86409, 110.42888 was established in 1994 and is the final waste repository area in Yogyakarta, and it is now completely closed; consequently, causing [...] Read more.
Unmanaged waste can cause environmental pollution, as well as hygiene and health problems. Sitimulyo Piyungan Bantul at the coordinates of −7.86409, 110.42888 was established in 1994 and is the final waste repository area in Yogyakarta, and it is now completely closed; consequently, causing joblessness in the surrounding community. There are activities that can be undertaken to recycle waste such as managing rubbish. Waste can be divided into four categories scrapping, composting, and producing maggot food. However, unmanaged and useful waste, namely, inorganic and hazardous waste, remains a big problem. This research work aims to solve the problem by re-engineering and making an initial simulation using computational fluid dynamics of an incinerator to complete unmanaged inorganic and hazardous rubbish. The incinerator was produced to process non-organic solid and medical waste, which should be combusted at temperatures higher than 800 °C to reduce combustible rubbish that can no longer be recycled, and toxic chemicals, to kill bacteria and viruses. The main incinerator frame is made of an iron elbow. Construction of the incinerator is divided into the chamber, recirculation zone, and chimneys. The wall of the incinerator machine is made of refractory stone and insulators. To measure and control the temperature, thermocouples and a thermocontrol are placed at the inner wall of the incinerator machine. The function of the incinerator machine was tested, and it ran normally. Initial operation of an incinerator for solid hazardous waste such as infusion bottles, pets, glass bottles, pampers, and expired medicines was undertaken. The performance showed that the achieved temperature was 705 °C during the process of the operation, and all of the hazardous waste became ash and the recycled material became a paving block that is economically worthwhile. Hence, the incinerator can be operated as a household industrial tool for a solid medical waste processing apparatus. An initial computational study of the incinerator was also carried out briefly using the student version of commercial software. Full article
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15 pages, 3735 KiB  
Article
Development of Smart Material Identification Equipment for Sustainable Recycling in Future Smart Cities
by Gaku Manago, Tadao Tanabe, Kazuaki Okubo, Tetsuo Sasaki and Jeongsoo Yu
Polymers 2025, 17(4), 462; https://doi.org/10.3390/polym17040462 - 10 Feb 2025
Cited by 2 | Viewed by 1258
Abstract
Waste recycling is critical for the development of smart cities. Local authorities are responsible for the disposal of waste plastics, but the extent of material recycling is insufficient, and much of the waste generated is incinerated. This conflicts with the trend of decarbonisation. [...] Read more.
Waste recycling is critical for the development of smart cities. Local authorities are responsible for the disposal of waste plastics, but the extent of material recycling is insufficient, and much of the waste generated is incinerated. This conflicts with the trend of decarbonisation. Of particular note are the effects of the COVID-19 pandemic, during and after which large quantities of waste plastics, such as plastic containers and packaging, were generated. In order to develop a sustainable smart city, we need an effective scheme where we can separate materials before they are taken to the local authorities and recyclers. In other words, if material identification can be performed at the place of disposal, the burden on recyclers can be reduced, and a smart city can be created. In this study, we developed and demonstrated smart material identification equipment for waste plastic materials made of PET, PS, PP, and PE using GaP THz and sub-THz wavelengths. As basic information, we used a GaP terahertz spectrometer to sweep frequencies from 0.5 THz to 7 THz and measure the spectrum, and the transmittance rate was measured using the sub-THz device. The sub-THz device used a specific frequency below 0.14 THz. This is a smaller, more carriable, and less expensive semiconductor electronic device than the GaP. Moreover, the sub-terahertz device used in the development of this equipment is compact, harmless to the human body, and can be used in public environments. As a result, smart equipment was developed and tested in places such as supermarkets, office entrances, and canteens. The identification of materials can facilitate material recycling. In this study, we found that measuring devices designed to identify the PET and PS components of transparent containers and packaging plastics, and the PP and PE components of PET bottle caps, could effectively identify molecular weights, demonstrating new possibilities for waste management and recycling systems in smart cities. With the ability to collect and analyse data, these devices can be powerful tools for pre-sorting. Full article
(This article belongs to the Special Issue Polymer Composites in Municipal Solid Waste Landfills)
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19 pages, 11551 KiB  
Article
Mechanical Performance of rPET Filament Obtained by Thermal Drawing for FFF Additive Manufacturing
by Pedro Pires, Martim Lima de Aguiar and André Costa Vieira
J. Manuf. Mater. Process. 2025, 9(1), 26; https://doi.org/10.3390/jmmp9010026 - 16 Jan 2025
Cited by 2 | Viewed by 2156
Abstract
The growing production of plastic waste and its recycling, from a circular economy perspective, faces challenges in finding solutions that are easy to implement, cheap in labor and energy during recycling, and locally implementable to avoid transportation. This work developed and validated a [...] Read more.
The growing production of plastic waste and its recycling, from a circular economy perspective, faces challenges in finding solutions that are easy to implement, cheap in labor and energy during recycling, and locally implementable to avoid transportation. This work developed and validated a methodology to address these challenges. Designed for small-scale use at home or in schools following a Do It Yourself (DIY) approach, it transforms water bottles into plastic strips, which, after passing through an extruder nozzle, become filaments with a diameter of 1.75 mm. These can replace commercially available thermoplastic filaments. Specimens produced by additive manufacturing with recycled PET (rPET) and commercial PETG showed similar mechanical properties and can serve as alternatives to commercial PETG. PETG shows higher strength (30 MPa) compared to rPET (24 MPa), a slightly higher Young’s modulus of 1.44 GPa versus 1.43 GPa, and greater strain at failure with 0.03 mm/mm against 0.02 mm/mm, making it stiffer and more ductile. This simple and widely applicable local solution may absorb a considerable amount of bottle waste, offering an economical, sustainable alternative to commercial filaments. Full article
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17 pages, 2765 KiB  
Article
Use of Hybrid Flame Retardants in Chemically Foamed rPET Blends
by Veronika Anna Szabó, Sándor Kálmán Jakab, András Kovács, Tamara Zsuzsanna Böcz and Gábor Dogossy
Crystals 2025, 15(1), 80; https://doi.org/10.3390/cryst15010080 - 15 Jan 2025
Cited by 1 | Viewed by 878
Abstract
The foamed structure of recycled polyethylene-terephthalate (rPET) is a promising solution for industrial applications; however, the remedy for its inherent melt-dripping property is still a challenging topic. In our research, we were able to improve the flame retardancy of the endothermic–exothermic hybrid rPET [...] Read more.
The foamed structure of recycled polyethylene-terephthalate (rPET) is a promising solution for industrial applications; however, the remedy for its inherent melt-dripping property is still a challenging topic. In our research, we were able to improve the flame retardancy of the endothermic–exothermic hybrid rPET foam by adding a different mixture of flame retardants to the formula. Three different kinds of halogen-free flame retardant agents were used: ammonium polyphosphate-based Exolit AP 422 (AP), organic aluminum phosphate in the form of Exolit OP 1240 (OP), and Budit 342 containing melamine polyphosphate (MPP). The hybrid flame retardant mixture, by combining the swelling and charring mechanism, increased the flame retardancy of the samples. The sample made with 15 phr OP and 5 phr MPP displayed outstanding performance, where five samples were capable of self-extinguishing in 5 s, while only slightly decreasing the tensile and flexural strength properties and simultaneously increasing the Young and flexural modulus compared to the reference sample. The addition of MPP reduced the porosity in many cases, while preventing cell coalescence. Our results prove that the hybrid flame retardant agent frameworks efficiently increase the flame retardancy of rPET foams, facilitating their application in industrial sectors such as the aerospace, packaging, renewable energy, and automotive industries to realize sustainability goals. The utilization of halogen-free flame retardants is beneficial for better air quality, reducing toxic gas and smoke emissions. Full article
(This article belongs to the Section Macromolecular Crystals)
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54 pages, 16154 KiB  
Article
Effect of rPET Content and Preform Heating/Cooling Conditions in the Stretch Blow Molding Process on Microcavitation and Solid-State Post-Condensation of vPET-rPET Blend: Part II—Statistical Analysis and Interpretation of Tests
by Paweł Wawrzyniak, Waldemar Karaszewski, Marta Safandowska and Rafał Idczak
Materials 2025, 18(1), 36; https://doi.org/10.3390/ma18010036 - 25 Dec 2024
Viewed by 793
Abstract
This research explores how varying proportions of virgin polyethylene terephthalate (vPET) and recycled polyethylene terephthalate (rPET) in vPET-rPET blends, combined with preform thermal conditions during the stretch blow molding (SBM) process, influence PET bottles’ microscopic characteristics. Key metrics such as viscosity, density, crystallinity, [...] Read more.
This research explores how varying proportions of virgin polyethylene terephthalate (vPET) and recycled polyethylene terephthalate (rPET) in vPET-rPET blends, combined with preform thermal conditions during the stretch blow molding (SBM) process, influence PET bottles’ microscopic characteristics. Key metrics such as viscosity, density, crystallinity, amorphous phase relaxation, and microcavitation were assessed using response surface methodology (RSM). Statistical analysis, including Analysis of variance (ANOVA) and its power, supported the interpretation of results. The first part of the work details the experimental design and statistical methods. Positron annihilation lifetime spectroscopy (PALS) and amorphous phase density analysis revealed reduced free volume size, a substantial increase in free volume quantity, and a transformation toward ellipsoidal geometries, highlighting significant structural changes in the material. At the same time, the intrinsic viscosity (IV) and PALS studies indicate that the solid-state post-condensation effect (SSPC) is linked with microcavitation through post-condensation product diffusion. The conclusions, which resulted from the microstructure analysis, affected the material’s mechanical strength and were validated by pressure resistance tests of the bottles. Full article
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15 pages, 1527 KiB  
Article
Decision Analysis Approaches on the Collection Methods of Polyethylene Terephthalate Waste
by Johnson A. Oyewale, Lagouge K. Tartibu and Imhade P. Okokpujie
Recycling 2024, 9(6), 124; https://doi.org/10.3390/recycling9060124 - 13 Dec 2024
Cited by 2 | Viewed by 1030
Abstract
The rising challenge of polyethylene terephthalate (PET) waste necessitates efficient collection methods to mitigate environmental impacts. The Analytic Hierarchy Process (AHP) is one of the Multi-Criteria Decision Analysis (MCDA) approaches utilized in this study. The Technique for Order of Preference by Similarity to [...] Read more.
The rising challenge of polyethylene terephthalate (PET) waste necessitates efficient collection methods to mitigate environmental impacts. The Analytic Hierarchy Process (AHP) is one of the Multi-Criteria Decision Analysis (MCDA) approaches utilized in this study. The Technique for Order of Preference by Similarity to the Ideal Solution (TOPSIS) was used to rank each alternative according to the objective weight that AHP had produced. Also, sensitivity analysis was performed to determine how robust the findings were when considering equal weights and entropy weights to maximize PET waste collection techniques. The alternative achieved the objective of obtaining the best collection method, Threshold Plastic Bottle Waste Collection (Tpbw), out of all the three alternatives considered. Another MCDA approach, VIseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR), was used to compare the results and validate the ranking result achieved by the TOPSIS method. The VIKOR technique’s validation of the TOPSIS approach showed that the outcomes were highly consistent. Data for the study were gathered from the archives of waste management companies on possible practices of plastic waste collection, addressing costs, environmental impacts, social acceptance, feasibility, and efficiency. The findings provide a prioritized framework for enhancing PET waste collection strategies, contributing to sustainable waste management. Many criteria are considered when deciding the best collecting method for PET waste recycling, making it challenging. By using criteria importance, MCDA was applied in this study, and the objective weight of the criteria was determined using the AHP. The five criteria considered in this study are Initial investment cost, operational cost, transportation cost, environmental risk, employment potential, and the objective weights allocated to them. AHP results 0.4952, 0.1997, 0.1565, 0.0870, and 0.0616 are, respectively, determined. Full article
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14 pages, 1604 KiB  
Article
Identification of the Compounds Used in Waste Bottle Caps Using Terahertz Radiation for Sustainable Resource Recycling to Benefit International Cooperation
by Gaku Manago, Kazuaki Okubo, Jeongsoo Yu, Tadao Tanabe and Tetsuo Sasaki
Sustainability 2024, 16(24), 10864; https://doi.org/10.3390/su162410864 - 11 Dec 2024
Cited by 2 | Viewed by 1481
Abstract
In Japan, when people take their waste bottle caps to designated recycling companies, JPY 5/kg is donated to developing countries for polio vaccine dissemination activities. The waste volume of plastic bottles and caps is increasing every year, and there is not a day [...] Read more.
In Japan, when people take their waste bottle caps to designated recycling companies, JPY 5/kg is donated to developing countries for polio vaccine dissemination activities. The waste volume of plastic bottles and caps is increasing every year, and there is not a day that goes by that we do not see more bottles and caps. PET bottles are more easily recycled, as the bottle body is made of a single material. However, bottle caps are made of two different materials (PP and PE), which are difficult to identify perfectly when utilising the existing NIR technology in the recycling field. This is because the designs and colours of PP and PE bottle caps are becoming more diverse, with black and dark-coloured caps being difficult to sort using NIR technology. In addition, their specific gravity is almost the same; therefore, it is difficult to separate them by their water-based specific gravity, which is an approach commonly used by recyclers. Unidentified caps are sent for thermal recycling, which runs counter to the need for decarbonisation. They may also be mixed with identified caps and sold as recycled raw material, resulting in a reduction in the purity of the recycled plastic. If PP and PE caps can be identified using simple technology, it is expected to promote high resource recycling. Therefore, in order to develop such a sorting process, this study proposes a new method for the material identification of waste caps using terahertz waves. Therefore, this research aims to identify a new identification method for waste plastic caps, which has been a challenge both domestically and internationally. Specifically, we describe the limitations of the conventional methods for identifying PP and PE bottle caps according to their weight, specific gravity, and melting point and propose an identification method using terahertz waves, demonstrating its measurement-related merits and high identification accuracy. Full article
(This article belongs to the Section Waste and Recycling)
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18 pages, 7279 KiB  
Article
Optimizing Waste Sorting for Sustainability: An AI-Powered Robotic Solution for Beverage Container Recycling
by Tianhao Cheng, Daiki Kojima, Hao Hu, Hiroshi Onoda and Andante Hadi Pandyaswargo
Sustainability 2024, 16(23), 10155; https://doi.org/10.3390/su162310155 - 21 Nov 2024
Cited by 4 | Viewed by 7073
Abstract
With Japan facing workforce shortages and the need for enhanced recycling systems due to an aging population and increasing environmental challenges, automation in recycling facilities has become a key component for advancing sustainability goals. This study presents the development of an automated sorting [...] Read more.
With Japan facing workforce shortages and the need for enhanced recycling systems due to an aging population and increasing environmental challenges, automation in recycling facilities has become a key component for advancing sustainability goals. This study presents the development of an automated sorting robot to replace manual processes in beverage container recycling, aiming to address environmental, social, and economic sustainability by optimizing resource efficiency and reducing labor demands. Using artificial intelligence (AI) for image recognition and high-speed suction-based grippers, the robot effectively sorts various container types, including PET bottles and clear and colored glass bottles, demonstrating a pathway toward more sustainable waste management practices. The findings indicate that stabilizing items on the sorting line may enhance acquisition success, although clear container detection remains an AI challenge. This research supports the United Nation’s 2030 Agenda for Sustainable Development by advancing recycling technology to improve waste processing efficiency, thus contributing to reduced pollution, resource conservation, and a sustainable recycling infrastructure. Further development of gripper designs to handle deformed or liquid-containing containers is required to enhance the system’s overall sustainability impact in the recycling sector. Full article
(This article belongs to the Section Waste and Recycling)
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20 pages, 22707 KiB  
Article
Utilization of Alternative Fibres Manufactured from Recycled PET Bottles in Concrete Technology for the Improvement of Fire Resistance
by Martin Sedlmajer, Jiří Zach, Jan Bubeník, Jiří Bydžovský and Vítězslav Novák
Polymers 2024, 16(22), 3145; https://doi.org/10.3390/polym16223145 - 12 Nov 2024
Viewed by 1225
Abstract
This article addresses the potential use of secondary polymer fibres in the field of structural concrete as a replacement for primary polymer fibres (mainly polypropylene/PP/), which are used in concrete to enhance its resistance when exposed to high temperatures (especially in the case [...] Read more.
This article addresses the potential use of secondary polymer fibres in the field of structural concrete as a replacement for primary polymer fibres (mainly polypropylene/PP/), which are used in concrete to enhance its resistance when exposed to high temperatures (especially in the case of fire). Research has shown that, in addition to PP fibres, polyethylene terephthalate/PET/fibres, produced by recycling packaging materials (mainly PET bottles), can also be used as an alternative. These fibres are industrially produced in similar dimensions as PP fibres and exhibit similar behaviour when added to fresh and hardened concrete. In terms of their effect on increasing resistance to extreme heat loads, it has been found that despite a higher melting point (Tm), concrete with these fibres demonstrates comparable fire resistance. Therefore, it can be concluded that secondary PET fibres represent an interesting alternative to primary PP fibres from the perspective of a circular economy, and their use in construction represents a potentially valuable application for PET obtained through the collection and recycling of PET packaging materials. Full article
(This article belongs to the Section Polymer Fibers)
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