Recycling

15 pages, 2042 KiB

Open AccessReview

Understanding the State Agency Policies toward RAP Usage in the United States: State of Practice

by Venkatsushanth Revelli and Ayman Ali

Recycling 2023, 8(6), 100; https://doi.org/10.3390/recycling8060100 - 18 Dec 2023

Viewed by 1800

The usage of Reclaimed Asphalt Pavement (RAP) material is a highly resource-conservative, economical, and sustainable practice in flexible pavement construction. However, its usage in hot mix asphalt (HMA) is capped at 25% by the majority of state transportation agencies due to its aging [...] Read more.

The usage of Reclaimed Asphalt Pavement (RAP) material is a highly resource-conservative, economical, and sustainable practice in flexible pavement construction. However, its usage in hot mix asphalt (HMA) is capped at 25% by the majority of state transportation agencies due to its aging levels, stiffness characteristics, and handling capabilities, which may result in early-age pavement distress. Though researchers suggest methodologies to increase RAP usage, higher RAP percentages in asphalt pavements require the support of state authorities. The main objective of this paper is to provide information on how different states design their mixtures with high RAP percentages. This study reviewed the current state of practice of fifty (50) state DOTs in the United States (US) with respect to RAP usage and the factors governing its regulations. It was observed that the limit of RAP content is mainly governed by traffic levels, gradation, binder content, and stiffness contributed by RAP and layer position in a pavement structure. The specifications also suggest that apart from volumetric and performance justification, blending charts, fractionation, and virgin binder grade selection would facilitate the use of higher RAP content in HMA. Controlled mixture design abiding by state specifications can increase the allowable RAP to 40–100%. Full article

(This article belongs to the Special Issue The Use of Recycled Materials to Promote Pavement Sustainability Performance II)

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16 pages, 3499 KiB

Open AccessArticle

Quantification of Plastics in Agriculture and Fisheries at a Regional Scale: A Case Study of South West England

by Maria Eugenia Correa-Cano, Kerry Burton, Markus Mueller, Victor Kouloumpis and Xiaoyu Yan

Recycling 2023, 8(6), 99; https://doi.org/10.3390/recycling8060099 - 14 Dec 2023

Viewed by 1671

Abstract

The use of plastics in agriculture and in fisheries has been vital to increase food production and meet the demands of an increasingly growing global population. However, there are several drawbacks to the use of plastics in these industries. Most plastics used in [...] Read more.

The use of plastics in agriculture and in fisheries has been vital to increase food production and meet the demands of an increasingly growing global population. However, there are several drawbacks to the use of plastics in these industries. Most plastics used in agriculture are disposed of after one single use and are highly susceptible to weathering. Abandoned, lost, or discarded fishing gear cause considerable damage to marine life. Quantification of plastic waste generation in these industries is scarce or non-existent in the case of fisheries. In this paper, we estimate the amount of plastic waste generated by agriculture and fisheries at a regional scale, considering the South West of the UK as a case study. We followed a mass balance approach to quantify the potential plastic waste generated by these industries. We find a generation of 49 kt of plastic waste in agriculture, 47% of which has an unknown fate. We estimate 454 t/year of fishing gear waste, with unclear end-of-life pathways. A detailed quantitative understanding of plastic waste generation per sector at a regional scale is fundamental for tracking plastic waste flows, locating hotspots of pollution, and planning actions to reduce the amount of plastic waste along the chain of end-users. Full article

(This article belongs to the Special Issue Advances in the Recycling, Processing and Use of Plastic Waste II)

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14 pages, 3126 KiB

Open AccessArticle

A Study on the Influence and Mechanism of Temperature and Dosage on PCDD/Fs Adsorption via Coal-Based Activated Carbon

by Peiyue Wang, Jianwen Lai, Xiaoqing Lin, Xiaodong Li and Shuaixi Xu

Recycling 2023, 8(6), 98; https://doi.org/10.3390/recycling8060098 - 11 Dec 2023

Cited by 1 | Viewed by 1530

Abstract

Using a trace polychlorinated-ρ-dibenzodioxins and dibenzofurans (PCDD/Fs) stabilizing generator, an experimental study related to the influence of temperature (150, 165, and 180 °C) and activated carbon (AC) dosage (0.10, 0.15, and 0.20 g) on the adsorption effect of gas-phase PCDD/Fs via coal-based AC [...] Read more.

Using a trace polychlorinated-ρ-dibenzodioxins and dibenzofurans (PCDD/Fs) stabilizing generator, an experimental study related to the influence of temperature (150, 165, and 180 °C) and activated carbon (AC) dosage (0.10, 0.15, and 0.20 g) on the adsorption effect of gas-phase PCDD/Fs via coal-based AC was conducted. Increasing the AC dosage is the most efficient method to improve the PCDD/Fs adsorption efficiency from 65.8% (0.10 g) to 93.0% (0.20 g) at 150 °C in an exponential trend. Both the polychlorinated-ρ-dibenzodioxins (PCDD)/polychlorinated dibenzofurans (PCDF) ratio and the Cl-PCDD/Fs value showed positive correlations, with the AC dosage under the same temperature. Increasing adsorption temperature declined the adsorption capacity of AC, resulting in the exponentially decreased average I-TEQ value adsorbed per gram of AC, from 131.3 ng TEQ/Nm³ (150 °C) to 55.9 ng TEQ/Nm³ (180 °C). The coal-based AC used in this study preferred to adsorb lower chlorinated PCDD/Fs, tetrachlorianted dibenzo-p-dioxin and dibenzofurans (TCDD/Fs), and pentachlorianted dibenzo-p-dioxin and dibenzofurans (PeCDD/Fs) than highly chlorinated PCDD/Fs, heptachlorianted dibenzo-p-dioxin and dibenzofurans (HpCDD/Fs), hexachlorinated dibenzo-p-dioxin and dibenzofurans (HxCDD/Fs), and octachlorianted dibenzo-p-dioxin and dibenzofurans (OCDD/Fs), which was aggravated by the increasing temperature. The characterization of the surface properties of AC revealed that slight oxidation occurred on the AC surface during the adsorption process, introducing oxygen to the competitive adsorption. In addition, it was found in this study that an increased temperature led to a higher content of hydrophilic carboxyl and anhydride groups and weakened π-π interactions, which were also partly responsible for the negative impact of the increasing temperature on the AC adsorption capacity. The results of this study can contribute to the operation optimization for controlling PCDD/F emissions from municipal solid waste incineration (MSWI). Full article

(This article belongs to the Special Issue Sustainable Recycling of Municipal Solid Waste)

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27 pages, 13352 KiB

Open AccessArticle

Multi-Layer Ceramic Capacitors in Lighting Equipment: Presence and Characterisation of Rare Earth Elements and Precious Metals

by Konstantinos M. Sideris, Dimitrios Fragoulis, Vassilis N. Stathopoulos and Panagiotis Sinioros

Recycling 2023, 8(6), 97; https://doi.org/10.3390/recycling8060097 - 04 Dec 2023

Viewed by 2002

Abstract

The need to reduce energy consumption in buildings, the emergence of light-emitting diode (LED) lamps in lighting around 2010, their long lifetime, and the 2025 target to use only LED lamps are changing the existing composition of Category 3 waste electrical–electronic equipment (WEEE) [...] Read more.

The need to reduce energy consumption in buildings, the emergence of light-emitting diode (LED) lamps in lighting around 2010, their long lifetime, and the 2025 target to use only LED lamps are changing the existing composition of Category 3 waste electrical–electronic equipment (WEEE) and creating expectations for simple, high-concentration recycling streams. In this study, multi-layer ceramic capacitors (MLCCs) detached from the lighting sector’s WEEE were characterised for the presence of rare earth elements (REEs) and precious metals (PMs). Their digestion was carried out with HNO₃ and aqua regia on a heating plate and characterised using inductively coupled plasma optical emission spectroscopy (ICP-OES) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). The contents of REEs and PMs found in the MLCCs were 0.84 wt% and 0.60 wt%, respectively, and create an economic stored value that is essentially defined by PMs of 98.67% and by palladium (Pd) of 78.37%. The analysis showed that the content of the main elements was: neodymium (Nd) 0.366 wt%, yttrium (Y) 0.220 wt%, dysprosium (Dy) 0.131 wt%, silver (Ag) 0.467 wt%, and Pd 0.105 wt%. These results indicate the need for selective removal and separate recycling processes of MLCCs from WEEE drivers. Full article

(This article belongs to the Special Issue Recovery of Valuable Metals and Nonmetals from E-Waste)

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22 pages, 6475 KiB

Open AccessReview

Acerola (Malpighia spp.) Waste: A Sustainable Approach to Nutraceutical, Pharmaceutical, and Energy Applications

by José Roberto Vega-Baudrit, Melissa Camacho, Diego Batista-Menezes, Yendry Corrales-Ureña, Juan Miguel Zúñiga, Arturo Mora Chacón, Nicole Lecot, Luis Castillo Henríquez and Mary Lopretti

Recycling 2023, 8(6), 96; https://doi.org/10.3390/recycling8060096 - 04 Dec 2023

Viewed by 1911

Abstract

This study reviews the many uses for waste generated from acerola (Malpighia spp.) production, a tropical fruit renowned for its nutrient-rich content. Traditionally considered an environmental burden, this waste is now gaining attention for its sustainable applications in green technology. This review [...] Read more.

This study reviews the many uses for waste generated from acerola (Malpighia spp.) production, a tropical fruit renowned for its nutrient-rich content. Traditionally considered an environmental burden, this waste is now gaining attention for its sustainable applications in green technology. This review outlines the extraction of valuable bioactive compounds, like polyphenols, carotenoids, and pectin, that can be extracted from the acerola fruit and acerola waste, and it also delves into its potential in materials science, particularly in the creation of pharmaceutical formulations, nanomaterials, composites, biofuels, and energy applications. On the medical front, the paper highlights the promise that acerola waste holds in anti-inflammatory, antihyperglycemic, and anticancer therapies. By outlining challenges and opportunities, the review emphasizes the untapped potential of acerola waste as a resource for high-value products. These findings suggest a paradigm shift, turning what has been considered waste into a sustainable asset, thereby encouraging environmentally responsible practices within the fruit industry. Full article

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17 pages, 2700 KiB

Open AccessReview

Review of the Policy, Social, Operational, and Technological Factors Affecting Cigarette Butt Recycling Potential in Extended Producer Responsibility Programs

by Aron Pazzaglia and Beatrice Castellani

Recycling 2023, 8(6), 95; https://doi.org/10.3390/recycling8060095 - 01 Dec 2023

Viewed by 1994

Abstract

Cigarette butts (CBs) are the most diffuse waste in the world, often abandoned into the environment without proper disposal. They are dangerous because of the numerous harmful chemicals potentially released by them into the environment. In the literature, there are several technological options [...] Read more.

Cigarette butts (CBs) are the most diffuse waste in the world, often abandoned into the environment without proper disposal. They are dangerous because of the numerous harmful chemicals potentially released by them into the environment. In the literature, there are several technological options for CB recycling, but some critical concerns could affect their effectiveness due to the quality and quantity of CB litter that is collected in the proper way. The extended producer responsibility scheme for CBs is proposed at the Europe level as an action to tackle CB litter and encourage sustainable product development. The present paper focuses on analyzing the existing literature to identify critical issues within the policy framework, social behavior, waste collection and transport, and technological processes. The collection and transport of CB waste is a major issue, being a key step for bringing CB to the recycling process. The main concern is the small quantity of CBs collected: 0.06% of the municipal waste and 0.18% of the unsorted waste in the case study’s administrative area of Perugia. Another crucial issue is the need for behavioral interventions to increase education and awareness of citizens that are smokers, addressing the discrepancy between smokers’ behaviors and beliefs. The main results, along with the critical issues related to the topics, are highlighted. Full article

(This article belongs to the Special Issue Feature Papers in Recycling 2023)

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16 pages, 5398 KiB

Open AccessArticle

Exploring the Plastic Collection and Recycling Trends in Sri Lanka

by Rohantha Rukshan Jayasinghe, Wasudha Prabodhani Abeyrathna, Krishani Rukmali Jayasingha, Manuja Promodya Hendawitharana, Thusitha Saman Bandara, Champika L. Liyanage and Karl S. Williams

Recycling 2023, 8(6), 94; https://doi.org/10.3390/recycling8060094 - 26 Nov 2023

Viewed by 3473

Abstract

This study examined plastic waste management in Sri Lanka, concentrating on the contributing factors to plastic waste generation and collection. Data were gathered through a questionnaire survey from registered plastic recycling and management centres. The analysis revealed a positive correlation between tourist arrivals [...] Read more.

This study examined plastic waste management in Sri Lanka, concentrating on the contributing factors to plastic waste generation and collection. Data were gathered through a questionnaire survey from registered plastic recycling and management centres. The analysis revealed a positive correlation between tourist arrivals and plastic waste generation, indicating increased plastic waste production due to tourism spanning from 2014 to 2022. However, plastic waste collection negatively correlated with precipitation levels, suggesting heavy rainfall hampers collection efforts. This study found HDPE, PVC, LDPE, and PP to be the most collected and recycled plastic types, whereas PS and PET recycling were less prevalent. The results demonstrate the need for enhanced recycling infrastructure and highlight the necessity for government participation in plastic waste management initiatives. This study recommends increasing waste collection and recycling during the tourist season. In addition to enhancing public and private awareness, there should be additional investment in recycling facilities. The findings offer crucial insights into plastic waste management in Sri Lanka, emphasizing the importance of collaborative efforts and comprehensive strategies to tackle plastic pollution. Full article

(This article belongs to the Special Issue Advances in the Recycling, Processing and Use of Plastic Waste II)

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14 pages, 4571 KiB

Open AccessArticle

Recycled Surgical Mask Waste as a Resource Material in Sustainable Geopolymer Bricks

by Kritish Thoudam, Nabil Hossiney, Srinidhi Lakshmish Kumar, Jacob Alex, Sanoop Prakasan, Sarath Chandra, Yogeshraj Urs and A. S. Arunkumar

Recycling 2023, 8(6), 93; https://doi.org/10.3390/recycling8060093 - 19 Nov 2023

Cited by 1 | Viewed by 2630

Abstract

With the advent of the COVID-19 pandemic, the global consumption of single-use surgical masks has risen immensely, and it is expected to grow in the coming years. Simultaneously, the disposal of surgical masks in the environment has caused plastic pollution, and therefore, it [...] Read more.

With the advent of the COVID-19 pandemic, the global consumption of single-use surgical masks has risen immensely, and it is expected to grow in the coming years. Simultaneously, the disposal of surgical masks in the environment has caused plastic pollution, and therefore, it is exigent to find innovative ways to handle this problem. In this study, surgical masks were processed in a laboratory using the mechanical grinding method to obtain recycled surgical masks (RSM). The RSM was added in doses of 0%, 1%, 2%, 3%, and 4% by volume of geopolymer bricks, which were synthesized with ground granulated blast furnace slag (GGBS), rice husk ash (RHA), sand, and sodium silicate (Na₂SiO₃) at ambient conditions for a duration of 28 days. The developed bricks were tested for compressive strength, flexural strength, density, water absorption, efflorescence, and drying shrinkage. The results of the study reveal that compressive strength and flexural strength improved with the inclusion of RSM in the bricks. The highest values of compressive strength and flexural strength were 5.97 MPa and 1.62 MPa for bricks with 4% RSM, respectively. Further, a reduction in the self-weight of the bricks was noticed with an increase in RSM. There was no pronounced effect of RSM on the water absorption and efflorescence properties. However, the RSM played a role in reducing the drying shrinkage of the bricks. The sustainability analysis divulges the catalytic role of RSM in improving material performance, thereby proving to be a potential candidate for low-carbon material in the construction industry. Full article

(This article belongs to the Special Issue Sustainable Materials from Waste and Renewable Sources)

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14 pages, 2692 KiB

Open AccessArticle

Recovery of Kish Graphite from Steelmaking Byproducts with a Multi-Stage Froth Flotation Process

by Ying-Liang Chen, Wei-Ping Chiang and Ping-Yu Hsieh

Recycling 2023, 8(6), 92; https://doi.org/10.3390/recycling8060092 - 18 Nov 2023

Viewed by 1716

Abstract

Steelmaking processes inevitably generate large amounts of byproducts, including slags, specks of dust, etc., and their treatment has been a critical issue for the steelmaking industry. Kish graphite is a valuable substance existing in steelmaking byproducts, and the recovery of Kish graphite has [...] Read more.

Steelmaking processes inevitably generate large amounts of byproducts, including slags, specks of dust, etc., and their treatment has been a critical issue for the steelmaking industry. Kish graphite is a valuable substance existing in steelmaking byproducts, and the recovery of Kish graphite has attracted more attention in recent years. The purpose of this study was to use a multi-stage froth flotation process for the beneficiation of Kish graphite and to investigate the influence of flotation conditions on the mass distribution of graphite and impurities. The results showed that the dust D2 contained ~34 wt.% of graphite and thus had the highest potential for the recovery of Kish graphite. The dosages of frother (methyl isobutyl carbinol, MIBC) at 0.005 kg/t and collector (kerosene) at 1 kg/t were optimal for the flotation of Kish graphite. After three-stage froth flotation, the graphite content of the concentrate was progressively increased to 84.09 wt.%, and the entire recovery rate was 93.05%. During the multi-stage froth flotation process, most of the impurities were separated in stage I, but the Fe-containing impurities were mainly separated in stage II. Some Ca²⁺, Na⁺, and K⁺ were leached out, and there were barely any heavy metals in the liquid phases. Full article

(This article belongs to the Special Issue Feature Papers in Recycling 2023)

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19 pages, 638 KiB

Open AccessArticle

Exploring the 5Rs Holistic Model for Zero Food Waste in Saudi Arabian Food Service Outlets

by Abu Elnasr E. Sobaih and Ahmed E. Abu Elnasr

Recycling 2023, 8(6), 91; https://doi.org/10.3390/recycling8060091 - 11 Nov 2023

Viewed by 1852

Abstract

Background: The proportion of food waste in the Kingdom of Saudi Arabia, particularly in food service outlets, sends an important and urgent call for a holistic model to either prevent or at least properly manage this high level of food waste. This study [...] Read more.

Background: The proportion of food waste in the Kingdom of Saudi Arabia, particularly in food service outlets, sends an important and urgent call for a holistic model to either prevent or at least properly manage this high level of food waste. This study draws on the European Union Waste Hierarchy Framework and the United States Environmental Protection Agency Food Recovery Framework to develop a holistic model to manage the high rate of food waste in Saudi food service outlets. Methods: This study adopted the Standards for Reporting Qualitative Research using one-to-one interviews with food service experts to explore the current and appropriate practices for food waste prevention. The in-depth interviews discussed the implementation of the 5Rs hierarchy, which includes reducing food surplus and waste at the source, redistributing food surplus to needy people, reusing food surplus/waste, recycling food waste, and recovering food waste benefits, i.e., bioenergy production. Results: The successful implementation of the 5Rs hierarchy depends on effective collaboration between the key stakeholders, i.e., policy makers, food industry administrators, non-governmental organizations, and customers. The effective management of the food supply chain is also vital to avoid food surplus and prevent waste in food service outlets. Additionally, sustainable production by staff and responsible consumption by consumers contribute effectively to the implementation of the 5Rs model, which contributes to the achievement of zero food waste and, ultimately, to sustainable development. Conclusions: This study provided a novel hierarchy model, which has five tiers, aiming to avoid food waste. The successful implementation of this model will lead to several significant positive impacts on the economy, community, and environment. Full article

(This article belongs to the Special Issue Feature Papers in Recycling 2023)

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17 pages, 1161 KiB

Open AccessReview

An Overview of Management Status and Recycling Strategies for Plastic Packaging Waste in China

by Chaojie Yu, Diyi Jin, Xichao Hu, Wenzhi He and Guangming Li

Recycling 2023, 8(6), 90; https://doi.org/10.3390/recycling8060090 - 11 Nov 2023

Viewed by 2609

Abstract

Given their exceptional performance, plastic packaging products are widely used in daily life, and the dramatic expansion in plastic packaging waste (PPW) has exacerbated environmental problems. Many countries have enacted laws and developed recycling technologies to manage plastic packaging waste in consideration of [...] Read more.

Given their exceptional performance, plastic packaging products are widely used in daily life, and the dramatic expansion in plastic packaging waste (PPW) has exacerbated environmental problems. Many countries have enacted laws and developed recycling technologies to manage plastic packaging waste in consideration of the nature of PPW as both garbage and a resource. As the world’s largest producer and consumer of plastics, China has also taken measures to address this issue. This paper presents the latest management regulations and recycling strategies for PPW in China. Based on an analysis of the current management status of PPW and recycling technologies and their carbon emission impacts, some management suggestions and a comprehensive full-chain recycling process were put forward. We supposed that management challenges that need to be overcome in the future can be solved through the improvement of green designs for plastic packaging, manufacturing technology updates, consumption concept changes, and the high-value utilization of PPW. This paper aims to provide valuable references for government decisions on PPW management and, furthermore, to set up an economically sensible and industrially feasible PPW solution and boost the development of PPW recycling. Full article

(This article belongs to the Special Issue Advances in the Recycling, Processing and Use of Plastic Waste II)

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11 pages, 2726 KiB

Open AccessArticle

Automated Battery Disassembly—Examination of the Product- and Process-Related Challenges for Automotive Traction Batteries

by Domenic Klohs, Christian Offermanns, Heiner Heimes and Achim Kampker

Recycling 2023, 8(6), 89; https://doi.org/10.3390/recycling8060089 - 08 Nov 2023

Viewed by 2747

Abstract

As the market share of electric vehicles continues to rise, the number of battery systems that are retired after their service life in the vehicle will also increase. This large growth in battery returns will also have a noticeable impact on processes such [...] Read more.

As the market share of electric vehicles continues to rise, the number of battery systems that are retired after their service life in the vehicle will also increase. This large growth in battery returns will also have a noticeable impact on processes such as battery disassembly. The purpose of this paper is, therefore, to examine the challenges of the battery disassembly process in relation to the required increase in the degree of automation. For this purpose, a survey of various experts along the battery value chain was conducted, and product-side hurdles, such as the wide range of variants, and process-side challenges, such as the opening of the housing cover or the removal of cables and connectors, were identified. Together with an assessment of the potential degree of automation in the context of downstream processes (reuse, repair, remanufacturing, and recycling), this results in a variety of streams for future research in the field of automated battery disassembly. The core aspect in this context is data availability consisting of product and component data as well as process-relevant parameters. Full article

(This article belongs to the Special Issue Recycling of Spent Batteries—Trash to Treasure)

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13 pages, 1630 KiB

Open AccessReview

Recent Recycling Innovations to Facilitate Sustainable Packaging Materials: A Review

by Idowu D. Ibrahim, Emmanuel R. Sadiku, Yskandar Hamam, Williams K. Kupolati, Julius M. Ndambuki, Tamba Jamiru, Azunna A. Eze and Jacques Snyman

Recycling 2023, 8(6), 88; https://doi.org/10.3390/recycling8060088 - 07 Nov 2023

Viewed by 3365

Abstract

Packaging materials play a significant role in the meat, fish, and seafood, pharmaceutical, beverages, and electronics industries. These materials protect the contents during handling and transportation from damage, contamination, and loss of quality, thus enhancing the shelf life of the products being packaged. [...] Read more.

Packaging materials play a significant role in the meat, fish, and seafood, pharmaceutical, beverages, and electronics industries. These materials protect the contents during handling and transportation from damage, contamination, and loss of quality, thus enhancing the shelf life of the products being packaged. Several materials, like paper and cardboard, plastics, metals, and glass, have been widely used. However, the vast consumption of these materials leads to high waste generation due to increasing demands globally. This article considers some aspects of recycling waste packaging materials, the need for recycling in terms of environmental impacts, and the energy-saving and economic benefits. It also provides some highlights on the sustainability of the processes of recycling and how the government and public can influence recycling operations. The impact of the COVID-19 pandemic on packaging systems and solid waste management is also highlighted. This study also provides a short note on the possible future methods to be adopted in the recycling process of waste packaging materials. Full article

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23 pages, 2100 KiB

Open AccessArticle

Safety Assessment of Recycled Plastics from Post-Consumer Waste with a Combination of a Miniaturized Ames Test and Chromatographic Analysis

by Elisa Mayrhofer, Lukas Prielinger, Victor Sharp, Bernhard Rainer, Christian Kirchnawy, Christian Rung, Anita Gruner, Mladen Juric and Arielle Springer

Recycling 2023, 8(6), 87; https://doi.org/10.3390/recycling8060087 - 04 Nov 2023

Cited by 1 | Viewed by 3006

Abstract

European circular economy goals require the use of recycled polymers in sensitive applications such as food packaging. As plastic recyclates can contain unknown post-consumer substances, the European Food Safety Authority evaluates recycling processes using a worst-case assumption: all contaminants are DNA-reactive mutagens/carcinogens with [...] Read more.

European circular economy goals require the use of recycled polymers in sensitive applications such as food packaging. As plastic recyclates can contain unknown post-consumer substances, the European Food Safety Authority evaluates recycling processes using a worst-case assumption: all contaminants are DNA-reactive mutagens/carcinogens with extremely low safety thresholds. The current data are insufficient to estimate whether this assumption is justified. To provide scientific evidence on the presence of DNA-reactive mutagens in recycled plastics, 119 input and output samples from plastic recycling were tested with a miniaturized Ames test. DNA-reactive mutagens were not detected in recycled polyethylene terephthalate, which is already approved for food contact. However, other types of recycled plastics (polyethylene, polypropylene and polystyrene), which are currently unauthorized for food contact, showed DNA-reactive, mutagenic effects in a total of 51 samples. The DNA-reactive substances that are responsible for the detected mutagenic activity could not be identified by comparison of the bioassay data with analytical results from a chromatographical screening. The data from the Ames test analysis of different independent batches and a comparison of input and output material indicate that the DNA-reactive contaminants are not randomly introduced through the misuse of recycled packaging by consumers, but are systematically formed during the recycling process from precursors in the input. This publication highlights the need to identify the source for this critical contaminant to enable the future use of polyethylene, polypropylene and polystyrene in sensitive applications. Full article

(This article belongs to the Special Issue Advances in the Recycling, Processing and Use of Plastic Waste II)

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25 pages, 725 KiB

Open AccessReview

A Systematic Literature Review of Waste Identification in Automatic Separation Systems

by Juan Carlos Arbeláez-Estrada, Paola Vallejo, Jose Aguilar, Marta Silvia Tabares-Betancur, David Ríos-Zapata, Santiago Ruiz-Arenas and Elizabeth Rendón-Vélez

Recycling 2023, 8(6), 86; https://doi.org/10.3390/recycling8060086 - 02 Nov 2023

Cited by 1 | Viewed by 5710

Abstract

Proper waste separation is essential for recycling. However, it can be challenging to identify waste materials accurately, especially in real-world settings. In this study, a systematic literature review (SLR) was carried out to identify the physical enablers (sensors and computing devices), datasets, and [...] Read more.

Proper waste separation is essential for recycling. However, it can be challenging to identify waste materials accurately, especially in real-world settings. In this study, a systematic literature review (SLR) was carried out to identify the physical enablers (sensors and computing devices), datasets, and machine learning (ML) algorithms used for waste identification in indirect separation systems. This review analyzed 55 studies, following the Kitchenham guidelines. The SLR identified three levels of autonomy in waste segregation systems: full, moderate, and low. Edge computing devices are the most widely used for data processing (9 of 17 studies). Five types of sensors are used for waste identification: inductive, capacitive, image-based, sound-based, and weight-based sensors. Visible-image-based sensors are the most common in the literature. Single classification is the most popular dataset type (65%), followed by bounding box detection (22.5%). Convolutional neural networks (CNNs) are the most commonly used ML technique for waste identification (24 out of 26 articles). One of the main conclusions is that waste identification faces challenges with real-world complexity, limited data in datasets, and a lack of detailed waste categorization. Future work in waste identification should focus on deployment and testing in non-controlled environments, expanding system functionalities, and exploring sensor fusion. Full article

(This article belongs to the Special Issue Featured Reviews in Recycling)

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40 pages, 7185 KiB

Open AccessReview

Gravity Concentration in Urban Mining Applications—A Review

by Weslei M. Ambrós

Recycling 2023, 8(6), 85; https://doi.org/10.3390/recycling8060085 - 01 Nov 2023

Cited by 1 | Viewed by 3139

Abstract

Urban mining has emerged as a concept that goes beyond conventional recycling, as it aims to tackle both the challenges of solid waste generation and management, as well as the scarcity of primary resources. Gravity concentration has gained increasing attention as a promising [...] Read more.

Urban mining has emerged as a concept that goes beyond conventional recycling, as it aims to tackle both the challenges of solid waste generation and management, as well as the scarcity of primary resources. Gravity concentration has gained increasing attention as a promising method for addressing crucial challenges in urban mining applications. In this sense, this review provides a comprehensive and up-to-date overview of gravity concentration in urban mining processes, covering principles, techniques, current applications, recent advancements, challenges, and opportunities. Emphasis was placed on shifting from the commonly found literature focus on ore processing to solid waste processing. Three types of solid waste, namely plastics, construction and demolition waste (CDW), and waste from electrical and electronic equipment (WEEE), were chosen for a more in-depth examination due to their massive production and widespread generation. Discussions also considered the potential of gravity concentration to address the unique challenges in their processing and explored possibilities for future developments. Full article

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13 pages, 1173 KiB

Open AccessArticle

X-ray Fluorescence Analysis of Waste Sm-Co Magnets: A Rational Approach

by Alexandra Alexandrovna Arkhipenko, Galina Evgenievna Marina, Marina Sergeevna Doronina, Natalya Alexandrovna Korotkova and Vasilisa Borisovna Baranovskaya

Recycling 2023, 8(6), 84; https://doi.org/10.3390/recycling8060084 - 01 Nov 2023

Viewed by 1708

Abstract

Determination of the chemical composition of waste Sm-Co magnets is required for their efficient recycling. The non-stereotypical composition of said magnets makes an analysis extremely challenging. X-ray fluorescence spectrometry is a promising analytical tool for this task. It offers high accuracy and simplicity [...] Read more.

Determination of the chemical composition of waste Sm-Co magnets is required for their efficient recycling. The non-stereotypical composition of said magnets makes an analysis extremely challenging. X-ray fluorescence spectrometry is a promising analytical tool for this task. It offers high accuracy and simplicity of sample preparation as it does not require sample dissolution. However, a serious limitation of X-ray fluorescence analysis is the spectral interference of matrix elements and impurities. In this work, a two-stage technique has been developed for the determination of the main components (Sm, Co) and impurities (Fe, Cu, Zr, Hf, Ti, Ni, Mn, Cr) in samples of spent samarium–cobalt magnets using wavelength dispersive X-ray fluorescence spectrometry. In order to overcome the main limitation of the chosen method and to maximize its capabilities of qualitative and quantitative analysis, we propose an approach to the selection of analytical lines and experimental conditions, as well as a preparation method for the calibration standards. The obtained results have been shown to have a good correlation with ICP-OES. The limits of detection are in the range of 0.001–0.02 wt%, and the limits of quantification are 0.003–0.08 wt%. Full article

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13 pages, 972 KiB

Open AccessSystematic Review

Alleviation of Selected Environmental Waste through Biodegradation by Black Soldier Fly (Hermetia illucens) Larvae: A Meta-Analysis

by Sunarto Zulkifli, Anuraga Jayanegara, Bambang Pramudya, Melta Rini Fahmi and Mardiah Rahmadani

Recycling 2023, 8(6), 83; https://doi.org/10.3390/recycling8060083 - 24 Oct 2023

Viewed by 1822

Abstract

Alleviation of environmental waste is a significant challenge, contributing to greenhouse gas emissions and wasting valuable resources. To address this issue sustainably, valorization techniques are being explored to convert environmental waste into valuable bio-based products. Additionally, the use of black soldier fly ( [...] Read more.

Alleviation of environmental waste is a significant challenge, contributing to greenhouse gas emissions and wasting valuable resources. To address this issue sustainably, valorization techniques are being explored to convert environmental waste into valuable bio-based products. Additionally, the use of black soldier fly (Hermetia Illucens) larvae has emerged as a potential solution to degrade environmental waste and produce biomass. This study aimed to quantify the waste reduction index (WRI) of environmental waste through biodegradation by black soldier fly (BSF) larvae. A meta-analysis method was employed, involving a comprehensive search in the Scopus database for analysis. A total of 45 articles were analyzed and the results indicate that kitchen waste and fruit and vegetable wastes have a positive effect on WRI and other variables. The WRI of kitchen waste and fruit and vegetable wastes is 4.77 ± 2.98 g/day and 2.72 ± 2.14 g/day, respectively. Fecal waste results in a lower WRI than those of other waste categories, i.e., 2.22 ± 1.29 g/day. Overall, the BSF larvae effectively reduce organic environmental wastes and convert them into their body mass, which is rich in protein. This study contributes to a deeper understanding of the potential of BSF in waste management, offering insights into sustainable waste reduction strategies. Full article

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20 pages, 5821 KiB

Open AccessArticle

Investigation of the Fiber Length and the Mechanical Properties of Waste Recycled from Continuous Glass Fiber-Reinforced Polypropylene

by Shiva MohammadKarimi, Benedikt Neitzel, Maximilian Lang and Florian Puch

Recycling 2023, 8(6), 82; https://doi.org/10.3390/recycling8060082 - 24 Oct 2023

Cited by 1 | Viewed by 1873

Abstract

This paper explores the mechanical recycling of continuous fiber-reinforced thermoplastics (CFRTPs) waste into injection molded products, focusing on the influence of recycling parameters on fiber length and mechanical properties. CFRTPs are gaining attention for their promising attributes, including weight-specific mechanical properties, short cycle [...] Read more.

This paper explores the mechanical recycling of continuous fiber-reinforced thermoplastics (CFRTPs) waste into injection molded products, focusing on the influence of recycling parameters on fiber length and mechanical properties. CFRTPs are gaining attention for their promising attributes, including weight-specific mechanical properties, short cycle times, storability, and recyclability, making them suitable for diverse applications. However, as CFRTP production rates rise, recycling strategies become crucial for sustainability. This study investigates the processability of CFRTP waste, defines size reduction conditions, and evaluates the impact of various compounding parameters such as temperature, screw speed, and fiber volume content during extrusion. The research findings indicate that higher screw speeds lead to fiber length reduction, whereas elevated temperatures result in longer fibers. Increased fiber volume intensifies interactions, resulting in shorter lengths. Additionally, the study examines the influence of injection molding parameters such as back pressure, screw speed, and initial fiber length on the resulting fiber length and mechanical properties of injection molded specimens, emphasizing the need for precise parameter control to optimize performance in recycled CFRTPs. Key findings are that increasing the initial fiber length from 260 μm to 455 μm results in an average fiber length after injection molding of 225 μm and 341 μm, respectively. This implies that longer initial fibers are more prone to breakage. Regarding the mechanical properties, increasing back pressure from 20 bar to 60 bar results in a reduction in Young’s modulus of approximately 40 MPa. Higher screw speed also reduces modulus by approximately 70 MPa due to intensified fiber–screw interactions. However, back pressure and screw speed have neutral effects on the tensile strength and the elongation at break. Full article

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Recycling, Volume 8, Issue 6 (December 2023) – 19 articles

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