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Recycling

Recycling is an international, peer-reviewed, open access journal on the recycling and reuse of material resources, including circular economy published bimonthly online by MDPI.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, ESCI (Web of Science), FSTA, Inspec, AGRIS, and other databases.
Journal Rank: JCR - Q2 (Green and Sustainable Science and Technology) / CiteScore - Q1 (Management, Monitoring, Policy and Law)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 20.9 days after submission; acceptance to publication is undertaken in 2.8 days (median values for papers published in this journal in the second half of 2024).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Impact Factor: 4.6 (2023); 5-Year Impact Factor: 4.3 (2023)

Imprint Information Journal Flyer Open Access ISSN: 2313-4321

Latest Articles

19 pages, 449 KiB

Open AccessArticle

Understanding Demographic and Behavioral Determinants of Engagement in Plastic Tableware Reduction: Behavior, Support, and Price Sensitivity

by Sai-Leung Ng and Yu-Chieh Hsieh

Recycling 2025, 10(3), 103; https://doi.org/10.3390/recycling10030103 - 20 May 2025

Plastic waste reduction has become a global priority, with consumer engagement playing a crucial role in the success of sustainability initiatives. This study examines the demographic and behavioral determinants of consumer engagement in plastic tableware reduction. Using survey data from Hong Kong residents [...] Read more.

Plastic waste reduction has become a global priority, with consumer engagement playing a crucial role in the success of sustainability initiatives. This study examines the demographic and behavioral determinants of consumer engagement in plastic tableware reduction. Using survey data from Hong Kong residents and a Multivariate Analysis of Variance (MANOVA) approach, this study analyzes how age, gender, education, income, housing type, order frequency, opt-out effectiveness, and their interactions influence the four dimensions of engagement, namely plastic tableware opt-out behavior, support for government policies, support for plastic-free restaurants, and price sensitivity. The results indicate that age significantly affects plastic tableware reduction engagement, with order frequency and opt-out effectiveness moderating the effects of age and education. The study contributes to the literature by providing empirical insights into consumer-driven sustainability efforts and the role of behavioral factors in shaping engagement in plastic waste reduction. These findings offer valuable implications for policymakers and businesses promoting sustainable consumption practices. Full article

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20 pages, 2880 KiB

Open AccessArticle

Measuring the Impact of Education on Waste Streams from Multi-Family Housing

by Dhanush Kenchanna, Tina Marie Waliczek and Xiangping Liu

Recycling 2025, 10(3), 102; https://doi.org/10.3390/recycling10030102 - 19 May 2025

Food waste is a significant global issue with substantial environmental, economic, and social implications. This exploratory study aimed to evaluate the impact of an educational composting program on reducing food waste generation and promoting proper waste sorting practices within multi-family housing units in [...] Read more.

Food waste is a significant global issue with substantial environmental, economic, and social implications. This exploratory study aimed to evaluate the impact of an educational composting program on reducing food waste generation and promoting proper waste sorting practices within multi-family housing units in San Marcos, Texas. A comprehensive methodology was employed, encompassing pre- and post-intervention waste audits, educational interventions, weekly organic waste collection, and quantitative data analyses. Nine multi-family complexes, spanning student housing, conventional family units, low-income residences, and senior living facilities, were targeted through strategic recruitment efforts and incentivization. The treatment group, consisting of 43 participants, received ongoing education throughout the eight-week implementation period, facilitated through informational resources, feedback mechanisms, and door-to-door organic waste collection. Conversely, the control group did not partake in the educational component. Statistical analyses, including descriptive statistics and paired t-tests, facilitated comparisons across various dimensions, such as housing types, treatment versus control groups, and pre- versus post-intervention periods. The findings revealed significant reductions in organic waste and compostable materials within the treatment group’s weekly landfill trash, underscoring the effectiveness of the educational program. Furthermore, insights into contamination patterns and housing-specific waste characteristics were garnered, informing targeted intervention strategies and policy recommendations for optimizing multi-family composting initiatives. Full article

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16 pages, 1164 KiB

Open AccessArticle

Value Extraction from End-of-Life Textile Products in Pakistan

by Muhammad Waqas Iqbal, Muhammad Babar Ramzan, Haleema Manzoor and Sheheryar Mohsin Qureshi

Recycling 2025, 10(3), 101; https://doi.org/10.3390/recycling10030101 - 19 May 2025

Overconsumption and unplanned disposal of garments result in millions of tons of textile products going to landfills. Understanding the environmental benefits and impact of various recycling options is crucial for integrating recycling into the apparel waste stream. This study aims to assess the [...] Read more.

Overconsumption and unplanned disposal of garments result in millions of tons of textile products going to landfills. Understanding the environmental benefits and impact of various recycling options is crucial for integrating recycling into the apparel waste stream. This study aims to assess the environmental impacts of products made from post-consumer textile waste fibers, highlighting the importance of closed-loop textile supply chains in developing countries. Using Open LCA software, the cradle-to-gate approach for life cycle assessment is used to calculate the environmental impacts of post-consumer textile waste, virgin cotton, virgin polyester fibers, and their blends in two different scenarios. The life cycle inventory data for functional units (1000 kg apparel) has been collected from the industrial units and the Ecoinvent v3.0 database. The results of 16 environmental impact categories are computed, showing that textile products made from virgin cotton fiber have 60% more global warming potential than those made from post-consumer textile waste fibers. Hence, the environmental impact of textile products can be controlled by recycling them. Consumption of post-consumer textile waste fiber is the key to reducing the new material needs in the textile supply chain. The closed-loop apparel supply chain can help developing countries generate maximum financial value with minimal environmental damage. In developing countries, value extraction from post-consumer textile waste recycling is essential to meet international consumer demands for cleaner production. Full article

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32 pages, 1460 KiB

Open AccessArticle

Evaluating Recycling Initiatives for Landfill Diversion in Developing Economies Using Integrated Machine Learning Techniques

by Muyiwa Lawrence Adedara, Ridwan Taiwo, Olusola Olaitan Ayeleru and Hans-Rudolf Bork

Recycling 2025, 10(3), 100; https://doi.org/10.3390/recycling10030100 - 19 May 2025

This study investigates the effectiveness of the Lagos Recycle Initiative (LRI) on landfill diversion (LFD) in Lagos, Nigeria, where evidence-based assessments of such initiatives are lacking. It evaluates the recycling diversion rate (RDR) of household recyclables (HSRs) across local government areas using field [...] Read more.

This study investigates the effectiveness of the Lagos Recycle Initiative (LRI) on landfill diversion (LFD) in Lagos, Nigeria, where evidence-based assessments of such initiatives are lacking. It evaluates the recycling diversion rate (RDR) of household recyclables (HSRs) across local government areas using field surveys and population data. Machine learning algorithms (logistic regression, random forest, XGBoost, and CatBoost) refined with Bayesian optimisation were employed to predict household recycling motivation. The findings reveal a low RDR of 0.37%, indicating that only approximately 2.47% (31,554.25 metric tonnes) of recyclables are recovered annually compared to a targeted 50% (638,750 metric tonnes). The optimised CatBoost model (accuracy and F1 score of 0.79) identified collection time and the absence of overflowing HSR bins as key motivators for household recycling via the SHapley Additive exPlanations (SHAP) framework. This study concludes that current LRI efforts are insufficient to meet recycling targets. It recommends expanding recovery efforts and addressing operational challenges faced by registered recyclers to improve recycling outcomes. The policy implications of this study suggest the need for stricter enforcement of recycling regulations, coupled with targeted financial incentives for both recyclers and households to boost recycling participation, thereby enhancing the overall effectiveness of waste diversion efforts under the LRI. This research provides a benchmark for assessing urban recycling initiatives (RIs) in rapidly growing African cities. Full article

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31 pages, 6419 KiB

Open AccessArticle

Fe₃O₄/SiO₂ Nanocomposite Derived from Coal Fly Ash and Acid Mine Drainage for the Adsorptive Removal of Diclofenac in Wastewater

by Dance Mabu, Ngwako Joseas Waleng, Tshimangadzo S. Munonde, Azile Nqombolo and Philiswa Nosizo Nomngongo

Recycling 2025, 10(3), 99; https://doi.org/10.3390/recycling10030099 - 16 May 2025

The ubiquity of diclofenac (DCF) in the environment has raised significant concerns. Diclofenac is a non-steroidal anti-inflammatory drug that has been found in various environmental matrices at minimum concentrations that are harmful to aquatic and terrestrial organisms. Traditional wastewater treatment plants (WWTPs) are [...] Read more.

The ubiquity of diclofenac (DCF) in the environment has raised significant concerns. Diclofenac is a non-steroidal anti-inflammatory drug that has been found in various environmental matrices at minimum concentrations that are harmful to aquatic and terrestrial organisms. Traditional wastewater treatment plants (WWTPs) are not fully equipped to remove a range of pharmaceuticals, and that explains the continued ubiquity of DCF in surface waters. In this study, an Fe₃O₄/SiO₂ nanocomposite prepared from acid mine drainage and coal fly ash was applied for the removal of DCF from wastewater. Major functional groups (Si–O–Si and Fe–O) were discovered from FTIR. TEM revealed uniform SiO₂ nanoparticle rod-like structures with embedded dark spherical nanoparticles. SEM-EDS analysis discovered a sponge-like structure fused with Fe₃O₄ nanoparticles that had significant Si, O, and Fe content. XRD demonstrated the crystalline nature of the nanocomposite. The surface properties of the nanocomposite were evaluated using BET and were 67.8 m²/g, 0.39 cm³/g, and 23.2 nm for surface area, pore volume, and pore size, respectively. Parameters that were suspected to be affecting the removal process were evaluated, including pH, nanocomposite dosage, and sample volume. The detection of DCF was conducted on high-performance liquid chromatography with diode-array detection (HPLC-DAD). Under optimum conditions, the adsorption process was monolayer, and physisorption was described using the Langmuir and Dubinin-Radushkevich (D-R) isotherm models. The kinetic data best fitted the pseudo-first order kinetic model, indicating a physisorption adsorption process. The thermodynamic experimental data confirmed that the adsorption process was spontaneous. The results obtained from real water samples showed 95.28% and 97.44% removal efficiencies from influent and effluent: 94.83% and 88.61% from raw sewage and final sewage, respectively. Overall, this work demonstrated that an Fe₃O₄/SiO₂ nanocomposite could be successfully prepared from coal fly ash and acid mine drainage and could be used to remove DCF in wastewater. Full article

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19 pages, 2682 KiB

Open AccessArticle

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

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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24 pages, 13260 KiB

Open AccessArticle

Upcycling of Cupric Chloride Waste Solution from PCB Manufacturing for Antibacterial Copper Nanoparticles

by Tapany Patcharawit, Chatisa Kansomket, Napat Mahiwan, Sumita Chailoi, Thanapon Chandakhiaw, Tanongsak Yingnakorn, Teerawut Tunnukij and Sakhob Khumkoa

Recycling 2025, 10(3), 97; https://doi.org/10.3390/recycling10030097 - 14 May 2025

Issues encompassing hazardous waste management face challenges, particularly those involving the manufacture of electronic devices such as PCBs that are in high demand with continual growth. Therefore, upcycling to create new products viable for highly valued markets emphasizes alternative solutions towards the circular [...] Read more.

Issues encompassing hazardous waste management face challenges, particularly those involving the manufacture of electronic devices such as PCBs that are in high demand with continual growth. Therefore, upcycling to create new products viable for highly valued markets emphasizes alternative solutions towards the circular economy. This research highlights the advantages of copper sulfate recovery from the cupric chloride etching waste solution from PCB manufacturing, combined with the synthesis of copper nanoparticles for antibacterial application. First, aluminium cementation, sulfuric acid leaching, and crystallization were incorporated in the recovery step to ensure a high purity of 99.95% and a recovery of 94.76%. Aluminium cementation selectively offered copper-containing precipitates suitable for leaching to gain high-purity recovered products. In the second step, copper nanoparticles were synthesized using 0.01–0.20 M copper sulfate precursors via sonochemical reduction. In total, 1–5 mL of hydrazine and 5–30 mL of 0.01 M ethylene glycol were added into a 50 mL precursor as reducing and capping agents, respectively. Hydrazine addition under high pH played a key role in controlling the shape, size, and purity of the copper nanoparticles, required for their antibacterial properties. The optimum condition gave spherical or polygonal copper nanoparticles of 54.54 nm at 99.95% purity and >92% recovery. The antibacterial test of the synthesized copper nanoparticles using E. coli via agar well diffusion exhibited a zone of inhibition (ZOI) of 50 mm at 127 mg/mL, similar to the antibiotic-controlled condition, proving their antibacterial potential. Along with process effectiveness, a feasibility study of the inventing process confirmed the environmental and economic impacts of minimizing energy consumption and processing time, which are competitive with respect to the existing recycling technologies. Full article

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37 pages, 6715 KiB

Open AccessArticle

Barriers to Mainstream Adoption of Circular Packaging in Indonesia

by Nazlı Terzioğlu, Fabrizio Ceschin, Yulianti Pratama, Emenda Sembiring and Susan Jobling

Recycling 2025, 10(3), 96; https://doi.org/10.3390/recycling10030096 - 13 May 2025

Achieving the mainstream adoption of circular packaging is essential for mitigating the environmental impacts of plastic waste. Its widespread adoption, however, remains hindered by significant user barriers. This study investigates the barriers to user adoption of upstream packaging solutions in Indonesia with the [...] Read more.

Achieving the mainstream adoption of circular packaging is essential for mitigating the environmental impacts of plastic waste. Its widespread adoption, however, remains hindered by significant user barriers. This study investigates the barriers to user adoption of upstream packaging solutions in Indonesia with the aim of reducing plastic packaging waste. Through a mixed-methods approach including case studies, expert workshops, and focus group discussions, nine key barriers were identified and analysed. These include inconvenience, resistance to changing habits and behaviours, higher costs and deposit schemes, contamination and hygiene concerns, wear and tear, functional and performance limitations, a lack of awareness about the environmental impacts, limited availability and variety, and a lack of trust. This research advances the literature by offering a detailed analysis of these barriers, categorising them into sociocultural, economic, contextual, and regulatory aspects. Additionally, barriers specific to Indonesia were identified such as a shift from being served to self-service refilling, some people not having smartphones, poor cellular signals in rural areas, a preference for plastic packaging due to its resale value, and a preference for cash payments due to limited access to credit or bank cards. The findings highlight the need for tailored, multidisciplinary strategies to overcome these barriers and promote the adoption of circular packaging solutions. This research provides valuable insights for researchers studying circular design, businesses seeking to innovate upstream packaging solutions, and policymakers aiming to develop regulations that support the adoption of circular packaging practices. Full article

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15 pages, 3312 KiB

Open AccessArticle

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

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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32 pages, 2154 KiB

Open AccessArticle

An Environmental and Economic Assessment of Household Food Waste Management Scenarios in Ireland

by Majid Bahramian, Courage Krah, Paul Hynds and Anushree Priyadarshini

Recycling 2025, 10(3), 94; https://doi.org/10.3390/recycling10030094 - 9 May 2025

Effective management of household food waste (HFW) is essential for sustainability and aligning with Ireland’s waste reduction goals. This study evaluates the environmental and economic impacts of four HFW management scenarios—incineration, anaerobic digestion (AD) with digestate composting, AD with digestate incineration, and AD [...] Read more.

Effective management of household food waste (HFW) is essential for sustainability and aligning with Ireland’s waste reduction goals. This study evaluates the environmental and economic impacts of four HFW management scenarios—incineration, anaerobic digestion (AD) with digestate composting, AD with digestate incineration, and AD with digestate gasification—using life cycle assessment (LCA) and life cycle costing (LCC) analyses. The functional unit is 1000 tons of daily HFW treatment. The results show that AD scenarios offer significant environmental advantages over incineration, with AD combined with digestate composting identified as the most sustainable option. This scenario achieves the greatest reduction in greenhouse gas emissions and enhances nutrient recovery. Economically, while AD involves higher capital investments (€677,000–€2,033,000), its long-term cost effectiveness is demonstrated through LCCs ranging from €1,016,000 to €3,386,000, partially offset by revenues of €339,000–€677,000. The sensitivity analysis highlights opportunities for improvement, such as optimizing water use and reducing emissions from biogas engines. The findings provide actionable insights for policymakers, emphasizing the environmental and economic benefits of integrating AD with composting as a preferred strategy for HFW management. Full article

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19 pages, 6562 KiB

Open AccessArticle

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

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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20 pages, 4247 KiB

Open AccessArticle

Redispersibility of Paper Under Low Agitation and How It Deteriorates over Time

by Andrea Christine Pfennich and Ulrich Hirn

Recycling 2025, 10(3), 92; https://doi.org/10.3390/recycling10030092 - 6 May 2025

In many paper applications the paper is supposed to disintegrate into its constituating fibers after disposal. This happens in water with only very little input of mechanical energy. The aim of this work is to understand the natural aging processes in different pulp [...] Read more.

In many paper applications the paper is supposed to disintegrate into its constituating fibers after disposal. This happens in water with only very little input of mechanical energy. The aim of this work is to understand the natural aging processes in different pulp types and their impact on the disintegration behavior under low agitation. We first introduce a laboratory testing method to assess the disintegration performance of various paper types in water under low mechanical energy input. Then we investigated the changes in paper disintegration and the corresponding physical properties over a nine-month period of paper storage. We measured wet strength, water retention value WRV, speed of water penetration, and contact angle. Our findings reveal substantial degradation of disintegration over time for unbleached paper. In contrast, for bleached paper the changes are much less pronounced. The best predictor of paper dispersibility turned out to be wet tensile strength. Furthermore, we found a strong relation between deterioration of dispersibility and fiber wetting (contact angle) and fiber swelling (WRV). We hence conclude that the observed decrease of low agitation paper dispersibility over time is related to a deteriorated water uptake into the fibers and fiber-fiber bonds which prevents the breaking of the bonds by the water. As potential aging mechanisms related to water uptake we identified hornification, crosslinking and lignin self-sizing as major factors influencing fiber-water interactions and ultimately the disintegration behavior. Full article

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9 pages, 2757 KiB

Open AccessArticle

Ergothioneine Circulation in Mushroom Cultivation Using Food Waste Recycling

by Ryota Kataoka, Ami Nigaki, Babla Shingha Barua and Ko Yamashita

Recycling 2025, 10(3), 91; https://doi.org/10.3390/recycling10030091 - 6 May 2025

Current food production systems generate and incinerate significant amounts of organic waste, which increases costs and energy consumption. In this study, we show that food waste, including food loss, can be used for mushroom cultivation. We also developed a new mushroom culture medium [...] Read more.

Current food production systems generate and incinerate significant amounts of organic waste, which increases costs and energy consumption. In this study, we show that food waste, including food loss, can be used for mushroom cultivation. We also developed a new mushroom culture medium to replace conventional sawdust. Oyster mushrooms cultivated using food waste, including food loss, as the primary component contain higher levels of ergothioneine than that in the oyster mushrooms grown using sawdust, which has an antioxidant effect. We found that the proportion of nitrogen derived from animal protein in the mushroom culture medium influences ergothioneine content in fruiting bodies. We showed that irradiation with blue LEDs might produce mushrooms with a higher ergothioneine content than T-2 media. Furthermore, we established that ergothioneine is absorbed by the plant body. We aimed to develop an agricultural technology using food waste, including food loss, as growing media for mushrooms. Ultimately, we hope to create a regional cyclical food production system centered on mushroom cultivation, using food waste, including food loss, to promote microcirculation. Full article

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21 pages, 4436 KiB

Open AccessArticle

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

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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18 pages, 4764 KiB

Open AccessArticle

Hydrothermal Carbonization of Biomass Waste for Solid Biofuel Production: Hydrochar Characterization and Its Application in Blast Furnace Injection

by Guangwei Wang, Junyi Wu, Haibo Li, Andrey Karasev, Xiaojun Ning and Chuan Wang

Recycling 2025, 10(3), 89; https://doi.org/10.3390/recycling10030089 - 4 May 2025

Hydrothermal carbonization (HTC) technology converts biomass into a carbon-rich, oxygen-containing solid fuel. Most studies have focused on hydrochar produced under laboratory conditions, leaving a gap in understanding the performance of industrially produced hydrochar. This study comprehensively analyzes three types of industrially produced hydrochar [...] Read more.

Hydrothermal carbonization (HTC) technology converts biomass into a carbon-rich, oxygen-containing solid fuel. Most studies have focused on hydrochar produced under laboratory conditions, leaving a gap in understanding the performance of industrially produced hydrochar. This study comprehensively analyzes three types of industrially produced hydrochar for blast furnace (BF) injection. The results indicate that hydrochar has a higher volatile and lower fixed carbon content. It has a lower high heating value (HHV) than coal and contains more alkali matter. Nevertheless, hydrochar exhibits a better grindability and combustion performance than coal. Blending hydrochar with anthracite significantly enhances the combustion reactivity of the mixture. The theoretical conversion rate calculations reveal a synergistic effect between hydrochar and anthracite during co-combustion. Environmental benefit calculations show that replacing 40% of bituminous coal with hydrochar can reduce CO₂ emissions by approximately 145 kg/tHM, which is equivalent to an annual reduction of 528 kton of CO₂ and 208 kton of coal in BF operations. While industrially produced hydrochar meets BF injection requirements, its low ignition point and high explosivity necessitate the careful control of the blending ratio. Full article

(This article belongs to the Special Issue Biomass Revival: Rethinking Waste Recycling for a Greener Future)

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15 pages, 3012 KiB

Open AccessArticle

Efficient Extraction of Lithium, Cobalt, and Nickel from Nickel-Manganese-Cobalt Oxide Cathodes with Cholin Chloride/Pyrogallol-Based Deep Eutectic Solvent

by Aisulu Batkal, Kaster Kamunur, Lyazzat Mussapyrova, Yerzhan Mukanov and Rashid Nadirov

Recycling 2025, 10(3), 88; https://doi.org/10.3390/recycling10030088 - 3 May 2025

This study explores the use of a deep eutectic solvent (DES) composed of choline chloride and pyrogallol (1:1 molar ratio) for the recovery of lithium, cobalt, and nickel from spent lithium-ion battery cathodes based on LiNi_0.33Co_0.33Mn_0.33O₂ [...] Read more.

This study explores the use of a deep eutectic solvent (DES) composed of choline chloride and pyrogallol (1:1 molar ratio) for the recovery of lithium, cobalt, and nickel from spent lithium-ion battery cathodes based on LiNi_0.33Co_0.33Mn_0.33O₂ (NMC111). The DES exhibits moderate viscosity, intrinsic redox activity, and strong complexation ability, enabling efficient metal dissolution under mild conditions. The effects of both temperature (50–80 °C) and time (up to 12 h) on leaching efficiency were systematically investigated. Optimal leaching parameters—80 °C, 8 h, and a liquid-to-solid ratio of 50—yielded extraction efficiencies of 92% for Li, 85% for Co, and 88% for Ni. Kinetic modeling indicated pseudo-first-order behavior with activation energies of 26.6, 22.1, and 25.2 kJ/mol for Li, Co, and Ni, respectively. Mechanistic analysis confirmed the dual role of pyrogallol as both reducing agent (facilitating Co³⁺ to Co²⁺ conversion) and chelating ligand. Full article

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24 pages, 1089 KiB

Open AccessReview

Bioleaching of Gold from Printed Circuit Boards: Potential Sustainability of Thiosulphate

by Zahra Ilkhani and Farid Aiouache

Recycling 2025, 10(3), 87; https://doi.org/10.3390/recycling10030087 - 3 May 2025

The rapid consumption and disposal of electronic waste due to technological innovations and changes in living commodities are causing the development of a significant environmental challenge. Among the components of these wastes, spent printed circuit boards are particularly considered to be among the [...] Read more.

The rapid consumption and disposal of electronic waste due to technological innovations and changes in living commodities are causing the development of a significant environmental challenge. Among the components of these wastes, spent printed circuit boards are particularly considered to be among the most valuable owing to their content of precious metals, such as gold first and potentially platinum, which may be available in a lower proportion. Effective methods as part of gold recovery strategies by industries and policymakers are developed and envisioned from economic and environmental perspectives. Currently, cyanidation dominates global gold production from e-waste due to its selectivity for gold. The high toxicity of cyanide, however, poses serious environmental issues, leading thiosulphate leaching to emerge as a non-toxic and promising alternative for gold extraction. Its industrial viability has been demonstrated by Barrick Gold Corporation at the Goldstrike site with the pretreatment of acidic or alkaline pressure oxidation. This review introduces bioleaching as a promising economic and environmentally friendly process for gold extraction. This review explores thiosulphate leaching of gold as an alternative to conventional cyanidation, with a particular focus on biothiosulphate production by adapted microorganisms. The factors that affect the pretreatment, chemical reaction mechanism, and design engineering are discussed. The consumption of thiosulphate was identified as one of the main challenges, restricting the reliability of the process. Various solutions for the reduction of its consumption and relevant process costs were discussed, with a particular examination from the engineering aspect of the process design and scalability to industrially relevant operating conditions by using bioreactors adapted to large pulp density loads of electrical waste. Full article

(This article belongs to the Special Issue Emerging Technologies in the Hydrometallurgical Recycling of Critical Metals)

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22 pages, 15469 KiB

Open AccessArticle

Electrolytic Recovery of Indium from Copper Indium Gallium Selenide Photovoltaic Panels: Preliminary Investigation of Process Parameters

by Monika Gajec, Anna Król, Jadwiga Holewa-Rataj, Ewa Kukulska-Zając and Tomasz Kuchta

Recycling 2025, 10(3), 86; https://doi.org/10.3390/recycling10030086 - 2 May 2025

The European Green Deal emphasizes the development of renewable energy sources to combat climate change. However, as photovoltaic expansion accelerates, so does the potential for increased waste, necessitating effective material recycling strategies. Indium, a scarce and valuable element crucial to the production of [...] Read more.

The European Green Deal emphasizes the development of renewable energy sources to combat climate change. However, as photovoltaic expansion accelerates, so does the potential for increased waste, necessitating effective material recycling strategies. Indium, a scarce and valuable element crucial to the production of photovoltaic panels, underscores the necessity for efficient recycling practices to reduce reliance on virgin resources. In a recent laboratory analysis, a CIGS photovoltaic panel underwent a series of processes including crushing, grinding, and homogenization. The concentration of indium, vital for recycling, was meticulously analyzed using ICP-MS and validated through microscopic and composition analyses. Subsequent extraction utilizing 3 M HCl and H₂O₂, followed by electrolysis, yielded a remarkable up to 52% indium recovery within a 48-h timeframe. Importantly, the study encompassed both averaged panel samples and samples from the absorbing layer, emphasizing the comprehensive approach required for efficient recycling. This underscores the critical importance of optimizing recycling processes to mitigate the environmental impact associated with the disposal of photovoltaic panels. By maximizing indium recovery, not only are environmental impacts reduced, but the long-term sustainability of renewable energy technologies is also ensured. This highlights the interconnectedness of recycling practices with the broader goals of achieving a circular economy and securing the viability of renewable energy systems in the fight against climate change. Full article

(This article belongs to the Special Issue Emerging Technologies in the Hydrometallurgical Recycling of Critical Metals)

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15 pages, 7197 KiB

Open AccessArticle

Chemical Recycling of Catalytic Glycolysis of Polyethylene Terephthalate with Potassium-Rich Biomass

by Zhe Bai, Zhixian Bao and Haoquan Hu

Recycling 2025, 10(3), 85; https://doi.org/10.3390/recycling10030085 - 2 May 2025

Polyethylene terephthalate (PET) products are ubiquitous in daily life, offering convenience but posing significant environmental challenges due to their persistence and the difficulty of recycling them. Improper disposal of waste PET contributes to severe pollution and resource loss. Chemical degradation has emerged as [...] Read more.

Polyethylene terephthalate (PET) products are ubiquitous in daily life, offering convenience but posing significant environmental challenges due to their persistence and the difficulty of recycling them. Improper disposal of waste PET contributes to severe pollution and resource loss. Chemical degradation has emerged as one of the most effective methods for recovering and reusing waste PET. This article introduces a catalytic glycolysis strategy for efficient and environmentally sustainable PET recycling using potassium-rich biomass, specifically banana peels. The study demonstrated that K₂O and K₂CO₃, derived from calcined banana peels, significantly catalyze the glycolysis of PET. Under optimal conditions, complete degradation of PET was achieved within 1.5 h at 180 °C, without additional chemical reagents. Product distribution confirmed that high-purity bis(2-hydroxyethyl) terephthalate could be obtained. The interaction between K₂CO₃ and ethylene glycol plays a critical role in determining the competition between glycolysis and alkaline hydrolysis. Furthermore, Density Functional Theory calculations provided valuable insights into the transesterification process during glycolysis. The reaction system also demonstrated excellent compatibility with colored PET products. This study successfully realized the simultaneous recycling of post-consumer PET and banana peels, offering a novel and sustainable approach to waste valorization. Full article

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23 pages, 3745 KiB

Open AccessArticle

Towards Circularity in Anaerobic Digestion: Methane Yield Enhancement Using Biochar from Co-Pyrolysis of Anaerobic Sludge and Residual Lignocellulosic Biomass

by César Omar Díaz Lara, Diana Cabañas Vargas, Julio César Sacramento Rivero, Sergio Baz-Rodríguez, Juan Enrique Ruiz Espinoza, Erick Alberto Aguilera-Cauich, José Martín Baas-López and Daniella E. Pacheco-Catalán

Recycling 2025, 10(3), 84; https://doi.org/10.3390/recycling10030084 - 1 May 2025

Improper management of anaerobic pig sludge poses significant environmental and health risks. Converting this waste into biochar to enhance methane production during anaerobic digestion (AD) presents an environmentally sound and circular solution, especially when the biochar is produced through co-pyrolysis with lignocellulosic biomass [...] Read more.

Improper management of anaerobic pig sludge poses significant environmental and health risks. Converting this waste into biochar to enhance methane production during anaerobic digestion (AD) presents an environmentally sound and circular solution, especially when the biochar is produced through co-pyrolysis with lignocellulosic biomass residues. This study first determined the co-pyrolysis biomass ratio (anaerobic sludge to lignocellulosic biomass) that caused the highest increase on methane yield. Subsequently, the effects of biochar dosage (6, 12, 18, 24, and 30 g/L) and particle size (0.5–1 cm, 212–355 µm, and <53 µm) on methane production were assessed. Biochar derived from up to 25 % anaerobic pig sludge increased methane yield by 74.49 ± 1.25 % without compromising its catalytic effect. Methane yield was significantly affected by both biochar dosage and particle size, with best results observed at dosages of 12–18 g/L. These findings highlight the feasibility of the co-pyrolysis of anaerobic pig sludge and lignocellulosic residues as an attractive circular solution for integrated waste management and energy production. Full article

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