Recycling

22 pages, 831 KB

Open AccessReview

Representing Reuse in the Circular Economy: A Study of Circularity Indicators

by Justine Gloz, Stuart Walker and Rachael Rothman

Recycling 2026, 11(9), 166; https://doi.org/10.3390/recycling11090166 - 10 Sep 2026

Reuse is widely regarded as a primary strategy to mitigate plastic packaging waste, occupying a higher position than recycling in the waste hierarchy. However, most existing circularity indicators do not include reuse or include it only as an inferior circularity strategy. This paper [...] Read more.

Reuse is widely regarded as a primary strategy to mitigate plastic packaging waste, occupying a higher position than recycling in the waste hierarchy. However, most existing circularity indicators do not include reuse or include it only as an inferior circularity strategy. This paper evaluates how existing circularity indicators applicable to packaging integrate reuse in their calculation methods and results. A literature review identified 88 circularity indicators, which were filtered to 11 based on active usage and packaging relevance. These 11 indicators were analysed against the ISO 59004:2024 circularity framework using a scoring matrix. The four most relevant indicators (Material Circularity Indicator, Product Circularity Indicator (PCI), Eco-efficient Value Ratio and UP Scorecard) were evaluated using a comparative assessment of a reusable plastic container. Three key variables were tested: recycled content, recycling rate, and number of reuses. No single indicator performed best across all three assessment methods. While combining PCI and the UP Scorecard provides the most thorough assessment currently available, this combination still fails to fully capture sensitivity to varying levels of reuse. Future circularity indicators must evaluate both the level and operational feasibility of reuse, rather than relying on binary inclusion. Full article

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25 pages, 1057 KB

Open AccessArticle

Eco-Audit Comparison of End-of-Life Strategies for Thermoset and Thermoplastic Wind Turbine Blades

by Navid Farazmandnia and Adrian Ilinca

Recycling 2026, 11(9), 165; https://doi.org/10.3390/recycling11090165 - 10 Sep 2026

Abstract

Wind turbine blade composites represent a growing end-of-life (EoL) waste challenge because thermoset blades lack commercially mature recycling routes, whereas thermoplastic blades offer improved recyclability through dissolution. This study compares the net environmental impact of ten EoL strategies for six 45 m blade [...] Read more.

Wind turbine blade composites represent a growing end-of-life (EoL) waste challenge because thermoset blades lack commercially mature recycling routes, whereas thermoplastic blades offer improved recyclability through dissolution. This study compares the net environmental impact of ten EoL strategies for six 45 m blade configurations comprising thermoset epoxy and thermoplastic Elium resin systems reinforced with glass fiber, carbon fiber, and hybrid laminates, using an eco-audit methodology based on cumulative primary energy demand. Solvolysis is the leading route for thermoset blades and dissolution for thermoplastic blades, reducing net impact to 74.9%, 31.7%, and 22.4% and to 53.6%, 23.4%, and 18.3% of the landfill benchmark for glass-fiber, hybrid, and carbon-fiber configurations, respectively. Thermoplastic blades therefore fall 296.0, 273.1, and 217.2 GJ below their thermoset counterparts. High-voltage fragmentation, conventional pyrolysis, and microwave-assisted pyrolysis are counterproductive for thermoset glass-fiber blades, exceeding landfill by 26.6%, 18.9%, and 8.1%, respectively, because of high process energy and the limited value of recovered glass fiber. Both material-system selection and recycling-route selection govern end-of-life performance, with the route dimension dominating for glass-fiber blades. A Monte Carlo analysis in which all parameters vary simultaneously confirms that solvolysis and dissolution remain the preferred routes for their respective material systems in every run. Thermoplastic blades fall below their thermoset counterparts in 100.0% and 98.8% of runs for glass-fiber and hybrid laminates, but in 80.3% for carbon fiber, where the advantage is indicated rather than established. These results highlight the importance of designing future wind turbine blades through material selection and recyclable composite systems. Full article

(This article belongs to the Special Issue Resource Recovery and High-Value Utilization of Renewable Energy Solid Waste)

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19 pages, 26683 KB

Open AccessArticle

Refining the Fe-Containing IMCs in Al-Fe Alloy Through a Heterogeneous Nucleation Interface for an Enhanced Ductility of Recycled Aluminum Alloys

by Zhicheng Yin, Xiaozu Zhang, Dongtao Wang, Hiromi Nagaumi, Rui Wang, Minghe Zhang, Lin Zhao, Dongsheng Gao and Ying Gao

Recycling 2026, 11(9), 164; https://doi.org/10.3390/recycling11090164 - 9 Sep 2026

Abstract

The coarse Fe-containing intermetallics (IMCs) induced by excessive Fe levels seriously degrade the mechanical and corrosion properties of recycled aluminum alloys. Controlling the nucleation and growth behavior has been confirmed as effective in refining the Fe-containing intermetallics (IMCs) and enhancing the ductility of [...] Read more.

The coarse Fe-containing intermetallics (IMCs) induced by excessive Fe levels seriously degrade the mechanical and corrosion properties of recycled aluminum alloys. Controlling the nucleation and growth behavior has been confirmed as effective in refining the Fe-containing intermetallics (IMCs) and enhancing the ductility of recycled aluminum alloys. In this work, the modification mechanism of Al–Ti–B in Al–2Fe alloy was systematically investigated by combining SEM microstructure, TEM characterization and DFT calculations. TEM observations reveal that TiB₂ particles are preferentially embedded within Al₁₃Fe₄ phases, forming coherent or semi-coherent interfaces, which act as nucleation sites and facilitate the refinement and uniform distribution of Fe-containing IMCs. Interface property calculation results show that the Al₁₃Fe₄ (620)/TiB₂ (01

\bar{1}

1) interface exhibits lower lattice mismatch (4.4%) and interface energy, indicating stronger interfacial bonding and higher interface stability. The electronic structure results showed that the enhanced interface stability is attribute to the pronounced charge redistribution. Stable interface structure reduces the heterogeneous nucleation barrier and promotes refinement efficiency of Fe-containing ICMs. This study provides theoretical guidance for the refinement of Fe-containing impurity phases and high-performance sustainable recycling of aluminum alloy scrap. Full article

(This article belongs to the Special Issue Resource Recovery and High-Value Utilization of Renewable Energy Solid Waste)

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27 pages, 15707 KB

Open AccessArticle

Silver Recovery from Jarosite Residue Using NADES (Reline)–Water Mixtures: Characterization and Leaching Performance

by Teresita del Refugio Jiménez Romero, Alejandro Cruz Ramírez, Ángel de Jesús Morales Ramírez, Jose Enrique Sanchez Vite, Margarita García Hernández, José Antonio Romero Serrano, Víctor Hugo Gutiérrez Pérez and Manuel Eduardo Flores Favela

Recycling 2026, 11(9), 163; https://doi.org/10.3390/recycling11090163 - 8 Sep 2026

Abstract

Jarosite residues generated during zinc hydrometallurgy may retain valuable metals such as silver within complex and poorly accessible mineral phases. In this study, hydrated reline, a choline chloride–urea natural deep eutectic solvent (NADES), was evaluated as an alternative leaching medium for silver recovery [...] Read more.

Jarosite residues generated during zinc hydrometallurgy may retain valuable metals such as silver within complex and poorly accessible mineral phases. In this study, hydrated reline, a choline chloride–urea natural deep eutectic solvent (NADES), was evaluated as an alternative leaching medium for silver recovery from an industrial jarosite residue. Reline/water mixtures containing 10, 20, and 30 wt.% water (RE9010, RE8020, and RE7030, respectively) were investigated to determine the influence of solvent hydration and temperature (25–80 °C) on silver extraction. Mineralogical characterization by XRD, SEM–EDS, and automated TIMA analysis revealed a heterogeneous residue in which silver-bearing phases are associated with complex mineral assemblages, potentially limiting their accessibility during leaching. Among the evaluated systems, RE9010 consistently exhibited the highest silver recovery, increasing from 12.83% at 25 °C to 24.10% at 80 °C. Successive leaching cycles further increased the cumulative silver recovery to 34.7% for RE9010. FTIR analysis showed that the characteristic spectral features of reline were preserved after the addition of up to 30 wt.% water. Kinetic analysis indicated that diffusion-based models provided the best description of the leaching behavior, with the Zhuravlev–Lesokhin–Templeman model showing the best overall fit. An apparent activation energy of 18.4 kJ mol⁻¹ was obtained, supporting the contribution of mass-transfer and diffusion phenomena to the overall process. These results demonstrate that controlled hydration and moderate heating can improve the leaching performance of reline while preserving its characteristic interactions, highlighting its potential as an alternative solvent for silver recovery from complex metallurgical residues. Full article

(This article belongs to the Topic Waste Management for Recycling and Environmental Protection)

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30 pages, 2802 KB

Open AccessArticle

Barriers to Construction and Demolition Waste Management in Australia: A Comparative Analysis for Advancing Circular Economy Practices

by Noushin Islam, Malindu Sandanayake, Shobha Muthukumaran and Dimuth Navaratna

Recycling 2026, 11(9), 162; https://doi.org/10.3390/recycling11090162 - 7 Sep 2026

Abstract

The Australian construction industry generated approximately 29.2 million metric tonnes (Mt) of construction and demolition waste (C&DW) in 2022–2023, of which about 23.7 Mt (81.2%) was recovered, primarily through recycling (80.6%). Recovery concentrated on concrete, bricks, and rubble from large constructions, while C&DW [...] Read more.

The Australian construction industry generated approximately 29.2 million metric tonnes (Mt) of construction and demolition waste (C&DW) in 2022–2023, of which about 23.7 Mt (81.2%) was recovered, primarily through recycling (80.6%). Recovery concentrated on concrete, bricks, and rubble from large constructions, while C&DW from smaller projects was often directed to landfills. Most recovered materials are downcycled, have low market demand and contribute to unstable markets and continued reliance on virgin materials. To investigate these gaps, nine semi-structured expert interviews, two case studies, and a SWOT (Strengths, Weaknesses, Opportunities and Threats) analysis were conducted. The findings were organised into four clusters: (1) regulatory and governance, (2) operational and technological, (3) procurement, cost and market, and (4) stakeholder management barriers significantly impact C&D waste management practices. The study recommends four drivers and six enablers to enhance circular economy 3R (reduce, reuse, recycle) practices, including standardisation and harmonisation of reused and recycled products’ quality and cost, mandating circular procurement, increasing incentives and penalties, on-site sorting, awareness and capacity building, and digital technology application for data management. This integrated approach can guide policymakers and practitioners in strengthening C&DW reduction practices and developing an economically viable market for reused and recycled products. Full article

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28 pages, 828 KB

Open AccessReview

Hydrodynamic Cavitation in Circular Hydrometallurgical Flowsheets: Function-Specific Evidence and Process Integration for Secondary-Resource Recovery

by Lorenzo Albanese

Recycling 2026, 11(9), 161; https://doi.org/10.3390/recycling11090161 - 3 Sep 2026

Abstract

Metal-bearing tailings, slimes, metallurgical residues, spent catalysts, ashes, sludges, batteries, and electronic wastes are increasingly important secondary resources, but recovery is constrained by low and variable grades, fine particles, complex phase associations, passivation, and impurity-sensitive downstream processing. Hydrodynamic cavitation (HC) can modify selected [...] Read more.

Metal-bearing tailings, slimes, metallurgical residues, spent catalysts, ashes, sludges, batteries, and electronic wastes are increasingly important secondary resources, but recovery is constrained by low and variable grades, fine particles, complex phase associations, passivation, and impurity-sensitive downstream processing. Hydrodynamic cavitation (HC) can modify selected flowsheet functions through interfacial renewal, localized mechanical action, gas–liquid transfer, fine-bubble generation, particle conditioning, and phase dispersion. The evidence was critically appraised across three independent dimensions: system relevance, causal attribution, and endpoint completeness. Application-level evidence is most developed for transport intensification in selected scheelite, uranium-bearing, and refractory-gold systems; particle conditioning and washing; spent-catalyst coating liberation; metal-bearing sludge treatment; copper cementation; and preparation of liquid emulsion membranes. Representative secondary-feed studies report conditioning, preconcentration, mobilization, and downstream separation responses, but complete feed-to-product recovery with controlled liquid and solid loops remains uncommon. Evidence is especially limited for battery black mass, electronic wastes, rare-earth-bearing residues, complex slags, metallurgical dusts, and multi-metal streams. HC is therefore most credible as a targeted module applied to a verified process limitation. A flowsheet advantage is established only when local gains persist through product recovery without offsetting increases in chemical use, water demand, energy consumption, equipment wear, or residual-stream burden. Full article

(This article belongs to the Special Issue Emerging Technologies in the Hydrometallurgical Recycling of Critical Metals, 2nd Edition)

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34 pages, 5008 KB

Open AccessArticle

Sustainable Cosmetic Packaging in China: Multi-Level Evaluation of Physical Elements Under ESG Principles

by Yueqian Gong and Charanya Phaholthep

Recycling 2026, 11(9), 160; https://doi.org/10.3390/recycling11090160 - 1 Sep 2026

Abstract

This study constructs a multi-level evaluation framework for sustainable cosmetic packaging design, guided by environmental, social, and governance (ESG) principles. The framework integrates sustainable packaging principles with the Environmental (E), Social (S), and Governance (G) dimensions and introduces Physical Elements (PE) as a [...] Read more.

This study constructs a multi-level evaluation framework for sustainable cosmetic packaging design, guided by environmental, social, and governance (ESG) principles. The framework integrates sustainable packaging principles with the Environmental (E), Social (S), and Governance (G) dimensions and introduces Physical Elements (PE) as a supplementary evidence layer for verifying packaging-related indicators through observation or documentary evidence. The framework was screened and weighted through expert evaluation, and 50 cosmetic packaging samples collected from Jiangsu and Shanghai, China, were evaluated. The direct principle weights for the Environmental, Social, and Governance dimensions were 0.394, 0.312, and 0.294, respectively, indicating relatively modest differences. Because Governance Indicators were not linked to packaging-level PE, the quantitative assessment focused on eight Environmental and ten Social Indicators, while Governance served as an interpretive dimension. Mean E–S composite scores were highest for bottle/tube and jar packaging, at 57% and 53%, followed by pouch packaging (43%), pen-type packaging (39%), and compact packaging (38%). Verified attributes were concentrated in basic functionality, product information, and selected recycling-related features, with less evidence of renewable-material use, reusable or refillable design, inclusive design, and detailed recycling guidance. The findings demonstrate how packaging-level evidence can identify design gaps while relating observable attributes to broader ESG responsibilities. Full article

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Graphical abstract

16 pages, 5093 KB

Open AccessArticle

Mechanical Performance and Environmental Assessment of Hybrid Reinforced Gypsum Composites Incorporating Commercial and Recycled Fibers

by Leonardo Lima, Alicia Zaragoza-Benzal, Daniel Ferrández, Alberto Leal Matilla and Paulo Santos

Recycling 2026, 11(9), 159; https://doi.org/10.3390/recycling11090159 - 1 Sep 2026

Abstract

The use of hybrid fiber reinforcement has been investigated to enhance the performance of gypsum-based materials, taking advantage of several types of fibers. This study develops hybrid fiber-reinforced gypsum composites (HFRGCs) incorporating sixteen combinations of recycled mineral wool (RMW) and polypropylene (PP) fibers, [...] Read more.

The use of hybrid fiber reinforcement has been investigated to enhance the performance of gypsum-based materials, taking advantage of several types of fibers. This study develops hybrid fiber-reinforced gypsum composites (HFRGCs) incorporating sixteen combinations of recycled mineral wool (RMW) and polypropylene (PP) fibers, with contents ranging from 0.25 to 1.00 wt.%. The samples are mechanically characterized, and statistical analyses of the measured values are conducted. Moreover, a life cycle assessment (LCA) is also performed regarding their environmental impacts. The HFRGC containing 0.50 wt.% RMW fibers and 1.00 wt.% PP fibers exhibited the highest surface hardness, with a 5.5% increase compared with the reference. The highest flexural and compressive strengths were achieved by HFRGCs containing 0.50 wt.% PP fibers, reaching increases of 7.5% and 9.0%, respectively, with only a minor influence of RMW fibers, whose greatest contribution was reducing environmental impacts due to the low energy demand for recycling this industrial waste compared with the high emissions from PP fiber production. A statistical analysis revealed no significant differences in the mechanical properties of HFRGCs containing 0.50 and 1.00 wt.% PP fibers, suggesting that increasing the PP fiber content beyond 0.50 wt.% did not result in significant mechanical improvements. Therefore, considering both mechanical and environmental aspects, the HFRGC incorporating 1.00 wt.% RMW fiber and 0.50 wt.% PP fibers provided the most balanced overall performance. Full article

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30 pages, 14755 KB

Open AccessSystematic Review

Artificial Intelligence in Circular Economy and Waste Management: A Systematic Review of Applications for Optimization Strategies and Resource Recovery Pathways

by Silvia Kaigugu, Asnidar Hanim Yusuf, Waris Ali Khan, Isaac Yeboah, Ajit Kumar Singh and Idris Oyewale Oyelakin

Recycling 2026, 11(9), 158; https://doi.org/10.3390/recycling11090158 - 1 Sep 2026

Abstract

Background: The transition from conventional waste management to circular economy systems has generated more interest in how artificial intelligence (AI) can enhance waste prevention, sorting and recycling, optimization, and resource recovery. Owing to the growing complexity and data-driven nature of waste systems, AI [...] Read more.

Background: The transition from conventional waste management to circular economy systems has generated more interest in how artificial intelligence (AI) can enhance waste prevention, sorting and recycling, optimization, and resource recovery. Owing to the growing complexity and data-driven nature of waste systems, AI has been used to aid operational and strategic decisions throughout the waste management chain. Methods: This study is a systematic review of the literature between 2016 and 2026 on AI in waste management in the circular economy, conducted according to the PRISMA 2020 guidelines based on three directions: AI application, optimization techniques, and recovery routes of resources. In this systematic review, 52 studies were included through systematic database searches, eligibility screening, clear inclusion criteria, and thematic synthesis of the literature to identify the key research areas of AI techniques, optimization strategies, and resource recovery pathways in the circular economy and waste management. Results: The review shows that optimization is the key to implementing the principles of the circular economy in waste management decision-making, and that AI is no longer seen as a taboo topic in the literature but as a functional application. System-level integration and the integration of systems in a holistic circular economy are not yet fully consolidated. To overcome the limitations of single-application studies, an Integrative AI–Circular Waste Value Chain (AI-CWVC) framework is proposed. Conclusions: This review highlights the importance of AI in supporting circular waste management and points to the need for further research that is more integrated, evidence-based, and policy-aligned. Full article

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22 pages, 785 KB

Open AccessArticle

The Use of Bioactive Extracts from Fish By-Products in Improving Microbiological Stability of Fish Based Food

by Kiana Bila, Lucas Comba, Edgar Perestrelo, Sara Tomé, Verónica Weng, Maria Paula Duarte, Isabel Coelhoso, Pedro Simões and Victor Gomes Lauriano Souza

Recycling 2026, 11(9), 157; https://doi.org/10.3390/recycling11090157 - 1 Sep 2026

Abstract

Fish is a food of high nutritional value, being an important source of proteins, fat, vitamins, and essential minerals. Atlantic horse mackerel is also rich in omega-3 polyunsaturated fatty acids (n3-PUFAs), recognized for their benefits to cardiovascular and neurological health. However, this composition [...] Read more.

Fish is a food of high nutritional value, being an important source of proteins, fat, vitamins, and essential minerals. Atlantic horse mackerel is also rich in omega-3 polyunsaturated fatty acids (n3-PUFAs), recognized for their benefits to cardiovascular and neurological health. However, this composition also makes it highly susceptible to lipid oxidation, reducing its shelf life. Oxidation is accelerated by high water activity and near-neutral pH, conditions common in fish and processed products such as fish burgers. This work aimed to develop fish burgers incorporated with bioactive extracts (protein hydrolysates from cod fish processing by-product—PH, or green tea extract—GTE) and study their shelf life. The PH was recovered from cod frames using subcritical water extraction, and GTE with hydro-alcoholic extraction. The fish burgers were prepared using minced fish meat incorporated with 1% (w/w) of extracts, in four formulations: (i) 1% (w/w) of PH; (ii) 1% (w/w) of GTE; (iii) a combination of both extracts at 0.5% (w/w) each; and (iv) control without extracts. Physical–chemical, antioxidant and microbiological analysis of the burgers was performed to evaluate their preservation over 6 days of refrigerated storage. Compared to the control, samples with only GTE or the combined GTE + PH presented a delay in oxidation (50% less in TBARS) and microbiological deterioration (reduction of 0.5–1.8 Log CFU/g in total psychrotropic microorganisms). No significant changes were observed in the fish burgers incorporated with only PH. The results demonstrate that the incorporation of bioactive extracts has potential in reducing oxidative degradation and improving microbiological stability in fish-based products; however, superior doses must be used. Moreover, the use of natural extracts aligns with current consumer demand for clean-label and functional foods. Full article

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23 pages, 7069 KB

Open AccessArticle

The Network Structure and Driving Mechanisms of Construction Waste Management Efficiency in the European Union

by Yanxin Zhou, Yufei Wang, Ning Zhao and Zhengshuang Wang

Recycling 2026, 11(9), 156; https://doi.org/10.3390/recycling11090156 - 1 Sep 2026

Abstract

This study measures construction waste management efficiency (CWME) in 27 EU member states (2016–2025) using a three-stage super-efficiency SBM-DEA model, constructs a spatial correlation network via a modified gravity model, and employs social network analysis and random forest to investigate network structure and [...] Read more.

This study measures construction waste management efficiency (CWME) in 27 EU member states (2016–2025) using a three-stage super-efficiency SBM-DEA model, constructs a spatial correlation network via a modified gravity model, and employs social network analysis and random forest to investigate network structure and driving mechanisms. Results reveal persistent cross-country heterogeneity and a widening East–West efficiency divide. The CWME network exhibits small-world characteristics, with CONCOR analysis partitioning member states into four blocks: Northern and Baltic states serve as the dominant Net Spillover bloc, whereas Southern periphery countries remain Net Beneficial recipients whose membership contracted from five to three by 2025. Random forest identifies government environmental protection expenditure, unit labour cost, and population density as the top three driving factors, with unit labour cost and government environmental protection expenditure exhibiting the strongest negative marginal effects on CWME, while urbanization rate shows a near-neutral relationship. These findings provide empirical support for policy interventions targeting the structural economic determinants of CWME. By integrating efficiency measurement, spatial network analysis, and machine learning-based driver identification, this study offers a comprehensive framework for diagnosing regional disparities in construction waste governance and informing cross-regional collaborative policy design. Full article

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22 pages, 2334 KB

Open AccessArticle

Life Cycle Assessment of Anaerobic Digestion Pathways for Winery Residues: Influence of Functional Unit Selection on Wastewater Treatment and Grape Pomace Valorization

by Mara Silva, Vitor Coelho Barroso, José Pereira and Ana Catarina Faria

Recycling 2026, 11(9), 155; https://doi.org/10.3390/recycling11090155 - 27 Aug 2026

Abstract

Winery activities generate large amounts of residues requiring sustainable management. Anaerobic digestion offers opportunities for resource recovery while reducing the environmental burdens associated with these residues. This study presents a gate-to-gate Life Cycle Assessment (LCA) of two anaerobic digestion pathways: winery wastewater treatment [...] Read more.

Winery activities generate large amounts of residues requiring sustainable management. Anaerobic digestion offers opportunities for resource recovery while reducing the environmental burdens associated with these residues. This study presents a gate-to-gate Life Cycle Assessment (LCA) of two anaerobic digestion pathways: winery wastewater treatment (Scenario A) and grape pomace valorization (Scenario B). Inventory data were obtained from pilot-scale operation and complemented with the Ecoinvent 3.10 database. Environmental impacts were assessed using the ReCiPe 2016 Midpoint (H) method across seven impact categories. To ensure comparability, results were evaluated using both process-based functional units and an energy-normalized functional unit of 1 MJ of useful electricity, applied as an exploratory indicator of energy-recovery intensity under pilot-scale conditions. Although grape pomace digestion showed higher impacts per unit of substrate processed, it achieved lower impacts per MJ of electricity generated, with reductions of approximately 8–10 times across categories. Higher methane yields and lower electricity demand were contributors to this performance. However, both pilot-scale systems exhibited negative net electricity balances, indicating that the energy-normalized comparison represents energy-recovery intensity rather than net energy delivery. The findings highlight the importance of functional unit selection and the complementary role of both pathways in circular winery residue management. Full article

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24 pages, 17632 KB

Open AccessArticle

TiO₂-Fly Ash Composites for Photocatalytic Degradation of Organic Loading from Real Municipal Wastewater

by Mirela Alina Constantin, Ioana Alexandra Ionescu, Florenta Daniela Constantinov, Cristina Mihaela Nicolescu, Marius Bumbac, Anca Irina Gheboianu and Lucian Alexandru Constantin

Recycling 2026, 11(8), 154; https://doi.org/10.3390/recycling11080154 - 20 Aug 2026

Abstract

Fly ash-TiO₂ composites were obtained by sol–gel, and their catalytic performance was evaluated on removal of organic loading and expressed as Chemical Oxygen Demand (COD) from real wastewater samples. SEM, X-ray fluorescence, XRD, IR, Raman analysis and determination of PZC characterized the [...] Read more.

Fly ash-TiO₂ composites were obtained by sol–gel, and their catalytic performance was evaluated on removal of organic loading and expressed as Chemical Oxygen Demand (COD) from real wastewater samples. SEM, X-ray fluorescence, XRD, IR, Raman analysis and determination of PZC characterized the catalysts. The photocatalytic tests were carried out in a laboratory reactor under UV-VIS irradiation and influence of fly ash (FA) content, and irradiation time was investigated. The catalysts with FA content of 10%, 20% and 30% showed COD removal efficiencies higher than 50% after 5 h of irradiation. The COD degradation followed a pseudo-first order kinetic model. Obtained results proved that FA-TiO₂ composites could represent a suitable alternative for removal of organic loading from real wastewater. Full article

(This article belongs to the Special Issue Advanced Wastewater Treatment and Resource Recovery: Pathways to Circular Valorization)

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23 pages, 308 KB

Open AccessArticle

Designing for Evaluability in Recycling and Waste Governance: A Review of Intervention Traditions and Socio-Technical Architecture

by Michael Carolan

Recycling 2026, 11(8), 153; https://doi.org/10.3390/recycling11080153 - 19 Aug 2026

Abstract

Research on recycling and waste governance has produced extensive knowledge about the factors influencing environmentally responsible behavior. Studies examine strategies—including feedback systems, incentives, social norms, gamification, and certification schemes—to encourage recycling and waste reduction. Although these approaches differ in their theoretical foundations and [...] Read more.

Research on recycling and waste governance has produced extensive knowledge about the factors influencing environmentally responsible behavior. Studies examine strategies—including feedback systems, incentives, social norms, gamification, and certification schemes—to encourage recycling and waste reduction. Although these approaches differ in their theoretical foundations and intervention designs, many seek to make environmental actions visible, measurable, and feasible. Less attention has been devoted to how such actions acquire social meaning and become recognizable as worthy of evaluation, distinction, and acknowledgment. This study addresses that gap through a configurative review of 37 documents selected to represent diverse recycling and waste-governance intervention traditions. A comparative analysis reconstructed the recurring explanatory mechanisms through which environmental actions become evaluable. The findings show that intervention traditions commonly treated as distinct repeatedly rely on an evaluative architecture comprising five interacting components: visibility, evaluation, credibility, distinction, and embedding. These components constitute recognition infrastructures—governance arrangements that produce evaluability by rendering environmental actions observable, publicly meaningful, and sustainable over time. The framework identifies similarities across intervention traditions often studied separately and shifts attention from individual intervention tools to the broader arrangements that make environmental actions significant, while providing a practical lens for designing more durable recycling and waste-governance interventions. Full article

20 pages, 20032 KB

Open AccessArticle

Integrating Sustainable Recycling Practices into Mechanical–Electrical and Industrial Engineering Education Programs: Sustainable PET Bottle Recycling

by Jorge Alberto Chagoya-Ramírez, Alondra González-Segura, Juan Rodrigo Laguna-Camacho, Héctor Daniel López-Calderón, Celia María Calderón-Ramón, Paul Ramírez-Sánchez, Javier Calderón-Sánchez and Víctor Velázquez-Martínez

Recycling 2026, 11(8), 152; https://doi.org/10.3390/recycling11080152 - 19 Aug 2026

Abstract

The increasing accumulation of polyethylene terephthalate (PET) bottles represents a significant environmental challenge due to their high consumption and limited recovery. The purpose of this study was to develop a sustainable alternative for reusing this waste by manufacturing educational test specimens for laboratory [...] Read more.

The increasing accumulation of polyethylene terephthalate (PET) bottles represents a significant environmental challenge due to their high consumption and limited recovery. The purpose of this study was to develop a sustainable alternative for reusing this waste by manufacturing educational test specimens for laboratory exercises in electrical mechanical engineering and industrial engineering programs. The proposed method was based on mechanical recycling and incorporated, as an innovation, a stage for measuring bottle parameters before processing to improve the quality and uniformity of the recycled material. The results were calculated with the participation of 6 students per test type, which showed that 66.66% of the specimens intended for impact tests and 83.33% of those intended for torsion tests exhibited adequate functional performance. Likewise, it was estimated that a weekly production of 1 kg of crushed PET would cover approximately half a week (three days) of laboratory practices, considering the large number of students. Therefore, it could use 60 to 80% of the total consumption during a standard 15-week course, depending on the situation, demonstrating that integrating recycling into academic activities supports the circular economy, reduces the environmental impact of plastic waste, and strengthens students’ practical training and professional skills. Full article

(This article belongs to the Special Issue Sustainability Education for Recycling: Multidisciplinary Approaches and Innovative Practices)

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18 pages, 25951 KB

Open AccessArticle

Composting Performance and Microbial Community Responses Under Different Treatment Modes During Food Waste Digestate–Straw Composting

by Tonghe Du, Tianzhi Wang, Zhitao Li, Yujie Zhao and Chuangchuang Zhang

Recycling 2026, 11(8), 151; https://doi.org/10.3390/recycling11080151 - 18 Aug 2026

Abstract

Food waste digestate is a high-moisture organic residue that requires effective stabilization before resource recovery or land application. This engineering-scale study compared high aeration (HA, 0.30 L·min⁻¹·kg⁻¹ dry matter), low aeration (LA, 0.15 L·min⁻¹·kg⁻¹ dry matter), and [...] Read more.

Food waste digestate is a high-moisture organic residue that requires effective stabilization before resource recovery or land application. This engineering-scale study compared high aeration (HA, 0.30 L·min⁻¹·kg⁻¹ dry matter), low aeration (LA, 0.15 L·min⁻¹·kg⁻¹ dry matter), and turning without forced bottom aeration (TG) during a 30-day food waste digestate–corn straw co-composting experiment. One engineering-scale pile was operated for each treatment. Physicochemical trajectories, bacterial succession, predicted functional potential, and microbial co-occurrence patterns were evaluated. All treatments rapidly entered the thermophilic phase. HA reached the highest temperature (63.70 °C) and remained above 55 °C for 340.8 h, but it also had the lowest final moisture reading (18.62%). LA achieved the greatest organic matter (OM) reduction (17.47%), compared with 13.47% in HA and 7.44% in TG, while retaining more moisture than HA at day 30. Bacillota became dominant in all treatments, although the intensity of thermophilic filtering and the pattern of late-stage succession differed among treatments. Functional predictions indicated the highest late-stage ureolysis potential in LA, whereas TG showed greater predicted representation of several nitrogen-transformation-related groups and the densest co-occurrence network. These findings suggest that engineering-scale composting performance depends on the balance among oxygen supply, heat accumulation, moisture conservation, and microbial organization rather than on thermophilic intensity alone. Under the tested conditions, LA provided the most favorable balance, particularly in terms of OM reduction and moisture retention. Full article

(This article belongs to the Topic The Role of Microorganisms in Waste Treatment)

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26 pages, 4128 KB

Open AccessArticle

Material Recovery Trade-Offs Under Inverter-Controlled Operation of a Full-Scale Municipal Solid Waste Mechanical Treatment Line

by Saw Shalton Roll, Noppharit Sutthasil, Sirintornthep Towprayoon, Suthum Patumsawad, Thapat Silalertruksa, Sakulrat Sutthiprapa, Abhisit Bhatsada and Komsilp Wangyao

Recycling 2026, 11(8), 150; https://doi.org/10.3390/recycling11080150 - 13 Aug 2026

Abstract

Mechanical treatment recovers combustible and recyclable fractions from mixed municipal solid waste (MSW), but full-scale performance is sensitive to front-end operation, line loading, and feedstock heterogeneity. This study examined material recovery trade-offs at a municipal mechanical treatment facility in Satun, Thailand. Four inverter-controlled [...] Read more.

Mechanical treatment recovers combustible and recyclable fractions from mixed municipal solid waste (MSW), but full-scale performance is sensitive to front-end operation, line loading, and feedstock heterogeneity. This study examined material recovery trade-offs at a municipal mechanical treatment facility in Satun, Thailand. Four inverter-controlled regimes were assessed by adjusting the bag opener and trommel motor frequencies, giving measured line throughputs of 14.75, 13.45, 8.03, and 6.54 t·h⁻¹. Output was classified as refuse-derived fuel (RDF), residual waste, recyclables, and bulky/loss material, with composition-based indicators of stream cleanliness and leakage. Each regime was a single short trial on waste from a different collection vehicle, without replication or input homogenization; no statistical comparison is possible, and results are reported as preliminary observations rather than isolated effects of inverter frequency. RDF yield fell from 42.06% of input at the highest throughput to 18.12% at the lowest, whereas recyclable recovery peaked at 4.95% under an intermediate regime that also returned the highest gross revenue. Residual-disposal methane generation potential was 7.78% higher under the lowest-throughput regime than under business-as-usual. Three trade-offs emerged: throughput against selectivity, RDF quantity against cleanliness, and recovery against leakage. The findings help operators select front-end settings on multi-criteria indicators rather than throughput alone. Full article

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20 pages, 2782 KB

Open AccessArticle

Waste-Treating-Waste: A Novel Method for Dye Decolorization from Wastewater Using Spent Mushroom Substrate—Efficiency and Adsorption Mechanisms

by Yan Zhang, Yuanyuan Sun, Yuting Li, Shaohua Bian, Li Meng and Zhuang Li

Recycling 2026, 11(8), 149; https://doi.org/10.3390/recycling11080149 - 13 Aug 2026

Abstract

Substantial dye wastewater from the textile industry poses serious ecological threats. Spent mushroom substrate (SMS) offers a cost-effective and eco-friendly decolorization option, yet traditional methods are hindered by prolonged processing times. This study introduces a column decolorization (CD) method using Auricularia cornea SMS, [...] Read more.

Substantial dye wastewater from the textile industry poses serious ecological threats. Spent mushroom substrate (SMS) offers a cost-effective and eco-friendly decolorization option, yet traditional methods are hindered by prolonged processing times. This study introduces a column decolorization (CD) method using Auricularia cornea SMS, demonstrating markedly higher efficiency and practicality. The CD method achieved over 50% decolorization for 10 of 12 tested dyes, outperforming conventional approaches for six dyes. Analyses via SEM, FTIR, and isotherm measurements indicated that the high efficiency stems from the SMS microstructure and functional groups, with mechanisms including electrostatic attraction, hydrogen bonding, and π-π conjugation, following Langmuir monolayer adsorption. The process requires no specific conditions, avoids extraction steps, and reduces treatment time to 4% of traditional methods. HPLC analysis further revealed partial biodegradation of Malachite Green, reducing its cytotoxicity. This work provides the first systematic comparison of SMS decolorization methods and a mechanistic analysis, supporting SMS application in dye wastewater treatment. Full article

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24 pages, 4906 KB

Open AccessArticle

Machine Learning Framework for Carbon Purification from Hazardous Spent Cathode Carbon via LightGBM Hyperparameter Optimization

by Shuangxiang Zeng, Lisha Dong, Jingtao Shao, Mohamed A. Deyab and Xiangning Bu

Recycling 2026, 11(8), 148; https://doi.org/10.3390/recycling11080148 - 13 Aug 2026

Abstract

Spent cathode carbon (SCC), a hazardous waste generated during primary aluminium production, contains valuable graphitic carbon resources but remains difficult to recycle because carbon purification is governed by complex interactions among multiple leaching parameters. Conventional process optimization relies on extensive laboratory experimentation, resulting [...] Read more.

Spent cathode carbon (SCC), a hazardous waste generated during primary aluminium production, contains valuable graphitic carbon resources but remains difficult to recycle because carbon purification is governed by complex interactions among multiple leaching parameters. Conventional process optimization relies on extensive laboratory experimentation, resulting in high chemical consumption, energy use, and development costs. This study presents an explainable machine learning framework for cleaner and more resource-efficient carbon purification from SCC under limited-data conditions. Six machine learning algorithms (GBDT, CatBoost, XGBoost, LightGBM, Random Forest, and Decision Tree) were evaluated using experimental data from alkaline leaching. The LightGBM model was systematically optimized by combining Response Surface Method (RSM), Orthogonal Experimental Design (OED), and local parameter optimization methods. The optimized model (min_child_samples = 2, num_leaves = 32, n_estimators = 500, and learning_rate = 0.5) achieved an R² of 0.8015, RMSE of 0.9163, and MAE of 0.6599. SHAP analysis identified initial alkali concentration, liquid–solid ratio, stirring rate, and leaching time as the dominant factors controlling carbon purification, whereas temperature had a comparatively smaller influence within the investigated operating range. The results indicate that improving reagent utilization and hydrodynamic conditions offers greater potential for enhancing carbon purification than increasing thermal input alone. By integrating statistical experimental design with explainable machine learning, this study establishes an efficient, interpretable, and transferable decision-support framework for optimizing hazardous waste recycling and other resource recovery processes under limited-data conditions, thereby supporting cleaner production and circular economy practices. Full article

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