Recycling

18 pages, 5405 KB

Open AccessArticle

Photovoltaic Panels’ Thermo-Mechanical Delamination by Electric Resistive Heating

by Valentin Kamburov, Mihail Zagorski, Dimitar Arnaudov, Valentin Mateev, Antonio Nikolov, Konstantin Dimitrov, Rayna Dimitrova, Evgeniy Tongov, Krum Petrov and Yana Stoyanova

Recycling 2026, 11(6), 108; https://doi.org/10.3390/recycling11060108 - 17 Jun 2026

Abstract

The present study investigates the application of electric resistive heating to photovoltaic (PV) panels, aimed at enabling their subsequent thermo-mechanical delamination. The key process parameters—namely current magnitude and applied voltage—required for direct electro-resistive heating are identified, and the process is experimentally demonstrated under [...] Read more.

The present study investigates the application of electric resistive heating to photovoltaic (PV) panels, aimed at enabling their subsequent thermo-mechanical delamination. The key process parameters—namely current magnitude and applied voltage—required for direct electro-resistive heating are identified, and the process is experimentally demonstrated under laboratory conditions. The electric resistive heating of a composite photovoltaic panel, consisting of a solar cell layer (crystalline silicon, c-Si, with a metallic grid), a backsheet, and a glass layer, is analyzed in detail using a virtual model of a single-crystal silicon solar cell implemented as coupled electric-thermal analysis. The temperature dependence of the electrical resistance of the solar cell layer is experimentally measured, and exponential relationships are derived and subsequently incorporated into the numerical model. The virtual model results are validated, demonstrating that, for a given geometry and configuration of the conductive metallic grid (busbars and fingers), the electrical resistance of the semiconductor layer containing the p–n junction governs the temperature achieved during electro-resistive heating as a function of the applied current. Furthermore, results for the terminal current and voltage, current density in the busbars and fingers, electric field intensity, and the resulting temperature within the semiconductor layer of the single-crystal silicon solar cell are presented and analyzed. Full article

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

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18 pages, 844 KB

Open AccessArticle

Laboratory Scale vs. Pilot Scale Recyclability Evaluation of a Brown Packaging Paper Containing Strength Additive

by Joana C. Vieira, Pedro Videira, António de O. Mendes, Paula Pinto, Belinda Soares, Mariana P. Costa, Paulo T. Fiadeiro, Joana M. R. Curto, Maria E. Amaral, Ana P. Costa and Vera L. D. Costa

Recycling 2026, 11(6), 107; https://doi.org/10.3390/recycling11060107 - 17 Jun 2026

Abstract

Harmonized laboratory methodologies, notably the CEPI recyclability laboratory test method (latest version 3, released February 2025) and the 4evergreen protocol (latest revision 1, released January 2025), are widely used to assess the recyclability of paper-based materials. However, the extent to which laboratory-scale results [...] Read more.

Harmonized laboratory methodologies, notably the CEPI recyclability laboratory test method (latest version 3, released February 2025) and the 4evergreen protocol (latest revision 1, released January 2025), are widely used to assess the recyclability of paper-based materials. However, the extent to which laboratory-scale results reflect pilot-scale behavior remains insufficiently documented. In this work, the recyclability of brown packaging paper was evaluated at both laboratory and pilot scales. Disintegration was performed under identical consistency, temperature, and duration, followed by screening, filtrate analysis, macro-stickies quantification, and paper sheet adhesion evaluation according to the CEPI methodology. In parallel, recycled paper prototypes were produced in a pilot paper machine and were mechanically characterized. The material was classified as technically recyclable in a conventional recycling mill at both scales, with closely aligned recyclability scores. Nevertheless, pilot-scale testing revealed higher dissolved and colloidal substances, increased macro-stickies content, and sheet adhesion phenomena not fully apparent at laboratory scale. These results demonstrate that while laboratory tests are robust for recyclability classification, pilot-scale trials provide essential insights into runnability and operational risks relevant for industrial implementation. Full article

31 pages, 82784 KB

Open AccessArticle

Valorization of Pb–Zn Mine Waste in Metakaolin-Based Geopolymers: A Circular Approach for Waste Reuse and Methylene Blue Removal

by Jihene Nouairi, Slávka Andrejkovičová, Oumaima Karoui, Tiago Pinho, Rafael Rebelo, Gil Gonçalves, Angelo Camerlenghi, Mounir Ghribi and Fernando Rocha

Recycling 2026, 11(6), 106; https://doi.org/10.3390/recycling11060106 - 15 Jun 2026

Abstract

The increasing accumulation of mine waste and the associated release of toxic elements represent a major environmental challenge, particularly in regions impacted by Pb–Zn mining activities. In this context, this study aims to investigate the valorization of mine waste from Lakhouat, an abandoned [...] Read more.

The increasing accumulation of mine waste and the associated release of toxic elements represent a major environmental challenge, particularly in regions impacted by Pb–Zn mining activities. In this context, this study aims to investigate the valorization of mine waste from Lakhouat, an abandoned Pb–Zn site in Northern Tunisia, as a sustainable additive in metakaolin-based geopolymers. This approach contributes to circular economy strategies by transforming hazardous waste into value-added materials for environmental and construction applications. Geopolymer formulations were synthesized by incorporating mine waste at different proportions (0, 5, 10, 20, and 30 wt.%) with metakaolin, while maintaining constant SiO₂/Al₂O₃ and Na₂O/Al₂O₃ molar ratios. The materials were prepared through alkali activation using sodium silicate and sodium hydroxide, followed by curing. Comprehensive characterization was carried out using X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM). In addition, adsorption experiments using methylene blue (MB) were conducted to evaluate the environmental performance of the synthesized geopolymers. The results revealed that the mine waste contains high concentrations of potentially toxic elements (up to 2.23 wt.% Pb and 8.2 wt.% Zn), highlighting the need for effective stabilization. Microstructural analysis confirmed the formation of predominantly amorphous geopolymer matrices with varying degrees of reaction depending on MW content. The highest compressive strengths (25–30 MPa) were achieved for formulations containing 5–10 wt.% MW after 28 days of curing. Furthermore, the geopolymers demonstrated efficient methylene blue removal, following pseudo-second-order kinetics and fitting the Langmuir isotherm model, with enhanced adsorption performance observed at higher MW contents. These findings indicate that MW-based geopolymers are promising materials for mine waste valorization and methylene blue removal. However, standardized leaching tests are required to confirm the long-term immobilization of Pb, Zn, Cd, As, and other potentially toxic elements within the geopolymer matrix. The study highlights their potential as sustainable, low-impact materials, supporting waste valorization and contributing to the development of environmentally resilient systems within a circular economy framework. Full article

(This article belongs to the Special Issue Celebrating 10 Years of Recycling: Shaping the Future of Waste Management)

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23 pages, 9399 KB

Open AccessArticle

Predicting the Properties of Construction Concrete Modified with a Nanopreparation and Containing E-Waste Plastic

by Ruslan Sapinov, Natalya A. Kulenova, Marzhan A. Sadenova, Nikolay Charykov, Olga V. Rudenko, Zhanserik Shoshay and Yegor Rakov

Recycling 2026, 11(6), 105; https://doi.org/10.3390/recycling11060105 - 14 Jun 2026

Abstract

This study addresses the pressing issue of utilising plastic from electronic waste as a filler to replace mineral sand. Currently, the use of plastic in construction concrete is limited due to a significant deterioration in the mechanical properties of modified concrete when plastic [...] Read more.

This study addresses the pressing issue of utilising plastic from electronic waste as a filler to replace mineral sand. Currently, the use of plastic in construction concrete is limited due to a significant deterioration in the mechanical properties of modified concrete when plastic filler is added at levels exceeding 15–20%. As a result of the research, it was established that the addition of a nano-preparation—fullerene—in amounts as low as 0.001% significantly improves the mechanical properties of concrete with plastic aggregate. Replacing 50% of the mineral aggregate with plastic aggregate, combined with the addition of fullerene at a concentration of 0.01% of the mixing water mass, more than doubles the mechanical properties of the concrete compared to concrete without the nano-additive, with compressive strength increasing by 65.2%, from 16.33 MPa to 26.97 MPa. The impact strength and freeze–thaw resistance of the concrete were also significantly increased. This makes it possible to use concrete with a high plastic aggregate content of up to 50% without a significant reduction in mechanical properties. The use of machine learning and AI data processing methods such as AdaBoost and Random Forest allows for highly accurate prediction of the characteristics of the resulting materials, with a coefficient of determination (R²) for the resulting models close to 1. Full article

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34 pages, 921 KB

Open AccessReview

Valorization of Coal-Based Solid Wastes as Soil Amendments: A Review of Modifications, Mechanisms, and Environmental Pathways in the Chinese Circular Economy

by Zhongli Jiang, Qinggang Wang, Yinnan Cao, Pengfei Chen, Hongyu Chen, Zhi Li and Chengjie Yin

Recycling 2026, 11(6), 104; https://doi.org/10.3390/recycling11060104 - 10 Jun 2026

Abstract

The massive generation of coal-based solid wastes (CBSWs) poses severe environmental challenges globally, while widespread soil degradation threatens food security and ecosystem stability. This review critically evaluates the technical feasibility and agro-ecological benefits of valorizing CBSWs—including coal gangue, fly ash, gasification slag, and [...] Read more.

The massive generation of coal-based solid wastes (CBSWs) poses severe environmental challenges globally, while widespread soil degradation threatens food security and ecosystem stability. This review critically evaluates the technical feasibility and agro-ecological benefits of valorizing CBSWs—including coal gangue, fly ash, gasification slag, and desulfurization gypsum—as soil amendments within a circular economy framework. We systematically examine the physicochemical characteristics of major CBSW types, analyze modification methods that enhance their performance and safety, and assess their multifaceted effects on soil physical structure, chemical properties, nutrient dynamics, heavy metal immobilization, and microbial communities. A dedicated section addresses environmental risks, particularly toxic element leaching, and outlines integrated control strategies from source selection to post-application monitoring. Critical knowledge gaps persist regarding long-term contaminant stability under climate change scenarios, molecular-scale immobilization mechanisms, and economic scalability. Future research must prioritize advanced low-energy modification technologies, robust long-term field studies, and harmonized international regulations. We conclude that with scientifically guided modification and stringent risk management, CBSWs can be transformed into safe, multifunctional soil conditioners, simultaneously addressing industrial waste management and contributing to global restoration of degraded soil health. Full article

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21 pages, 15557 KB

Open AccessArticle

Detailed Characterization and Zoning of Landfills to Reduce Their Environmental Impact in Armenia

by Andrey Medvedev, Gevorg Tepanosyan, Grigor Ayvazyan and Shushanik Asmaryan

Recycling 2026, 11(6), 103; https://doi.org/10.3390/recycling11060103 - 9 Jun 2026

Abstract

The research aims to develop methodologies for the detailed characterization and spatial zoning of landfills as a means of assessing their environmental impact. The principal objective is to establish an integrated framework for evaluating landfill conditions through multisource data analysis, encompassing remote sensing, [...] Read more.

The research aims to develop methodologies for the detailed characterization and spatial zoning of landfills as a means of assessing their environmental impact. The principal objective is to establish an integrated framework for evaluating landfill conditions through multisource data analysis, encompassing remote sensing, field investigations, and geochemical analyses. The proposed framework incorporates several critical components: satellite and UAV-based remote sensing, multispectral vegetation assessment, geochemical soil profiling, temporal and functional zoning, and morphodynamic evaluation. Research findings indicate substantial environmental pollution in the vicinity of landfill sites, at levels that exceed the natural self-purification capacity of surrounding ecosystems. This encompasses the contamination of all principal environmental components, including groundwater, surface water, soil, vegetation, and atmosphere. The key findings demonstrate that only a comprehensive environmental impact analysis, conducted in conjunction with detailed landfill zoning, yields a thorough understanding of the associated adverse effects. Remote sensing methodologies are shown to play a pivotal role in data acquisition and ongoing monitoring. The practical contribution of this study lies in the development of methodological frameworks for detailed landfill zoning, environmental impact assessment, monitoring, damage mitigation measures, and waste management optimisation. The results obtained have the potential to improve waste management systems, inform the development of effective monitoring protocols, and underpin strategies aimed at reducing the environmental footprint of landfills. Overall, this research advances scientific and technical knowledge in the field of waste management and contributes towards efforts to mitigate environmental impact—a matter of persistent concern given rising rates of waste generation and the increasingly constrained availability of suitable landfill capacity. Full article

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15 pages, 2265 KB

Open AccessArticle

Improved Methane Production and COD Removal from Food Waste Under High Organic Loads in Laboratory Anaerobic Digesters Incorporating Microbial Electrolysis Systems

by Soranosuke Shimizu, Takuma Kariyada, Mizuki Toda, Keisuke Tomita and Kazuya Watanabe

Recycling 2026, 11(6), 102; https://doi.org/10.3390/recycling11060102 - 4 Jun 2026

Abstract

Anaerobic digesters (ADs) are widely used for the recovery of energy from biomass waste, while performance deterioration of ADs sometimes occurs under high organic loads. Microbial electrolysis cells (MECs) have been examined for incorporation into ADs to improve methane production, while responses of [...] Read more.

Anaerobic digesters (ADs) are widely used for the recovery of energy from biomass waste, while performance deterioration of ADs sometimes occurs under high organic loads. Microbial electrolysis cells (MECs) have been examined for incorporation into ADs to improve methane production, while responses of MEC-assisted ADs (MEC-ADs) to changes in operational conditions have yet to be sufficiently examined. Here we operated laboratory ADs and MEC-ADs with food waste as a feed, and organic loading rates (OLRs) were varied by changing hydraulic residence times (HRTs). Analyses of AD performances, including methane production and chemical oxygen demand (COD) removal, show that MEC-ADs exhibit higher performances than ADs at OLRs of 7 g COD L⁻¹ D⁻¹ or higher (HRT of 10 days or less). In addition, pH was stably maintained in MEC-ADs at high OLRs. Metabarcoding of rRNA gene amplicons showed that Desulfuromonadaceae bacteria were enriched at the anodes in MEC-ADs, while Methanobacteriaceae archaea were increased at the cathodes. It is suggested that the MEC system is useful for stably operating ADs at high OLRs and/or short HRTs. Full article

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23 pages, 94019 KB

Open AccessArticle

Advancing Real-Time Sensor-Based Quality Monitoring in Construction and Demolition Waste Processing for the Prediction of Weight-Based Particle Size Distributions

by Lieve Göbbels, Karoline Raulf, Setenay Orbatu and Kathrin Greiff

Recycling 2026, 11(6), 101; https://doi.org/10.3390/recycling11060101 - 1 Jun 2026

Abstract

In this work, the development and validation of an AI- and sensor-based inline quality monitoring system for the analysis of particle size distributions (PSDs) of comminuted construction and demolition waste (CDW) material flows are described. In this, a custom-developed multitask CNN (CDW-MT-CNN) was [...] Read more.

In this work, the development and validation of an AI- and sensor-based inline quality monitoring system for the analysis of particle size distributions (PSDs) of comminuted construction and demolition waste (CDW) material flows are described. In this, a custom-developed multitask CNN (CDW-MT-CNN) was developed using manually sieve analyzed particles. This model is able to rapidly and simultaneously predict the particle class and weight, essential for the determination of the PSD. The single particle data are then aggregated per raw image, usually consisting of around 1000 particles for full-scale experiments, to acquire a per-image PSD. The inline mounted RGB line scan sensor records high-resolution images in subsecond frequencies. With an inference time of around 54 ms for a single image, this model would be able to provide a PSD every minute in a full-scale plant. For the purpose of inline monitoring of CDW material flows in a comminution process, such intervals are sufficient according to experts and solve existing gaps regarding the upscaling of laboratory-developed systems. Together with the high predictive performance of the model, especially in terms of classification (82% accuracy), it is shown that this technology has potential for monitoring in full-scale plants, for instance by offering operators new insights to improve operation efficiency. Further research should focus on increasing the precision for weight prediction, for instance by increasing the labeled data set with a larger number of unique particles and on methods to verify the performance of the model on pilot or full-scale plants during live operation. Full article

(This article belongs to the Special Issue Celebrating 10 Years of Recycling: Shaping the Future of Waste Management)

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21 pages, 5472 KB

Open AccessArticle

Improving Valorization of Waste Textiles: Assessing Separation Efficiency of Cotton–PET Blends via Alkaline and Enzymatic Hydrolysis

by Pablo Kählig, Wolfgang Ipsmiller, Andreas Bartl and Jakob Lederer

Recycling 2026, 11(6), 100; https://doi.org/10.3390/recycling11060100 - 29 May 2026

Abstract

Recycling cotton–PET textile blends using alkaline solutions has gained increasing attention, with studies showing promising treatment pathways with diverse process setups. However, these separation processes use various input materials and focus on a small number of treatment parameter values which render the comparison [...] Read more.

Recycling cotton–PET textile blends using alkaline solutions has gained increasing attention, with studies showing promising treatment pathways with diverse process setups. However, these separation processes use various input materials and focus on a small number of treatment parameter values which render the comparison of results over a large parameter range difficult. This study presents the feasibility of recovering cotton or PET at fabric level from cotton–PET blends across a wide range of temperatures (from −30 °C to 95 °C) and alkaline concentrations (from 0 to 40% (w/w)). The focus of this study is centered on the share of separation and recoverable fiber mass after hydrolyzing one component using alkaline hydrolysis or alkaline pre-treatment followed by enzymatic hydrolysis. A comparison of purity and material loss of the recovered polymers for all parameter sets is given. Experiments were performed on two distinct textiles while process parameters were selected in a straightforward manner, excluding catalysts, co-solvents and defibration. The results map temperature and alkaline concentration areas where these cotton–PET separation processes are feasible regarding recoverable fiber mass. Based on these results, separation efficiency could be optimized to design economic and environmentally friendlier process conditions. Full article

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47 pages, 14563 KB

Open AccessReview

Circular Economy Approaches for Sustainable Waste Management: A Review on Integration of AI, Advanced Technologies and Policy Recommendations

by Abhishek N. Srivastava, Arun Krishna Vuppaladadiyam, Rakhi Punnadan Koroth, Christoph Pfeifer, Ajay Kumar Kaviti, Jafar Fathi, Alan Maslani, Praveen Barmavatu, Maksym Buryi, Michael Pohorely and Vineet Singh Sikarwar

Recycling 2026, 11(6), 99; https://doi.org/10.3390/recycling11060099 - 29 May 2026

Abstract

Landfilling remains the dominant waste disposal method worldwide, particularly in developing countries, posing serious environmental, health, and climate challenges. Inefficient practices, weak regulations, and un-engineered sites contribute to massive greenhouse gas (GHG) emissions and resource loss. Transitioning to a circular economy (CE) offers [...] Read more.

Landfilling remains the dominant waste disposal method worldwide, particularly in developing countries, posing serious environmental, health, and climate challenges. Inefficient practices, weak regulations, and un-engineered sites contribute to massive greenhouse gas (GHG) emissions and resource loss. Transitioning to a circular economy (CE) offers a transformative path for sustainable waste management. By closing material loops, recovering energy, urban mining, controlling emissions and CE strategies can convert traditional landfills into eco-efficient systems. The integration of artificial intelligence (AI) further enhances this transition, enabling real-time monitoring, predictive management, and optimized resource recovery, thereby maximizing environmental and economic benefits. This review presents a three-level CE framework at micro (individual organizations), meso (industrial networks), and macro (national and international) levels designed to extract maximum value from waste streams and mitigate climate impacts. The proposed strategies demonstrate the potential to drastically reduce GHG emissions, promote clean energy via waste-to-energy routes, and contribute to SDGs 7, 11, 12, 13 and 15. By combining technology, innovation, and strategic management, this work highlights how AI-driven CE approaches can transform landfills from environmental liabilities into engines of sustainability and climate action. In implementing CE strategies at various levels, various challenges including technological, socio-economic, ethical, policy-based, and unintended consequences are encountered which impact sustainability initiatives. This review comprehensively discusses challenges associated with CE implementation and identifies technological advancement, social awareness and data-driven AI/ML-based modeling which could ensure success in circularity and ultimately curb climate change impacts in the long term. Full article

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22 pages, 7794 KB

Open AccessArticle

The Use of MSWI Fly Ash in Promoting Low-Titanium Slag Activation for Use in Low-Carbon Cementitious Materials

by Bo Su, Jie Chi, Siqi Zhang, Jia Li, Keqing Li, Xingyang Xu and Wen Ni

Recycling 2026, 11(6), 98; https://doi.org/10.3390/recycling11060098 - 27 May 2026

Abstract

A quaternary solid-waste-based binder was prepared from low-titanium slag, municipal solid waste incineration (MSWI) fly ash, steel slag, and flue-gas desulfurization gypsum (FGDG) to clarify the activating effect of MSWI fly ash on low-titanium slag and its influence on hydrate evolution. Unlike conventional [...] Read more.

A quaternary solid-waste-based binder was prepared from low-titanium slag, municipal solid waste incineration (MSWI) fly ash, steel slag, and flue-gas desulfurization gypsum (FGDG) to clarify the activating effect of MSWI fly ash on low-titanium slag and its influence on hydrate evolution. Unlike conventional solid-waste-based binders in which MSWI fly ash is mainly regarded as a hazardous residue requiring stabilization, this study demonstrates its specific role as a Ca-rich alkaline activator for promoting low-titanium slag depolymerization and coordinated hydrate formation. The results showed that the compressive strength first increased and then decreased with increasing MSWI fly ash content. Considering both strength development and MSWI fly ash utilization, the optimum mixture was identified as low-titanium slag:MSWI fly ash:steel slag:FGDG = 43.0:17.2:25.8:14.0, with compressive strengths of 9.51 and 46.32 MPa at 3 and 90 d, respectively. These values corresponded to 5.66 and 1.04 times those of the reference mixture without MSWI fly ash, respectively. Ettringite and C-(A)-S-H gel were the main strength-contributing hydration products, while Friedel’s salt was identified as a chloride-bearing AFm phase. Moderate MSWI fly ash addition promoted alkaline activation and low-titanium slag depolymerization, leading to increased formation of ettringite, C-(A)-S-H gel, and Friedel’s salt, which contributed to improved compressive strength. In contrast, excessive MSWI fly ash disturbed the Ca-Si-Al balance and inhibited effective hydrate formation. These results demonstrate that MSWI fly ash can serve as an effective Ca-rich activator for low-titanium-slag-based low-carbon cementitious materials and provide a feasible route for the synergistic utilization of multiple solid wastes. Full article

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18 pages, 6499 KB

Open AccessArticle

Waste Bakelite Thermoset as Slag Foaming and Iron Oxide Reduction Agents in EAF Steelmaking: Advancing Fossil Fuel Reduction in Steel Industry

by Thanaporn Chandransu, Krishmanust Sunankingphet and Somyote Kongkarat

Recycling 2026, 11(6), 97; https://doi.org/10.3390/recycling11060097 - 27 May 2026

Abstract

This study evaluates the feasibility of using waste Bakelite thermoset as a slag foaming and iron oxide reduction agent in electric arc furnace (EAF) steelmaking. Bakelite was blended with metallurgical coke at three ratios (10–30 wt% Bakelite), designated as Blend#1 to Blend#3. All [...] Read more.

This study evaluates the feasibility of using waste Bakelite thermoset as a slag foaming and iron oxide reduction agent in electric arc furnace (EAF) steelmaking. Bakelite was blended with metallurgical coke at three ratios (10–30 wt% Bakelite), designated as Blend#1 to Blend#3. All carbon samples were heat-treated at 1000 °C under an argon atmosphere to produce char and were subsequently assessed for carbon–slag interactions at 1550 °C, with emphasis on slag foaming behavior and FeO reduction. The incorporation of Bakelite increased the total carbon content and significantly altered coke ash chemistry, marked by reduced SiO₂ and Al₂O₃ and increased CaO contents. Structural analysis revealed enhanced carbon graphitization with increasing Bakelite proportion. Among all samples, Blend#3 exhibited the most stable and pronounced slag foaming, achieving a maximum volume ratio of approximately 1.7 and forming uniformly distributed, multi-sized gas bubbles within the slag. FeO reduction improved with Bakelite addition, with metallization degrees of 77.30, 81.65, 80.56, and 84.41% for coke, Blend#1, Blend#2, and Blend#3, respectively. Blend#3 produced the lowest total gas emission (186,000 ppm), approximately 30% lower than that of pure coke. These findings demonstrate that waste Bakelite thermoset is an effective low-carbon alternative carbon source for EAF steelmaking, enhancing FeO reduction, slag foaming stability, and overall environmental performance. Full article

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17 pages, 1748 KB

Open AccessArticle

Production of Packaging Materials by Recycling of Corn and Common Reed Fibers with the Addition of Wollastonite: Structural and Mechanical Properties

by Yerlan Doszhanov, Adilkhan Orazbayev, Murat Zhumabayev, Saule Kaldybayeva, Aigerim Kerimkulova, Aliya Alimbetova, Nariman Pravin, Arman Zhumazhanov, Aitugan Sabitov, Ospan Doszhanov and Dauren Baiseitov

Recycling 2026, 11(6), 96; https://doi.org/10.3390/recycling11060096 - 24 May 2026

Abstract

This study explores the possibility of making cardboard and molded egg carton packaging from corn residues and common reed as alternatives to wood-based pulp. Six formulations were made: corn husks (CHs), corn leaves (CLs), corn leaves (35%) plus corn husks (30%) and a [...] Read more.

This study explores the possibility of making cardboard and molded egg carton packaging from corn residues and common reed as alternatives to wood-based pulp. Six formulations were made: corn husks (CHs), corn leaves (CLs), corn leaves (35%) plus corn husks (30%) and a corn blend (15%) of wollastonite (CaSiO₃) (CH + CL + W), a corn blend (CH + CL: husks 60%, leaves 40%), mixed corn waste (MCW) and shredded common reed (SR). Optical microscopy was used to evaluate the fiber morphology, including the calculation of the flexibility coefficient, the cell wall rigidity and the Runkel ratio, for raw materials and fiber after alkaline hydrolysis and casting of egg cartons in silicone molds. The grammage, burst strength and index, folding endurance, thickness and moisture content were measured in the cardboard samples, while warping, compressive deformation, moisture and ink absorption were measured in the egg cartons. The flexibility coefficient of the common reed fibers (64.5%) was better than that of the corn fibers (23.6%), and so was the Runkel ratio (0.86 vs. 1.2). In the case of cardboard formulations, the maximum burst strength (462.4 kPa) and the maximum burst index (3.0 kPa·g/m²) values were obtained with the MCW formulation, and the highest folding endurance (42 and 38 double folds) was obtained with the CH and SR formulations, respectively. The addition of wollastonite improved folding endurance to 28 double folds and reduced moisture content to 4.1%, whereas the moisture content was reduced but burst strength decreased to 250.5 kPa. Egg cartons made from corn were found to satisfy all the requirements tested for good packaging, while the reed-based cartons were found to have inadequate ink absorbency time (20 min), making them less printable. Overall, mixed corn residues seem to be the most promising raw materials for sustainable packaging, and wollastonite can be used to adjust the flexibility–strength balance. Full article

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22 pages, 15985 KB

Open AccessArticle

Mussel Shell Recycling for Sustainable Bio-Cement Mortar in 3D-Printed Artificial Reefs: Material and Process Insights

by Letizia Caroscio, Cristian Chiavetta, Adrian I. Yoris-Nobile, Eva Cuesta-Astorga, Alessandra Bonoli and Elena Blanco-Fernandez

Recycling 2026, 11(5), 95; https://doi.org/10.3390/recycling11050095 - 15 May 2026

Abstract

This study investigates the reuse of mussel shell waste as a secondary raw material in bio-cement mortars designed for the additive manufacturing of artificial reefs for marine habitat restoration. The novelty of the research lies in combining a high recycled shell content (60 [...] Read more.

This study investigates the reuse of mussel shell waste as a secondary raw material in bio-cement mortars designed for the additive manufacturing of artificial reefs for marine habitat restoration. The novelty of the research lies in combining a high recycled shell content (60 wt.%), low-clinker cement, and two 3D-printing techniques: Extruded Material Systems (EMS) and Powder-Based Systems (PBS). Mechanical performance was evaluated through flexural and compressive tests after 7, 28, and 91 days under both air and freshwater curing conditions, while environmental impacts were assessed through Life Cycle Assessment (LCA). The LCA evaluated both the environmental performance of shell-based mixtures compared with conventional materials and the impacts associated with the investigated fabrication techniques. The best-performing bio-mixtures achieved compressive strengths up to 46.01 MPa and flexural strengths up to 9.91 MPa after freshwater curing, demonstrating the suitability of shell-based mortars for submerged applications. LCA results showed reduced impacts in land use and mineral resource depletion compared with conventional mixtures, despite slightly higher energy and water demands associated with shell pre-treatment. The results demonstrate the technical and environmental feasibility of integrating aquaculture waste into sustainable 3D-printed marine restoration solutions. Full article

(This article belongs to the Special Issue Celebrating 10 Years of Recycling: Shaping the Future of Waste Management)

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17 pages, 2490 KB

Open AccessArticle

Life Cycle Assessment of Recycled Aggregate Production in the Federal District, Brazil

by Igor Cleyton Ferreira de Sousa, Cláudio Henrique de Almeida Feitosa Pereira and Yuri Sotero Bomfim Fraga

Recycling 2026, 11(5), 94; https://doi.org/10.3390/recycling11050094 - 13 May 2026

Abstract

The excessive generation and improper disposal of Construction and Demolition Waste (CDW) represent one of the main environmental challenges in the sector. However, its potential for reuse and recycling enables the mitigation of these impacts through sustainable practices. In this context, the present [...] Read more.

The excessive generation and improper disposal of Construction and Demolition Waste (CDW) represent one of the main environmental challenges in the sector. However, its potential for reuse and recycling enables the mitigation of these impacts through sustainable practices. In this context, the present study aimed to estimate reference values for the Federal District, Brazil, regarding the environmental impacts associated both with the transportation stage of CDW—from its point of origin to the processing facility—and with the operations involved in its conversion into recycled aggregates, through the application of a simplified Life Cycle Assessment approach. The analysis focused on quantifying the consumption of electricity, water, and fossil fuels, as well as carbon dioxide emissions and the generation of contaminant residues throughout the analyzed process. The system boundary adopted corresponds to a “cradle-to-gate” scope, with a declared unit of 1 tonne of recycled aggregate. Additionally, a survey of scientific studies providing life cycle inventory data related to aggregate production was conducted, enabling a consistency analysis with the data obtained in this study. Primary data related to the recycled aggregate production process were collected through direct field observations, in situ measurements, and the analysis of operational records from the studied facility. For the year 2024, the environmental indicators obtained showed that the production of 1 tonne of recycled aggregate required 1.23 kWh of electricity, 5.65 L of water, and 2.14 L of diesel, in addition to resulting in emissions of 6.64 kg CO₂ eq and the generation of 2.3 kg of contaminant waste. Full article

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50 pages, 7052 KB

Open AccessReview

Advances in Technologies for the Treatment of and Resource Recovery from Organic Wastes: A Review

by Jiani Tian, Daohong Zhang, Ning Jiang, Chengze Yu, Jiaqi Hou, Chunming Hu, Panpan Wang and Chaocan Li

Recycling 2026, 11(5), 93; https://doi.org/10.3390/recycling11050093 - 13 May 2026

Abstract

Effective management of organic wastes is essential for green and low-carbon development. Conventional technologies, including incineration, pyrolysis, hydrothermal carbonization (HTC), gasification, anaerobic digestion (AD), and composting, have supported waste reduction and basic resource recovery, but they remain limited in high-efficiency conversion and high-value [...] Read more.

Effective management of organic wastes is essential for green and low-carbon development. Conventional technologies, including incineration, pyrolysis, hydrothermal carbonization (HTC), gasification, anaerobic digestion (AD), and composting, have supported waste reduction and basic resource recovery, but they remain limited in high-efficiency conversion and high-value utilization. This review comparatively evaluates these conventional routes together with advanced and intensified technologies, including microwave-assisted pyrolysis (MAP), plasma treatment, supercritical water gasification (SCWG), and flash joule heating (FJH), with emphasis on suitable feedstocks, performance characteristics, application boundaries, and integration potential. In general, wastes with high moisture content are more suitable for HTC, AD, and SCWG, whereas relatively dry wastes and wastes with high carbon content are more suitable for pyrolysis, gasification, plasma treatment, and FJH upgrading. The review also discusses representative integrated pathways, such as HTC-SCWG, pyrolysis and plasma coupling, AD and gasification coupling, and pyrolysis and FJH coupling, which may improve carbon conversion, broaden product portfolios, and reduce residual pollutants. However, large-scale implementation is still constrained by feedstock heterogeneity, heat and mass transfer limitations, catalyst deactivation, reactor corrosion, and system cost. Overall, no single technology is universally optimal; technology selection should depend on feedstock properties, moisture content, and target products. Full article

(This article belongs to the Special Issue Feature Reviews in Recycling: Waste Processing Technologies)

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18 pages, 4449 KB

Open AccessArticle

Recycling of Dental Zirconia into CAD/CAM Systems for Potential Industrial Applications

by Maria del Carmen Aragón-Duarte, Hilda Esperanza Esparza-Ponce, Lillian Vianey Tapia-Lopez, Antonia Luna-Velasco, Luis Fernando Jiménez-Tinoco and Javier Servando Castro-Carmona

Recycling 2026, 11(5), 92; https://doi.org/10.3390/recycling11050092 - 12 May 2026

Abstract

This study proposes the development of a recycling process for the reintegration of dental zirconia waste into CAD/CAM systems for rapid prototyping, with the objective of demonstrating the feasibility of manufacturing functional products from recycled zirconia obtained from a commercial dental laboratory. The [...] Read more.

This study proposes the development of a recycling process for the reintegration of dental zirconia waste into CAD/CAM systems for rapid prototyping, with the objective of demonstrating the feasibility of manufacturing functional products from recycled zirconia obtained from a commercial dental laboratory. The proposed methodology aims to explore a simple and economically viable process, which involves the purification and processing of a heterogeneous zirconia powder, followed by the fabrication of pre-sintered blocks suitable for CAD/CAM applications. The recycled bulk ceramic was characterized and compared with commercial zirconia through density measurements, X-ray diffraction, scanning electron microscopy, Vickers hardness, flexural strength testing, and sintering shrinkage analysis. The results indicated that, although recycled zirconia exhibits lower property values than the commercial reference material, it retains adequate characteristics for specific practical applications. Consequently, to demonstrate industrial feasibility, four components were designed using CAD and machined using CAM from the recycled blocks, simulating a rapid prototyping process. The fabricated components exhibited a smooth and flawless surface, were mechanically robust and solid to the touch, and showed well-defined contours with sharp edges. Dimensional analysis demonstrated high accuracy, with an average percentage error of 0.53% ± 0.14. These findings demonstrate that high-value ceramic waste can be reintegrated into the production chain as functional industrial components through a process that is closely aligned with the real conditions of industrial recycling, while also mitigating environmental contamination from hazardous industrial waste. Full article

(This article belongs to the Special Issue Celebrating 10 Years of Recycling: Shaping the Future of Waste Management)

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32 pages, 4031 KB

Open AccessArticle

A Data Science Framework for Municipal Solid Waste Systems Based on Behavioral Segmentation

by Ivan Gaytán Aguilar, María del Consuelo Hernández Berriel, Federico del Razo López, Everardo Efrén Granda Gutiérrez, María del Consuelo Mañón Salas and Roberto Alejo Eleuterio

Recycling 2026, 11(5), 91; https://doi.org/10.3390/recycling11050091 - 12 May 2026

Abstract

Municipal solid waste management (MSWM) systems in Latin America are constrained by limited access to high-resolution operational data, compelling local authorities to depend on aggregated national statistics that are inadequate for behaviorally informed intervention design. This limitation is particularly evident in the State [...] Read more.

Municipal solid waste management (MSWM) systems in Latin America are constrained by limited access to high-resolution operational data, compelling local authorities to depend on aggregated national statistics that are inadequate for behaviorally informed intervention design. This limitation is particularly evident in the State of Mexico, which generates about 16,187 tons of waste every day but only recycles only 11%. In this context, this study introduces a diagnostic data science framework to identify behaviorally grounded citizen segments and their defining attributes, supporting evidence-based decision-making in MSWM. Primary survey data from 560 households across three municipalities were used, and a three-stage analytical pipeline was implemented to account for contextual heterogeneity. First, k-means clustering was applied to identify behavioral segments. Second, random forest classifiers were used to validate cluster coherence and quantify feature importance. Third, the Apriori algorithm was used to extract association rules that capture recurrent material-mixing behaviors. The results revealed municipality-specific segmentation structures (Tequixquiac: K = 6; Tlalpujahua: K = 3; Xalatlaco: K = 2), with material-specific disposal behaviors emerging as stronger segmentation drivers. Random forest classifiers validated cluster coherence with 100% accuracy, confirming that segments represent behaviorally distinct archetypes. The proposed framework converts raw behavioral data into actionable municipal visions. This approach focuses on finding diagnostic patterns instead of making predictions by utilizing machine-learning-driven MSWM research. Full article

(This article belongs to the Topic Recent Advances in Municipal Solid Waste Management and Technology)

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22 pages, 9826 KB

Open AccessReview

The Drop-In Delusion: Technical and Systemic Impacts of PLA Contamination on the HDPE Circular Economy

by Anayansi Estrada-Monje, Sergio Alonso-Romero, Anayansi Zaragoza-Estrada, María Cristina Kantún-Uicab, Claudia Ivone Piñón-Balderrama, Claudia Alejandra Hernández-Escobar and Erasto Armando Zaragoza-Contreras

Recycling 2026, 11(5), 90; https://doi.org/10.3390/recycling11050090 - 12 May 2026

Abstract

The increasing use of biodegradable polymers, especially poly (lactic acid) (PLA), has raised concern about their entry into conventional post-consumer recycling streams. This review examines the technical and systemic consequences of PLA contamination in the high-density polyethylene (HDPE) circular economy through the “drop-in [...] Read more.

The increasing use of biodegradable polymers, especially poly (lactic acid) (PLA), has raised concern about their entry into conventional post-consumer recycling streams. This review examines the technical and systemic consequences of PLA contamination in the high-density polyethylene (HDPE) circular economy through the “drop-in delusion,” defined here as the mistaken assumption that a sustainability-marketed polymer can enter an established recycling stream without compromising system compatibility. Focusing on contamination-sensitive conditions in which segregation, sorting, or stream purity are insufficient to prevent cross-contamination, the review discusses the immiscibility of HDPE/PLA blends and the resulting changes in stiffness, ductility, toughness, and aging behavior. It also analyzes mitigation routes such as improved sorting, compatibilization, and policy measures, while emphasizing that the practical severity of contamination depends on local infrastructure and contamination levels. In addition, it considers the risk that contaminated materials diverted into lower-value applications may become more vulnerable to interfacial damage, weathering, and secondary fragmentation. Overall, the review argues that circular-plastics strategies must distinguish biodegradability from recycling-system compatibility to protect the quality and value of HDPE recyclates. Full article

(This article belongs to the Special Issue Advancing the Circular Economy: A Life Cycle Perspective on Waste Valorization)

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