Recycling

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

Viewed by 339

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

Viewed by 306

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

Viewed by 534

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

Viewed by 483

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

Viewed by 815

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

Viewed by 505

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

Viewed by 250

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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43 pages, 11090 KB

Open AccessSystematic Review

Closing the Loop Locally: A Systematic Review and Framework for Distributed Recycling of Post-Consumer Plastics with a Focus on HDPE and PP

by Johan Montenegro, Carmen Castaño, María De Los Ángeles Ortega-Del-Rosario, Ricardo Caballero, Max Medina, Dennis Keiser and Michael Freitag

Recycling 2026, 11(8), 147; https://doi.org/10.3390/recycling11080147 - 11 Aug 2026

Viewed by 460

Abstract

This systematic review evaluated technical evidence and system-level conditions for Distributed Recycling and Additive Manufacturing (DRAM) of post-consumer high-density polyethylene (HDPE) and polypropylene (PP). Peer-reviewed journal articles, conference papers, and reviews published from 2020 to 2025 were eligible when they addressed recycled-polymer preparation, [...] Read more.

This systematic review evaluated technical evidence and system-level conditions for Distributed Recycling and Additive Manufacturing (DRAM) of post-consumer high-density polyethylene (HDPE) and polypropylene (PP). Peer-reviewed journal articles, conference papers, and reviews published from 2020 to 2025 were eligible when they addressed recycled-polymer preparation, feedstock conversion, extrusion-based additive manufacturing, printing performance, or circularity-related implementation; studies focused only on virgin polymers, outside the publication period, or lacking relevance were excluded. Scopus and Web of Science were searched on 17 October 2025 using four thematic strategies. Methodological completeness and applicability were appraised across six domains for the HDPE/PP material-specific evidence. Findings were synthesized narratively and thematically; meta-analysis was not performed because of substantial heterogeneity in feedstock, formulation, equipment, specimens, test methods, and outcomes. The final corpus comprised 119 unique sources: 28 material-specific sources (11 HDPE and 17 PP) and 91 contextual or system-level sources. Of the material-specific subset, 24 provided direct or partially direct recycled experimental evidence and four provided indirect or secondary evidence. Most appraised material-specific sources showed methodological concerns related to feedstock provenance, processing history, parameter reporting, replication, or test conditions. Recycled HDPE and PP could be converted into extrusion-based additive manufacturing feedstocks under study-specific conditions, but the evidence did not support universal processing windows, property ranges, degradation rates, cost competitiveness, environmental superiority, or generalized industrial readiness. Most evidence remained at laboratory or demonstrator scale. The Circular DRAM Viability Framework provides an evidence-informed structure intended to support application-specific diagnosis, monitoring, and qualification. Full article

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21 pages, 10215 KB

Open AccessArticle

Thermal–Physical Pretreatment and Extraction of Indium from LCD Waste Stream

by Napat Mahiwan, Chatisa Kansomket, Sumita Chailoi, Natthicha Ma-Ud, Sakhob Khumkoa, Teerawut Tunnukij and Tapany Patcharawit

Recycling 2026, 11(8), 146; https://doi.org/10.3390/recycling11080146 - 10 Aug 2026

Viewed by 984

Abstract

Liquid Crystal Display (LCD) waste from various sources, such as TVs, desktop monitors, and computer notebooks, is increasing and has become an environmental issue, requiring legalized disposal and practical recycling technologies to address it. LCD screens generally contain Indium–Tin–Oxide (ITO), which are critical [...] Read more.

Liquid Crystal Display (LCD) waste from various sources, such as TVs, desktop monitors, and computer notebooks, is increasing and has become an environmental issue, requiring legalized disposal and practical recycling technologies to address it. LCD screens generally contain Indium–Tin–Oxide (ITO), which are critical and valuable metals worth recovering. The aim of this research is to optimize the thermal–physical pretreatment of LCD screens after dismantling to effectively recover indium via leaching and solvent extraction at an acceptable recovery rate. A comparative study was conducted on the recovery of indium from LCD waste from TVs and a mixed waste stream, where the latter source represents the total proportion of LCD waste accumulation. This comparison aimed to identify key factors for effective recovery from TV and mixed waste streams, containing lower and higher amounts of indium, respectively. The recovery process consisted of waste pretreatment, leaching, and solvent extraction. In the first pretreatment, ethanol immersion was found to be the most practical for polarizing film removal for both streams in comparison with manual peeling, water immersion, surface heating, and calcination. Comminution in the second pretreatment aimed to increase the surface area for the subsequent chemical reaction. For both streams, HCl leaching allowed effective indium recovery of >99.9% at the optimal conditions of 5 M HCl with 10% H₂O₂ addition and an S/L ratio of 500 g/L under ultrasonication for 1 h. Subsequent purification via solvent extraction was conducted to exclude iron as the key impurity. In solvent extraction, D2EHPA concentration, pH, and the organic-to-aqueous ratio (O:A) was investigated. Optimal solvent extraction was achieved using 0.25 M D2EHPA at pH 1 and an O/A ratio of 1:5 for 5 min, while ascorbic acid was added to eliminate undesirable iron. Although both waste streams achieved >99.9% leaching efficiency, they exhibited different extraction behaviors after scrubbing and stripping. The TV waste stream achieved 74.32% solvent extraction efficiency. The higher indium recovery of 84.34% via solvent extraction through the stripping of the mixed stream might be due to the higher initial indium concentration reacting with D2EHPA. This led to the overall recovery of the two waste streams as 70.22% and 80.24% for TV and mixed waste streams, respectively, possibly due to higher amounts of indium in the initial waste stream. The findings of this study serve as research and practical guidance for indium recovery and EOL–LCD recycling. Full article

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13 pages, 3126 KB

Open AccessArticle

Production of Direct Reduction Grade Iron Concentrate from Pickling Sludge by Reduction Calcination and Magnetic Separation

by Chunqing Gao, Huifen Yang, Jian Xu and Ning Wang

Recycling 2026, 11(8), 145; https://doi.org/10.3390/recycling11080145 - 10 Aug 2026

Viewed by 353

Abstract

Taking pickling sludge generated from the steel rolling process at a Chinese steel mill as the subject of study, this research investigates a combined mineral processing and metallurgical process involving gasification-reduction roasting, magnetic separation, and waste acid recovery. The main elements in this [...] Read more.

Taking pickling sludge generated from the steel rolling process at a Chinese steel mill as the subject of study, this research investigates a combined mineral processing and metallurgical process involving gasification-reduction roasting, magnetic separation, and waste acid recovery. The main elements in this pickling sludge are Fe and Cl, with contents of 46.50% and 12.70%, respectively. The primary component is chlorine-containing iron oxide, and a significant amount of amorphous material is also present. The study investigated the effects of various calcination temperatures, calcination times, reducing agent dosages, and material thicknesses on gasification-reduction performance indicators. The results indicate that using a reduction calcination–grinding–magnetic separation process, with coal as the reducing agent, a calcination temperature of 1100 °C, a reducing agent dosage of 15%, and a calcination time of 2 h, the chlorine volatilization rate exceeds 97%. Furthermore, when the roasted ore is ground to a particle size where 85% passes through a −0.076 mm screen and is recovered via magnetic separation, an iron concentrate with a grade of over 69.50% can be obtained. This iron concentrate meets the quality requirements for high-grade iron concentrates used in direct reduced iron (DRI) production. The small amount of tailings from the iron concentration process can be utilized in the production of bricks, cement, and other products, thereby achieving the efficient comprehensive utilization of acid washing sludge. Full article

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21 pages, 341 KB

Open AccessArticle

Waste Literacy Among Portuguese First-Year Tertiary Students After Compulsory Environmental Education

by Hélder Spínola, Jacinta Fernandes, Cátia Sousa, Clarice Campos, Sandra Mourato, Lizete Heleno, Maria Anunciação Mateus Ventura, Sandra Caeiro, Paula Bacelar-Nicolau, Mahsa Mapar, Ulisses M. Azeiteiro, Sandra C. Guimarães, Liliana Rodrigues, Sílvia Mateus Carreira, Rute Martins and Sílvia Quadros

Recycling 2026, 11(8), 144; https://doi.org/10.3390/recycling11080144 - 9 Aug 2026

Viewed by 362

Abstract

Waste management is essential for addressing local and global environmental challenges. Failure to manage waste effectively results in several consequences, including environmental degradation, public health risks, and economic costs. Besides the need for adequate and up-to-date waste management systems, citizens’ cooperation is crucial [...] Read more.

Waste management is essential for addressing local and global environmental challenges. Failure to manage waste effectively results in several consequences, including environmental degradation, public health risks, and economic costs. Besides the need for adequate and up-to-date waste management systems, citizens’ cooperation is crucial to achieving sustainable waste management in any community, which depends on their waste literacy levels, comprising the knowledge, attitudes, and behaviours required. This study assessed waste literacy among students completing compulsory education in Portugal to provide evidence regarding the outcomes of environmental education policies related to waste management. A representative sample of 1506 freshmen students was surveyed at the start of their undergraduate programmes. An online questionnaire was administered to the sample and the data were analyzed using statistical tests for assessing the influential factors associated with students’ waste knowledge, attitudes and behaviours. Results show that, on average, students demonstrated good levels of knowledge and practices on waste management, together with a predominantly ecocentric worldview. A higher performance in waste management knowledge and practices was observed among younger students, with higher grades and higher paternal educational attainment. Besides these variables, best practices were significantly more prevalent among those with a higher participation in environmental activities and holding membership in environmental organizations. The findings suggest that upon completing compulsory education in Portugal, students display generally high levels of waste literacy, while also revealing specific gaps in knowledge and practices that warrant further educational attention. The study identifies these areas for improvement, highlighting the potential value of more practical, participatory and community-based approaches to waste education. Full article

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

37 pages, 12088 KB

Open AccessArticle

Improving the Performance of Recycled Multilayer PET Through Reactive Compatibilization Strategies

by Aritz Unamuno Garay, Fernando Galera Pérez, Ana Ibáñez-García, Asunción Martínez-García and María Dolores Samper

Recycling 2026, 11(8), 143; https://doi.org/10.3390/recycling11080143 - 7 Aug 2026

Viewed by 432

Abstract

The recycling of post-industrial multilayer polyethylene terephthalate (mPET) packaging waste remains a major challenge due to the coexistence of incompatible polymeric phases and the deterioration of properties during reprocessing. In this work, different reactive compatibilization strategies were evaluated to improve the processability and [...] Read more.

The recycling of post-industrial multilayer polyethylene terephthalate (mPET) packaging waste remains a major challenge due to the coexistence of incompatible polymeric phases and the deterioration of properties during reprocessing. In this work, different reactive compatibilization strategies were evaluated to improve the processability and performance of recycled multilayer PET scraps generated during industrial packaging manufacturing processes. Several functional compatibilizers were investigated, including poly(ethylene-co-acrylic acid) (EAA), poly(ethylene-alt-maleic anhydride) (EMA), poly(ethylene-co-glycidyl methacrylate) (EGMA), poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) (EMAGMA), and maleic anhydride (MA). The influence of compatibilization on the thermal, mechanical, chemical, surface, and morphological properties of recycled mPET was systematically analyzed. Processing behavior revealed that EMA- and MA-based formulations could not be successfully injection molded. In contrast, EAA-, EGMA-, and EMAGMA-based formulations showed suitable processability and enabled the production of defect-free specimens. Thermogravimetric analysis revealed only minor changes in thermal degradation behavior after compatibilization. In contrast, differential scanning calorimetry revealed changes in the melting behavior of the recycled formulations, while tensile and impact tests demonstrated marked improvements in ductility and toughness for EGMA- and EMAGMA-modified systems. Among them, EMAGMA provided the highest elongation at break and impact resistance. Contact angle measurements showed moderate changes in surface wettability, whereas density and hardness remained largely unaffected. FESEM analysis revealed a more homogeneous phase distribution and reduced dispersed-domain size in the compatibilized formulations, particularly for EGMA, indicating improved interfacial compatibility. These results demonstrate that glycidyl methacrylate-based compatibilizers are effective reactive agents for upgrading post-industrial multilayer PET waste into higher-performance recycled materials for different applications. Full article

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29 pages, 3241 KB

Open AccessArticle

Assessment of Recycling Pathways for Black Masses Derived from Lithium-Ion Batteries to Recover Critical Raw Materials and Valuable Elements

by Parinaz Seifollahzadeh, Bettina Rutrecht, Stefanie Lesiak, Lalropuia Lalropuia, Stephan Stuhr, Lukas Schmidt, Rebeka Frueholz, Anna Sieber, Sabine Spiess, Markus Ellersdorfer, Johannes Rieger and Roland Pomberger

Recycling 2026, 11(8), 142; https://doi.org/10.3390/recycling11080142 - 7 Aug 2026

Viewed by 509

Abstract

Recycling of lithium-ion batteries (LIBs) remains challenging due to high energy requirements, losses of key elements like lithium, and the heterogeneity of waste streams arising from different cathode chemistries. This study evaluates multiple recycling methods for LIBs black mass (BM), to recover critical [...] Read more.

Recycling of lithium-ion batteries (LIBs) remains challenging due to high energy requirements, losses of key elements like lithium, and the heterogeneity of waste streams arising from different cathode chemistries. This study evaluates multiple recycling methods for LIBs black mass (BM), to recover critical raw materials and other valuable components. Three types of BM including nickel–manganese–cobalt (NMC), lithium iron phosphate (LFP) and a heterogeneous mixture of cell phones and laptops (HL; German: Handy/Laptops), were treated using froth flotation, pyrometallurgy, and biohydrometallurgy and their respective recovery efficiencies were assessed. The flotation results revealed that the HL sample had the lowest mis-recovery of non-ferrous metals into the froth product (around 10%), leading to further flotation only for HL. During screening, 94–99% of iron, phosphorus, and carbon in LFP-type BM were recovered in the fine fraction (<45 µm), while 92–99% of lithium, cobalt, manganese, nickel, and carbon in NMC-type BM were recovered in the same fraction. During precipitation, 99% of iron and 100% of phosphorus were recovered from LFP bioleachates at pH 3, while ~97–100% of dissolved cobalt, manganese, and nickel were recovered from NMC bioleachates. These findings confirm that no single recycling method is optimal for all battery chemistries. Full article

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

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26 pages, 2430 KB

Open AccessArticle

From E-Waste to Agricultural Solutions: Technical and Energy Performance of an Upcycled Heat Pump Dryer for Red Dragon Fruit

by Sutida Phitakwinai and Wanich Nilnont

Recycling 2026, 11(8), 141; https://doi.org/10.3390/recycling11080141 - 6 Aug 2026

Viewed by 368

Abstract

This study evaluated the technical viability and thermodynamic performance of an open-loop upcycled heat pump dryer, repurposed from a decommissioned window-type air conditioner, for thin-layer red dragon fruit (Selenicereus costaricensis) drying. Experiments were executed at 50 °C under controlled air velocities [...] Read more.

This study evaluated the technical viability and thermodynamic performance of an open-loop upcycled heat pump dryer, repurposed from a decommissioned window-type air conditioner, for thin-layer red dragon fruit (Selenicereus costaricensis) drying. Experiments were executed at 50 °C under controlled air velocities (0.5, 1.0, and 1.5 m/s), using open-sun drying as a control. Mathematical modeling revealed that the Wang and Singh model best described the drying process (

R^{2}

: 0.996368–0.999539). Accounting for volumetric shrinkage via equivalent average thickness (L_eq = 0.75 L₀), corrected effective moisture diffusivity (D_eff) ranged from 1.194 × 10⁻⁹ to 3.138 × 10⁻⁹ m²/s, while convective mass transfer coefficients (

h_{m}

) ranged from 5.241 × 10⁻⁷ to 1.880 × 10⁻⁶ m/s, both peaking at 1.5 m/s due to thinned concentration boundary layers. Thermodynamic assessments showed a maximum COP_hp of 3.41 at 1.0 m/s and a maximum SMER of 0.231 kg/kWh at 1.5 m/s. Individual statistical analysis of L*, a*, and b* parameters confirmed no statistically significant differences (p > 0.05) between heat-pump-dried and fresh samples. Concurrently, a remarkably low descriptive total color difference (ΔE = 1.24) was obtained, compared to open-sun drying (ΔE = 16.22), confirming high color retention. These findings highlight e-waste upcycling as an efficient and sustainable agricultural solution. Full article

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33 pages, 4345 KB

Open AccessSystematic Review

From Waste Management to Strategic Integration: A Systematic Review of the Thematic and Conceptual Evolution of the Circular Economy in Agri-Food Systems (2018–2025)

by Mihaela Adriana Tița, Cristina Maria Bătușaru, Andreea Simina Porancea-Răulea, Alina Rădoiu and Ovidiu Tița

Recycling 2026, 11(8), 140; https://doi.org/10.3390/recycling11080140 - 6 Aug 2026

Viewed by 734

Abstract

The adoption of circular economy (CE) in agri-food systems has been accelerated by rising environmental pressures and resource inefficiencies. This systematic review examines the thematic and conceptual evolution of CE research in agri-food systems between 2018 and 2025, focusing on the transition from [...] Read more.

The adoption of circular economy (CE) in agri-food systems has been accelerated by rising environmental pressures and resource inefficiencies. This systematic review examines the thematic and conceptual evolution of CE research in agri-food systems between 2018 and 2025, focusing on the transition from waste management toward the strategic integration of circular principles across food value chains. By combining bibliometric mapping with a structured literature review, the study analyzes publication trends, intellectual structures, dominant research themes, and emerging directions within the field. The findings reveal a rapid growth in scientific output and a shift from conceptual frameworks toward applied management strategies, including performance measurement, organizational innovation, and decision-support tools. Technological solutions for waste valorization increasingly support regenerative food system models. Despite these advances, important research gaps remain, particularly regarding geographical concentration, the limited integration of consumer perspectives, and the need for broader assessment frameworks capable of evaluating the systemic impacts of circular strategies. Although nutrition-related aspects appear only marginally in the current literature, they represent a promising avenue for future interdisciplinary research rather than a dominant research theme. Overall, the field is evolving toward a more systemic and implementation-oriented perspective capable of supporting resilient and sustainable food systems. Full article

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

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20 pages, 4900 KB

Open AccessArticle

Microstructural Evolution and Mechanical Performance of Concrete Incorporating Palm Oil Fuel Ash as a Partial Cement Replacement

by Ramon Torres-Ortega, Manuel Saba and Jair Arrieta-Baldovino

Recycling 2026, 11(8), 139; https://doi.org/10.3390/recycling11080139 - 6 Aug 2026

Viewed by 282

Abstract

The incorporation of supplementary cementitious materials derived from agro-industrial residues has emerged as a promising strategy to reduce the environmental impact associated with Portland cement production while promoting circular economy principles. This study investigates the influence of palm oil fuel ash (POFA) as [...] Read more.

The incorporation of supplementary cementitious materials derived from agro-industrial residues has emerged as a promising strategy to reduce the environmental impact associated with Portland cement production while promoting circular economy principles. This study investigates the influence of palm oil fuel ash (POFA) as a partial cement replacement on the mechanical and microstructural properties of concrete. Concrete mixtures containing 0%, 10%, 15%, and 20% POFA by mass of cement were produced using a constant water-to-binder ratio of 0.47. Compressive strength was evaluated at 7, 14, 28, and 56 days, while microstructural characterization was performed using scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM–EDS) to assess hydration products and the interfacial transition zone (ITZ). The incorporation of POFA resulted in lower compressive strength at early curing ages, with reductions of approximately 16–21% compared with the control mixture, reflecting the slower kinetics of pozzolanic reactions. However, prolonged curing promoted significant strength development. At 56 days, concretes containing 10% and 15% POFA exhibited compressive strengths 3.7% and 9.2% higher, respectively, than the control concrete, whereas the 20% replacement level resulted in a 14.6% reduction. SEM observations revealed a denser cementitious matrix, improved aggregate–paste bonding, and a more refined ITZ in mixtures containing 10–15% POFA. EDS analysis showed Ca/Si ratios of 1.22 and 1.08 for the 10% and 15% POFA mixtures, respectively, indicating the formation of silica-rich C–S–H gel associated with effective pozzolanic activity. The results demonstrate that POFA can be successfully utilized as a supplementary cementitious material in concrete. While the 15% replacement level produced the highest 56-day compressive strength, both the 10% and 15% mixtures exhibited favorable microstructural characteristics and effective pozzolanic activity, indicating that both replacement levels are suitable for sustainable concrete production. Full article

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25 pages, 16357 KB

Open AccessArticle

Binder-Level Rheological Evaluation of Virgin HDPE, LDPE, and PP as Asphalt Binder Modifiers: Baseline Assessment for Plastic Waste Recycling Applications

by Nafisa Tarannum, Shahjalal Selim, Nazimuddin M. Wasiuddin and Andrew Peters

Recycling 2026, 11(8), 138; https://doi.org/10.3390/recycling11080138 - 6 Aug 2026

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Abstract

Increasing plastic waste and limited recycling rates underscore the need for value-added recycling applications. Polymers commonly present in plastic waste streams, including packaging films, bottles, caps, and rigid containers, may provide a practical pathway for developing plastic-modified asphalt binder (PMAB) systems. In this [...] Read more.

Increasing plastic waste and limited recycling rates underscore the need for value-added recycling applications. Polymers commonly present in plastic waste streams, including packaging films, bottles, caps, and rigid containers, may provide a practical pathway for developing plastic-modified asphalt binder (PMAB) systems. In this study, virgin high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP) were selected as reference modifiers to evaluate their intrinsic effects on performance grade (PG) 58-28 and PG 67-22 base binders. Conventional high-, intermediate-, and low-temperature gradings were complemented by

Δ T_{c}

, the Christensen–Anderson R-value (R-value), the Glover–Rowe (G-R) parameter, Linear Amplitude Sweep (LAS) fatigue analysis modeled via Viscoelastic Continuum Damage (VECD), rheological master curves, and extended Bending Beam Rheometer (BBR) testing. Modification improved high-temperature grading and LAS-based fatigue response while increasing master-curve stiffness. However,

Δ T_{c}

, G-R parameter, and extended BBR results indicated increased low-temperature cracking susceptibility. High-temperature grades increased by 3.4 °C, 2.8 °C, and 2.3 °C per percent HDPE, LDPE, and PP, respectively, whereas low-temperature grade losses reached 7.8 °C; HDPE produced the highest high-temperature grade improvement, while LDPE showed the greatest extended BBR grade loss, and PP exhibited the fastest physical hardening rate. These results provide a controlled binder-level baseline for evaluating HDPE, LDPE, and PP as modifiers for future PMAB development. Full article

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10 pages, 961 KB

Open AccessArticle

Monitoring Municipal Solid Waste Along the Collection Chain: Composition and Property Shifts from Source to Communal Storage and Dumpsite in Sialkot, Pakistan

by Muhammad Imran, Aamena Batool, Nazish Hina, Rao Taha Tauqeer and Shaban Shahzad

Recycling 2026, 11(8), 137; https://doi.org/10.3390/recycling11080137 - 1 Aug 2026

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Abstract

Municipal waste composition is commonly measured at a single point, even though recovery, mixing and handling can alter the stream before disposal. This study examined municipal solid waste in Sialkot, Pakistan, during an eight-day campaign from 27 December 2021 to 3 January 2022. [...] Read more.

Municipal waste composition is commonly measured at a single point, even though recovery, mixing and handling can alter the stream before disposal. This study examined municipal solid waste in Sialkot, Pakistan, during an eight-day campaign from 27 December 2021 to 3 January 2022. A total of 672 physical-characterization samples was obtained from residential, commercial, institutional, industrial and street-sweeping sources. Household generation was 0.42, 0.46 and 0.51 kg per person per day in low-, middle- and high-income proxy areas, respectively. Kitchen waste declined from 45.91% at the source to 34.20% at communal storage and 23.45% at the dumpsite. Recyclable paper and plastic also declined, whereas dust and fines increased from 2.05% at the source to 19.60% at storage and 21.78% at disposal. Six mixed-waste composites showed moisture contents of 30.72–53.06%, ash contents of 15.85–45.04% and gross calorific values of 2924–12,530 kcal kg⁻¹. The results demonstrate that monitoring location materially affects estimated recycling and treatment potential. A multi-point monitoring protocol is therefore recommended for cities with mixed collection and informal material recovery. Full article

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18 pages, 6182 KB

Open AccessArticle

The Impact of Social Norm Versus Educational Message Framing on Residential Recycling: A Randomized Field Trial

by Suraksha Baral and Brian E. Roe

Recycling 2026, 11(8), 136; https://doi.org/10.3390/recycling11080136 - 30 Jul 2026

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Abstract

National recycling rates have stagnated at approximately 32 percent in the United States, suggesting that existing programs are not achieving desired levels of diversion. A growing body of field experiments has examined whether informational and norm-based messaging interventions can shift recycling behavior, though [...] Read more.

National recycling rates have stagnated at approximately 32 percent in the United States, suggesting that existing programs are not achieving desired levels of diversion. A growing body of field experiments has examined whether informational and norm-based messaging interventions can shift recycling behavior, though most studies rely on self-reported outcomes or stated preferences rather than objective behavioral measures. Using bin-level audit data from a randomized field trial among 200 voluntarily enrolled households in Columbus, Ohio, we find that norm-based and educational message framing produce statistically indistinguishable average effects on recycling fill level, participation, and contamination over a 29-week program. However, the analysis identifies that norm-based messaging outperforms educational messaging when adverse weather raises participation costs, while educational messaging holds up better during high-distraction community events. These patterns point toward adaptive messaging designs that condition content on observable contextual triggers as a promising direction for extracting greater behavioral returns from recycling outreach investment. Full article

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

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20 pages, 8109 KB

Open AccessArticle

Bio-Based Solvents for the Recycling of Post-Consumer HDPE Waste—Determination of Residual Content and Cleaning Efficiency

by Javier Blázquez-Martín, Marta Jiménez-Salcedo, Jorge García-Barrasa and María Teresa Tena

Recycling 2026, 11(8), 135; https://doi.org/10.3390/recycling11080135 - 24 Jul 2026

Viewed by 1149

Abstract

Seven bio-based solvents ((-)-β-pinene, α-phellandrene, α-terpinene, p-cymene, DL-limonene, γ-terpinene and terpinolene) are tested as environmentally friendly alternatives for use in a plastic recycling process based on dissolution–precipitation of post-consumer high-density polyethylene (PC-HDPE). In addition to evaluating cleaning performance, this work aims to develop [...] Read more.

Seven bio-based solvents ((-)-β-pinene, α-phellandrene, α-terpinene, p-cymene, DL-limonene, γ-terpinene and terpinolene) are tested as environmentally friendly alternatives for use in a plastic recycling process based on dissolution–precipitation of post-consumer high-density polyethylene (PC-HDPE). In addition to evaluating cleaning performance, this work aims to develop and validate a new analytical method for the determination of residual bio-based solvents in the treated polymer, a critical aspect for evaluating the safety and quality of recycled materials. The suitability of the solvents for contaminant removal was assessed via challenge test, showing high cleaning efficiencies (>93.3%) for volatile, non-volatile, polar and non-polar compounds in most cases. To monitor residual solvent levels, a pressurized liquid extraction and gas chromatography–mass spectrometry (PLE-GC/MS) method was developed, optimized and validated. The method demonstrated adequate sensitivity (with LODs ranging between 2 and 4 mg kg⁻¹), accuracy and precision (with intra- and inter-day relative standard deviations of less than 11 and 31%, respectively) for the simultaneous determination of the seven bio-based solvents in recycled HDPE. Overall, results demonstrate both the potential of bio-based solvents in polymer recycling and the importance of robust analytical tools to assess residual contamination, supporting the development of safer and more sustainable recycling processes. Full article

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15 pages, 9669 KB

Open AccessArticle

Assessment of Mechanical Recycling Potential of Plastic Waste from End-of-Life LFP Battery Cases

by Chiara Gnoffo, Rossella Arrigo, Valentina Piergrossi, Letizia Tuccinardi, Riccardo Tuffi and Alberto Frache

Recycling 2026, 11(8), 134; https://doi.org/10.3390/recycling11080134 - 24 Jul 2026

Viewed by 529

Abstract

This study evaluated the feasibility of mechanical recycling of plastic waste recovered from the disassembly of end-of-life lithium iron phosphate battery cases. In particular, the work focused on the case fraction, corresponding to the outer battery envelope, which represents the largest share of [...] Read more.

This study evaluated the feasibility of mechanical recycling of plastic waste recovered from the disassembly of end-of-life lithium iron phosphate battery cases. In particular, the work focused on the case fraction, corresponding to the outer battery envelope, which represents the largest share of the plastic waste by weight. A preliminary characterization was carried out to determine the physico-chemical properties of the material and assess its suitability for mechanical recycling. The polymer matrix was found to consist of polypropylene, with glass fibers and calcium carbonate as inorganic fillers, each present at 18 wt%. X-ray fluorescence and elemental analysis confirmed the absence of elements of concern and subsequently, recycled material processability was investigated, with particular attention to injection molding, the same technology used to manufacture the original battery cases. Rheological analyses confirmed that the material exhibits Newtonian rheological behavior, suitable for injection molding, as also supported by a melt flow index value equal to 7.5 g/10 min (230 °C, 2.16 kg). The material was then reprocessed, and the resulting specimens were subjected to mechanical tests, with impact energy equal to 30.5 kJ/m² and flexural strength amounting to 36.8 MPa. Overall, the recycled material exhibited adequate processability and mechanical performance after one reprocessing step, suggesting its potential for high-value mechanical recycling. Full article

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Recycling, Volume 11, Issue 8 (August 2026) – 21 articles

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