Recycling

Research

19 pages, 2267 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 (registering DOI) - 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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14 pages, 670 KB

Open AccessArticle

Advancing Plastic Waste Circularity Through Modular Portable Pyrolysis Systems

by Dimitrios-Aristotelis Koumpakis, Dimitrios Christoforidis, Vasileios Diamantis, Alexandra V. Michailidou and Christos Vlachokostas

Recycling 2026, 11(4), 67; https://doi.org/10.3390/recycling11040067 - 1 Apr 2026

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Abstract

The lack of centralized waste management infrastructure in certain regions makes plastic waste an escalating environmental and economic problem. This research investigates how modular portable pyrolysis systems function as sustainable decentralized solutions. A standard shipping container houses a custom-designed pyrolysis unit which demonstrates [...] Read more.

The lack of centralized waste management infrastructure in certain regions makes plastic waste an escalating environmental and economic problem. This research investigates how modular portable pyrolysis systems function as sustainable decentralized solutions. A standard shipping container houses a custom-designed pyrolysis unit which demonstrates flexibility and adaptability. The system contains a batch rotary kiln reactor with a processing capacity of 750 kg per batch which is fed with urban plastic waste, to produce pyrolytic oil, syngas and char. The produced pyrolytic oil exhibits an energy content comparable to that of conventional diesel fuel. Additionally, the integration of biomass briquettes and recycled pyrolytic gas can reduce to a big extent the external energy requirements, improving the system’s overall energy autonomy. Therefore, the system becomes economically reliable due to its low operational expenses and the short cycle of approximately 7-h operation. The unit’s mobility enables on-site treatment operations which reduces both transportation emissions and expenses. The analysis includes technical design elements together with performance metrics for different plastics. This conceptual study demonstrates the feasibility of containerized pyrolysis as a practical method to enhance plastic waste chemical recycling rates while presenting a scalable framework for industrial symbiosis and local waste-to-energy conversion. Full article

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

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18 pages, 1282 KB

Open AccessArticle

The Use of Fresnel Lens Softening Stations to Improve Recycling Feasibility of Injection-Molding Purges

by Ma. Guadalupe Plaza, Maria Luisa Mendoza López, José de Jesús Pérez Bueno, Edain Belén Pérez Mendoza and Martha Elva Pérez Ramos

Recycling 2026, 11(3), 57; https://doi.org/10.3390/recycling11030057 - 5 Mar 2026

Viewed by 515

Abstract

Injection-molding purges are heterogeneous, bulky residues whose uncertain composition and irregular geometry hinder direct reinsertion, making cold shredding costly and maintenance-intensive. This work develops a low-infrastructure solar-assisted pre-processing route using a PMMA Fresnel lens to induce controlled sub-onset softening and enable clean shear [...] Read more.

Injection-molding purges are heterogeneous, bulky residues whose uncertain composition and irregular geometry hinder direct reinsertion, making cold shredding costly and maintenance-intensive. This work develops a low-infrastructure solar-assisted pre-processing route using a PMMA Fresnel lens to induce controlled sub-onset softening and enable clean shear cutting without destructive thermal histories. The sub-onset softening is here defined into a viscoelastically active range (at or above T_g for the amorphous phase) while remaining below the melting onset (T_m, onset) and below the onset of thermal degradation (T_d, onset). The station was engineered via QFD and risk-oriented design tools, while a weighted Pugh matrix selected shear cutting over saw-based alternatives. A screening factorial DOE showed that lens height, angle, and their interaction significantly govern focal-spot diameter and receiver temperature, yielding linear relations for conservative set-point selection. Receiver benchmarking further indicated that copper reaches substantially higher temperatures than graphite under identical exposure conditions, supporting copper as the simplest, rapid-heating receiver. Under DOE-calibrated operation, tear-free shear cutting was achieved across representative purge families (PP–ABS, PC–ABS–PP, PA66, PA66-filler, and POM) without forced convection. From a recycling and waste-management perspective, the approach converts bulky purge scrap into mill-compatible feedstock with reduced mechanical resistance, lowering tool wear and fines generation, accelerating downsizing, and limiting stockpiling that elevates combustible-inventory fire risk. Overall, the proposed DOE-calibrated, operator-friendly framework improves recycling feasibility by enabling safer handling, more stable preprocessing throughput, and reduced reliance on disposal or long-term storage for heterogeneous industrial purges. Full article

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

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13 pages, 1797 KB

Open AccessArticle

Mechanochemical Recycling of Tire-Derived Styrene–Butadiene Rubber Using a Regeneration Agent

by Matheus Silva de Oliveira, Leila Lea Yuan Visconte and Elen Beatriz Acordi Vasques Pacheco

Recycling 2026, 11(2), 37; https://doi.org/10.3390/recycling11020037 - 6 Feb 2026

Viewed by 1354

Abstract

Mechanochemical regeneration aims to selectively cleave the crosslinked network of vulcanized rubber. In this study, a tire-grade styrene–butadiene rubber (SBR) compound was vulcanized and then subjected to mechanochemical regeneration using a zinc (II) dithiocarbamate complex (ZNIBU) at 6, 8, and 10 phr. The [...] Read more.

Mechanochemical regeneration aims to selectively cleave the crosslinked network of vulcanized rubber. In this study, a tire-grade styrene–butadiene rubber (SBR) compound was vulcanized and then subjected to mechanochemical regeneration using a zinc (II) dithiocarbamate complex (ZNIBU) at 6, 8, and 10 phr. The regenerated materials were subsequently revulcanized, and their properties were assessed before and after both processing steps. The regenerated (non-revulcanized) samples exhibited reduced crosslink density and increased swelling, indicating effective network cleavage by the regenerator. After revulcanization, the compounds presented higher hardness (23%) but lower tensile strength (75%) and tear strength (25%) compared to the virgin vulcanizate. Overall, ZNIBU proved highly effective for the mechanochemical regeneration of SBR, with optimum performance observed at 8 phr. Full article

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

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22 pages, 8313 KB

Open AccessArticle

A Technical Feasibility Assessment of Chemically Recycling PET Fibers Through Glycolysis to Produce Functional Oligoesters

by Elaine Meireles Senra, Ana Carolina da Silva Guimarães, Renan Henriques Gonçalves de Almeida, Ana Lúcia Nazareth da Silva, José Carlos Costa da Silva Pinto, Christine Rabello Nascimento and Elen Beatriz Acordi Vasques Pacheco

Recycling 2026, 11(2), 36; https://doi.org/10.3390/recycling11020036 - 5 Feb 2026

Viewed by 1273

Abstract

This study investigated the chemical recycling of poly(ethylene terephthalate) (PET) fiber residues from two sources—high-molar mass mooring ropes and low-molar mass textile-grade fibers—to produce functional oligomers. Glycolysis was carried out using polyethylene glycol (PEG400) as the depolymerizing agent, and two catalysts were assessed, [...] Read more.

This study investigated the chemical recycling of poly(ethylene terephthalate) (PET) fiber residues from two sources—high-molar mass mooring ropes and low-molar mass textile-grade fibers—to produce functional oligomers. Glycolysis was carried out using polyethylene glycol (PEG400) as the depolymerizing agent, and two catalysts were assessed, zinc acetate and lithium octoate, with the latter reported on for the first time in this application. Reactions were performed for 180 min under mechanical stirring, inert atmosphere, reflux, and controlled heating. The resulting oligomers were characterized by Fourier-transform infrared spectroscopy (FTIR), hydroxyl and acidity indices, and thermogravimetric analysis (TGA). Both PET feedstocks showed high reactivity toward glycolysis. Monitoring the reactions by acidity index indicated that conversion reached equilibrium at approximately 120 min. ATR-FTIR confirmed the formation of ester and hydroxyl groups, consistent with oligomer structures. Glycolysis of PET derived from mooring ropes produced oligoesters with hydroxyl values of 228 and 242 mgKOH/g for zinc acetate and lithium octoate, respectively, and molar masses of 1296 and 1338 g/mol for zinc acetate and lithium octoate, respectively. These values are suitable for subsequent syntheses such as polyester polyol production. Full article

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

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25 pages, 2696 KB

Open AccessArticle

Recycled Lignocellulosic Resources for Circular Bioeconomy Applications: Heat-Treated Eucalyptus Fibers in Polyester Composites

by Douglas Lamounier Faria, Tamires Galvão Tavares Pereira, Danillo Wisky Silva, Mário Vanoli Scatolino, Julio Soriano, Thiago de Paula Protásio and Lourival Marin Mendes

Recycling 2026, 11(2), 34; https://doi.org/10.3390/recycling11020034 - 3 Feb 2026

Viewed by 706

Abstract

The pursuit of alternatives to nonrenewable materials has stimulated the development of sustainable materials with improved performance, particularly polymer composites reinforced with plant-based fibers. In this study, eucalyptus fibers were thermally treated and evaluated as eco-friendly reinforcements for polyester composites, aiming to enhance [...] Read more.

The pursuit of alternatives to nonrenewable materials has stimulated the development of sustainable materials with improved performance, particularly polymer composites reinforced with plant-based fibers. In this study, eucalyptus fibers were thermally treated and evaluated as eco-friendly reinforcements for polyester composites, aiming to enhance their physical and mechanical properties. The fibers were subjected to heat treatments between 140 and 230 °C in a Macro-ATG oven, followed by analyses of anatomical characteristics and chemical composition. Composites containing 25% fiber reinforcement were produced using an orthophthalic unsaturated polyester matrix catalyzed with methyl ethyl ketone peroxide, with untreated fibers used as references. Thermal treatment induced significant modifications in fiber morphology and composition, including increases in cell wall fraction at 170 and 200 °C and higher cellulose contents at 140 and 170 °C. Mechanical performance was assessed through tensile, flexural (modulus of rupture—MOR), modulus of elasticity (E_B), and impact tests. Composites reinforced with heat-treated fibers exhibited lower apparent density and, notably, those treated at 230 °C showed markedly reduced water absorption and enhanced tensile strength compared with the control. Overall, treatment at 230 °C proved most effective, highlighting the potential of thermally modified eucalyptus fibers as viable reinforcements for high-performance, bio-based polymer composites. 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, 1824 KB

Open AccessArticle

Recycling of Plastic Waste: How the Conditions of Thermal Cracking and the Composition of Plastic Mixtures Affect Product Yield

by Ulyana A. Frolova, Khoshim Kh. Urazov, Nikita N. Sviridenko and Ekaterina N. Kolobova

Recycling 2026, 11(2), 31; https://doi.org/10.3390/recycling11020031 - 2 Feb 2026

Viewed by 1047

Abstract

This study examines the effect of different heat treatment conditions on different mixtures of plastic waste to produce fuel fractions. The mixtures included polypropylene, polystyrene, polyethylene terephthalate, low-density polyethylene, and high-density polyethylene in various ratios. The experiments revealed optimal process parameters, including the [...] Read more.

This study examines the effect of different heat treatment conditions on different mixtures of plastic waste to produce fuel fractions. The mixtures included polypropylene, polystyrene, polyethylene terephthalate, low-density polyethylene, and high-density polyethylene in various ratios. The experiments revealed optimal process parameters, including the heating rate, process temperature, process duration, and environment, as well as the composition of the plastic waste mixture. This made it possible to extract more than 80% of the liquid, while gasoline and diesel fractions amounted to 35.7 and 30.5% wt., respectively. A detailed analysis of the gasoline fraction and diesel fuel obtained by cracking has demonstrated favorable properties confirming their potential as alternative sources of hydrocarbons or fuel components. A detailed study of the characteristics of the initial coke, as well as coke after alkaline treatment and calcination, revealed conditions conducive to the formation of porous carbon structures with a high specific surface area. The use of coke obtained from a mixture of plastic waste as a cracking additive slows down gas formation (by 1–5 ± 0.2% wt.) and increases the yield of low-boiling fractions (by 8.4 ± 0.4% wt.). Alkaline treatment of coke slows down its formation by increasing the specific area of micropores (from 154.8 to 219.1–286.5 m²/g) and decreasing the specific area of mesopores (from 311.2 to 76.4–187.3 m²/g), and also increases the yield of gasoline fractions. The results indicate effective ways to recycle plastic waste into valuable fuels and carbon materials, contributing to the development of technologies for sustainable waste management and resource recovery. Full article

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

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28 pages, 2189 KB

Open AccessArticle

A Comparative Evaluation of Three Valorisation Pathways for Waste Electric Arc Furnace Slag to Improve Its Use as an Eco-Logical Binder

by Bruno Machini, Diogo Simões, Pedro Humbert, Julieta António and João Almeida

Recycling 2026, 11(2), 25; https://doi.org/10.3390/recycling11020025 - 1 Feb 2026

Viewed by 595

Abstract

The urgent need to reduce greenhouse gas emissions and enhance resource circularity is driving the cement and construction industry to explore alternatives to clinker-based binders. Electric arc furnace slag (EAFS), a major steelmaking by-product, is currently underutilised as a binder due to its [...] Read more.

The urgent need to reduce greenhouse gas emissions and enhance resource circularity is driving the cement and construction industry to explore alternatives to clinker-based binders. Electric arc furnace slag (EAFS), a major steelmaking by-product, is currently underutilised as a binder due to its low intrinsic reactivity. This study provides a comparative evaluation of three distinct valorisation pathways for the same EAFS—use as a supplementary cementitious material (SCM), as a precursor for alkali-activated binders, and as a component in accelerated carbonation systems—thereby highlighting its multifunctional and more ecological binding potential. A comprehensive physicochemical characterisation was conducted, followed by mechanical performance assessment under different curing regimes. When used as an SCM, partial cement replacement resulted in no loss of mechanical performance and a compressive strength increase of up to 8.9% at 10% replacement, demonstrating its suitability for structural applications. Under accelerated carbonation, specimens with 50% replacement of cement and sand achieved compressive strengths of 46.7 MPa, comparable to the non-carbonated reference (47 MPa), indicating full strength recovery despite high substitution levels. Full replacement systems based on alkali activation or carbonation of EAFS achieved moderate compressive strengths (~10 MPa), suitable for non-structural applications, with clear potential for improvement through optimisation of activation and curing conditions. Overall, this work demonstrates that EAFS can be effectively valorised through multiple reaction routes, supporting its role as a versatile and low-carbon resource for sustainable cementitious materials. 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, 2207 KB

Open AccessArticle

Integrated Optimization Framework for a RF-ICP Plasma-Based System for Solid Waste Treatment

by Roman Stetsiuk, Mustafa A. Aldeeb and Hossam A. Gabbar

Recycling 2026, 11(2), 23; https://doi.org/10.3390/recycling11020023 - 28 Jan 2026

Viewed by 1121

Abstract

Waste management remains a major challenge worldwide, as rapidly expanding urban populations put greater pressure on traditional disposal methods such as landfilling and incineration. Plasma-based waste treatment offers an innovative, sustainable waste-to-energy solution capable of converting a wide range of waste types. Although [...] Read more.

Waste management remains a major challenge worldwide, as rapidly expanding urban populations put greater pressure on traditional disposal methods such as landfilling and incineration. Plasma-based waste treatment offers an innovative, sustainable waste-to-energy solution capable of converting a wide range of waste types. Although plasma technologies provide significant environmental benefits, such as greatly reducing waste volume and emissions compared to conventional approaches, their widespread adoption faces notable economic hurdles. Primary among these is high operational cost due to system inefficiencies. These costs mainly arise from energy losses within the plasma torch, energy consumed during plasma torch tuning with the plasma reactor, and power inefficiencies when processing unsuitable waste loads. These issues not only increase costs but also impact process stability, which can influence stakeholder support and the technology’s commercial potential. Optimizing the process through simulation presents an effective approach to overcoming this inefficiency. However, relying solely on these advanced tools can be time-consuming and requires substantial domain expertise, creating a bottleneck in design and optimization. This paper introduces a new integrated platform combining COMSOL Multiphysics v6.2, Ansys Fluent 2024 R1, and Aspen Plus v12.1 to address these challenges. Using a genetic algorithm, the platform automates the complex task of designing an optimal plasma torch, optimizes it for peak performance, and dynamically adjusts plasma conditions. This intelligent optimization system aims to maximize energy output and process efficiency, directly tackling key cost-related issues. 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, 689 KB

Open AccessArticle

Predicting Municipal Solid Waste Separation Intentions in Italy: Psychosocial Similarities and Differences Between Northern and Southern Regions

by Monica Pivetti, Francesca Giorgia Paleari, Mariangela Vespa and Maristella Tutolo

Recycling 2026, 11(1), 6; https://doi.org/10.3390/recycling11010006 - 26 Dec 2025

Viewed by 646

Abstract

This study examines the psychosocial factors predicting municipal solid waste separation in Italy, applying and extending a model originally developed for Southern regions. The model integrates the Theory of Reasoned Action and the Value-Belief-Norm framework to explain how values, norms, and attitudes shape [...] Read more.

This study examines the psychosocial factors predicting municipal solid waste separation in Italy, applying and extending a model originally developed for Southern regions. The model integrates the Theory of Reasoned Action and the Value-Belief-Norm framework to explain how values, norms, and attitudes shape waste separation intentions and behaviours. Using data from 321 online survey respondents, this study tests the model’s validity in Northern Italy. Additionally, the study examines the relationships among the variables under investigation in people residing in the Northern and Southern regions of Italy. Findings confirm the model (χ² (10) = 28.118, p = 0.002, CFI = 0.956; RMSEA = 0.075; AIC = 8.118): bio-altruistic values and social norms significantly predict positive attitudes, which in turn determine behavioural intentions. Perceived distributive unfairness is negatively associated with attitudes toward waste separation. Separation behaviour is mainly influenced by internal attributions and knowledge, while egoistic values show a negative relationship. The multi-group analysis indicates a good model fit for both Northern and Southern samples (χ² (31) = 45.059, p = 0.049, CFI = 0.969; RMSEA = 0.053; AIC = −16.941), suggesting consistent psychosocial mechanisms. By integrating psychosocial insights with behavioural data, this research highlights the importance of knowledge, fairness, and social norms in promoting sustainable waste management. The findings provide practical guidance for policymakers and practitioners to design regionally communication and participation strategies that enhance the long-term sustainability of waste separation systems in Italy. Full article

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

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13 pages, 659 KB

Open AccessArticle

A Carbon Footprint Comparative Analysis of Anaerobic Digestion vs. Landfill Gas Recovery in Brazil

by Juliene Maria da Silva Amancio, Kelly Alonso Costa, Welington Kiffer de Freitas, Givanildo de Gois, Paulo Miguel de Bodas Terassi, Francisco Santos Sabbadini, Josimar da Silva Freitas, Juaneza Barroso Falcão, Marco Antonio Conejero and Ana Paula Martinazzo

Recycling 2026, 11(1), 5; https://doi.org/10.3390/recycling11010005 - 25 Dec 2025

Cited by 1 | Viewed by 1440

Abstract

This study compares the carbon footprints of two municipal solid waste treatment technologies—anaerobic digestion and a gas recovery system—with the aim of evaluating their potential for biogas recovery and greenhouse gas (GHG) mitigation. The analysis applies the 2006 IPCC model to real operational [...] Read more.

This study compares the carbon footprints of two municipal solid waste treatment technologies—anaerobic digestion and a gas recovery system—with the aim of evaluating their potential for biogas recovery and greenhouse gas (GHG) mitigation. The analysis applies the 2006 IPCC model to real operational data from the Paracambi Waste Treatment Complex (Rio de Janeiro, Brazil), integrating carbon footprint estimation and environmental compensation modeling through tree planting. From a different perspective, this work evaluates the replacement of biogas recovery with a biologically controlled system based on material segregation. Within the limits and parameters defined for the system, anaerobic digestion achieved net emissions of 0.0029 tCO₂eq per ton of organic waste, compared to 1.14 tCO₂eq per ton for the biogas recovery system. This represents a potential 393-fold reduction in GHG emissions. However, this result is specific to the modeled conditions and does not consider the full life cycle impacts of non-organic waste fractions. The results suggest that anaerobic digestion, when integrated into an efficient selective collection system, can significantly improve energy recovery and mitigate the carbon footprint of waste management 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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18 pages, 6237 KB

Open AccessArticle

The Potential for Glass Wool Waste as a Filler in UF Adhesive to Promote Particleboard Strength

by Michelângelo Vargas Fassarella, Izabella Luzia Silva Chaves, Pedro Gutemberg Alcântara Segundinho, Juarez Benigno Paes, Roberto Carlos Costa Lelis, Michel Picanço Oliveira, Emilly Soares Gomes Silva and Fabricio Gomes Gonçalves

Recycling 2025, 10(6), 220; https://doi.org/10.3390/recycling10060220 - 5 Dec 2025

Cited by 2 | Viewed by 1002

Abstract

Wastes, biomasses, and nanoparticles have motivated reformulations of adhesives in the wood-based-panel industry. This study investigated the incorporation of glass wool (GW) waste as a filler material in urea–formaldehyde (UF) adhesive, evaluating its effects on the adhesive properties as well as on the [...] Read more.

Wastes, biomasses, and nanoparticles have motivated reformulations of adhesives in the wood-based-panel industry. This study investigated the incorporation of glass wool (GW) waste as a filler material in urea–formaldehyde (UF) adhesive, evaluating its effects on the adhesive properties as well as on the physical, mechanical, fire-retardant, and acoustic properties of particleboards. Panels with a target density of 700 kg m⁻³ were produced with different proportions of glass wool in the adhesive (T1: 0%; T2: 3.34%; T3: 4.93%; T4: 6.52%; T5: 9.49%; T6: 12.35%). The adhesive-coated particle mat was pressed in a hydraulic press at 160 °C under a compression force of 72 tons for 10 min. The panels were subjected to analyses of their physical, mechanical, fire-retardant, and acoustic properties, as well as scanning electron microscopy (SEM) analyses. Statistical analysis involved regression, analysis of variance, and a Scott–Knott test (p < 0.05). The results indicated that adding 3.34% GW to the adhesive improved the modulus of rupture, internal bond strength, screw withdrawal resistance, and acoustic efficiency of the panels. A glass wool content of 12.35% enhanced the hardness and the damping factor. These findings highlight the potential of glass wool as a functional filler material in UF adhesive, promoting the development of stronger and more sustainable particleboards. Full article

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

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25 pages, 2626 KB

Open AccessArticle

The Use of Agricultural Waste in Developing Nutrient-Rich Pasta: The Use of Beet Stalk Powder

by Nikoletta Solomakou, Dimitrios Fotiou and Athanasia M. Goula

Recycling 2025, 10(6), 217; https://doi.org/10.3390/recycling10060217 - 3 Dec 2025

Viewed by 1198

Abstract

The valorization of agricultural by-products such as beetroot stalks (BSs) offers a sustainable strategy for reducing food waste while enhancing nutritional value of staple foods. This study investigates the incorporation of BS powder, an agricultural waste rich in phenolics, betalains, and dietary fibers, [...] Read more.

The valorization of agricultural by-products such as beetroot stalks (BSs) offers a sustainable strategy for reducing food waste while enhancing nutritional value of staple foods. This study investigates the incorporation of BS powder, an agricultural waste rich in phenolics, betalains, and dietary fibers, into durum wheat semolina pasta. Pasta containing 5–20% BS were evaluated for bioactive compounds, cooking performance parameters, texture, color, and sensory acceptance. Enrichment increased total phenolics, antioxidant activity, and betalain concentration in a dose-dependent manner, with 20% BS pasta reaching 2.24 mg gallic acid equivalents/g phenolics and 1.53 mg/g betalains. Although drying and boiling reduced bioactive retention, enriched pasta maintained up to eightfold higher antioxidant activity than the control. Cooking performance showed increased water uptake and swelling index at higher substitution levels, while texture analysis revealed reduced hardness and cohesiveness above 15% BS substitution. Color analysis confirmed intense red hues from betalain pigments, enhancing consumer perception. Sensory evaluation indicated that control pasta was preferred for flavor and texture, but 10–15% BS samples were well accepted for their appealing color and mild vegetal notes. Overall, BS powder demonstrates strong potential for upcycling agricultural waste into functional, sustainable pasta with enhanced nutritional quality and alignment with circular economy practices. Full article

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

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19 pages, 6292 KB

Open AccessArticle

A Novel Biocomposite Made of Citrus Peel Waste and Mushroom Mycelium: Mechanical, Thermal, and Bio-Repellency Studies

by Natalia Fernández, Ana Valentina Basso, Lucas Ernesto Peisino, Sandra López, Alejandro Tapia and Jerónimo Kreiker

Recycling 2025, 10(6), 216; https://doi.org/10.3390/recycling10060216 - 30 Nov 2025

Viewed by 1075

Abstract

The growing environmental pollution and the imminent depletion of natural resources highlight the need for alternative building materials derived from renewable sources, including those that promote waste recycling and biodegradability. One promising alternative is biocomposites produced from filamentous fungal mycelium. In Argentina, orange [...] Read more.

The growing environmental pollution and the imminent depletion of natural resources highlight the need for alternative building materials derived from renewable sources, including those that promote waste recycling and biodegradability. One promising alternative is biocomposites produced from filamentous fungal mycelium. In Argentina, orange and lemon peels are among the most abundant organic waste generated by the citrus industry. This study explores the development of a sustainable insulating biocomposite using Pleurotus ostreatus mycelium grown on mixtures of citrus peels, paper, and cardboard. The test specimens were prepared using varying concentrations of these components. The resulting fungal biocomposite exhibited a density approximately ten times higher than expanded polystyrene, with drying shrinkage ranging from 28% to 51%, depending on the formulation. Key properties were evaluated, including compressive strength (

σ_{10}

= 7–33 kPa), bulk density (

ρ

= 152–181 kg/m³), and thermal conductivity (

λ

= 0.29–0.36 W/mK), indicating advantageous performance for thermal insulation in construction applications. Specimens containing orange peel also demonstrated repellent activity against Triatoma infestans, main vector of transmission of Chagas’ disease, attributed to the residual limonene content retained from the citrus peels. This fungal biocomposite aligns with principles of green chemistry and circular economy, offering a biodegradable, low-impact solution with potential use in construction. The citrus waste proved to be an effective substrate for mycelial growth, producing a material with desirable mechanical and thermal properties, and added resistance to biodeterioration. Full article

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

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24 pages, 1983 KB

Open AccessArticle

Municipal Solid Waste as a Renewable Energy Source: Evaluating the Potential for Sustainable Electricity Generation in the Minas Gerais Region in Brazil

by Adma Viana Santos, Lauana Lopes dos Santos, Maurício Santana de Paula, Juliene Maria da Silva Amancio, Julia Eduarda Araujo, Ivana Pires de Sousa Baracho, Lucas da Costa Santos, Ricardo Siqueira da Silva and Jéfferson de Oliveira Costa

Recycling 2025, 10(6), 205; https://doi.org/10.3390/recycling10060205 - 5 Nov 2025

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Abstract

Valorization of municipal solid waste (MSW) for energy represents a strategic alternative for developing countries, as it mitigates emissions, reduces pressure on landfills, and diversifies the electricity matrix. This study quantified the potential for electricity generation from MSW in the Jequitinhonha Valley, Minas [...] Read more.

Valorization of municipal solid waste (MSW) for energy represents a strategic alternative for developing countries, as it mitigates emissions, reduces pressure on landfills, and diversifies the electricity matrix. This study quantified the potential for electricity generation from MSW in the Jequitinhonha Valley, Minas Gerais, Brazil, using primary gravimetric characterization data, a method rarely employed in tropical areas. The identified composition showed a predominance of the organic fraction (47.6–73.3%), confirming the relevance of biological routes. The results indicated a consolidated potential of 106,640 MWh·year⁻¹, of which 94.7% was from biogas recovery and 5.3% from incineration. Almenara, one of the three locations analyzed, showed the highest potential (48,200 MWh·year⁻¹), followed by Diamantina (34,540 MWh·year⁻¹) and Capelinha (23,900 MWh·year⁻¹). The specific yields ranged from 0.33 to 0.53 MWh·ton⁻¹ MSW and the per capita indicators from 1.01 to 1.49 MWh·cap⁻¹·year⁻¹. The climate mitigation potential reached 1.0 Mt of CO₂eq·year⁻¹. It is concluded that valorization in the Jequitinhonha Valley should prioritize biogas recovery, complemented by the incineration of rejects. The materialization of this potential requires advancements in infrastructure, selective collection, and socio-productive inclusion. This study provides evidence for public policies and contributes to the literature by demonstrating that valorization can boost energy transition and socio-environmental equity in developing tropical regions. Full article

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

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Review

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23 pages, 8122 KB

Open AccessReview

Recycling of Printed Circuit Boards to Recover Critical Materials

by Md Kaviul Islam, Anirudha Karati, Ikenna C. Nlebedim and Pranav Shrotriya

Recycling 2026, 11(5), 89; https://doi.org/10.3390/recycling11050089 (registering DOI) - 9 May 2026

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Abstract

The printed circuit board (PCB), a central component of most electronic devices, represents a significant fraction of the electronic product waste stream. The complex composition of PCBs, consisting of metals, polymers, and fiberglass, requires specialized recovery steps to reclaim valuable and critical materials [...] Read more.

The printed circuit board (PCB), a central component of most electronic devices, represents a significant fraction of the electronic product waste stream. The complex composition of PCBs, consisting of metals, polymers, and fiberglass, requires specialized recovery steps to reclaim valuable and critical materials and the safe disposal of brominated compounds. In this review paper, we describe the current state of critical material recovery and traditional recycling technologies and identify key obstacles to large-scale implementation. Metals present at high concentrations, such as copper, lead, and iron, are conventionally recovered from PCBs using hydrometallurgical, pyrometallurgical, or electrometallurgical processes. Hydrometallurgical methods achieve high selectivity through chemical leaching but pose significant challenges for effluent and reagent recovery. Pyrometallurgical methods facilitate rapid metal separation through smelting but require substantial energy and may release harmful gases. Electrometallurgical techniques produce high-purity metals but are constrained by pretreatment requirements and the consumption of energy. The non-metallic fraction of PCB waste is recycled using thermochemical conversion, microwave-aided heating, and direct recycling of epoxy–fiberglass composites, enabling material or energy recovery. The recovered polymer from direct recycling may have reduced mechanical strength and poor compatibility with new polymer matrices, and the resulting products from the thermal conversion suffer from incomplete conversion, degradation of quality, and residual contamination, as compared to synthetic polymers. Recent process developments have focused on extracting rare earth and supply-critical materials present at lower concentrations in the waste stream. The literature on existing and emerging approaches for recycling PCB wastes is reviewed to identify sustainable, economically viable, and environmentally responsible strategies for the recovery and reuse of critical materials from waste streams. Full article

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

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38 pages, 1809 KB

Open AccessReview

A Review of Organic Municipal Waste Management in Medium Cities in Latin America

by Linda Y. Pérez-Morales, Adriana Guzmán-López, Rita Miranda-López, Micael Gerardo Bravo-Sánchez and José E. Botello-Álvarez

Recycling 2026, 11(4), 73; https://doi.org/10.3390/recycling11040073 - 5 Apr 2026

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Abstract

Latin America faces growing challenges in the management of municipal solid waste (MSW). This is particularly evident in medium-sized and metropolitan cities where rapid urbanization, limited infrastructure, and high proportions of organic waste (40–70%) converge. This review synthesizes the most recent advances in [...] Read more.

Latin America faces growing challenges in the management of municipal solid waste (MSW). This is particularly evident in medium-sized and metropolitan cities where rapid urbanization, limited infrastructure, and high proportions of organic waste (40–70%) converge. This review synthesizes the most recent advances in organic waste management, valorization strategies, environmental performance, and policy frameworks in Mexico and Latin America. To provide a comprehensive overview, evidence from studies on informal recycling systems, route optimization, sustainable landfill siting, food waste valorization, life cycle assessments (LCAs), and biogas production is integrated. Techno-economic analyses of energy recovery from organic fractions are specifically reviewed. This review highlights that valorization of organic waste through composting, anaerobic digestion, food supplementation, and bioproduct generation can reduce greenhouse gas emissions by 40–70% compared to landfilling, with AD–composting hybrids achieving the highest reductions of 60–70%. Community composting achieved moderate reductions, 30–50%, but at significantly lower cost and with greater social co-benefits. These alternatives for valorizing the organic fraction extend the lifespan of both confined and open landfills. It also contributes to mitigating the public health impacts related to open dumping, disease vectors, and contaminated leachate. In short, this review also highlights shortcomings in policy coherence, financial mechanisms, source separation, and technology adoption. A strategic framework is proposed that prioritizes decentralized treatment systems, the integration of informal recyclers, tax incentives, community-based waste separation, and planning based on Life Cycle Assessment (LCA). The findings point to a viable strategy for transitioning from landfill dependency to circular waste management systems that improve the quality of life for the population of Latin America and the Caribbean. Full article

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

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46 pages, 4242 KB

Open AccessReview

A Review of Current and Emerging Strategies for Recycling Waste: Bicycle Tires and Inner Tubes

by Xiao Yuan Chen and Denis Rodrigue

Recycling 2026, 11(2), 33; https://doi.org/10.3390/recycling11020033 - 2 Feb 2026

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Abstract

Bicycle tires and inner tubes constitute a growing waste stream mainly composed of natural rubber, butyl rubber, synthetic elastomers, carbon black, and reinforcing materials. Their multi-material structure and highly crosslinked networks make their recycling challenging, yet efficient recovery is essential for advanced circular [...] Read more.

Bicycle tires and inner tubes constitute a growing waste stream mainly composed of natural rubber, butyl rubber, synthetic elastomers, carbon black, and reinforcing materials. Their multi-material structure and highly crosslinked networks make their recycling challenging, yet efficient recovery is essential for advanced circular economy practices. This review summarizes the current and emerging strategies for recycling bicycle tires and inner tubes. It first outlines the materials and additives present in tire casings and butyl inner tubes, which determine their recycling behavior. Mechanical pre-processing methods, including shredding, grinding, and fiber/steel separation, are presented as essential feedstock preparation steps. Thermochemical approaches, such as pyrolysis and thermolysis, are discussed with emphasis on producing value-added fractions, including pyrolysis oil, recovered carbon black, and fuels. Solvent-based feedstock recycling and chemical dissolution are highlighted as promising routes for selective recovery of rubber polymers and additives. Physical, chemical, and biological devulcanization methods are also reviewed for their potential to restore partial processability to reuse reclaimed rubber. Finally, current and prospective applications of recycled materials are discussed, and key challenges with future research needs are identified, including improving devulcanization efficiency, expanding collection systems, and increasing the value of recovered products. 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, 2500 KB

Open AccessSystematic Review

Recycled Concrete Aggregate in Self-Consolidating Concrete: A Systematic Review and Meta-Analysis of Mechanical Properties, RCA Pre-Treatment and Durability Behaviour

by Ariana C. Morales Rapallo and Kerstin Kuchta

Recycling 2025, 10(6), 214; https://doi.org/10.3390/recycling10060214 - 26 Nov 2025

Cited by 3 | Viewed by 1667

Abstract

This systematic review and meta-analysis per PRISMA 2020 addresses the use of recycled concrete aggregates as a replacement for aggregates in self-consolidating concrete for structural and non-structural use. It provides a comprehensive evaluation of the available research and offers a synthesised overview of [...] Read more.

This systematic review and meta-analysis per PRISMA 2020 addresses the use of recycled concrete aggregates as a replacement for aggregates in self-consolidating concrete for structural and non-structural use. It provides a comprehensive evaluation of the available research and offers a synthesised overview of the potential use of recycled concrete aggregate in self-consolidating concrete beyond standardised replacement levels. A total of 256 research papers were obtained from different databases, and after a detailed content review, only 24 unique experimental research studies fulfilled the review criteria. Data were extracted on recycled concrete aggregate source, pre-treatment, replacement ratio, mix proportions, fresh properties, strength, stiffness, and durability. It was observed across all studies that the recycled concrete aggregates originated from precast concrete rejected elements with a low water-to-cement ratio, producing an equal or stronger concrete than the reference concrete in the studies; however, none of the studies included in this research resulted in a higher modulus of elasticity than the corresponding reference concrete. Additionally, moderate aggregate replacement (20–50%) preserved the workability, whereas high replacements (75–100%) affected fresh concrete properties as well as increased shrinkage and creep. The inclusion of fine recycled concrete aggregate in addition to coarse recycled concrete aggregate has a larger effect on lowering compressive strength and stiffness in the concrete. Overall, high-quality coarse recycled concrete aggregate (precast rejects or screened demolition waste)—an aggregate replacement level of around 50%—facilitates the production of sustainable self-consolidating concrete, whereas full replacement requires aggregate pre-treatment and a carefully optimised mix design. Full article

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

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