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Transforming Waste into Sustainable Construction Materials
Quality Assurance Framework for Recovered Binders and Aggregates from Asphalt Mixtures Incorporating Recycled Materials

Journal Description

Recycling

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

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, ESCI (Web of Science), FSTA, Inspec, AGRIS, and other databases.
Journal Rank: CiteScore - Q1 (Management, Monitoring, Policy and Law)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 20.9 days after submission; acceptance to publication is undertaken in 4.9 days (median values for papers published in this journal in the first half of 2025).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Impact Factor: 4.6 (2024); 5-Year Impact Factor: 4.9 (2024)

Imprint Information Journal Flyer Open Access ISSN: 2313-4321

Latest Articles

22 pages, 1039 KB

Open AccessReview

On the Potential of Waste Tire Pyrolysis in Carbon Mitigation: A Review

by Yezi Wu, Qingzi Zhao, Junshi Xu, Shiqi Liu, Junqing Xu, Haochen Zhu and Guangming Li

Recycling 2025, 10(5), 172; https://doi.org/10.3390/recycling10050172 - 5 Sep 2025

This review aims to evaluate the carbon mitigation potential of waste tire (WT) pyrolysis through a life cycle assessment (LCA) perspective, with a focus on clarifying methodological differences across studies. The scope of the review covers the three main pyrolysis products—tire pyrolysis oil [...] Read more.

This review aims to evaluate the carbon mitigation potential of waste tire (WT) pyrolysis through a life cycle assessment (LCA) perspective, with a focus on clarifying methodological differences across studies. The scope of the review covers the three main pyrolysis products—tire pyrolysis oil (TPO), recovered carbon black (rCB), and tire pyrolysis gas (TPG)—and their roles in two interconnected mitigation pathways: (i) material substitution, where TPO can displace fossil diesel (≈2.7–3.2 kg CO₂e/kg) and rCB can replace virgin carbon black (≈1.8–2.2 kg CO₂e/kg), and (ii) energy self-sufficiency, where TPG (≈30–40 MJ/m³) offsets external fuels. Unlike earlier reviews that emphasized technical feasibility, this study synthesizes comparative LCA evidence to explain why reported mitigation factors vary widely, highlighting the influence of system boundaries, substitution ratios, and product quality. Harmonizing these conventions provides a consistent basis for cross-study comparison and positions WT pyrolysis as a strategic contributor to circular economy and decarbonization agendas. Full article

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18 pages, 9239 KB

Open AccessArticle

Sustainable Upcycling of Spent Battery Graphite into High-Performance PEG Anodes via Flash Joule Heating

by Yihan Luo, Jing Sun, Wenxin Chen, Shuo Lu and Ziliang Wang

Recycling 2025, 10(5), 171; https://doi.org/10.3390/recycling10050171 - 2 Sep 2025

The upcycling of spent lithium-ion battery graphite constitutes an essential pathway for mitigating manufacturing expenditures and alleviating ecological burdens. This study proposes an integrated strategy to upcycle spent graphite into high-performance porous expanded graphite (PEG) anodes, leveraging flash Joule heating (FJH) as a [...] Read more.

The upcycling of spent lithium-ion battery graphite constitutes an essential pathway for mitigating manufacturing expenditures and alleviating ecological burdens. This study proposes an integrated strategy to upcycle spent graphite into high-performance porous expanded graphite (PEG) anodes, leveraging flash Joule heating (FJH) as a core technique for efficient decontamination, interlayer expansion, and active etching. Results show that the binders and impurities are efficiently removed by FJH treatment, and the graphite interlayer spacing is expanded. The iron oxide, which acts as an etching reagent, can then be easily intercalated and laid into the decontaminated graphite for subsequent etching. A subsequent FJH treatment simultaneously releases oxidized intercalants and triggers in-situ metal oxide etching, yielding PEG with a rich porous architecture and enhanced specific surface area. This method successfully prepared high-performance porous expanded graphite anode material with a mesoporous structure. The resulting anode delivers a remarkable capacity retention of 419 mAh·g⁻¹ after 600 cycles at 2C, outperforming the performance of commercial graphite anodes. This innovative approach offers a promising route for sustainable graphite reclamation. Full article

(This article belongs to the Special Issue Lithium-Ion and Next-Generation Batteries Recycling)

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25 pages, 457 KB

Open AccessReview

Transformation of Brewer’s Spent Grain Through Solid-State Fermentation: Implications for Nutrition and Health

by Marcos Barrera-León, Elí Terán-Cabanillas, Roberto de Jesús Avena-Bustillos, Feliznando Isidro Cárdenas-Torres, Bianca Anabel Amézquita-López, Mario Armando Gómez-Favela, David Moroni Alemán-Hidalgo and Mayra Arias-Gastélum

Recycling 2025, 10(5), 170; https://doi.org/10.3390/recycling10050170 - 2 Sep 2025

Brewer’s spent grain (BSG), a by-product originating from the brewing industry, contains substantial amounts of fibers, proteins, and bioactive compounds; however, its utility is restricted by anti-nutritional factors. Solid-state fermentation (SSF) presents a viable method for improving the nutritional and functional properties of [...] Read more.

Brewer’s spent grain (BSG), a by-product originating from the brewing industry, contains substantial amounts of fibers, proteins, and bioactive compounds; however, its utility is restricted by anti-nutritional factors. Solid-state fermentation (SSF) presents a viable method for improving the nutritional and functional properties of BSG. Microorganisms such as Rhizopus oligosporus have been demonstrated to enhance nutrient bioavailability, facilitate the degradation of complex carbohydrates, and improve protein digestibility while simultaneously reducing anti-nutritional components. Furthermore, this fermentation process yields bioactive compounds that exhibit antioxidant, anti-inflammatory, and prebiotic properties, thereby contributing to improved gut health, the prevention of metabolic disorders, and enhanced nutritional outcomes. Additionally, SSF seeks sustainability by repurposing agro-industrial by-products, reducing waste, and promoting the principles of a circular economy. Collectively, these advantages underscore the transformative potential of SSF in converting BSG into a functional food ingredient, effectively addressing contemporary health and environmental challenges and offering innovative solutions for food security and sustainable development. Full article

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24 pages, 8697 KB

Open AccessArticle

Recycling of Marine Sediments in Cement-Based Materials by Stabilization/Solidification Treatment: Effect on the Mechanical and Microstructural Properties

by Claudio Moreno Cino, Andrea Petrella, Francesco Todaro and Michele Notarnicola

Recycling 2025, 10(5), 169; https://doi.org/10.3390/recycling10050169 - 1 Sep 2025

Port maintenance causes large quantities of dredged sediment throughout the world. The disposal of this material in authorised landfills is economically disadvantageous, as well as being at odds with a circular economy model with a reduced impact on the environment. The application of [...] Read more.

Port maintenance causes large quantities of dredged sediment throughout the world. The disposal of this material in authorised landfills is economically disadvantageous, as well as being at odds with a circular economy model with a reduced impact on the environment. The application of stabilization/solidification treatment to dredged marine sediments allows an improvement of their physical and mechanical properties, together with the production of cement-based materials that can be used for road construction, as well as for making blocks and bricks. In this study, an experimental laboratory investigation is carried out on two samples of sandy sediments collected from the Mola di Bari harbour (Southern Italy), to identify sustainable management options for recovering materials that will be dredged. To assess the influence on mortars made from sediments with variable organic matter content and seawater, these were characterised from a chemical–physical point of view before and after washing treatment and oxidative processes. The products of the Stabilization/Solidification (S/S) treatment were evaluated in terms of workability, flexural and compressive strengths, and, furthermore, a microstructural study was conducted using SEM-EDX and optical microscopy to analyse the internal structure of the materials. The mechanical performance evaluation clearly demonstrated organic matter’s negative impact on strength development, resulting in a 16% reduction. Pre-treatments, such as sediment washing, effectively improved the performance of treated sediments (e.g., 24% increase in compressive strength). This study aims to demonstrate the benefits of recycling marine sediments in cement-based materials, highlighting how this process can enhance circularity and sustainability while reducing the environmental impact of dredging activities. Full article

(This article belongs to the Topic Advances and Innovations in Waste Management)

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14 pages, 4168 KB

Open AccessArticle

Manufacturing and Recycling of 3D-Printed All-Polymer Composites

by Itsari Phuangmali, Yao Xu, Leyu Lin and Alois K. Schlarb

Recycling 2025, 10(5), 168; https://doi.org/10.3390/recycling10050168 - 26 Aug 2025

The reinforcement of polymers with carbon or glass fibers is the reason for their incredible success as ideal lightweight construction materials. However, one challenge with these materials is their recyclability. True recycling, meaning achieving the same performance level as virgin material, is impossible, [...] Read more.

The reinforcement of polymers with carbon or glass fibers is the reason for their incredible success as ideal lightweight construction materials. However, one challenge with these materials is their recyclability. True recycling, meaning achieving the same performance level as virgin material, is impossible, especially with mechanical recycling processes, because the reinforcement structure is destroyed. Additionally, thermoplastics undergo molecular degradation and changes in the properties of the materials. Therefore, polymer fiber-reinforced plastics may have an advantage here, as polymer fibers are much more flexible than glass or carbon fibers. We investigated the production and recyclability of microfibrillar composites (MFCs) made of polypropylene (PP) and polyethylene terephthalate (PET). The samples were produced using extrusion-based 3D printing with different parameters, and their morphology and mechanical properties were examined. The samples were crushed, and the residue was fed back into the production line. The process was repeated with the samples produced from regenerate. The results prove that the printing process can be controlled to ensure the presence of fibers in samples made from recycled material. However, it is important to note that the mechanical properties decrease with each additional processing cycle. The choice of manufacturing parameters, especially in 3D printing, is crucial for achieving good properties. Full article

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12 pages, 1894 KB

Open AccessArticle

Pyrometallurgical Process to Recover Lead and Silver from Zinc Leaching Residue

by Cancio Jiménez-Lugos, Manuel Flores-Favela, Antonio Romero-Serrano, Aurelio Hernández-Ramírez, Alejandro Cruz-Ramírez, Enrique Sanchez-Vite, José Ortiz-Landeros and Eduardo Colin-García

Recycling 2025, 10(5), 167; https://doi.org/10.3390/recycling10050167 - 25 Aug 2025

During the roasting, leaching, and electrodeposition of zinc ores, lead–silver residues are produced. These residues contain valuable metals (Pb, Zn, and Ag) and toxic metals (Cd and As). In this study, a pyrometallurgical process is proposed for treating Pb-Ag residues, consisting of drying, [...] Read more.

During the roasting, leaching, and electrodeposition of zinc ores, lead–silver residues are produced. These residues contain valuable metals (Pb, Zn, and Ag) and toxic metals (Cd and As). In this study, a pyrometallurgical process is proposed for treating Pb-Ag residues, consisting of drying, roasting, and reduction steps to recover valuable metals, such as silver in a metallic Pb phase, while converting the waste into an environmentally friendly slag. First, the Pb-Ag residue is dried at 100 °C, then roasted at 700 °C, and finally reduced at a high temperature, with Na₂CO₃ as a flux and CaSi as a reducing agent, rather than carbon-based reducing agents (carbon or carbon monoxide), to minimize greenhouse gas production. The effects of the reduction temperature and the mass of the reducing agent were investigated on a laboratory scale. The metallic phase and slag obtained in the reduction step were characterized by their chemical composition and mineralogy via chemical analysis, X-ray diffraction, and SEM-EDS. The results showed that silver and lead formed a metallic phase, and that silver content decreased from 1700 ppm in the Pb-Ag residue to 32 ppm in the final slag at 1300 °C. The Pb-Ag residue and final slag were leached with an aqueous acetic acid solution to evaluate their chemical stability. Full article

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17 pages, 1102 KB

Open AccessArticle

Sustainable Valorization of Brewer’s Spent Grain via Submerged Fermentation Using Talaromyces stollii for Laccase and Phenolic Compounds Production

by Eric Coelho S. Lima, Ana Caroline B. do Nascimento, Rodrigo P. do Nascimento and Ivaldo Itabaiana, Jr.

Recycling 2025, 10(4), 166; https://doi.org/10.3390/recycling10040166 - 21 Aug 2025

Brewer’s spent grain (BSG) is the main solid byproduct of the brewing industry, generated in large quantities worldwide. Its high organic content and availability make it an attractive substrate for biotechnological valorization and recycling within a circular economy framework, contributing to the recovery [...] Read more.

Brewer’s spent grain (BSG) is the main solid byproduct of the brewing industry, generated in large quantities worldwide. Its high organic content and availability make it an attractive substrate for biotechnological valorization and recycling within a circular economy framework, contributing to the recovery and reuse of agro-industrial residues. This study investigates the potential of Talaromyces stollii I05.06 to simultaneously produce laccase and release phenolic compounds through submerged fermentation (SmF) using BSG as the sole carbon source. Initial SmF trials confirmed the fungus’s capacity to metabolize BSG. Subsequent fermentations with phosphate buffer supplementation (100 mM) significantly enhanced laccase activity (1535 ± 151.6 U·L⁻¹ on day 5) and phenolic content (6.28 ± 0.07 mg GAE per 100 g on day 1 with 50 mM buffer). However, the addition of typical laccase inducers (Cu²⁺ and Mn²⁺) led to inhibitory effects. The results highlight T. stollii I05.06 as a promising microorganism for the integrated valorization of BSG, contributing to sustainable agro-industrial waste management and the development of value-added bioproducts. Full article

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

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18 pages, 1319 KB

Open AccessArticle

Extraction of Rare Earth Elements from Organic Acid Leachate Using Formo-Phenolic-like Resins

by Evan Lelong, Julien Couturier, Clément Levard, Stéphane Pellet-Rostaing and Guilhem Arrachart

Recycling 2025, 10(4), 165; https://doi.org/10.3390/recycling10040165 - 17 Aug 2025

Formo-phenolic-like resins were synthesized by replacing phenol with phloroglucinol, a biobased and biocompatible compound, and using different aldehydes, such as biomass-derived furaldehyde and glyoxal. Studies on the adsorption of rare earth elements from an aqueous organic acid solution indicate that these resins follow [...] Read more.

Formo-phenolic-like resins were synthesized by replacing phenol with phloroglucinol, a biobased and biocompatible compound, and using different aldehydes, such as biomass-derived furaldehyde and glyoxal. Studies on the adsorption of rare earth elements from an aqueous organic acid solution indicate that these resins follow the Langmuir isotherm model, with maximum adsorption capacities ranging from 0.38 to 0.75 mmol/g. Adsorption was temperature-independent but strongly influenced by pH, with an up to fourfold increase between pH 2 and 5. Extraction kinetics were rapid, reaching equilibrium within two hours. Complete metal recovery was achieved within ten minutes using a 1 mol/L HCl desorption solution. Selectivity also varied with pH; glyoxal- and furfural-based resins showed superior separation performance at pH 2–3 and 3–4, respectively. The application of this method to real-world samples, including permanent magnet and red mud organic acid leachates, demonstrated effective extraction of rare earth elements and promising selectivity over iron (Fe), cobalt (Co), and nickel (Ni). Full article

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

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10 pages, 880 KB

Open AccessArticle

Grape Marc Flour as a Horticulture By-Product for Application in the Meat Industry

by Manuel Alejandro Vargas-Ortiz, Armida Sánchez-Escalante, Gastón R. Torrescano-Urrutia, Rey David Vargas-Sánchez, Brisa del Mar Torres-Martínez and Eber Addí Quintana-Obregón

Recycling 2025, 10(4), 164; https://doi.org/10.3390/recycling10040164 - 15 Aug 2025

Using agro-industrial byproducts as functional ingredients represents a sustainable approach to food development. This study aimed to characterize the physicochemical and techno-functional properties of grape marc flour and evaluate the metabolite content and antioxidant activity of the extract obtained from these residues. Grape [...] Read more.

Using agro-industrial byproducts as functional ingredients represents a sustainable approach to food development. This study aimed to characterize the physicochemical and techno-functional properties of grape marc flour and evaluate the metabolite content and antioxidant activity of the extract obtained from these residues. Grape marc flour analysis included pH, color, and techno-functional parameter assessment. The metabolite content and antioxidant activity of the extracts were determined in vitro and in a meat system. The grape marc flour exhibited low pH, lightness (L*), and yellowness (b*) index values, as well as increased redness (a*) values. It also showed the ability to retain water and oil, along with notable swelling capacity. The extracts exhibited high levels of phenolic, tannins, flavonoids, and chlorogenic acid, as well as anti-radical activity and reducing power. When incorporated into a cooked meat system, the extracts decreased pH and lipid oxidation levels. These findings suggest that grape marc flour has potential as a functional ingredient in the formulation of meat products. Full article

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23 pages, 1776 KB

Open AccessArticle

Assessment of Greenhouse Gas Emissions, Energy Demand and Solid Waste Generation Between Two Manufacturing Processes: A Case Study

by Fernando Nogueira Cardoso, João da Cruz Payão Filho, Margareth Nascimento de Souza Lira and Claudinei de Souza Guimarães

Recycling 2025, 10(4), 163; https://doi.org/10.3390/recycling10040163 - 13 Aug 2025

Additive manufacturing (AM) is an Industry 4.0 technology that assists or replaces the conventional manufacturing (CM) of complex geometries in various sectors, including transport, steel, aerospace, military, and architecture. The aim is to improve processes, reduce energy consumption, atmospheric emissions, and solid waste, [...] Read more.

Additive manufacturing (AM) is an Industry 4.0 technology that assists or replaces the conventional manufacturing (CM) of complex geometries in various sectors, including transport, steel, aerospace, military, and architecture. The aim is to improve processes, reduce energy consumption, atmospheric emissions, and solid waste, and streamline stages while complying with the new environmental regulations. The main objective of this work was to carry out a cradle-to-gate Life Cycle Assessment (LCA), considering the raw material extraction, pre-processing, manufacturing, and post-processing stages, comparing two manufacturing methods for the same ER-90 metal flange part, conventional forging and wire and arc additive manufacturing (WAAM), all following the requirements and operations proposed by the ISO 14040/44 standard. WAAM is a Directed Energy Deposition (DED) technology that uses welding techniques to produce 3D objects with more complex geometries. Compared to the forging industry, which requires a lot of heat and kinetic energy in its metal part production stages, WAAM is a more sustainable and modern alternative because it does not require high temperatures and energy to produce the same parts. The environmental indicators compared in the process stages were energy consumption, greenhouse gas (GHG) emissions, and solid waste. The total energy consumption in AM was 18,846.61 MJ, the GHG emissions were 864.49 kgCO₂-eq, and the solid waste generated was 142.34 kg, which were 63.8 %, 90.5%, and 31.6% lower than the environmental indicators calculated for CM, respectively. Full article

(This article belongs to the Topic Circular Economy in Interdisciplinary Perspective: Valorization of Raw Materials, Sustainable Products, and Pro-Ecological Industrial Developments)

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29 pages, 1873 KB

Open AccessArticle

Robust Statistical Approaches for Stratified Data of Municipal Solid Waste Composition: A Case Study of the Czech Republic

by Radovan Šomplák, Veronika Smejkalová, Vlastimír Nevrlý and Jaroslav Pluskal

Recycling 2025, 10(4), 162; https://doi.org/10.3390/recycling10040162 - 12 Aug 2025

Accurate information on waste composition is essential for strategic planning in waste management and developing environmental technologies. However, detailed analyses of individual waste containers are both time- and cost-intensive, resulting in a limited number of available samples. Therefore, it is crucial to apply [...] Read more.

Accurate information on waste composition is essential for strategic planning in waste management and developing environmental technologies. However, detailed analyses of individual waste containers are both time- and cost-intensive, resulting in a limited number of available samples. Therefore, it is crucial to apply statistical methods that enable reliable estimation of average waste composition and its variability, while accounting for territorial differences. This study presents a statistical approach based on territorial stratification, aggregating data from individual waste container analyses to higher geographic units. The methodology was applied in a case study conducted in the Czech Republic, where 19.4 tons of mixed municipal waste (MMW) were manually analyzed in selected representative municipalities. The method considers regional heterogeneity, monitors the precision of partial estimates, and supports reliable aggregation across stratified regions. Three alternative approaches for constructing interval estimates of individual waste components are presented. Each interval estimate addresses variability from the random selection of waste containers and the selection of strata representatives at multiple levels. The proposed statistical framework is particularly suited to situations where the number of samples is small, a common scenario in waste composition analysis. The approach provides a practical tool for generating statistically sound insights under limited data conditions. The main fractions of MMW identified in the Czech Republic were as follows: paper 6.7%, plastic 7.3%, glass 3.6%, bio-waste 28.4%, metal 2.1%, and textile 3.0%. The methodology is transferable to other regions with similar waste management systems. Full article

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22 pages, 895 KB

Open AccessArticle

Platform-Driven Sustainability in E-Commerce: Consumer Behavior Toward Recycled Fashion

by Eleni Sardianou and Maria Briana

Recycling 2025, 10(4), 161; https://doi.org/10.3390/recycling10040161 - 11 Aug 2025

Digital platforms in fashion e-commerce are progressively shaping sustainable consumption practices. This research explores the interplay between consumer behaviors toward recycled and second-hand fashion, and the adoption of digital platform-driven innovations. The analysis is based on a structured questionnaire and an online survey [...] Read more.

Digital platforms in fashion e-commerce are progressively shaping sustainable consumption practices. This research explores the interplay between consumer behaviors toward recycled and second-hand fashion, and the adoption of digital platform-driven innovations. The analysis is based on a structured questionnaire and an online survey of 1000 consumers conducted in 2025, employing a combination of descriptive and inferential statistical techniques, including both cluster and factor analysis. The findings suggests that demographic factors—particularly age, education, and gender—significantly shape consumer attitudes toward digital innovations in fashion e-commerce apps. The analysis also confirms that the perceived effectiveness of AI and AR tools is significantly correlated with an increased interest in circular fashion options, including second-hand marketplaces and recycled clothing. The study emphasizes the strategic importance of platform features in fostering conscious fashion choices, thereby offering practical insights for retailers aiming to harmonize technological innovation with sustainability goals. Full article

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20 pages, 2007 KB

Open AccessArticle

Value-Added Recycling of Pre-Consumer Textile Waste: Performance Evaluation of Cotton Blend Knitted T-Shirts

by Muhammad Babar Ramzan, Sajida Ikram, Sheheryar Mohsin Qureshi, Muhammad Waqas Iqbal and Muhammad Qamar Khan

Recycling 2025, 10(4), 160; https://doi.org/10.3390/recycling10040160 - 8 Aug 2025

This study investigates the effects of waste for value addition in form of use of textile waste to comfortable and durable garments based on blending recycled cotton fibers extracted from spinning, weaving, and cutting waste with virgin cotton in different ratios of 70:30, [...] Read more.

This study investigates the effects of waste for value addition in form of use of textile waste to comfortable and durable garments based on blending recycled cotton fibers extracted from spinning, weaving, and cutting waste with virgin cotton in different ratios of 70:30, 80:20, and 90:10 to produce yarns of 22/1 count, which are used to develop single jersey knitted T-Shirt, examining key properties such as mechanical and thermos-physiological properties. Grey fabric (unprocessed fabric) with a higher virgin cotton content and from spinning waste exhibited superior bursting strength, overall moisture management capacity, and thermal conductivity. In contrast, air permeability and water vapor permeability were highest in fabric made with weaving waste. After scouring and bleaching, the finished fabric (processed fabric) was compared with the grey fabrics. The results demonstrate that the finished fabric has slightly reduced bursting strength, water vapor permeability, and moisture management capacity while significantly enhancing air permeability and maintaining thermal conductivity. T-shirt properties were evaluated across various blend ratios and waste types over multiple washing cycles. Overall, the study demonstrates that recycled cotton fibers, particularly those from spinning waste, can be successfully produced into high-performance knitted t-shirts, offering a sustainable alternative to fully virgin cotton products without compromising performance significantly. Full article

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25 pages, 339 KB

Open AccessArticle

Pro-Environmental Behavior and Attitudes Towards Recycling in Slovak Republic

by Silvia Lorincová and Mária Osvaldová

Recycling 2025, 10(4), 159; https://doi.org/10.3390/recycling10040159 - 7 Aug 2025

Climate changes have increased interest in the circular economy, an alternative model that seeks to minimize environmental impact and maximize resource reuse. A key element of this model is individuals’ behaviors and attitudes, which determine the overall efficiency of recycling processes. The study [...] Read more.

Climate changes have increased interest in the circular economy, an alternative model that seeks to minimize environmental impact and maximize resource reuse. A key element of this model is individuals’ behaviors and attitudes, which determine the overall efficiency of recycling processes. The study fills the gap by investigating how selected socio-demographic factors affect attitudes and intentions toward recycling and material reuse in the Slovak Republic, by using the Perceived Characteristics of Innovating (PCI) framework. Through a two-way ANOVA, we tested the hypotheses that higher education correlates with stronger recycling attitudes and that women are more willing than men to engage in circular practices. The results show that gender differences in consumer attitudes towards the circular economy do occur, but their magnitude is often conditioned by education level. Education proved to be the strongest predictor of ecological behavior: respondents with higher education reported stronger beliefs in the importance of recycling and a greater willingness to act sustainably. The interaction between gender and education revealed that university-educated women hold the most pronounced pro-environmental attitudes, underscoring the importance of gender-sensitive educational strategies. It is recommended that environmental education and outreach focus on less-educated groups, particularly women, who have high potential to influence their communities. Full article

16 pages, 1369 KB

Open AccessArticle

Recycling Waste Cottonseed Hulls to Biomaterials for Ammonia Adsorption

by Thomas Klasson, Bretlyn Pancio and Allen Torbert

Recycling 2025, 10(4), 158; https://doi.org/10.3390/recycling10040158 - 6 Aug 2025

Ammonia emissions in poultry houses are common and pose health concerns for animals and workers. However, effective control of these emissions with sustainable products is lacking. Therefore, we investigated if an agricultural byproduct, cottonseed hulls, could be recycled through pyrolysis and used to [...] Read more.

Ammonia emissions in poultry houses are common and pose health concerns for animals and workers. However, effective control of these emissions with sustainable products is lacking. Therefore, we investigated if an agricultural byproduct, cottonseed hulls, could be recycled through pyrolysis and used to remove ammonia from air. In this study, the efficacy of ammonia removal was observed using cottonseed hull biomaterials pyrolyzed at seven different temperatures: 250, 300, 350, 400, 500, 600, and 700 °C. In this study, ammonia was passed through a column filled with pyrolyzed material, and ammonia in the filtered air was monitored. The results showed that materials pyrolyzed at intermediate temperatures of 350 and 400 °C were the most efficient at ammonia removal and were able to adsorb approximately 3.7 mg NH₃/g of material. Despite extensive characterization, ammonia adsorption could not be linked to intrinsic material properties. Evaluation of the materials showed that the carbon in the pyrolyzed materials would be stable over time should the spent material be used as a soil amendment. Full article

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21 pages, 19752 KB

Open AccessArticle

Phase Characterisation for Recycling of Shredded Waste Printed Circuit Boards

by Laurance Donnelly, Duncan Pirrie, Matthew Power and Andrew Menzies

Recycling 2025, 10(4), 157; https://doi.org/10.3390/recycling10040157 - 6 Aug 2025

In this study, we adopt a geometallurgical analytical approach common in mineral processing in the characterization of samples of shredded waste printed circuit board (PCB) E-waste, originating from Europe. Conventionally, bulk chemical analysis provides a value for E-waste; however, chemical analysis alone does [...] Read more.

In this study, we adopt a geometallurgical analytical approach common in mineral processing in the characterization of samples of shredded waste printed circuit board (PCB) E-waste, originating from Europe. Conventionally, bulk chemical analysis provides a value for E-waste; however, chemical analysis alone does not provide information on the textural variability, phase complexity, grain size, particle morphology, phase liberation and associations. To address this, we have integrated analysis using binocular microscopy, manual scanning electron microscopy, phase, textural and compositional analyses by automated (SEM-EDS), phase analysis based on (Automated Material Identification and Classification System (AMICS) software, and elemental analysis using micro-XRF. All methods used have strengths and limitations, but an integration of these analytical tools allows the detailed characterization of the texture and composition of the E-waste feeds, ahead of waste reprocessing. These data can then be used to aid the design of optimized processing circuits for the recovery of the key payable components, and assist in the commercial trading of e-scrap. Full article

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18 pages, 7363 KB

Open AccessArticle

Agronomic Evaluation of Compost Formulations Based on Mining Tailings and Microbial Mats from Geothermal Sources

by María Jesús Puy-Alquiza, Miren Yosune Miranda Puy, Raúl Miranda-Avilés, Pooja Vinod Kshirsagar and Cristina Daniela Moncada Sanchez

Recycling 2025, 10(4), 156; https://doi.org/10.3390/recycling10040156 - 5 Aug 2025

This study, conducted in Mexico, evaluates the agricultural potential of three compost formulations BFS1, BFS2, and BFS3 produced from mining tailings and thermophilic microbial mats and collected from geothermal environments. The physicochemical characterization included pH, electrical conductivity (EC), macronutrients (N, P, K, Ca, [...] Read more.

This study, conducted in Mexico, evaluates the agricultural potential of three compost formulations BFS1, BFS2, and BFS3 produced from mining tailings and thermophilic microbial mats and collected from geothermal environments. The physicochemical characterization included pH, electrical conductivity (EC), macronutrients (N, P, K, Ca, Mg, and S), micronutrients (Fe, Zn, B, Cu, Mn, Mo, and Ni), organic matter (OM), and the carbon-to-nitrogen (C/N) ratio. All composts exhibited neutral pH values (7.38–7.52), high OM content (38.5–48.4%), and optimal C/N ratios (10.5–13.9), indicating maturity and chemical stability. Nitrogen ranged from 19 to 21 kg·t⁻¹, while potassium and calcium were present in concentrations beneficial for crop development. However, EC values (3.43–3.66 dS/m) and boron levels (>160 ppm) were moderately high, requiring caution in saline soils or with boron-sensitive crops. A semi-quantitative Compost Quality Index (CQI) ranked BFS3 highest due to elevated OM and potassium content, followed by BFS1. BFS2, while rich in nitrogen, scored lower due to excessive boron. One-way ANOVA revealed no significant difference in nitrogen (p > 0.05), but it did reveal significant differences in potassium (p < 0.01) and boron (p < 0.001) among formulations. These results confirm the potential of mining tailings—microbial mat composts are low-cost, nutrient-rich biofertilizers. They are suitable for field crops or as components in nursery substrates, particularly when EC and boron are managed through dilution. This study promotes the circular reuse of geothermal and industrial residues and contributes to sustainable soil restoration practices in mining-affected regions through innovative composting strategies. Full article

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31 pages, 1741 KB

Open AccessReview

Recycled Concrete Aggregate in Asphalt Mixtures: A Review

by Juan Gabriel Bastidas-Martínez, Hugo Alexander Rondón-Quintana and Luis Ángel Moreno-Anselmi

Recycling 2025, 10(4), 155; https://doi.org/10.3390/recycling10040155 - 2 Aug 2025

Effective management and handling of construction and demolition waste (CDW) can yield significant technical and environmental benefits for road pavement construction. This article aims to provide a comprehensive and up-to-date chronological review of studies on the mechanical performance of asphalt mixtures—primarily hot mix [...] Read more.

Effective management and handling of construction and demolition waste (CDW) can yield significant technical and environmental benefits for road pavement construction. This article aims to provide a comprehensive and up-to-date chronological review of studies on the mechanical performance of asphalt mixtures—primarily hot mix asphalt (HMA)—incorporating recycled concrete aggregate (RCA). Since the main limitation of RCA is the presence of residual adhered mortar, the review also includes studies that applied various surface treatments (mechanical, chemical, and thermal, among others) to enhance mixture performance. The article summarizes the experimental procedures used and highlights the key findings and conclusions of the reviewed research. Although the results are varied and sometimes contradictory—mainly due to the source variability and heterogeneity of RCA—the use of these materials is technically viable. Moreover, their application can provide environmental, social, and economic advantages, particularly in the construction of low-traffic roadways. Finally, the article identifies research gaps and offers recommendations for future researches. Full article

(This article belongs to the Special Issue Recycled Materials in Sustainable Pavement Innovation)

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30 pages, 2603 KB

Open AccessReview

Sugarcane Industry By-Products: A Decade of Research Using Biotechnological Approaches

by Serafín Pérez-Contreras, Francisco Hernández-Rosas, Manuel A. Lizardi-Jiménez, José A. Herrera-Corredor, Obdulia Baltazar-Bernal, Dora A. Avalos-de la Cruz and Ricardo Hernández-Martínez

Recycling 2025, 10(4), 154; https://doi.org/10.3390/recycling10040154 - 2 Aug 2025

The sugarcane industry plays a crucial economic role worldwide, with sucrose and ethanol as its main products. However, its processing generates large volumes of by-products—such as bagasse, molasses, vinasse, and straw—that contain valuable components for biotechnological valorization. This review integrates approximately 100 original [...] Read more.

The sugarcane industry plays a crucial economic role worldwide, with sucrose and ethanol as its main products. However, its processing generates large volumes of by-products—such as bagasse, molasses, vinasse, and straw—that contain valuable components for biotechnological valorization. This review integrates approximately 100 original research articles published in JCR-indexed journals between 2015 and 2025, of which over 50% focus specifically on sugarcane-derived agroindustrial residues. The biotechnological approaches discussed include submerged fermentation, solid-state fermentation, enzymatic biocatalysis, and anaerobic digestion, highlighting their potential for the production of biofuels, enzymes, and high-value bioproducts. In addition to identifying current advances, this review addresses key technical challenges such as (i) the need for efficient pretreatment to release fermentable sugars from lignocellulosic biomass; (ii) the compositional variability of by-products like vinasse and molasses; (iii) the generation of metabolic inhibitors—such as furfural and hydroxymethylfurfural—during thermochemical processes; and (iv) the high costs related to inputs like hydrolytic enzymes. Special attention is given to detoxification strategies for inhibitory compounds and to the integration of multifunctional processes to improve overall system efficiency. The final section outlines emerging trends (2024–2025) such as the use of CRISPR-engineered microbial consortia, advanced pretreatments, and immobilization systems to enhance the productivity and sustainability of bioprocesses. In conclusion, the valorization of sugarcane by-products through biotechnology not only contributes to waste reduction but also supports circular economy principles and the development of sustainable production models. Full article

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19 pages, 4487 KB

Open AccessArticle

Recycling Volcanic Lapillus as a Supplementary Cementitious Material in Sustainable Mortars

by Fabiana Altimari, Luisa Barbieri, Andrea Saccani and Isabella Lancellotti

Recycling 2025, 10(4), 153; https://doi.org/10.3390/recycling10040153 - 1 Aug 2025

This study investigates the feasibility of using volcanic lapillus as a supplementary cementitious material (SCM) in mortar production to improve the sustainability of the cement industry. Cement production is one of the main sources of CO₂ emissions, mainly due to clinker production. [...] Read more.

This study investigates the feasibility of using volcanic lapillus as a supplementary cementitious material (SCM) in mortar production to improve the sustainability of the cement industry. Cement production is one of the main sources of CO₂ emissions, mainly due to clinker production. Replacing clinker with SCMs, such as volcanic lapillus, can reduce the environmental impact while maintaining adequate mechanical properties. Experiments were conducted to replace up to 20 wt% of limestone Portland cement with volcanic lapillus. Workability, compressive strength, microstructure, resistance to alkali-silica reaction (ASR), sulfate, and chloride penetration were analyzed. The results showed that up to 10% replacement had a minimal effect on mechanical properties, while higher percentages resulted in reduced strength but still improved some durability features. The control sample cured 28 days showed a compressive strength of 43.05 MPa compared with 36.89 MPa for the sample containing 10% lapillus. After 90 days the respective values for the above samples were 44.76 MPa and 44.57 MPa. Scanning electron microscopy (SEM) revealed good gel–aggregate adhesion, and thermogravimetric analysis (TGA) confirmed reduced calcium hydroxide content, indicating pozzolanic activity. Overall, volcanic lapillus shows promise as a sustainable SCM, offering CO₂ reduction and durability benefits, although higher replacement rates require further optimization. Full article

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