Recycling

27 pages, 2159 KB

Open AccessArticle

Technical Evaluation and Recycling Potential of Polyolefin and Paper Separation in Mixed Waste Material Recovery Facilities

by Anna-Maria Lipp, Dominik Blasenbauer, Hana Stipanovic, Gerald Koinig, Alexia Tischberger-Aldrian and Jakob Lederer

Recycling 2025, 10(5), 176; https://doi.org/10.3390/recycling10050176 (registering DOI) - 12 Sep 2025

Abstract

Mixed municipal solid waste (MSW) of cities and tourist-heavy areas typically contains elevated amounts of recyclable materials. In Austria, numerous material recovery facilities exist for processing this waste; however, they primarily focus on separating metals, neglecting the recovery potential of other recyclables. To [...] Read more.

Mixed municipal solid waste (MSW) of cities and tourist-heavy areas typically contains elevated amounts of recyclable materials. In Austria, numerous material recovery facilities exist for processing this waste; however, they primarily focus on separating metals, neglecting the recovery potential of other recyclables. To evaluate such potential for polyolefins and paper-based materials, two pilot-scale trials were conducted in a model region in Tyrol, Western Austria, accompanied by comprehensive sampling, waste characterisation, and material flow analysis. Pre-concentrates with up to 70% purity were obtained using two stages of near-infrared sorting, although challenges arose due to the presence of textiles and composite materials. This study found that separating polyolefins from mixed MSW could increase recycling rates in the region by up to 16% (absolute). Paper recovery also showed a modest increase. Polyolefin recovery slightly lowered, whereas paper recovery moderately raised the heating value. Recycling such materials is technically feasible, and forthcoming legislative changes are expected to create a market for these materials. Although fundamental questions remain regarding the optimal balance between recycling and refuse-derived fuel, as well as concerns about microbiological or chemical hazards, it can enhance resource efficiency, develop circularity, and aid comparison in regions with similar demographic and tourism characteristics. Full article

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28 pages, 6514 KB

Open AccessArticle

Integrated Circuits from Lighting Equipment: Presence and Characterisation of Precious Metals (Ag, Au, Pd, and Pt)

by Konstantinos M. Sideris, Konstantinos A. Liogas, Dimitrios Fragkoulis, Vassilis N. Stathopoulos and Panagiotis Sinioros

Recycling 2025, 10(5), 175; https://doi.org/10.3390/recycling10050175 - 12 Sep 2025

Abstract

To reduce energy consumption in buildings and to maintain comfortable conditions, lighting equipment that includes light-emitting diode (LED) lamps and lighting management equipment is utilised. In this study, integrated circuits detached from lighting equipment were characterised for the presence of precious metals (silver, [...] Read more.

To reduce energy consumption in buildings and to maintain comfortable conditions, lighting equipment that includes light-emitting diode (LED) lamps and lighting management equipment is utilised. In this study, integrated circuits detached from lighting equipment were characterised for the presence of precious metals (silver, gold, palladium, and platinum). Their digestion was carried out with HNO₃ and aqua regia solution on a hot plate and characterised using inductively coupled plasma optical emission spectroscopy (ICP-OES). The concentration of each element as a function of the type and origin of the integrated circuits varied as follows: silver, 652–3876 mg/kg; gold, 0–993 mg/kg; palladium, 0–74 mg/kg; and platinum was detected at a concentration below the quantification limit. These results indicate the need for selective removal and separate recycling processes for integrated circuits from the lighting equipment. Full article

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34 pages, 7313 KB

Open AccessReview

Recycling Mineral Wool Waste: Towards Sustainable Construction Materials

by Martina Milat, Sandra Juradin, Nives Ostojić-Škomrlj and Anže Tesovnik

Recycling 2025, 10(5), 174; https://doi.org/10.3390/recycling10050174 - 12 Sep 2025

Abstract

This literature review critically examines the incorporation of mineral wool waste (MWW), a byproduct of insulation materials, into new construction materials as a sustainable recycling strategy. Covering research published between 2000 and 2025, the review focuses on the effects of MWW on various [...] Read more.

This literature review critically examines the incorporation of mineral wool waste (MWW), a byproduct of insulation materials, into new construction materials as a sustainable recycling strategy. Covering research published between 2000 and 2025, the review focuses on the effects of MWW on various material properties and performance, including concrete, mortar, alkali-activated materials (AAMs), geopolymers (GPs), building ceramics, and asphalt. Experimental evidence demonstrates that MWW can enhance or alter the performance of these materials, offering promising opportunities for waste valorization. The review also identifies challenges related to optimizing material compositions and production methods, and highlights the need for further research to facilitate the industrial-scale application of MWW-recycled construction materials. By synthesizing current knowledge, this work aims to inform sustainable development and circular economy practices in the construction sector. Full article

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21 pages, 6426 KB

Open AccessArticle

Co-Pelletization of Rice Husk and Corncob Residues: Evaluation of Physicochemical Properties and Combustion Performance

by Eduardo D. Arroyo Dagobeth, Daniel D. Otero Meza, Juan J. Cabello Eras, Jorge L. Moya Rodríguez and Jairo G. Salcedo Mendoza

Recycling 2025, 10(5), 173; https://doi.org/10.3390/recycling10050173 - 10 Sep 2025

Abstract

This study aimed to assess the physical, chemical, and combustion properties of pellets made from corncob and rice husk residues sourced in Sucre, Colombia, and to evaluate the performance of different blending ratios. Before pelletization, the residues were ground and processed using a [...] Read more.

This study aimed to assess the physical, chemical, and combustion properties of pellets made from corncob and rice husk residues sourced in Sucre, Colombia, and to evaluate the performance of different blending ratios. Before pelletization, the residues were ground and processed using a small-scale flat die pellet mill equipped with a 6 mm die. Physical properties were evaluated according to ISO standards for particle density, bulk density, and impact resistance assessment. Proximate and ultimate analyses, as well as heating values, were determined and compared against the ISO 17225-6:2021 classification for herbaceous biomass. The 70:30 corncob-to-rice husk blend (CC70:RH30) showed good quality, with 7.23% ash, 9.18% moisture, and an LHV of 15.19 MJ/kg, meeting the criteria for Class B pellets. Combustion performance was assessed using a custom-designed macro-TGA, revealing that co-pelletized blends exhibited improved ignition temperatures and comprehensive combustion indices compared to the individual feedstocks. Additionally, calorific values were proportional to the blending ratios. In summary, controlling the blending ratio of corncob and rice husk residues during pellet production allows modulation of both the total ash content and the lower heating value of the resulting solid biofuels, making them more suitable for thermochemical conversion routes such as combustion and/or gasification. Full article

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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

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Abstract

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

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Abstract

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

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Abstract

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

Viewed by 378

Abstract

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

Viewed by 503

Abstract

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

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Abstract

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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Recycling, Volume 10, Issue 5 (October 2025) – 10 articles

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