Recycling

22 pages, 1899 KB

Open AccessReview

Integrated Bioprocesses for Urban Food Waste: Insights into Biological Pathways, Process Integration, and Circular Economy Perspectives

by Sophia Bezerra da Silva, Rayssa Karla Silva, Íthalo Barbosa Silva de Abreu, Maria Helena de Sousa, Emmanuel Damilano Dutra, Allan Almeida Albuquerque, Marcos Antonio de Morais Junior and Rafael Barros de Souza

Recycling 2025, 10(5), 188; https://doi.org/10.3390/recycling10050188 - 2 Oct 2025

Abstract

Food waste (FW) presents a critical issue, representing an environmental liability and a largely untapped resource. Its heterogeneity and low valorization rate among main-stream alternative treatments challenge its integration into economically and environmentally sustainable bioprocesses. We explore biorefineries as a solution that can [...] Read more.

Food waste (FW) presents a critical issue, representing an environmental liability and a largely untapped resource. Its heterogeneity and low valorization rate among main-stream alternative treatments challenge its integration into economically and environmentally sustainable bioprocesses. We explore biorefineries as a solution that can address the complexity of urban food waste through biological strategies capable of converting food waste into valuable products. Exploring the current landscape of FW biorefineries, this study focused on the interplay between feedstock heterogeneity, pretreatment strategies, microbial dynamics, and integration potential. We propose a framework distinguishing between robust fermentations that can use minimally treated FW and tailored fermentations, which require refined media pretreatment and/or supplementation to yield higher-value compounds. Drawing on recent techno-economic and life cycle assessments, this article evaluates process viability and environmental impacts across multiple scales, reinforcing the need for robust analysis to support decision-making. Real-world initiatives and policy frameworks are analyzed to contextualize technological advances within regulatory and infrastructural realities. By linking practical constraints to biochemical and operational strategies, this work outlines how food waste biorefineries can contribute meaningfully to circular economy goals. Instead of treating FW as an intractable problem, it is seen as a versatile feedstock that demands integration, investment, and adaptive process design. Full article

► Show Figures

Figure 1

41 pages, 1309 KB

Open AccessReview

Unconventional Mining of End-of-Life Aircrafts: A Systematic Review

by Silvia Zecchi, Giovanni Cristoforo, Carlo Rosso, Alberto Tagliaferro and Mattia Bartoli

Recycling 2025, 10(5), 187; https://doi.org/10.3390/recycling10050187 - 29 Sep 2025

Abstract

Advancements in material science have allowed us to exploit the potential of new era for aircraft production. High-performance composites and alloys have allowed us to improve the performance and durability of aircraft, but they have become more and more precious with time. These [...] Read more.

Advancements in material science have allowed us to exploit the potential of new era for aircraft production. High-performance composites and alloys have allowed us to improve the performance and durability of aircraft, but they have become more and more precious with time. These materials can provide significant advantages in use but are costly, energy-intensive to produce, and their recovery and reuse has become a critical step to be addressed. Accordingly, a new approach in which end-of-life aircrafts represent unconventional mines rather than a disposal challenge is becoming increasingly relevant, providing access to high-value strategic raw materials and aligning with circular economy principles including European Green Deal and the United Nations Sustainable Development Goals. The complexity of dismantling and processing hybrid structures composed of metal alloys, ceramics, and advanced composites requires multiple approaches able to integrate chemical, mechanical, and thermal recovery routes. Accordingly, this review critically discusses the state of the art of the routes of end-of-life aircraft treatments, evaluating the connections between technology and regulation, and positions material recycling and reuse as central pillars for advancing sustainability in aerospace. Furthermore, this review provides a comprehensive reference for addressing the technical, economic, and policy challenges of waste management in aviation, contributing to broader goals of resource circularity and environmental preservation set forth by international sustainability agendas. Full article

► Show Figures

Figure 1

15 pages, 1154 KB

Open AccessArticle

Treatment of Agro-Industrial Residue and Organic Community Waste Using Black Soldier Fly Larvae: Overall Performance Assessment

by Rathanit Sukthanapirat, Natpapat Chansakhatana, Somchai Baotong, Wannapa Pukdee, Kanda Lokaewmanee, Ramin Sriyoha, Ekkachai Kanchanatip and Samonporn Suttibak

Recycling 2025, 10(5), 186; https://doi.org/10.3390/recycling10050186 - 29 Sep 2025

Abstract

The growing global population and rising organic waste generation necessitate innovative and sustainable waste management solutions. This study investigated the potential of black soldier fly larvae (BSFL) as a bioconversion agent for agro-industrial and community organic waste, with an emphasis on optimizing substrate [...] Read more.

The growing global population and rising organic waste generation necessitate innovative and sustainable waste management solutions. This study investigated the potential of black soldier fly larvae (BSFL) as a bioconversion agent for agro-industrial and community organic waste, with an emphasis on optimizing substrate composition for enhanced treatment performance of BSFL. Six rearing substrates were formulated by mixing brewery waste, vegetable and fruit waste, food waste, and sugar filter cake in varying ratios. The performance of BSFL was assessed using five key performance indicators, and an overall performance score was derived to compare substrate suitability across three dimensions: biomass yield, waste reduction, and larval development time. The results revealed that BSFL survival exceeded 97% for all substrates. The highest waste reduction rate of 67.52% was achieved with a 50:50 mixture of brewery waste and food waste. This mixture also attained an overall performance score of 0.77 out of 1, classified as “good”. In contrast, sugar filter cake proved unsuitable for BSFL rearing due to its low nutritional value. These findings offer practical guidelines for selecting optimal waste mixtures to improve the efficiency of BSFL-based waste management. Full article

► Show Figures

Figure 1

17 pages, 1639 KB

Open AccessArticle

Obtaining Nutraceutical Compounds from Agroindustrial Waste by Biotransformation with Pleurotus djamor

by Byanka A. Cruz-Moreno, Benito Parra-Pacheco, Linda Gilary Acosta-Lizárraga, Juan C. Silva-Jarquín, Juan Fernando García-Trejo, Humberto Aguirre-Becerra and Ana A. Feregrino-Pérez

Recycling 2025, 10(5), 185; https://doi.org/10.3390/recycling10050185 - 28 Sep 2025

Abstract

This study explores the production of nutritious edible mushrooms from mixtures of agave bagasse, an abundant agroindustrial byproduct, through the biotechnological application of solid-state fermentation using the edible mushroom Pleurotus djamor. The ability of the fungus to biotransform different mixtures of agave [...] Read more.

This study explores the production of nutritious edible mushrooms from mixtures of agave bagasse, an abundant agroindustrial byproduct, through the biotechnological application of solid-state fermentation using the edible mushroom Pleurotus djamor. The ability of the fungus to biotransform different mixtures of agave bagasse and corn stover into secondary metabolites of nutraceutical interest, such as polyphenols, organic acids, and bioactive polysaccharides, was evaluated. Biological efficiency (BE), morphological change, texture, and antioxidant capacity were also assessed, correlating the results with the impact of substrates and fungal developmental stages. The color, size, and margin of P. djamor basidiomas were observed to vary among treatments; BE progressively decreased from T0 (106.5%) to T4 (33.16%). Treatments with higher amounts of agave bagasse (T4) generated firmer fungi, with a fracture toughness of 7.06 ± 3.06 newtons. During fungal development, phenols, flavonoids, and tannins fluctuated. Treatment T0 showed the highest concentration of phenols (5.41 ± 0.92 mg GAE g⁻¹). Treatment T4 stood out for its high antioxidant capacity (DPPH) (61.83 ± 12.16% inhibition). Finally, 17 non-phenolic secondary metabolites were found: L-valine, L-leucine, L-isoleucine, L, D-phenylalanine, L-proline, alanine, L-asparagine, serine, glutamic acid, linoleic acid, palmitic acid, butanoic acid, propanoic acid, pyrimidine, succinic acid, hexanedioic acid, and phosphoric acid. In conclusion, P. djamor can biotransform agroindustrial waste into edible fungi containing nutraceutical compounds. Full article

► Show Figures

Figure 1

29 pages, 2522 KB

Open AccessArticle

Recycling of Post-Consumer Silica Gel Desiccants as Reinforcing Filler in Natural Rubber Composites: The Effect of Coupling Agents and Comparison with Commercial Silicas

by Dener da Silva Souza, Ricardo Henrique dos Santos, Marcos Alves dos Santos, Gleyson Tadeu de Almeida Santos, Naiara Lima Costa, Samara Araújo Kawall, Abubakar Muhammad Dadile, Gabriel Deltrejo Ribeiro, Leila Maria Sotocorno e Silva, Fernando Sérgio Okimoto, Leandro Ferreira Pinto, Carlos Toshiyuki Hiranobe, Erivaldo Antônio da Silva and Renivaldo José dos Santos

Recycling 2025, 10(5), 184; https://doi.org/10.3390/recycling10050184 - 28 Sep 2025

Abstract

This study presents, for the first time, a systematic investigation of the use of micronized post-consumer silica gel as a reinforcing filler in natural rubber composites, in direct comparison with commercial silicas. Thirteen formulations were prepared using three types of silica (recycled, Copasil, [...] Read more.

This study presents, for the first time, a systematic investigation of the use of micronized post-consumer silica gel as a reinforcing filler in natural rubber composites, in direct comparison with commercial silicas. Thirteen formulations were prepared using three types of silica (recycled, Copasil, and ZC-185P) and three coupling agents (TESPT, VTMO, and Chartwell C-515.71HR^®). The recycled silica exhibited high purity (97.33% Si) and irregular morphology but resulted in lower crosslink density (0.47–0.59 × 10⁻⁴ mol·cm⁻³) and inferior mechanical performance, with tensile strength up to 7.9 MPa and high abrasion loss (878–888 mm³). In contrast, ZC-185P silica combined with TESPT achieved the best results, with a tensile strength of 18.5 MPa, tear resistance of 99.36 N·mm⁻¹, and minimum abrasion loss of 170 mm³. Although less efficient in reinforcement, composites containing recycled silica were successfully applied in the production of a functional rubber mat, demonstrating their practical viability. The results confirm the potential for valorization of spent silica gel as an alternative raw material for sustainable composites, contributing to the circular economy. Full article

► Show Figures

Figure 1

23 pages, 1903 KB

Open AccessArticle

Decarbonising Island Kitchens: Assessing the Small-Scale Flexible Balloon Digester’s Clean Cooking Potential in Fiji

by Rinal Rinay Prasad, Ramendra Prasad, Malvin Kushal Nadan, Shirlyn Vandana Lata, Antonio Comparetti and Dhrishna Charan

Recycling 2025, 10(5), 183; https://doi.org/10.3390/recycling10050183 - 28 Sep 2025

Abstract

Access to clean cooking technologies is crucial for achieving SDG7 for remote households in small Pacific Islands like Fiji and for developed countries alike. Many small households in Fiji still rely on traditional biomass for cooking. This study explores the environmental sustainability and [...] Read more.

Access to clean cooking technologies is crucial for achieving SDG7 for remote households in small Pacific Islands like Fiji and for developed countries alike. Many small households in Fiji still rely on traditional biomass for cooking. This study explores the environmental sustainability and clean cooking potential of the Home Biogas 2.0 flexible balloon digester installed at Kamil Muslim College in Ba, Fiji. Comparative bench experiments were also performed. The bench-scale experiments produced higher biogas yields than the digester trials, with optimal outputs recorded from fresh cow dung (541 mL of cumulative biogas) and vegetable waste excluding rice (125 mL). When scaled, annual energy production from fresh cow dung reached 4644.64 MJ, equivalent to replacing 7.82 standard LPG cylinders, while vegetable waste produced 3763.76 MJ, offsetting 6.34 cylinders. Notably, biogas from cow dung exceeded the estimated annual household cooking demand of 3840 MJ for a family of four persons. The biogas produced from fresh cow dung provided an average cooking duration of 1 h 29 min, while biogas from vegetable waste lasted for 1 h 21 min. The economic analysis indicated that combining liquid digestate, used as biofertiliser, and biogas from cow dung resulted in the highest financial return, with a 67% Internal Rate of Return, a Net Present Value of $12,364.30, a Benefit Cost Ratio of 5.12, and a Discounted Payback Period of 1.28 years. This indicates the potential of Home Biogas 2.0 as a climate-smart technology that integrates renewable energy production, waste reduction, and sustainable agriculture, making it particularly suitable for rural and remote communities. Full article

► Show Figures

Figure 1

16 pages, 6965 KB

Open AccessArticle

Upcycling RDF with Mill Scale and Waste Glass for Eco-Friendly Ferrosilicon Alloy Synthesis via Carbothermic Reduction

by Krishmanust Sunankingphet, Thanaporn Chandransu, Sitichoke Amnuanpol and Somyote Kongkarat

Recycling 2025, 10(5), 182; https://doi.org/10.3390/recycling10050182 - 25 Sep 2025

Abstract

This study investigates the valorization of refuse-derived fuel (RDF), waste glass, and mill scale for sustainable ferrosilicon alloy production, contributing to zero-waste practices. RDF was blended with anthracite at ratios of 100, 90, 80, 70, 60 and 50 wt% (designated R1–R6) and applied [...] Read more.

This study investigates the valorization of refuse-derived fuel (RDF), waste glass, and mill scale for sustainable ferrosilicon alloy production, contributing to zero-waste practices. RDF was blended with anthracite at ratios of 100, 90, 80, 70, 60 and 50 wt% (designated R1–R6) and applied as a reducing agent in the carbothermic reduction of SiO₂ and Fe₂O₃, thereby decreasing reliance on conventional fossil-based reductants. Ferrosilicon synthesis was conducted at 1550 °C using glass–mill scale blends with reducing agents R1–R6, producing samples named blends A–F. XRD analysis confirmed that the metallic products consisted predominantly of the FeSi intermetallic phase, with characteristic (110) and (310) peaks at 2θ ≈ 45.02° and 78°. The metallic products appeared as numerous small, shiny droplets, with yields ranging from 14.85 to 19.47 wt%; blends D–F exhibited the highest yields. In contrast, blends A–C produced metals with higher Si contents (23.34–27.11 wt%) due to enhanced SiO₂ reduction and efficient Si incorporation into the Fe matrix. Gas analysis and oxygen removal showed that blend B achieved the highest CO generation and reduction extent. Cl removal during RDF heat treatment indicated minimal potential for dioxin and furan formation. Overall, blends A and C were identified as optimal, providing high Si content, satisfactory metallic yield, and reduced CO/CO₂ emissions, demonstrating the effectiveness of RDF-based carbons for environmentally friendly ferrosilicon production. Full article

(This article belongs to the Topic Converting and Recycling of Waste Materials)

► Show Figures

Figure 1

27 pages, 3239 KB

Open AccessArticle

Determination of Quantitative Ratios (Mechanical and Dissolved) of Copper, Gold and Silver Losses in Vanyukov Furnace Slags Under the Conditions of the Balkhash Copper Smelter in Kazakhstan

by Nurlan Dosmukhamedov, Bakhtiyar Shambulayev, Leonid Dityatovskiy, Yerzhan Zholdasbay and Aidar Argyn

Recycling 2025, 10(5), 181; https://doi.org/10.3390/recycling10050181 - 25 Sep 2025

Abstract

This article focuses on the problem of processing slag waste from non-ferrous metallurgy, in particular, the loss of copper, gold and silver with slag during autogenous smelting in the Vanyukov furnace at the Balkhash Copper Smelter (BMZ). An analysis of factors affecting metal [...] Read more.

This article focuses on the problem of processing slag waste from non-ferrous metallurgy, in particular, the loss of copper, gold and silver with slag during autogenous smelting in the Vanyukov furnace at the Balkhash Copper Smelter (BMZ). An analysis of factors affecting metal losses, including electrochemical and mechanical components, is presented. This paper offers a comprehensive study of the distribution of Cu, Pb, As, Au and Ag between matte and slag, taking into account the unique characteristics of the raw material and the technological conditions of the copper smelter, which distinguishes it from previous studies. This paper establishes numerical values of dissolved and mechanical losses of valuable metals. It has been established that the most important quantitative result of smelting polymetallic raw materials in a Vanyukov furnace is the proportion of mechanical copper losses in the slag, which is approximately 75–80% of the total copper content in the slag. Mathematical models are proposed to predict the distribution of metals in the process of smelting and loss of copper, gold and silver with slag. It is proposed to integrate model representations into the technology control loop, which will optimize the process of metal recovery. This will lead to an increase in profitability and a reduction in the negative impact on the environment during copper production. Full article

► Show Figures

Figure 1

16 pages, 2383 KB

Open AccessArticle

Recycling Disassembled Automotive Plastic Components for New Vehicle Components: Enabling the Automotive Circular Economy

by Neeki Meshkat, Matthew Korey, Amber M. Hubbard, Kathryn Slavny, Ashish L. S. Anilal, Arit Das, Logan Kearney, Soydan Ozcan and Uday Vaidya

Recycling 2025, 10(5), 180; https://doi.org/10.3390/recycling10050180 - 25 Sep 2025

Abstract

As the automotive industry increasingly relies on plastic components to meet fuel efficiency and emissions targets, the challenge of managing end-of-life vehicle (ELV) plastics continues to grow. Currently, more than 80% of ELV plastics in the U.S. are landfilled due to limited economic [...] Read more.

As the automotive industry increasingly relies on plastic components to meet fuel efficiency and emissions targets, the challenge of managing end-of-life vehicle (ELV) plastics continues to grow. Currently, more than 80% of ELV plastics in the U.S. are landfilled due to limited economic incentives and technical barriers to recycling. This study examines a mechanical recycling pathway for thermoplastic components disassembled from ELVs and assesses their usability for reintegration into new vehicle parts. Four representative materials were chosen based on material labels embedded in recovered parts and aligned with their virgin industrial equivalents: polypropylene (PP), 10% talc-filled PP (PP-T10), 20% talc-filled PP (PP-T20), and a 20% glass-/mineral-filled polyamide (PA6 + GF7 + MF13). The materials underwent shredding, drying, and injection molding before being characterized by particle size analysis, density measurement, thermal analysis (TGA, DSC), mechanical testing, and heat deflection temperature (HDT) evaluation. The results in this work indicated that minor differences in crystallinity were observed and small differences between model materials and ELV materials could have contributed to these changes. Mechanical testing revealed that neat polypropylene suffered a 15–20% reduction in stiffness and tensile strength, but talc-filled polypropylene and glass/mineral-filled nylon retained >90% of their modulus, strength, and heat deflection temperature values relative to virgin controls. Differences between virgin and ELV materials could have been attributed to use life degradation, contamination during use life, or even chemical/processing differences in model materials and ELV materials. However, these findings suggest that mechanically recycled, disassembled ELV plastics can retain sufficient structural performance to support circularity efforts in the automotive sector. Full article

(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)

► Show Figures

Figure 1

20 pages, 5612 KB

Open AccessArticle

Enhanced Waste Sorting Technology by Integrating Hyperspectral and RGB Imaging

by Georgios Alexakis, Marina Pellegrino, Laura Rodriguez-Turienzo and Michail Maniadakis

Recycling 2025, 10(5), 179; https://doi.org/10.3390/recycling10050179 - 22 Sep 2025

Viewed by 284

Abstract

Identifying the material composition of objects is crucial for many recycling sector applications. Traditionally, object classification relies either on hyperspectral imaging (HSI), which analyses the chemometric properties of objects to infer material types, or on RGB imaging, which captures an object’s visual appearance [...] Read more.

Identifying the material composition of objects is crucial for many recycling sector applications. Traditionally, object classification relies either on hyperspectral imaging (HSI), which analyses the chemometric properties of objects to infer material types, or on RGB imaging, which captures an object’s visual appearance and compares it to a reference sample. While both approaches have their strengths, each also suffers from limitations, particularly in challenging scenarios such as robotic municipal waste sorting, where objects are often heavily deformed or contaminated with various forms of dirt, complicating material recognition. This work presents a novel method for material-based object classification that jointly exploits HSI and RGB imaging. The proposed approach aims to mitigate the weaknesses of each technique while amplifying their respective advantages. It involves the real-time alignment of HSI and RGB data streams to ensure reliable result correlation, alongside a machine learning framework that learns to exploit the strengths and compensate for the weaknesses of each modality across different material types. Experimental validation on a municipal waste sorting facility demonstrates that the combined HSI–RGB approach significantly outperforms the individual methods, achieving robust and accurate classification even in highly challenging conditions. Full article

► Show Figures

Figure 1

18 pages, 2394 KB

Open AccessArticle

Harnessing Wheat Bran as a Phytochemical Bioresource: Release of Ferulic Acid Using Organosolv Treatment with Acidic/Alkaline Deep Eutectic Solvents

by Spyros Grigorakis and Dimitris P. Makris

Recycling 2025, 10(5), 178; https://doi.org/10.3390/recycling10050178 - 22 Sep 2025

Viewed by 177

Abstract

Wheat bran (WB) is a very abundant residual biomass, resulting from wheat processing. Although it can be used as feed without further processing, the utilization of WB as a bioresource of high valued-added chemicals would require task-specific treatments. In this context, the present [...] Read more.

Wheat bran (WB) is a very abundant residual biomass, resulting from wheat processing. Although it can be used as feed without further processing, the utilization of WB as a bioresource of high valued-added chemicals would require task-specific treatments. In this context, the present work aimed to used two newly reported deep eutectic solvents (DESs) for the effective organosolv treatment of WB to achieve a high-performance polyphenol recovery. One of the DESs used was alkaline, composed of glycerol and sodium carbonate (GL-SCar), and the other one was acidic, composed of glycerol and oxalic acid (GL-OA), and the treatments carried out were evaluated based on severity. Further optimization with a response surface methodology showed that treatment with GL-SCar could afford a maximum total polyphenol yield of 24.30 ± 2.34 mg ferulic acid equivalents per g of dry WB mass, the optimal settings being t = 172 min and T = 90 °C. Likewise, the GL-OA treatment yielded 23.21 ± 3.82 mg ferulic acid equivalents per g of dry WB mass, with the corresponding optimal conditions being t = 180 min and T = 90 °C. The examination of the polyphenolic profile of the extracts obtained revealed important differences in the composition, as the extract obtained with GL-SCar treatment was dominated by ferulic acid, whereas the extract produced with GL-OA treatment was enriched in a ferulate derivative, previously identified as a ferulate pentose ester. However, both treatments were shown to liberate only part of the bound phenolics, as judged by comparison with a reference alkaline hydrolysis. The difference in composition most probably defined the antioxidant effects of the extracts, with the GL-OA extract displaying more powerful antiradical and ferric-reducing power activity, despite the significantly lower polyphenolic concentration. The evidence that emerged from this investigation pointed to both DESs as solvents with high potency in polyphenol recovery from WB, yet further improvements are required to maximize yield. Moreover, it was shown that, due to their different nature (alkaline/acidic), both DESs could be suitably tuned for delivering extracts enriched in different phytochemicals. Full article

► Show Figures

Figure 1

21 pages, 3420 KB

Open AccessArticle

Characterisation of Fibre Mechanical Recycled Cotton Denim Fibres and the Effects of Their Properties on Yarns and Knits

by Ella Kärkkäinen, Taina Kamppuri, Lea Heikinheimo, Carla Joana Silva and Joana M. Gomes

Recycling 2025, 10(5), 177; https://doi.org/10.3390/recycling10050177 - 19 Sep 2025

Viewed by 285

Abstract

The purpose of this study was to obtain a holistic view of mechanically recycled cotton from denim fabrics and the repurposing and recycling methods for similar fibres. A pre-consumer denim and three types of post-consumer denims were shredded into new fibres, which were [...] Read more.

The purpose of this study was to obtain a holistic view of mechanically recycled cotton from denim fabrics and the repurposing and recycling methods for similar fibres. A pre-consumer denim and three types of post-consumer denims were shredded into new fibres, which were characterised with single-fibre tensile testing, SEM imaging and DSC analysis. The opened cotton fibres were then blended with primary cotton with varying ratios and spun into yarns of 40 tex with a ring spinning machine. A ratio of 75/25 of recycled fibres to virgin fibres was obtained, with promising tensile strength results. Further, the yarns were knitted into single jersey fabrics, and abrasion testing was performed to evaluate their wearing out. Best abrasion resistance was obtained for knits consisting of 100% virgin cotton fibres and the knits consisting of a blend of pre-consumer and virgin fibres. The results suggest the yarns made with mechanically opened fibres are suitable for single jersey knits. SEM and DSC confirm the input of mechanical recycling defines the output. Moreover, the SEM pictures indicate there is little to no damage to single fibres caused by mechanical shredding, causing no further barriers for secondary use as raw materials. Full article

► Show Figures

Figure 1

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 - 12 Sep 2025

Viewed by 370

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

► Show Figures

Figure 1

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

Viewed by 369

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

► Show Figures

Graphical abstract

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

Viewed by 411

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

► Show Figures

Figure 1

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

Viewed by 382

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

► Show Figures

Figure 1

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

Viewed by 708

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

► Show Figures

Figure 1

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

Viewed by 473

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)

► Show Figures

Figure 1

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

Viewed by 1181

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

► Show Figures

Graphical abstract

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 491

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)

► Show Figures

Figure 1

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 591

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

► Show Figures

Figure 1

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

Viewed by 539

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

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Recycling, Volume 10, Issue 5 (October 2025) – 22 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI