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Secondary Treatment Facilitating the Mechanical Recycling of Film-Coated Waste Automobile Bumpers
Sustainable Recycling of End-of-Life Electric Vehicle Batteries: EV Battery Recycling Frameworks in China and the USA

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

24 pages, 1983 KB

Open AccessArticle

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

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

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

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

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

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

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21 pages, 2383 KB

Open AccessArticle

Strength Characterization by Vibrational Analysis of Building Demolition Wood to Assess Reuse Potential

by Odran Lemaitre, Laurent Bléron, Caroline Simon and Pierre-Jean Méausoone

Recycling 2025, 10(6), 204; https://doi.org/10.3390/recycling10060204 - 5 Nov 2025

The objective of the study is to develop a methodology for strength characterization by vibrational analysis of a batch of wood from building demolitions with a view to its reuse. This approach is part of an experimental deconstruction/reconstruction project located in the Vosges [...] Read more.

The objective of the study is to develop a methodology for strength characterization by vibrational analysis of a batch of wood from building demolitions with a view to its reuse. This approach is part of an experimental deconstruction/reconstruction project located in the Vosges “département” of France and led by the social housing landlord, VOSGELIS. The main constraint related to this intention of reuse is the obtention of the strength class of the elements, which is not recorded in the standards. The comparative study of different non-destructive technologies has shown that the values of the longitudinal dynamic modulus of elasticity obtained by the vibrational method are closer on average (15%) to the actual value obtained by the bending tests than those obtained by the ultrasonic method (35%). A portable measuring bench suitable for the deconstruction site was also developed during the study for the utilization of the vibrational method. The values of the dynamic modules of elasticity obtained on this bench are close, on average, to the values of the modulus of elasticity obtained by bending tests executed on a test slab (13%). This study made it possible to extend the use of the NF EN 14081-2+A1 standard to woods from building demolitions. However, this standard needs to be adapted for the classification of that typology of wood, with a reference batch constituted of 15 to 20 samples. Full article

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19 pages, 2963 KB

Open AccessArticle

Environmental Perspectives on Distributed Generation: Economic Feasibility and Risk-Based Assessment of Poultry Waste Biogas Power Plants

by André Moscon Mendes, Clainer Bravin Donadel and Danieli Soares Oliveira

Recycling 2025, 10(6), 203; https://doi.org/10.3390/recycling10060203 - 31 Oct 2025

The growing demand for sustainable energy requires solutions that combine economic feasibility, environmental benefits, and positive social impacts. In this context, the use of poultry waste as feedstock for biogas production emerges as a promising alternative, contributing to waste reduction and the mitigation [...] Read more.

The growing demand for sustainable energy requires solutions that combine economic feasibility, environmental benefits, and positive social impacts. In this context, the use of poultry waste as feedstock for biogas production emerges as a promising alternative, contributing to waste reduction and the mitigation of greenhouse gas emissions. This study assesses the economic feasibility and risk of implementing a consortium-based biogas-fired power plant within Brazil’s Micro and Mini Distributed Generation (MMDG) framework. Two scenarios were evaluated: the first included the cost of acquiring poultry manure, while the second excluded this expense. In both cases, the results confirmed economic feasibility, with positive Net Present Value (NPV), Modified Internal Rate of Return (MIRR) above the Minimum Attractive Rate of Return (MARR), and favorable Discounted Payback Periods. Scenario 2 provided greater investment security, as only 0.05% of simulations indicated infeasibility, compared to 0.12% in Scenario 1. Risk analysis using Monte Carlo simulations revealed that the availability and cost of poultry manure were the most critical variables influencing economic performance. Beyond financial indicators, the consortium-based distributed generation model demonstrates potential to attract investors, diversify the energy mix, and deliver socio-economic and environmental benefits. This study contributes to both academic research and practical applications by providing valuable guidance for investors and policymakers in renewable distributed generation. Full article

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13 pages, 2272 KB

Open AccessArticle

Enhanced Recoverability and Recycling of Resistant Waste Crosslinked Polyethylene via FeTiO₃ Catalyst-Assisted Slow Pyrolysis

by Pavel Straka, Olga Bičáková and Jaroslav Cihlář

Recycling 2025, 10(6), 202; https://doi.org/10.3390/recycling10060202 - 31 Oct 2025

Crosslinked polyethylene (XLPE) is a widely used material which—unlike polyethylene—is very stable both chemically and mechanically. Therefore, waste from this material is difficult to process. A very promising way is slow pyrolysis catalyzed by FeTiO₃ (ilmenite), which allows the conversion of this [...] Read more.

Crosslinked polyethylene (XLPE) is a widely used material which—unlike polyethylene—is very stable both chemically and mechanically. Therefore, waste from this material is difficult to process. A very promising way is slow pyrolysis catalyzed by FeTiO₃ (ilmenite), which allows the conversion of this waste into hydrocarbons via degradation of the rigid chemical structure of crosslinked material. High liquid hydrocarbon yields were achieved by slow pyrolysis both without and with a catalyst at a final temperature of 470 °C (65 and 75–76 wt.%, respectively), but with the catalyst significantly changing the composition of the resulting hydrocarbons. To reveal the possibilities of using the FeTiO₃ catalyst for processing waste XLPE, the effect of this catalyst on the degradation of the XLPE structure was investigated. The degradation is probably greatly facilitated by the action of the FeTiO₃ catalyst at the defect sites of the XLPE structure, i.e., at the tertiary carbons in the main chain where branching into cross-links occurs. In this way, the FeTiO₃ catalyst, even in very small amounts (1%), significantly promotes the degradation of the XLPE structure. This leads to the formation of liquid hydrocarbons, up to 92 wt.% of the products obtained. The novelty of this work lies in a technologically feasible method for processing resistant crosslinked waste material using an inexpensive catalyst; the proposed method provides hydrocarbons with high utility value. On the whole, slow pyrolysis of XLPE waste catalyzed by FeTiO₃ at a final temperature of 470 °C and carried out under well-defined conditions appears to be a promising method for converting this waste into valuable hydrocarbons and energy gas. Full article

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16 pages, 2038 KB

Open AccessArticle

Separation of Silver and Cellulosic Fibers for Recycling and Reuse of Printed Electronic Devices Components

by Ramzi Khiari, Nathalie Marlin, Denis Curtil, Marc Aurousseau, Lenka Svecová and Nadège Reverdy-Bruas

Recycling 2025, 10(6), 201; https://doi.org/10.3390/recycling10060201 - 29 Oct 2025

The printed electronics sector is experiencing significant growth driven by societal expectations. The use of cellulosic substrates is an excellent strategy that offers interesting research prospects, but also sets challenges in terms of management and recycling of these new wastes to avoid their [...] Read more.

The printed electronics sector is experiencing significant growth driven by societal expectations. The use of cellulosic substrates is an excellent strategy that offers interesting research prospects, but also sets challenges in terms of management and recycling of these new wastes to avoid their accumulation. This work investigates the recycling ability of paper-based printed electronics (a simple RFID antenna printed on paper), containing silver particles in the functional ink, using processes already applied in conventional paper and board recycling lines. These operations, commonly used in the papermaking industry, are pulping, screening, centrifugal cleaning, and flotation. The efficiency of each unit operation was evaluated. Mass balances between the inlet and the outlet of each studied operation have been established in order to evaluate the separation efficiency of Ag and cellulosic fibers, the objective being to reuse the fibers to manufacture a recycled paper, and to recover Ag in another fraction for further valorization. The results are encouraging, with more than 70% of silver and over 80% of cellulose fibers recovered, demonstrating a higher recovery efficiency compared to typical recycling methods reported in the literature. Thus, it has been shown that existing processes used in conventional recycling lines can be adapted to efficiently separate functional materials from cellulosic fibers, offering an improvement in both metal and fibers’ recovery. Full article

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16 pages, 5466 KB

Open AccessArticle

Effects of Contamination on the Recyclability of NdFeB Permanent Magnets via Short-Loop Processing: Review of Common Contaminants and Study on Ni Coating Residues

by Laura Grau, Fabian Burkhardt, Nicolas Moll, Stefan Rathfelder, Spomenka Kobe and Carlo Burkhardt

Recycling 2025, 10(6), 200; https://doi.org/10.3390/recycling10060200 - 29 Oct 2025

Short-loop recycling of NdFeB trades a reduced ecological burden for a higher sensitivity towards contamination, as the powder is usually further processed as-is. In this investigation, the known effects of common contaminants (O, C, Ni, Cu, and Zn) introduced due to product design [...] Read more.

Short-loop recycling of NdFeB trades a reduced ecological burden for a higher sensitivity towards contamination, as the powder is usually further processed as-is. In this investigation, the known effects of common contaminants (O, C, Ni, Cu, and Zn) introduced due to product design choices, namely from coating material and adhesive residue or a lack of corrosion protection, are reviewed. This study focuses on the impact of such contaminants on the magnetic properties and microstructure of recycled magnets via HPMS and re-sintering. Because of the lack of information regarding the practical effects of metallic coating residues, the impact of Ni contamination on the properties of re-sintered NdFeB magnets is assessed. HPMS processed scrap powder is blended with Ni powder and recycled by sintering. It is found that Ni partially substitutes Fe in the φ-phase, as expected from the literature review, leading to detrimental effects on the coercivity and remanence. The formation of an α-(Fe, Ni) phase is observed. The acceptable limit of Ni contamination without detrimental effects is found to be around 0.25 wt.%; however, due to the substitution in the φ-phase, the contamination is irreversible via short-loop recycling and would accumulate over multiple lifecycles. Full article

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15 pages, 5582 KB

Open AccessArticle

Design of an Energy-Efficient Pilot-Scale Pyrolysis Reactor Using Low-Cost Insulating Materials

by José Alfredo Torres Tovar, Hermelinda Servín-Campuzano, Mauricio González-Avilés, Hugo Sobral, Francisco Javier Sánchez-Ruiz and Saúl Leonardo Hernández Trujillo

Recycling 2025, 10(6), 199; https://doi.org/10.3390/recycling10060199 - 28 Oct 2025

A pilot-scale reactor prototype was designed to produce hydrocarbons through the catalytic pyrolysis process of low-density polyethylene, thereby extending its life cycle and contributing to energy efficiency and sustainability. The reactor consists of a stainless-steel tank encased in a ceramic jacket with refractory [...] Read more.

A pilot-scale reactor prototype was designed to produce hydrocarbons through the catalytic pyrolysis process of low-density polyethylene, thereby extending its life cycle and contributing to energy efficiency and sustainability. The reactor consists of a stainless-steel tank encased in a ceramic jacket with refractory cement and clay bricks. The tank, made of 304 stainless steel, ensures mechanical strength and efficient heat transfer to the reactor core. A spiral condenser was incorporated into a water tank to cool the vapors and recover the liquid oil. The insulating materials, ceramic, refractory cement and clay brick, demonstrated a high combined thermal resistance of 0.159 m²·K/W. Simulations and energy flow calculations demonstrated that heat is efficiently directed to the reactor core, reaching 350 °C with only 3000–3800 W, while the outside of the jacket remained close to 32 °C. These results confirm that the proposed design improves thermal efficiency and optimizes energy use for catalytic pyrolysis. The novelty of this design lies in its energy-efficient configuration, which can be replicated in rural regions worldwide due to the accessibility of its construction materials. This reactor was developed based on a smaller-scale model that previously yielded excellent results. Full article

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20 pages, 13496 KB

Open AccessArticle

Effect of Pretreatment on the Structure and Enzymatic Hydrolysis of Pineapple Waste Biomass in Hydrothermal Deconstruction

by Carlos Méndez-Durazno, Nilo M. Robles Carrillo, Valeria Ramírez, Oscar M. Rodriguez-Narváez, Pablo A. Cisneros-Pérez, Diego Chulde, Alexis Debut and Patricio J. Espinoza-Montero

Recycling 2025, 10(6), 198; https://doi.org/10.3390/recycling10060198 - 28 Oct 2025

Pineapple biomass represents an abundant renewable source of carbon and a promising feedstock with considerable potential for the production of sustainable fuels. In the present study, the influence of liquid hot water (LHW) pretreatment on the pineapple mother plant was investigated at different [...] Read more.

Pineapple biomass represents an abundant renewable source of carbon and a promising feedstock with considerable potential for the production of sustainable fuels. In the present study, the influence of liquid hot water (LHW) pretreatment on the pineapple mother plant was investigated at different controlled severities, then characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Results show that LHW pretreatment causes structural changes, leading to lignin and hemicellulose depolymerization up to a severity factor of 2.36–3.55, whereas at severity factors in the range of 4.13–5.90, cellulose, hemicellulose, and lignin appear to repolymerize. This pretreatment resulted in a higher hydrolysis efficiency (94.92 ± 0.04%) at 50 °C for 72 h. Compared with the untreated sample, the hydrolysis rate under these conditions increased by a factor of 2.16. SEM imaging revealed significant disruption of the PMP microstructure following LHW treatment, while XRD data confirmed an increase in the crystallinity index. FTIR analysis further indicated modifications in functional group profiles, supporting the structural and compositional changes induced by pretreatment. Overall, this study demonstrates the effectiveness of LHW pretreatment in enhancing the enzymatic digestibility and modifying the physicochemical properties of PMP biomass, providing a foundation for its valorization into high value bioproducts. Full article

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13 pages, 643 KB

Open AccessArticle

Recycling of Post-Consumer HDPE Bottle Caps into New Caps for Food Contact

by Frank Welle

Recycling 2025, 10(6), 197; https://doi.org/10.3390/recycling10060197 - 22 Oct 2025

HDPE caps are collected together with PET bottles, which have been recycled into new bottles for decades. Due to Deposit Return Schemes, the bottle caps are sorted by type and are suitable to be recycled again for sensitive applications e.g., food contact. While [...] Read more.

HDPE caps are collected together with PET bottles, which have been recycled into new bottles for decades. Due to Deposit Return Schemes, the bottle caps are sorted by type and are suitable to be recycled again for sensitive applications e.g., food contact. While there are evaluation criteria for mechanical PET recycling processes, no such evaluation crite-ria have been published for recycled HDPE caps in food contact. As part of the study, possible evaluation criteria are derived from other polymers or applications and critically discussed. Recycling of post-consumer caps from beverage bottles into new HDPE caps in direct contact with food is realistic even if worst-case considerations on the evaluation criteria are applied. The required cleaning efficiencies are within a range that is technically feasible for today’s mechanical HDPE recycling processes. The evaluation criteria can be used for a preliminary assessment of post-consumer HDPE recyclate in food contact. Based on the evaluation, the recycling of HDPE caps is to be submitted as a novel technology according to Regulation 2022/1616. Full article

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25 pages, 10369 KB

Open AccessArticle

Properties of Green Foam-Type Composites Made from Recycled Paper and Cardboard

by Mohammad Hassan Mazaherifar, Antonela Lungu, Maria Cristina Timar, Sergiu Valeriu Georgescu, Mihai Ispas and Camelia Cosereanu

Recycling 2025, 10(6), 196; https://doi.org/10.3390/recycling10060196 - 22 Oct 2025

This study developed sustainable foam-type composites from recycled paper (P), corrugated cardboard (C), and their 1:1 mixture (PC) for use in thermal and acoustic insulation. The materials were produced by water-assisted defibration, gas foaming with sodium bicarbonate and yeast, and oven curing, resulting [...] Read more.

This study developed sustainable foam-type composites from recycled paper (P), corrugated cardboard (C), and their 1:1 mixture (PC) for use in thermal and acoustic insulation. The materials were produced by water-assisted defibration, gas foaming with sodium bicarbonate and yeast, and oven curing, resulting in lightweight porous panels without synthetic binders. The composites exhibited distinct density and porosity profiles that influenced moisture behavior and stability. Cardboard-based panels absorbed the most water and swelled the most, while paper-based panels were more resistant. Despite these differences, all materials showed uniformly low thermal conductivity, confirming their strong insulation capability. Acoustic performance was enhanced by perforation and multilayer assembly. Cardboard panels with a triple-layer perforated design achieved the highest sound absorption, while mixed paper–cardboard composites provided balanced broadband performance. Microscopy revealed that fiber morphology—coarse in cardboard, fine in paper, and interlaced in mixtures—shaped the porous structure and bonding. Mechanical tests indicated comparable stiffness and strength across all types, with cardboard showing the strongest internal bonding. Overall, the results demonstrate that fiber structure and porosity govern material performance. These foam composites combine effective thermal insulation, competitive sound absorption, and sufficient mechanical strength, positioning them as biodegradable, low-cost alternatives for sustainable construction and acoustic applications. Full article

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19 pages, 2477 KB

Open AccessArticle

Development of an Advanced Life Cycle Impact Assessment Method to Evaluate Radioactivity in Construction Materials

by Cansu Özcan Kilcan, Uku Andreas Reigo and Alan H. Tkaczyk

Recycling 2025, 10(5), 195; https://doi.org/10.3390/recycling10050195 - 21 Oct 2025

While reducing industrial environmental impacts, it is essential to verify that the perceived improvements do not cause unexpected side effects. In the construction materials sector, certain circular economy practices may potentially increase the exposure from natural radioactivity due to the elevated radionuclide content [...] Read more.

While reducing industrial environmental impacts, it is essential to verify that the perceived improvements do not cause unexpected side effects. In the construction materials sector, certain circular economy practices may potentially increase the exposure from natural radioactivity due to the elevated radionuclide content in processed naturally occurring radioactive material (NORM). This study presents the development of a life cycle impact assessment (LCIA) methodology accounting for NORM impacts in construction material life cycles from cradle to use. The methodology builds upon the LCA-NORM life cycle assessment framework previously established by the research group. The novel contributions include enhancements in (1) the dose units, (2) the use-stage exposure scenario, (3) the inclusion of radionuclide inhalation as an occupational exposure pathway and (4) the revisions of key parameters, including the dose conversion coefficients (DCCs). The updated characterisation factors yielded more conservative values at the use stage (e.g., 7 times higher exposure under pessimistic conditions due to radon inhalation) compared to the previous LCA-NORM outputs. An important advancement is the implementation of the new methodology in a novel custom-developed Python package (i.e., NORMIA) to integrate the custom elementary flows into LCA calculations of the Python library Brightway v.2.5. NORMIA generates characterisation factors that quantify the equivalent stochastic risk for human health and non-human biota per unit radionuclide emission and activity, based on user-defined inputs such as construction material type and density. With this study, a more holistic and accurate assessment of the environmental sustainability of construction materials is targeted. Full article

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14 pages, 1367 KB

Open AccessArticle

Introducing Reverse Osmosis and Membrane Distillation in the Recovery Process of N-Methylmorpholine N-Oxide in Cellulose Fiber Production

by Sofia Plakantonaki, Ioannis Tournis, Nikolaos Zacharopoulos, Evangelos Kouvelos, Andreas A. Sapalidis and Chrysoula Athanasekou

Recycling 2025, 10(5), 194; https://doi.org/10.3390/recycling10050194 - 20 Oct 2025

This study serves as a proof of concept for the evaluation of two membrane technologies, reverse osmosis combined with membrane distillation, for the recovery of N-methylmorpholine N-oxide (NMMO) and water from generated wastewater by the textile manufacturing “Lyocell process”. This method utilizes NMMO [...] Read more.

This study serves as a proof of concept for the evaluation of two membrane technologies, reverse osmosis combined with membrane distillation, for the recovery of N-methylmorpholine N-oxide (NMMO) and water from generated wastewater by the textile manufacturing “Lyocell process”. This method utilizes NMMO to dissolve cellulose for the production of cellulosic yarn, resulting in wastewater that contains 1–2 %w/w NMMO. After an initial pretreatment to remove suspended solids, followed by a mixed ion-exchange resin, the stream was fed into a reverse osmosis membrane unit, concentrating the solution to approximately 10 %w/w NMMO. Following this step, the RO concentrate was introduced to a DCMD setup equipped with a PTFE microporous membrane, achieving a final concentration of a 70.5 %w/w NMMO aqueous solution, which is considered suitable for reuse. The main contribution of the present study is to establish, in principle, that the newly proposed method can be a modular and scalable alternative to the dominant multi-stage evaporation technologies. Full article

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27 pages, 8857 KB

Open AccessArticle

Second-Generation Recycled Concrete Aggregates: Comprehensive Characterization of Physical, Mechanical, and Microstructural Properties

by Farshad Ameri and Ildiko Merta

Recycling 2025, 10(5), 193; https://doi.org/10.3390/recycling10050193 - 15 Oct 2025

The rapid expansion of concrete production has intensified the depletion of natural aggregate (NA) resources, necessitating sustainable alternatives in the construction industry. Recycling construction and demolition (C&D) waste offers a solution to enhance environmental sustainability and resource efficiency. Most existing studies have mainly [...] Read more.

The rapid expansion of concrete production has intensified the depletion of natural aggregate (NA) resources, necessitating sustainable alternatives in the construction industry. Recycling construction and demolition (C&D) waste offers a solution to enhance environmental sustainability and resource efficiency. Most existing studies have mainly focused on first-generation RCAs (RCA1), with little work on second-generation RCAs (RCA2), especially fine fractions. This study examined the properties of recycled concrete aggregates (RCAs) across first and second recycling cycles, focusing on their upcycling potential. Therefore, commercially sourced NAs and RCA1 were compared with lab-produced RCA2, both coarse and fine, derived from further recycling of first-generation recycled aggregate concrete (RAC1). Comprehensive tests assessed morphology and physical, mechanical, and microstructural properties to provide a clear insight into how RCA2 differs from RCA1. Average sphericity for coarse RCA1 was 0.81, an 8% decrease from NA’s 0.88, while RCA2 had an average sphericity of 0.76, a 14% decrease. The results revealed a progressive decline in aggregate quality with each cycle. RCA1 exhibited water absorption of 9.53% (fine) and 5.55% (coarse), while RCA2 showed higher absorption at 13.16% (fine) and 6.88% (coarse). RCA1’s crushing value was 25.9%, a 41% rise over NA’s 18.09%, while RCA2’s reached 29.2%, a 61% increase. Coarse RCA2 contained 51.03% attached old mortar, 50% more than the 33.95% in RCA1. Fine RCA2 showed significant performance reductions, limiting these aggregates to non-structural downcycling applications. Microstructure analyses confirmed RCA2’s porous structure, attributed to increased adhered old mortar, including multiple weak interfaces, and numerous microcracks compared to RCA1, necessitating careful consideration when using coarse RCA2 for upcycling in sustainable construction. Full article

(This article belongs to the Topic Solid Waste Recycling in Civil Engineering Materials)

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19 pages, 1315 KB

Open AccessArticle

Valorization of Industrial Wastewater Treatment Sludge in Eco-Friendly Mortars: Enhancing Thermal Insulation and Sustainability

by El Mokhtar El Hafidi, Abdelhadi Mortadi, Brahim Lizoul, El Ghaouti Chahid and Said Laasri

Recycling 2025, 10(5), 192; https://doi.org/10.3390/recycling10050192 - 15 Oct 2025

The construction industry increasingly seeks sustainable solutions to reduce environmental impact and energy consumption. This study explores the innovative use of industrial sludge generated from the wastewater treatment of detergent manufacturing as a partial substitute for Portland cement in mortar production. The sludge, [...] Read more.

The construction industry increasingly seeks sustainable solutions to reduce environmental impact and energy consumption. This study explores the innovative use of industrial sludge generated from the wastewater treatment of detergent manufacturing as a partial substitute for Portland cement in mortar production. The sludge, characterized by high SiO₂ (46.58%) and CaO (28.66%) content, was incorporated at substitution rates of 0% to 30%. Mortars were prepared and tested according to NF EN 196-1 standards for mechanical strength, and thermophysical properties were assessed using the Hot Disk TPS 1500 system. The results demonstrate that up to 20% sludge replacement maintains acceptable mechanical performance (compressive strength: 12.63 MPa at 28 days vs. 13.91 MPa for the control; flexural strength: 3.93 MPa vs. 4.65 MPa) while significantly enhancing thermal insulation. Thermal conductivity decreased from 1.054 W/m·K (0% sludge) to 0.797 W/m·K (20% sludge), and thermal diffusivity dropped from 0.6096 mm²/s to 0.504 mm²/s. XRD analysis revealed the formation of new phases, such as gismondine, indicating beneficial pozzolanic activity. These findings highlight the dual benefit of valorizing detergent sludge and improving building energy efficiency, offering an eco-efficient alternative to traditional mortars aligned with circular economy and low-carbon construction goals. Full article

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15 pages, 475 KB

Open AccessArticle

Wood Waste Valorization Using Organosolv Pretreatment and Enzymatic Hydrolysis: Experimental and Process Evaluation

by Aron Pazzaglia, Giacomo Fabbrizi, Mattia Gelosia, Tiziano Galmacci, Tommaso Giannoni, Alessandro Iapino, Andrea Nicolini and Beatrice Castellani

Recycling 2025, 10(5), 191; https://doi.org/10.3390/recycling10050191 - 13 Oct 2025

Wood is a versatile resource within the circular economy, widely used across various applications. However, in the European Union, demand for wood continues to rise, leading to increased reliance on imports. The pulp and paper industry, closely linked to wood production, is also [...] Read more.

Wood is a versatile resource within the circular economy, widely used across various applications. However, in the European Union, demand for wood continues to rise, leading to increased reliance on imports. The pulp and paper industry, closely linked to wood production, is also experiencing supply shortages. To address these challenges, this study explores the use of wood waste (WW) as an alternative feedstock for pulp and glucose production. WW was collected from a mechanical treatment plant in Perugia, Italy, and processed using the organosolv method. This approach yielded a cellulose pulp with improved quality compared to previous research, achieving a cellulose content of 79.33% and a cellulose recovery rate of 94.59%. The optimized pulp was then subjected to enzymatic hydrolysis, producing 20.66 g of glucose per 100 g of initial WW, corresponding to a glucose concentration of 44.08 g/L and a cellulose digestibility of 51.03%. Additionally, a simulation model of a pilot-scale process was developed using Aspen PLUS software, assuming an annual processing capacity of approximately 5500 t of wood waste—equivalent to the quantity managed annually by a local waste treatment company in Perugia. This study highlights the potential of wood waste as a sustainable raw material for pulp and glucose production, supporting circular economy goals and laying the groundwork for future scale-up investigations. Full article

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36 pages, 8903 KB

Open AccessArticle

Sustainable Valorization of Bovine–Guinea Pig Waste: Co-Optimization of pH and EC in Biodigesters

by Daniela Geraldine Camacho Alvarez, Johann Alexis Chávez García, Yoisdel Castillo Alvarez and Reinier Jiménez Borges

Recycling 2025, 10(5), 190; https://doi.org/10.3390/recycling10050190 - 10 Oct 2025

The agro-industry is among the largest methane emitters, posing a critical challenge for sustainability. In rural areas, producers lack effective technologies to manage daily organic waste. Anaerobic digestion (AD) offers a circular pathway by converting waste into biogas and biofertilizers; however, its adoption [...] Read more.

The agro-industry is among the largest methane emitters, posing a critical challenge for sustainability. In rural areas, producers lack effective technologies to manage daily organic waste. Anaerobic digestion (AD) offers a circular pathway by converting waste into biogas and biofertilizers; however, its adoption is limited by inappropriate designs and insufficient operational control. Theoretical-applied research addresses these barriers by improving the design and operation of small-scale biodigesters, elevating pH and Electrical Conductivity (EC) from passive indicators to first-order control variables. Based on the design of a compact biodigester previously validated in the Chillón Valley and replicated in Huaycán under a utility model patent process (INDECOPI, Exp. 001087-2025/DIN), a stoichiometric NaHCO

_{3}

strategy with joint pH–EC monitoring was formalized, defining operational windows (pH 6.92–6.97; EC 6200–6300 μS/cm and dose–response curves (0.3–0.4 kg/day for 3–4 day) to buffer VFA shocks and preserve methanogenic ionic strength. The system achieved stable productions of 370–462 L/day, surpassing the theoretical potential of 352.88 L/day calculated by Buswell’s equation. A multivariable predictive model (linear, quadratic, interaction terms pH × EC, temperature, and loading rate) was developed and validated with field data: R² = 0.78; MAPE = 2.7%; MAE = 11.2 L/day; RMSE = 13.8 L/day; r = 0.89; residuals normally distributed (Shapiro–Wilk p = 0.79). The proposed approach enables daily decision-making in low-instrumentation environments and provides a replicable and scalable pathway for the safe valorization of organic waste in rural areas. The design consolidates the shift from reactive to proactive and co-optimized pH–EC control, laying the foundation not only for standardized protocols and training in rural systems but also for improved environmental sustainability. Full article

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11 pages, 3893 KB

Open AccessArticle

Investigation of Aqueous Delamination Processes for Lithium-Ion Battery Anodes

by Eric Trebeck, Anting Grams, Jan Talkenberger, Sricharana Prakash, Julius Eik Grimmenstein, Thomas Krampitz, Holger Lieberwirth and Adrian Valenas

Recycling 2025, 10(5), 189; https://doi.org/10.3390/recycling10050189 - 7 Oct 2025

Recycling of lithium-ion batteries (LIBs) requires efficient separation of active material from current collectors to enable high-quality recovery of both the coating and the metal foil. In this study, a water-based delamination process for anode foils was systematically investigated under variations in temperature, [...] Read more.

Recycling of lithium-ion batteries (LIBs) requires efficient separation of active material from current collectors to enable high-quality recovery of both the coating and the metal foil. In this study, a water-based delamination process for anode foils was systematically investigated under variations in temperature, particle size, ultrasonic power, and prior mechanical stressing of the particles. Mechanically cut and pre-folded foil pieces were treated in a batch setup at different temperatures (room temperature to 100 °C) and ultrasonic power levels (50 and 100%). Results show that higher temperatures strongly promote delamination, with 100% removal of the active layer achieved on the smooth foil side at 80 °C without ultrasonic treatment. Ultrasonic treatment at moderate power (50%) yielded greater delamination than at full power (100%), likely due to more effective cavitation dynamics at moderate intensity. Mechanical pre-stressing by folding significantly reduced delamination, with three folds effectively preventing separation. In comparison, mechanically comminuted particles from a granulator achieved similar delamination to three-folded particles after 5 min treatment, and higher delamination after 30 min. These findings highlight the importance of process parameters in achieving efficient aqueous delamination, providing insights for scaling low-energy recycling processes for LIB production scrap. Full article

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

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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

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

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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

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

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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

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

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