Recycling

25 pages, 5651 KiB

Open AccessArticle

Kinetic and Thermodynamic Analysis of Fried Tilapia Fish Waste Pyrolysis for Biofuel Production

by Mohamed Koraiem M. Handawy, Ik-Tae Im, Gyo Woo Lee and Hamada Mohamed Abdelmotalib

Recycling 2025, 10(2), 61; https://doi.org/10.3390/recycling10020061 - 1 Apr 2025

Viewed by 45

Converting food waste into biofuel resources is considered a promising approach to address the rapid increase in energy demand, reduce dependence on fossil fuels, and decrease environmental hazards. In Egypt, large quantities of fried tilapia fish waste are produced in restaurants and households, [...] Read more.

Converting food waste into biofuel resources is considered a promising approach to address the rapid increase in energy demand, reduce dependence on fossil fuels, and decrease environmental hazards. In Egypt, large quantities of fried tilapia fish waste are produced in restaurants and households, posing challenges for proper waste management due to its decaying nature. The current study investigates the kinetic triplet and thermodynamic parameters of fried tilapia fish waste (FTFW) pyrolysis. Kinetic analysis was carried out using four iso-conversional models, Friedman, Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Starink, at heating rates of 10, 15, and 20 °C/min. The study findings indicate that FTFW decomposes within the temperature range of 382–407 °C. The estimated activation energy using the Friedman, FWO, KAS, and Starink methods ranged from 43.2 to 208.2, 31.3 to 148.3, 22.3 to 179.3, and 24.1 to 181.3 kJ/mol, respectively, with average values of 118.4, 96.7, 109.7, and 100.5 kJ/mol, respectively. The average enthalpy change determined using the Friedman, FWO, KAS, and Starink methods was 113.45, 91.78, 95.58, and 104.73 kJ/mol, respectively. The average values of Gibbs free energy change for the Friedman, KAS, FWO, and Starink, methods were 192.71, 171.04, 174.83, and 183.99 kJ/mol, respectively. Full article

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

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32 pages, 328 KiB

Open AccessReview

Rutting and Aging Properties of Recycled Polymer-Modified Pavement Materials

by Nuha S. Mashaan and Chathurika Dassanayake

Recycling 2025, 10(2), 60; https://doi.org/10.3390/recycling10020060 - 1 Apr 2025

Viewed by 47

Abstract

Recycled polymer-modified binders have emerged as a sustainable solution for improving the performance and durability of pavement materials. This review examines the rutting and aging properties of pavements modified with recycled polymers, highlighting their potential for sustainable infrastructure development. The incorporation of recycled [...] Read more.

Recycled polymer-modified binders have emerged as a sustainable solution for improving the performance and durability of pavement materials. This review examines the rutting and aging properties of pavements modified with recycled polymers, highlighting their potential for sustainable infrastructure development. The incorporation of recycled polymers into bitumen enhances resistance to rutting and aging by improving the binder’s mechanical stability and oxidative durability. Key laboratory techniques, including the rolling thin-film oven test (RTFOT) and the pressure aging vessel (PAV), are evaluated for their effectiveness in assessing the thermal and oxidative aging behavior of modified binders. The review demonstrates that recycled polymers improve binder elasticity, delay oxidative degradation, and mitigate deformation under repeated loading, thus extending pavement lifespan and reducing maintenance costs. However, challenges such as optimizing polymer dosage, ensuring homogeneity, and predicting long-term performance require further investigation. This paper underscores the environmental and economic benefits of utilizing recycled polymers in pavement construction and advocates for improved testing protocols and advanced characterization techniques to enhance the reliability and sustainability of polymer-modified pavements. Full article

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

19 pages, 7778 KiB

Open AccessArticle

Mechanical and Thermal Properties of Recycled Fishing Net-Derived Polyamide 6/Switchgrass Fiber Composites for Automotive Applications

by Zakariae Belmokhtar, Patrice Cousin, Saïd Elkoun and Mathieu Robert

Recycling 2025, 10(2), 59; https://doi.org/10.3390/recycling10020059 - 1 Apr 2025

Viewed by 64

Abstract

The increasing demand for sustainable materials in automotive applications, coupled with the critical need to address marine plastic pollution, presents an opportunity for innovative material development. This study explores composites made from recycled polyamide 6 (PA6) fishing nets reinforced with switchgrass fibers (0–30 [...] Read more.

The increasing demand for sustainable materials in automotive applications, coupled with the critical need to address marine plastic pollution, presents an opportunity for innovative material development. This study explores composites made from recycled polyamide 6 (PA6) fishing nets reinforced with switchgrass fibers (0–30 wt%). The composite with 30 wt% switchgrass fibers increased tensile strength by 23% and Young’s modulus by 126% compared to unreinforced recycled PA6, achieving 93% of the tensile strength of commercial automotive-grade neat PA6 and surpassing another grade by 22%. However, higher fiber loading hindered processability, as evidenced by incomplete mold filling and reflected by a decrease in melt flow rate from 19.35 to 8.63 g/10 min. Thermal analysis revealed reduced crystallinity and crystallization temperatures with fiber addition, attributed to restricted polymer chain mobility. While dynamic mechanical analysis demonstrated improved stiffness below the glass transition temperature, scanning electron microscopy indicated optimal fiber-matrix adhesion at up to 20 wt% fiber loading, with aggregation at higher concentrations. These findings establish recycled fishing net-derived PA6/switchgrass fiber composites as a viable alternative to virgin materials in automotive applications, with mechanical properties comparable to commercial grades. Although the composites demonstrate enhanced mechanical strength and modulus, the significant reduction in ductility restricts their use to rigid, semi-structural components where flexibility is not critical. Future research should address processing challenges to enhance fiber dispersion and interfacial adhesion at higher loadings. Full article

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29 pages, 3321 KiB

Open AccessArticle

Environmental Performance Assessment of a Decentralized Network of Recyclable Waste Sorting Facilities: Case Study in Montreal

by Jessy Anglehart-Nunes and Mathias Glaus

Recycling 2025, 10(2), 58; https://doi.org/10.3390/recycling10020058 - 1 Apr 2025

Viewed by 52

Abstract

The generation of waste grows yearly. In a centralized approach, more trucks are dispatched to collect the growing demand, with a higher pressure on the road network and greenhouse gas emissions. In contrast, a decentralized approach creates a network of distributed facilities. This [...] Read more.

The generation of waste grows yearly. In a centralized approach, more trucks are dispatched to collect the growing demand, with a higher pressure on the road network and greenhouse gas emissions. In contrast, a decentralized approach creates a network of distributed facilities. This study analyzes the impact of a decentralized approach for recyclable waste sorting facilities. It models waste generation, collection, and location of recyclable waste sorting facilities. This approach is applied to a case study in Montreal for polyethylene terephthalate. The case study computes two performance indicators: costs and CO₂ emissions. Six scenarios were developed and compared to a baseline scenario. The results show that decentralization reduces greenhouse gas emissions by 20.3% and operation costs by 8.04%. However, investment costs for the new facilities remain an obstacle. These costs can represent up to 89.7% of the expenses in a decentralized context. Nonetheless, decentralization increases the flexibility of waste collection under growing demand, since the distance to collect one ton has reduced by 35.3% and the average truck load per trip has reduced by 12.8%. To apply the model to the real world, further improvements are required. They span technical, economic, and social acceptability constraints. Full article

(This article belongs to the Special Issue Waste Management Scenario Design and Sustainability Assessment)

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18 pages, 2496 KiB

Open AccessArticle

Efficient Recovery of Gadolinium from Contaminated Waters Using Manganese Ferrite Nanoparticles

by Joana Sousa, João Pinto, Helena Barbosa, Daniela S. Tavares, Rosa Freitas, Tito Trindade, João Rocha and Eduarda Pereira

Recycling 2025, 10(2), 57; https://doi.org/10.3390/recycling10020057 - 1 Apr 2025

Viewed by 47

Abstract

The widespread use of gadolinium (Gd) in medical and industrial applications, especially as a contrast agent in magnetic resonance imaging (MRI), has led to its increasing presence in surface waters, disrupting natural geochemical cycles and posing risks to aquatic ecosystems. Addressing this challenge, [...] Read more.

The widespread use of gadolinium (Gd) in medical and industrial applications, especially as a contrast agent in magnetic resonance imaging (MRI), has led to its increasing presence in surface waters, disrupting natural geochemical cycles and posing risks to aquatic ecosystems. Addressing this challenge, recent studies have explored the potential of magnetic materials, such as spinel ferrite nanoparticles, in the removal of Gd from contaminated water sources. The present study specifically focused on the use of MnFe₂O₄ nanoparticles to remove Gd from contaminated solutions, employing response surface methodology (RSM) to optimize sorption conditions. Key variables evaluated included salinity (0–30 g/L), initial Gd concentration (1–5 μmol/L), and sorbent dose (20–180 mg/L), at a fixed pH of 6. The results revealed that salinity had a minimal impact on Gd sorption, likely due to the high sorbent mass used. Optimal conditions were identified as a sorbent dose of 165 mg/L, an initial Gd concentration of 1.3 μmol/L, and a salinity level of 13.4 g/L, at pH 6. The process was efficient and rapid, achieving over 90% Gd removal within 1 h in both freshwater and saline conditions, and over 75% removal in mineral water within 3 h. The high efficiency and celerity of this method suggest that MnFe₂O₄ nanoparticles are a promising solution for treating Gd-contaminated hospital effluents. Future research should focus on validating these results in real-world effluent matrices and addressing the environmental and economic aspects of large-scale implementation, thereby contributing to sustainable water remediation strategies. Full article

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17 pages, 3834 KiB

Open AccessArticle

Evaluation of the Removal of PVDF Using ToF-SIMS: Comparing Dihydrolevoglucosenone and Pyrolysis as Pretreatments for Cathode Materials of Lithium-Ion Batteries

by Marc Simon Henderson, Aliza Marie Salces, William D. A. Rickard, Denis Fougerouse, Álvaro José Rodríguez Medina, Elsayed A. Oraby, Chau Chun Beh, Martin Rudolph, Anna Vanderbruggen and Jacques Eksteen

Recycling 2025, 10(2), 56; https://doi.org/10.3390/recycling10020056 - 1 Apr 2025

Viewed by 82

Abstract

Effective and environmentally benign removal of polyvinylidene fluoride (PVDF) binders from spent battery electrodes remains a critical hurdle in sustainable recycling, primarily due to issues related to the mitigation of fluorinated compound emissions. This work evaluates PVDF binder removal from cathode active material [...] Read more.

Effective and environmentally benign removal of polyvinylidene fluoride (PVDF) binders from spent battery electrodes remains a critical hurdle in sustainable recycling, primarily due to issues related to the mitigation of fluorinated compound emissions. This work evaluates PVDF binder removal from cathode active material using either a green solvent-based dissolution process or pyrolysis, analyzed by time-of-flight secondary ion mass spectrometry (ToF-SIMS). The solvent pretreatment involved mixing dihydrolevoglucosenone (Cyrene™) with PVDF-coated NMC811 at 100 °C, followed by hot filtration to separate the Cyrene-PVDF solution. Pyrolysis was conducted at 800 °C under an argon atmosphere. Positive ToF-SIMS spectra for Cyrene showed characteristic peaks at ketene (42 m/z) and 1,3-dioxole (86 m/z), along with intense C₂H₃O⁺, C₃H₃O⁺, C₄H₇⁺, and C₃H₅O⁺ peaks. The characteristic peaks used to identify PVDF were C₃H₂F₅⁺ (133 m/z), C₃H₂F₃⁺ (95 m/z), and C₃HF₄⁺ (113 m/z). Both processes resulted in PVDF removal, with pyrolysis demonstrating higher effectiveness. Particle agglomeration was observed in both pretreated NMC811 samples, however agglomeration was more pronounced with Cyrene pretreatment due to PVDF redeposition. Following pyrolysis, PVDF was transformed into a defluorinated carbonaceous material. Full article

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

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21 pages, 11384 KiB

Open AccessArticle

Optimization of the Recycling Process for Aligned Short Carbon Fiber TuFF Composites

by Uday Kiran Balaga, Aydin Gunes, Tekin Ozdemir, Chris Blackwell, Mark Davis, Steven Sauerbrunn, Lukas Fuessel, Joseph M. Deitzel and Dirk Heider

Recycling 2025, 10(2), 55; https://doi.org/10.3390/recycling10020055 - 1 Apr 2025

Viewed by 63

Abstract

Recycling of carbon fibers enables a sustainable feedstock for industrial applications of high-performance composite materials. This allows light weighting with recycled carbon fibers due to their superior mechanical properties while reducing the high embodied energy and cost of virgin carbon fiber composites. This [...] Read more.

Recycling of carbon fibers enables a sustainable feedstock for industrial applications of high-performance composite materials. This allows light weighting with recycled carbon fibers due to their superior mechanical properties while reducing the high embodied energy and cost of virgin carbon fiber composites. This study optimizes a pyrolysis cycle for fiber recovery of an aerospace-grade thermoset prepreg and a cleaning (oxidation) step to minimize fiber degradation and left-over resin residue, enabling dispersion and alignment of the recycled, discontinuous fibers in the Tailorable Universal Feedstock for Forming alignment process. The study balances the influence of the optimized thermal cycle (pyrolysis + oxidation step) on recycled carbon fiber strength retention with the ability to disperse at the filament level to create aligned, recycled carbon fiber composite samples with high fiber volume fraction. The optimized thermal cycle for efficient fiber recovery applied a pyrolysis step at 500 °C for 4 h in an inert gas environment and an additional oxidation step at the same temperature for 100 min. This resulted in ~20% strength degradation of the fiber compared to the virgin fiber. The processed recycled composite achieved 44% fiber volume fraction with full modulus translation (~128 GPa) compared to the virgin continuous composite with strength translation (~870 MPa), reaching ~50%. Full article

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

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16 pages, 4676 KiB

Open AccessArticle

The Characterization of Black Mass from Spent Lithium-Ion Scooter Batteries Using Multi-Analytical Techniques

by Mahsa Pourmohammad, Josep Oliva Moncunill, Hernan Anticoi, Carlos Hoffmann Sampaio, Pura Alfonso, César Valderrama and Jose Luis Cortina Pallas

Recycling 2025, 10(2), 54; https://doi.org/10.3390/recycling10020054 - 1 Apr 2025

Viewed by 63

Abstract

The process of recycling lithium-ion batteries is drawing global attention due to a shortage of critical raw materials (CRMs), a sustainable and environmentally friendly approach that meets the needs of many industries. Characterization is an important step in the recycling of black mass [...] Read more.

The process of recycling lithium-ion batteries is drawing global attention due to a shortage of critical raw materials (CRMs), a sustainable and environmentally friendly approach that meets the needs of many industries. Characterization is an important step in the recycling of black mass resulting from the processing of a lithium-ion battery at the beginning and the end of the processes because of the complexity of the feed material and to evaluate the process. This research proposes a beneficiation flowchart for the further separation of graphite particles from metal oxides based on the characterization results by combining scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), laser-induced breakdown spectroscopy, laser scattering particle size distribution analysis, X-ray fluorescence (XRF), X-ray diffraction analysis (XRD), inductively coupled plasma–optical emission spectroscopy (ICP-OES), and thermogravimetry–differential thermal analysis (TG/DTA). Based on these characterization results, it is suggested that black mass with coarser particle size (0.2–1 mm) goes to the liberation process for beneficiation of the Al and Cu and black mass with a size range of 0.053–0.2 mm goes to the froth flotation for beneficiation of the Mn, Ni, Fe, and Co. Finally, a black mass with a size range of <0.053 mm goes through the froth flotation after the agglomeration process. Full article

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14 pages, 3797 KiB

Open AccessArticle

Effect of PCL Nanocomposite Coatings on the Recyclability of Paperboard Packaging

by Marina Vukoje and Josip Bota

Recycling 2025, 10(2), 53; https://doi.org/10.3390/recycling10020053 - 1 Apr 2025

Viewed by 49

Abstract

When it comes to the disposal of paperboard and cardboard packaging waste to reduce their environmental impact, recycling is one of the most desirable options. With innovations and development of biopolymer coatings and their application in packaging materials, new paper-based packaging solutions are [...] Read more.

When it comes to the disposal of paperboard and cardboard packaging waste to reduce their environmental impact, recycling is one of the most desirable options. With innovations and development of biopolymer coatings and their application in packaging materials, new paper-based packaging solutions are expected on the market. Besides evaluating their mechanical and barrier properties, it is essential to assess their environmental impact. Therefore, this study investigated the impact of biodegradable polycaprolactone (PCL) polymer coating, as well as PCL modified with SiO₂, Al₂O₃, and ZnO nanoparticles, on the recycling behavior of paperboard. The coating samples were prepared by dissolving PCL polymer in ethyl acetate and nanoparticle dispersion. Paperboard (230 g/m²) was printed by offset printing process and then coated with PCL and PCL nanocomposite coatings. Recycling was performed under controlled laboratory conditions following a standardized method. Deinkability was assessed by evaluating the optical properties and using an image analysis system. From the obtained results, it can be concluded that the use of PCL coatings and PCL coating modified with SiO₂, Al₂O₃, and ZnO nanoparticles do not significantly impact the optical properties of the recycled pulp, thereby not restricting the implementation in paperboard production and waste management. Full article

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19 pages, 4959 KiB

Open AccessArticle

Exploring Refuse-Derived Fuel Production from Seafood-Processing Sludge and Landfill-Mined Plastic Waste Co-Pelletization

by Wittawat Wulyapash, Awassada Phongphiphat, Johann Fellner and Sirintornthep Towprayoon

Recycling 2025, 10(2), 52; https://doi.org/10.3390/recycling10020052 - 20 Mar 2025

Viewed by 216

Abstract

This study explores the co-pelletization of sludge with landfill-mined plastic waste as a method to create high-energy refuse-derived fuel (RDF), addressing both plastic and sludge waste streams. Key variables used in RDF pelletization included sludge-to-plastic mixing ratios (50:50, 75:25, and 100:0 wt%), mold [...] Read more.

This study explores the co-pelletization of sludge with landfill-mined plastic waste as a method to create high-energy refuse-derived fuel (RDF), addressing both plastic and sludge waste streams. Key variables used in RDF pelletization included sludge-to-plastic mixing ratios (50:50, 75:25, and 100:0 wt%), mold temperatures (100 °C and 120 °C), and compression pressures (60–80 MPa). Results showed that the characteristics of pellets improved considerably as the mass percentage of plastic waste increased. The 75% sludge mixture produced pellets with high compressive strength (15.9–16.4 MPa), indicating rigid and ductile properties, and achieved a calorific value of up to 33.4 MJ/kg. Mercury levels of the RDF (0.02–0.04 mg/MJ) met solid recovered fuel standards. However, the elevated chlorine content (>3 wt%_db) highlighted the necessity of removing PVC from the plastic waste before pelletization. Carbon emission factors for the pellets (23–25 kg CO₂/GJ) were comparable to commercial RDFs and notably lower than coal, demonstrating their potential as a sustainable alternative fuel source. An assessment of the entire production and utilization chain, including sludge drying, plastic sorting, pelletization, and combustion, revealed that co-pelletization reduces greenhouse gas emissions by more than 24.3% compared to current practices. Full article

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20 pages, 5667 KiB

Open AccessArticle

Performance of Cement Composites with Partial Replacement with Organic Aggregate from Waste Coconut Shell

by Yurii Barabanshchikov, Kseniia Usanova and Alexandra Koneva

Recycling 2025, 10(2), 51; https://doi.org/10.3390/recycling10020051 - 20 Mar 2025

Viewed by 194

Abstract

The properties of cement composites with a partial replacement of sand with an organic aggregate from coconut shell are investigated. Due to the fact that the endocarp of coconut shell increases its volume up to 60–70% when swelling in water, which is many [...] Read more.

The properties of cement composites with a partial replacement of sand with an organic aggregate from coconut shell are investigated. Due to the fact that the endocarp of coconut shell increases its volume up to 60–70% when swelling in water, which is many times greater than the volumetric deformation of the swelling of the cement matrix, the possibility of obtaining a cement composition capable of withstanding alternating deformations of wetting and drying was investigated in this work. When replacing 50% of the sand with coarse coconut aggregate of the fraction 5–20 mm, starting from the 5th–10th cycle of wetting–drying, progressive expansion and cracking of 28-day samples took place. When using a fine coconut aggregate fraction < 2.5 mm and replacing sand from 2 to 15%, a slight accumulated expansion was observed only in the first 4–5 test cycles, then accumulated shrinkage followed. A gradual decrease in the average weight of the samples from cycle to cycle was established. The loss of mass of the samples increases with the increase in the percentage of replacement of sand with coconut aggregate. Partial replacement of sand with fine coconut aggregate from 2 to 15% by weight reduces the bending and compressive strength of cement mortar from 14 to 40%. Full article

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38 pages, 2822 KiB

Open AccessReview

The Role of the Triple Helix Model in Promoting the Circular Economy: Government-Led Integration Strategies and Practical Application

by Maximilian Espuny, José Salvador da Mota Reis, Elen Cristina Bravos Giupponi, Aglaé Baptista Torres Rocha, Ana Carolina Ferreira Costa, Camila Fabricio Poltronieri and Otávio José de Oliveira

Recycling 2025, 10(2), 50; https://doi.org/10.3390/recycling10020050 - 20 Mar 2025

Viewed by 327

Abstract

The Circular Economy (CE) has become an essential management model to address the environmental challenges of the traditional linear model employed by companies, protecting society and ecosystems from resource depletion and intensified ecological emissions. Thus, this study proposes a framework with recommendations for [...] Read more.

The Circular Economy (CE) has become an essential management model to address the environmental challenges of the traditional linear model employed by companies, protecting society and ecosystems from resource depletion and intensified ecological emissions. Thus, this study proposes a framework with recommendations for CE implementation, structured around the Triple Helix (TH) model and designed to be government-led in guiding joint actions among government, organizations, and academia. The framework comprises 21 recommendations distributed across six interconnected stages: (1) Policy Generation from Academic Inputs, (2) Development of Pilot Projects with Industry, (3) Analysis and Academic Validation of Results, (4) Policy Improvement and Scaling, (5) Promotion of Innovation and Technology Transfer, and (6) Global Connection and Replicability. These stages collectively enhance policies and practices, accelerating the transition to a CE. This framework underscores the importance of regionally adapted public policies, technological innovations to extend material lifespans, and the promotion of conscious consumption. It also emphasizes the need for intersectoral collaboration to foster sustainability and efficiency in resource management. Methodologically, this study employs an integrative review to map technical and scientific CE practices in the United Kingdom, China, and the United States. The theoretical contribution validates the TH model as a strategic tool for developing the CE. Furthermore, the practical contribution is the structured pathway to implementing the CE, detailing the main phases of collaboration among TH actors to ensure the effective operationalization of circular strategies. Full article

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28 pages, 725 KiB

Open AccessArticle

Lost Institutional Memory and Policy Advice: The Royal Society of Arts on the Circular Economy Through the Centuries

by Pierre Desrochers

Recycling 2025, 10(2), 49; https://doi.org/10.3390/recycling10020049 - 19 Mar 2025

Viewed by 112

Abstract

Circular economy theorists and advocates typically describe traditional market economies as linear “take, make, use and dispose” systems. Various policy interventions, from green taxes to extended producer responsibility, are therefore deemed essential to ensure the systematic (re)introduction of residuals, secondary materials and components [...] Read more.

Circular economy theorists and advocates typically describe traditional market economies as linear “take, make, use and dispose” systems. Various policy interventions, from green taxes to extended producer responsibility, are therefore deemed essential to ensure the systematic (re)introduction of residuals, secondary materials and components in manufacturing activities. By contrast, many nineteenth- and early twentieth-century writers documented how the profit motive, long-distance trade and actors now largely absent from present-day circularity discussions (e.g., waste dealers and brokers) spontaneously created ever more value out of the recovery of residuals and waste. These opposite assessments and underlying perspectives are perhaps best illustrated in the nineteenth classical liberal and early twenty-first century interventionist writings on circularity of Fellows, members and collaborators of the near tricentennial British Royal Society for the Encouragement of Arts, Manufactures and Commerce. This article summarizes their respective contributions and compares their stance on market institutions, design, intermediaries, extended producer responsibility and long-distance trade. Some hypotheses as to the sources of their analytical discrepancies and current beliefs on resource recovery are then discussed in more detail. A final suggestion is made that, if the analysis offered by early contributors is more correct, then perhaps the most important step towards greater circularity is regulatory reform (or deregulation) that would facilitate the spontaneous recovery of residuals and their processing in the most suitable, if sometimes more distant, locations. Full article

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27 pages, 3758 KiB

Open AccessReview

Recycling or Sustainability: The Road of Electric Vehicles Toward Sustainable Economy via Blockchain

by Katarina Dimic-Misic, Shailesh Singh Chouhan, Vesna Spasojević Brkić, Milica Marceta-Kaninski and Michael Gasik

Recycling 2025, 10(2), 48; https://doi.org/10.3390/recycling10020048 - 19 Mar 2025

Viewed by 265

Abstract

This semi-systematic review paper discusses four research questions based on findings from the last 10 years: What are the crucial issues in the ongoing debate on the development of the electric vehicle (EV) concept? Where are the major conflicting points and focuses between [...] Read more.

This semi-systematic review paper discusses four research questions based on findings from the last 10 years: What are the crucial issues in the ongoing debate on the development of the electric vehicle (EV) concept? Where are the major conflicting points and focuses between sustainable economy and EVs? How does the mining of metals and minerals follow current zero-waste sustainability trends, and how does the prediction of the magnitude of the future demand for EV batteries guide strategic decision-making in policies throughout the globe? As it is not easy to currently predict how metals necessary for EV productions will be produced, this article suggests a strategy that is diverse regarding its approaches to shaping the sustainable mining and further development of EVs, along with the involvement of urban planning. Using broad literature and a published pool of prediction scenarios, we provide a comprehensive assessment of future EV battery raw materials development under a range of scenarios, accounting for factors such as developments in battery technology, variations in the EV fleet composition, sustainability aspects of development of second use and recycling technologies. Additionally, this paper demonstrates how blockchain technology is likely to force mineral and metal supply chains to become significantly more traceable and transparent. Full article

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14 pages, 3111 KiB

Open AccessArticle

Study of the Effect of Temperature to Optimize the Anaerobic Digestion of Slaughterhouse Sludge by Co-Digestion with Slaughterhouse Wastewater

by Maria Candel, Laura Ballesteros, Juana Fernandez-Rodriguez, Montserrat Perez and Rosario Solera

Recycling 2025, 10(2), 47; https://doi.org/10.3390/recycling10020047 - 19 Mar 2025

Viewed by 195

Abstract

The anaerobic co-digestion (ACoD) of sludge (S) and slaughterhouse wastewater (SW) can improve biomethane production and removal efficiency in terms of organic matter. The aim of this study was to determine the impact of temperature on co-digestion, considering different hydraulic retention times (HRTs). [...] Read more.

The anaerobic co-digestion (ACoD) of sludge (S) and slaughterhouse wastewater (SW) can improve biomethane production and removal efficiency in terms of organic matter. The aim of this study was to determine the impact of temperature on co-digestion, considering different hydraulic retention times (HRTs). The substrates were selected at a 50:50 weight ratio and two single-stage digesters of 2 L capacity were used, operating under ideal thermophilic (55 °C) and mesophilic (35 °C) conditions. The HRTs studied were 30, 25, 20 and 15 days. The biomethane production reached 588 mL CH₄/d at 55 °C and 477 mL CH₄/d at 35 °C for an HRT of 15 days, indicating a significantly higher yield under the thermophilic process. The volatile solids removal efficiency ranged from 41% to 66% for the thermophilic digester and between 32% and 42% for the mesophilic digester. This further highlights the superior performance at higher temperatures. Full article

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20 pages, 1068 KiB

Open AccessArticle

FTIR-Based Microplastic Classification: A Comprehensive Study on Normalization and ML Techniques

by Octavio Villegas-Camacho, Iván Francisco-Valencia, Roberto Alejo-Eleuterio, Everardo Efrén Granda-Gutiérrez, Sonia Martínez-Gallegos and Daniel Villanueva-Vásquez

Recycling 2025, 10(2), 46; https://doi.org/10.3390/recycling10020046 - 18 Mar 2025

Viewed by 286

Abstract

This study examines the potential of machine learning (ML) and deep learning (DL) techniques for classifying microplastics using Fourier-transform infrared (FTIR) spectroscopy. Six commonly used industrial plastics (PET, HDPE, PVC, LDPE, PP, and PS) were analyzed. A significant contribution of this research is [...] Read more.

This study examines the potential of machine learning (ML) and deep learning (DL) techniques for classifying microplastics using Fourier-transform infrared (FTIR) spectroscopy. Six commonly used industrial plastics (PET, HDPE, PVC, LDPE, PP, and PS) were analyzed. A significant contribution of this research is the use of broader and more varied spectral ranges than those typically reported in the state of the art. Furthermore, the impact of different normalization techniques (Min-Max, Max-Abs, Sum of Squares, and Z-Score) on classification accuracy was evaluated. The study assessed the performance of ML algorithms, such as k-nearest neighbors (k-NN), support vector machines (SVM), naive Bayes (NB), random forest (RF), and artificial neural networks architectures (including convolutional neural networks (CNNs) and multilayer perceptrons (MLPs)). Models were trained and validated using the FTIR-PLASTIC-c4 dataset with a 10-fold cross-validation approach to ensure robustness. The results showed that Z-score normalization significantly improved stability and generalization across most models, with CNN, MLP, and RF achieving near-perfect values in accuracy, precision, recall, and F1-score. In contrast, the sum of squares normalization was less effective, particularly for CNNs, due to its sensitivity to scale and data distribution. Notably, naive Bayes consistently underperformed because of its limitations in analyzing complex spectral data. The findings highlight the effectiveness of FTIR spectra with broad and variable ranges for the automated classification of microplastics using ML techniques, along with appropriate normalization methods. Full article

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

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17 pages, 3558 KiB

Open AccessArticle

Sustainable Fire-Resistant Materials: Recycled Polyethylene Composites with Non-Halogenated Intumescent Flame Retardants for Construction Applications

by Oluwatobi Elijah Akindele, Erick Gabriel Ribeiro dos Anjos, Antonio Benjamim Mapossa and Uttandaraman Sundararaj

Recycling 2025, 10(2), 45; https://doi.org/10.3390/recycling10020045 - 13 Mar 2025

Viewed by 264

Abstract

This study explores the development of sustainable fire-resistant composites using a blend of recycled linear low-density polyethylene (rLLDPE) and low-density polyethylene (rLDPE) for construction applications. The incorporation of non-halogenated intumescent flame retardants (IFRs), specifically ammonium polyphosphate (APP) and melamine polyphosphate (MPP), was shown [...] Read more.

This study explores the development of sustainable fire-resistant composites using a blend of recycled linear low-density polyethylene (rLLDPE) and low-density polyethylene (rLDPE) for construction applications. The incorporation of non-halogenated intumescent flame retardants (IFRs), specifically ammonium polyphosphate (APP) and melamine polyphosphate (MPP), was shown to enhance the flame retardance, thermal stability, and mechanical performance of these recycled polymer blends. IFRs were introduced at 5 wt.% and 10 wt.% concentrations, and their effects were evaluated using limiting oxygen index (LOI) testing and thermogravimetric analysis (TGA). Results showed that 10 wt.% APP and a combination of 5 wt.% APP with 5 wt.% MPP increased LOI values from 18.5% (neat polymer blend) to 21.2% and 22.4%, respectively, demonstrating improved fire resistance. Enhanced char formation, facilitated by IFRs, contributes to superior thermal stability and fire protection. TGA results confirmed higher char yields, with the rLLDPE/rLDPE/MPP5/APP5 composition exhibiting the highest residue (3.00%), indicating a synergistic effect between APP and MPP. Rheological and mechanical analysis showed that APP had more impact on viscoelastic behavior, while the combination of IFRs provided balanced mechanical properties despite a slight reduction in tensile strength. This research highlights the potential of recycled polyethylene composites in promoting circular economy principles by developing sustainable, fire-resistant materials for the construction industry, reducing plastic waste, and enhancing the safety of recycled polymer-based applications. Full article

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19 pages, 1415 KiB

Open AccessArticle

Carbon Footprint of Composting and Vermicomposting of Household Biowaste: A Decision-Making Factor for Regional Biowaste Recovery Policies?

by Chantal Berdier, Muriel Maillefert and Mathilde Girault

Recycling 2025, 10(2), 44; https://doi.org/10.3390/recycling10020044 - 12 Mar 2025

Viewed by 453

Abstract

Since 1 January 2024, French local authorities will be required to offer householders a means of recovering biowaste, either as a soil improver or as an energy source. Several criteria influence their choice: cost, availability of operators and equipment, social facilitation, etc. However, [...] Read more.

Since 1 January 2024, French local authorities will be required to offer householders a means of recovering biowaste, either as a soil improver or as an energy source. Several criteria influence their choice: cost, availability of operators and equipment, social facilitation, etc. However, greenhouse gas (GHG) emissions are rarely taken into account in the decision-making process. This article compares the emissions of four biowaste recovery systems, differentiated by their process (composting or vermicomposting) and management type (community or industrial). It is based on the carbon footprint method defined by the French Agency for Ecological Transition (ADEME). The assumptions and emission factors come from two sources: a field survey of composting and vermicomposting companies and associations in the Lyon area and a review of the literature on GHG emissions from the decomposition of organic matter. The carbon footprint of the processes was determined by estimating the CO₂ equivalent per ton of composted biowaste. The results show that industrial composting emits the most carbon (CO₂). Depending on whether biogenic carbon is taken into account or not, the ranking of the other three processes changes. When biogenic CO₂ is taken into account, it is the process that has the greatest influence on the result; on the other hand, when biogenic CO₂ emissions are not taken into account, the type of management determines the ranking. These results are discussed in relation to the methodological limitations of the comparison, other biowaste management options and the reduction of biowaste-related emissions. For example, by studying the agricultural use of biowaste compost, the carbon balance could be refined by including the emissions avoided from the production of nitrogen fertiliser. However, environmental assessment is only one of a number of decision-making factors (social, economic, agricultural, etc.) in waste management. Full article

(This article belongs to the Special Issue Waste Management Scenario Design and Sustainability Assessment)

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16 pages, 6286 KiB

Open AccessArticle

Technospheric Mining of Cobalt and Nickel from Waste Nickel Furnace Slag by Ascorbic Acid-Assisted Citric Acid Leaching

by K. Yamini, Laurence Dyer, Bona Lim and Richard Diaz Alorro

Recycling 2025, 10(2), 43; https://doi.org/10.3390/recycling10020043 - 12 Mar 2025

Viewed by 310

Abstract

With the growing demand for critical metals, extraction from secondary sources such as slag, tailings, and end-of-life materials has become inevitable. Processing from such secondary sources is described as technospheric mining. Technospheric mining is a broad term for extracting valuable resources from anthropogenic [...] Read more.

With the growing demand for critical metals, extraction from secondary sources such as slag, tailings, and end-of-life materials has become inevitable. Processing from such secondary sources is described as technospheric mining. Technospheric mining is a broad term for extracting valuable resources from anthropogenic materials that are currently excluded from the material flow. The study utilises technospheric mining to extract cobalt and nickel from nickel furnace slag using organic acids such as ascorbic and citric acid. The experiments were designed using one variable at a time (OVAT) to optimise the different parameters: temperature, time, particle size, and reagent concentration. A maximum recovery of 79% Co and 80% Ni were obtained by leaching the nickel furnace slag using 0.5 mol/L citric acid and 0.5 mol/L ascorbic acid for 6 h at 80 °C. It is proposed that citric acid leaches the surface and ascorbic acid acts as a reducing agent, thereby reducing the slag matrix and leaching the metals trapped in it. The results show that treating nickel furnace slag via a mixture of organic acids is promising, as it is environmentally friendly. Retreating this material would reduce the net waste generated and aid in building a circular economy. Full article

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

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17 pages, 5964 KiB

Open AccessArticle

Recycling Decommissioned Wind Turbine Blades for Post-Disaster Housing Applications

by Cihan Turhan, Murat Durak, Yousif Abed Saleh Saleh and Alper Kalaycı

Recycling 2025, 10(2), 42; https://doi.org/10.3390/recycling10020042 - 12 Mar 2025

Viewed by 278

Abstract

The growing adoption of wind energy has resulted in an increasing number of decommissioned wind turbine blades, which pose significant disposal challenges due to their size, material composition, and environmental impact. Recycling these blades has thus become essential. To this aim, this study [...] Read more.

The growing adoption of wind energy has resulted in an increasing number of decommissioned wind turbine blades, which pose significant disposal challenges due to their size, material composition, and environmental impact. Recycling these blades has thus become essential. To this aim, this study explores the potential of using recycled wind turbine blades in post-disaster housing applications and examines the feasibility of re-purposing these durable composite materials to create robust, cost-effective, and sustainable building solutions for emergency housing. A case study of a post-earthquake relief camp in Hatay, Türkiye, affected by the 2023 earthquake, is used for analysis. First, the energy consumption of thirty traditional modular container-based post-disaster housing units is simulated with a dynamic building simulation tool. Then, the study introduces novel wind turbine blade-based housing (WTB-bH) designs developed using the same simulation tool. The energy consumption of these (WTB-bH) units is compared to that of traditional containers. The results indicate that using recycled wind turbine blades for housing not only contributes to waste reduction but also achieves 27.3% energy savings compared to conventional methods. The novelty of this study is in demonstrating the potential of recycled wind turbine blades to offer durable and resilient housing solutions in post-disaster situations and to advocate for integrating this recycling method into disaster recovery frameworks, highlighting its ability to enhance sustainability and resource efficiency in construction. Overall, the output of this study may help to present a compelling case for the innovative reuse of decommissioned wind turbine blades, providing an eco-friendly alternative to traditional waste disposal methods while addressing critical needs in post-disaster scenarios. Full article

(This article belongs to the Topic Sustainable Building Materials)

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51 pages, 13853 KiB

Open AccessArticle

Prospective Use and Assessment of Recycled Plastic in Construction Industry

by Aaroon Joshua Das and Majid Ali

Recycling 2025, 10(2), 41; https://doi.org/10.3390/recycling10020041 - 11 Mar 2025

Viewed by 848

Abstract

The accumulation of plastic waste poses a significant environmental challenge, necessitating sustainable solutions. This study investigates the potential of recycling waste plastics for use in the construction industry, emphasizing their integration into building materials and components. Earlier waste plastic recycling was excessively studied [...] Read more.

The accumulation of plastic waste poses a significant environmental challenge, necessitating sustainable solutions. This study investigates the potential of recycling waste plastics for use in the construction industry, emphasizing their integration into building materials and components. Earlier waste plastic recycling was excessively studied as an ingredient in concrete composites, roads, and other use in research. However, in this study, recycled plastic is assessed for use as a sole material for structural products. Raw plastics, including high-density polyethylene, Low-Density Polyethylene, polypropylene, polyolefin, samicanite, and virgin polyethylene, were analyzed for recycling through mechanical extrusion, and their mechanical properties were analyzed to determine their feasibility for construction applications. In this study, the extrusion process, combined with engineered dyes, was investigated with comprehensive material testing as per the ASTM standards to obtain the properties desired for construction. Advanced characterization techniques, including SEM, FTIR, and TGA, were employed to evaluate the chemical composition, thermal stability, and impurities of these waste plastics collected from municipal waste. A gas emission analysis during extrusion confirmed a minimal environmental impact, validating the sustainability of the recycling process. Municipal waste plastic has a considerable quantum of HDPE, PP, and LDPE, which was considered in this research for recycling for construction products. A total of 140 samples were recycled through extrusion and tested across shear, flexural, tensile, and compression categories: 35 samples each. The results showed that rHDPE and PP had good tensile strength and shear resistance. The findings pave the way for developing cost-effective, durable, and eco-friendly building materials, such as rebars, corrugated sheet, blocks, and other products, contributing to environmental conservation and resource efficiency for the construction Industry. Full article

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26 pages, 4595 KiB

Open AccessArticle

COVID-19 Induced Changes in Residual Municipal Waste Management in Provincial Territories of the Marche Region (Italy): Flow Analysis and Environmental Assessment

by Massimiliano Boccarossa, Lidia Lombardi, Fabio Tatàno, Adele Folino, Valentina Spadi, Francesca Tuci and Piero Sirini

Recycling 2025, 10(2), 40; https://doi.org/10.3390/recycling10020040 - 10 Mar 2025

Viewed by 212

Abstract

The COVID-19 pandemic posed challenges to pre-crisis waste management systems. In this study, two sequential scenarios were identified and compared to investigate the quantitative and environmental impacts of COVID-19 induced changes in the generation and management of residual municipal waste (RMW) in two [...] Read more.

The COVID-19 pandemic posed challenges to pre-crisis waste management systems. In this study, two sequential scenarios were identified and compared to investigate the quantitative and environmental impacts of COVID-19 induced changes in the generation and management of residual municipal waste (RMW) in two provincial territories (PT_PU, PT_MC) of the Marche region (Central Italy, Adriatic Sea side). The pandemic implied, in 2020 (COVID-19 scenario), quantitative reductions in RMW compared to the preceding year, 2019 (Pre-COVID-19 scenario), which were limited to −3.9 and −1.9% in PT_PU and PT_MC, respectively. Life cycle assessment (LCA) results showed that adapted RMW management practices in 2020 (COVID-19 scenario) improved all the considered environmental indicators in PT_MC, compared to the preceding year, 2019 (Pre-COVID-19 scenario), and most of them in PT_PU, with the exception of climate change (CC), human toxicity, non-cancer (HTnc), and eutrophication, marine (Em). The hypothetical option of waste-to-energy (WtE) for the RMW, originally destined for direct landfilling in 2020 (COVID-19 scenario), would have represented a safe and environmentally sound option in terms of health protection and CC indicator. Full article

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14 pages, 3473 KiB

Open AccessArticle

Characterization and Property Evaluation of Glasses Made from Mine Tailings, Glass Waste, and Fluxes

by Miguel Ángel Escobedo-Bretado, Patricia Ponce-Peña, Martha Poisot, Alicia Rodríguez-Pulido, Diola Marina Núñez-Ramírez, Luis Alberto Bretado-Aragón, René H. Lara, Luis Medina-Torres, Zoe V. Quiñones-Jurado, Roberto Briones-Gallardo and María Azucena González-Lozano

Recycling 2025, 10(2), 39; https://doi.org/10.3390/recycling10020039 - 9 Mar 2025

Viewed by 333

Abstract

The present investigation introduces a novel approach, using As-Zn-Fe mining tailings (MT) and recycled bottle glass (cullet) to enable the manufacturing of a new glass for ornamental articles, with characteristics similar to those of soda–lime–silicate glass (SLS), and at the same time, immobilizing [...] Read more.

The present investigation introduces a novel approach, using As-Zn-Fe mining tailings (MT) and recycled bottle glass (cullet) to enable the manufacturing of a new glass for ornamental articles, with characteristics similar to those of soda–lime–silicate glass (SLS), and at the same time, immobilizing potentially toxic elements (PTEs) from mining tailings, which cause environmental pollution with severe risks to human health. The glass used was obtained from transparent glass bottles collected from urban waste, which were later washed to remove impurities and then crushed until they reached No. 70 mesh (212 μm) level; in the case of mining tailings, the sample used comes from the ore benefit process, with 96.8% of particles below the No. 50 mesh level (300 μm). Six mixtures were made by varying the composition of the mining tailings and glass, K₂CO₃ and H₃BO₃ as fluxes were also used in constant proportion. The mixtures were melted at 1370 °C, and later, the glass samples were cast on a steel plate at room temperature. The characteristics of the glasses were studied using thermal analysis (TA), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM). Likewise, their chemical resistance in acid and basic media and density were evaluated. The results unequivocally demonstrate the feasibility of manufacturing glasses with a light green color, the increase in the content of mining tailings increased the apparent T_g from 625 to 831 °C. Glasses with 17 and 21.3% MT presented lower density values due to a better-polymerized glass structure, attributed to the increase in SiO₂ and Al₂O₃ and the decrease in alkaline oxides, which allowed for the retention of PTEs in their structure. Full article

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21 pages, 1803 KiB

Open AccessArticle

Evaluation of the Potential for the Development of the Circular Industry in the Region: A New Approach

by Olga I. Dolgova and Anastasia Y. Nikitaeva

Recycling 2025, 10(2), 38; https://doi.org/10.3390/recycling10020038 - 7 Mar 2025

Viewed by 295

Abstract

The construction of circular economic models in industry represents a critical mechanism for achieving sustainable development goals. However, data on the development of the circular economy, derived from diverse metrics and assessment methodologies, often yield contradictory results. In light of this, the study [...] Read more.

The construction of circular economic models in industry represents a critical mechanism for achieving sustainable development goals. However, data on the development of the circular economy, derived from diverse metrics and assessment methodologies, often yield contradictory results. In light of this, the study suggested a new approach to evaluating the potential for circularization. This approach entails identifying key factors influencing circularization and assessing their suitability for the implementation of circular models of different levels. The study identified factors and indicators of the potential for industrial circularization at the regional level. The paper proposed a classification of circular economy models that simultaneously take into account the length of the production cycle and the degree of proximity to the circular economy. The rating method is employed to evaluate the potential of a region for the successful implementation of circular economy models. The rating is calculated by constructing both a general integral circularization potential index and individual sub-indices. The application of this methodology enabled the development of a ranking of Russian regions based on their potential for industrial circularization. To make recommendations, the analyzed regions were divided into four groups, according to an evaluation of the circularization potential. Full article

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14 pages, 799 KiB

Open AccessArticle

Recycling of Post-Consumer Polystyrene Packaging Waste into New Food Packaging Applications—Part 3: Initial Contamination Levels in Washed Flakes from Europe

by Valeria Guazzotti and Frank Welle

Recycling 2025, 10(2), 37; https://doi.org/10.3390/recycling10020037 - 7 Mar 2025

Viewed by 138

Abstract

Polystyrene pots and trays are a promising input material for a closed packaging-to-packaging cycle. For the evaluation of the food law compliance it is necessary to know the possible contamination with substances from the first use but also from cross-contamination during recollection or [...] Read more.

Polystyrene pots and trays are a promising input material for a closed packaging-to-packaging cycle. For the evaluation of the food law compliance it is necessary to know the possible contamination with substances from the first use but also from cross-contamination during recollection or even from possible misuse of the packing for storage of hazardous chemicals. As part of the study, 49 conventionally recycled PS samples from six European countries were analyzed for contamination. A rapid screening method was used, which has already been applied to PET recyclates. The 30 most highly concentrated substances were semi-quantified and identified. Overall, 10,310 individual post-consumer PS packages were investigated. Evidence of misuse of the PS pots and trays was found in one samples with the substance pinene at a concentration of 475 to 711 mg/kg. The incidence of misuse is therefore 0.0097%. The maximum initial concentration was determined 0.069 mg/kg or to 0.65 mg/kg under worst-case assumptions. Based on the data, an initial concentration of 1 mg/kg in post-consumer washed post-consumer rPS flakes is suggested as pragmatic worst-case approach in the evaluation of consumer safety of rPS containing food packaging. Full article

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9 pages, 773 KiB

Open AccessCommunication

Precise and Accurate Assessment of the Copper Scrap Composition by the X-Ray Fluorescence Spectrometry

by Jacek Anyszkiewicz, Sonia Kasierot, Tadeusz Gorewoda and Justyna Kostrzewa

Recycling 2025, 10(2), 36; https://doi.org/10.3390/recycling10020036 - 4 Mar 2025

Viewed by 437

Abstract

This paper evaluates the possibility of analyzing the composition of high-quality copper scrap with X-ray fluorescence spectrometry (XRF) instead of electrogravimetry combined with flame atomic absorption spectroscopy (EG+FAAS) method. The evaluation of the methods was performed on three real copper scraps, the composition [...] Read more.

This paper evaluates the possibility of analyzing the composition of high-quality copper scrap with X-ray fluorescence spectrometry (XRF) instead of electrogravimetry combined with flame atomic absorption spectroscopy (EG+FAAS) method. The evaluation of the methods was performed on three real copper scraps, the composition of which were estimated in average samples taken after re-melting. Traceability of XRF results was ensured by the use of new certified reference materials (CRMs) dedicated to copper scrap analysis. The copper content results obtained by XRF were characterized by high agreement with the reference results obtained by EG+FAAS method. The estimated expanded uncertainty for Cu of both methods was 0.23%. In addition to significant time savings without compromising accuracy, the XRF method additionally provided information on the content of 12 other elements, such as Sn, Zn, Co, Cd, Sb, Ni, Fe, Pb, Bi, Ag, Al, and P. This may make the XRF method attractive compared to the commonly used EG+FAAS method. Full article

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22 pages, 7568 KiB

Open AccessArticle

Developing a Chemical Process for Optimizing Oil Extraction from Cooking Oil Secondary Waste

by Satyanarayana Narra and Masoud Shahpasand

Recycling 2025, 10(2), 35; https://doi.org/10.3390/recycling10020035 - 3 Mar 2025

Viewed by 406

Abstract

Waste generated during used cooking oil (UCO) collection poses significant environmental challenges due to its high oil content. This study investigates the efficacy of coagulation and flocculation in separating oil from cooking oil secondary waste (COSW), which typically contains 53% oil. Two additives, [...] Read more.

Waste generated during used cooking oil (UCO) collection poses significant environmental challenges due to its high oil content. This study investigates the efficacy of coagulation and flocculation in separating oil from cooking oil secondary waste (COSW), which typically contains 53% oil. Two additives, aluminum sulfate (Alum—Al₂(SO₄)₃) and polyacrylamide (PAM), were employed to enhance the separation process. Experimental results demonstrate that the combined application of coagulation and flocculation using these additives achieved 82% oil removal efficiency. These findings suggest a promising approach for recovering valuable oil resources from COSW while addressing environmental concerns associated with its improper disposal. Full article

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29 pages, 3818 KiB

Open AccessArticle

Supply Chain (Re)Design and Pricing for Biomass Ash Valorization as Supplementary Cementitious Materials

by Juan G. Villegas, Germán Álvarez-López, Leyla Y. Jaramillo and Manuel Romero-Sáez

Recycling 2025, 10(2), 34; https://doi.org/10.3390/recycling10020034 - 1 Mar 2025

Viewed by 367

Abstract

Biomass ash is a byproduct of renewable energy generation that can be used in the cement and concrete industries as a supplementary cementitious material (SCM) to reduce their environmental impact. However, using biomass ashes as an SCM presents challenges, such as the distant [...] Read more.

Biomass ash is a byproduct of renewable energy generation that can be used in the cement and concrete industries as a supplementary cementitious material (SCM) to reduce their environmental impact. However, using biomass ashes as an SCM presents challenges, such as the distant location of crops and processing plants from cement and concrete plants, the absence of a supply chain to connect the biomass ash and cement/concrete producers, and the lack of a mechanism to set the price of the ash. We adopted a supply chain perspective to evaluate the environmental and economic impact of incorporating biomass ashes as an SCM in the cement and concrete industries. We developed a bilevel optimization model considering the strategic behavior of the two stakeholders of the supply chain: the biomass ash generator, which maximizes its profits by setting the price of the ash, and the cement/concrete manufacturer and minimizes its total operating costs, including the processes necessary to adapt its supply chain for the use of new raw material. We validated the model using data from the Colombian context at a nationwide industrial level. Our results indicate that introducing SCMs can potentially reduce CO₂ emissions without increasing the cost of the supply chain. Full article

(This article belongs to the Topic Circular Economy Innovations and Breakthroughs for Built Environments)

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17 pages, 1971 KiB

Open AccessArticle

Evaluating Plastic Waste Management Strategies: Logistic Regression Insights on Pyrolysis vs. Recycling

by Dimitrios-Aristotelis Koumpakis, Christos Vlachokostas, Apostolos Tsakirakis and Savvas Petridis

Recycling 2025, 10(2), 33; https://doi.org/10.3390/recycling10020033 - 1 Mar 2025

Viewed by 816

Abstract

The global plastic production total has risen to more than 400 million tons per year; this number is mainly driven by industrial appliances. In the EU, where the annual production is about 30 million tons, only 32% of plastic waste is recycled. Therefore, [...] Read more.

The global plastic production total has risen to more than 400 million tons per year; this number is mainly driven by industrial appliances. In the EU, where the annual production is about 30 million tons, only 32% of plastic waste is recycled. Therefore, a need for a robust and efficient waste management strategy has emerged. This study will introduce a novel logistic regression-based decision-making framework that focuses on the environment and the economy while also considering energy intensity and logistics. These factors reflect the use of Life Cycle Assessment (LCA) in this study, which is an approach that determines the selection of waste management strategies across different European countries. This study introduces a model with 94% sensitivity and 97% overall accuracy in order to compare pyrolysis and plastic waste recycling management methods. One of the main findings is the fact that pyrolysis demonstrated a maximum conversion efficiency of 88%; in comparison, the conversion efficiency for recycling was approximately 58%. Pyrolysis also generates by-products, such as syngas and pyrolytic oil, which are valuable. To conclude, this study is a tool for policymakers and industry leaders, so that they can make sustainable waste management decisions with data-driven and evidence-based reasoning. Full article

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

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19 pages, 2012 KiB

Open AccessArticle

Application of Electrical Resistivity Measurements for Continuous Monitoring of the Municipal Solid Waste Biodrying Process

by Bongkoch Chungam, Hiroyuki Ishimori, Soydoa Vinitnantharat, Sirintornthep Towprayoon, Chart Chiemchaisri and Komsilp Wangyao

Recycling 2025, 10(2), 32; https://doi.org/10.3390/recycling10020032 - 24 Feb 2025

Viewed by 268

Abstract

Waste-to-energy technology has proven effective in reducing the mass and volume of waste, thereby minimizing contamination sources and residual fractions. However, high moisture content in waste significantly reduces the efficiency of energy recovery. Biodrying has shown great potential for moisture reduction through microbial [...] Read more.

Waste-to-energy technology has proven effective in reducing the mass and volume of waste, thereby minimizing contamination sources and residual fractions. However, high moisture content in waste significantly reduces the efficiency of energy recovery. Biodrying has shown great potential for moisture reduction through microbial activity, enhancing the efficiency of waste-to-energy processes. While the lack of proper real-time monitoring methods hinders the optimization of the biodrying processes. This study proposes an efficient method for monitoring the biodrying of municipal solid waste based on real-time electrical resistivity monitoring. During biodrying, resistivity was measured alongside key parameters like temperature, weight, gas emissions from the biodrying process, relative air humidity, moisture, and waste density. The results indicate a good correlation between bulk electrical resistivity (441–614 Ω·m) and temperature increases above ambient within the first 36 h (r² = 0.97–0.99). Statistical analyses also revealed the correlations of electrical resistivity with waste density (negative correlation, r² = 0.68–0.97) and gas emissions (moderate to strong, r² = 0.45–0.72) during different biodrying phases. These findings demonstrate the relationship between electrical resistivity and key biodrying parameters, which can be used for the development of biodrying and to enhance process control efficiency, thus enhancing sustainable waste management efficiency. Full article

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