Search Results (433)

This study aimed to evaluate the effect of seasonal dynamics of phytoplankton biomass in the Bay of Gdansk (Southern Baltic Sea, Poland) on its usability for anaerobic digestion. Biomass samples were collected between May and October (2023–2024) for quantitative, taxonomic, and chemical analyses as well as for anaerobic digestion in mesophilic periodical bioreactors. Study results demonstrated substantial seasonal variations in the taxonomic composition of phytoplankton, with green algae and dinoflagellates prevailing in the spring, cyanobacteria in the summer, and diatoms in the autumn. These fluctuations were also reflected in the chemical composition of the biomass and its anaerobic digestion efficiency. The highest methane yield of 270 ± 13 mL CH₄/g VS and its highest production rate reaching 32.5 ± 1.6 mL CH₄/g VS·d were recorded in August, i.e., in the period of cyanobacteria predominance with the maximal contents of TOC (51.4 ± 2.1% TS), sugars (599 ± 42 mg/g TS), and lipids (126 ± 13 mg/g TS) in the biomass. In contrast, the lowest biomethanation efficiency was determined in October under diatom prevalence. A strong correlation was found between taxonomic, structural, and chemical properties of the substrate, and anaerobic digestion efficiency. This study’s findings underscore the enormous potential of phytoplankton biomass from summer blooms for energy production as a crucial element of sustainable management of coastal ecosystems and the circular economy. Full article

The growing amount of waste worldwide requires new solutions for its management. Agricultural by-products account for almost 10% of the waste generated. One of them is sheep wool, a natural fibre with beneficial physicochemical properties. Currently, sheep wool production amounts to approximately 1–2 million tonnes per year, of which 60% is used in the manufacture of clothing. Nevertheless, it poses a considerable challenge in terms of disposal due to its keratin-rich composition and slow biodegradability. This review analyses the chemical and physical properties of sheep wool and assesses its potential as biomass based on its carbon content and other elemental components. This allows us to provide a critical comparative analysis of the main technological pathways for the use of waste sheep wool as biomass, including anaerobic digestion, pyrolysis, direct combustion and gasification. The review highlights both the opportunities and limitations of these processes, comparing sheep wool in terms of energy potential and carbon footprint with other biomass. The review shows that the calorific value of sheep wool (19.5 MJ/kg) is competitive with traditional plant-based biofuels and the use of waste sheep wool as biomass source can contribute to reduction in CO₂ emissions of 2.1 million tonnes per year. The use of sheep wool as biomass can not only contribute to waste reduction but also supports the goals of sustainable agriculture and climate neutrality. The selected methods may offer a new and effective way of reducing waste and allow all sheep wool produced to be introduced into the circular economy. Full article

Wind power is integral to the transformation of energy systems towards sustainability. However, the increasing number of wind turbines approaching the end of their service life presents significant challenges in terms of waste management and environmental sustainability. Rotor blades, typically composed of thermoset polymer composites reinforced with glass or carbon fibres, are particularly problematic due to their low recyclability and complex material structure. The aim of this article is to provide a system-level review of current end-of-life strategies for wind turbine components, with particular emphasis on blade recycling and decision-oriented comparison, and its integration into circular economy frameworks. The paper explores three main pathways: operational life extension through predictive maintenance and design optimisation; upcycling and second-life applications; and advanced recycling techniques, including mechanical, thermal, and chemical methods, and reports qualitative/quantitative indicators together with an indicative Technology Readiness Level (TRL). Recent innovations, such as solvolysis, microwave-assisted pyrolysis, and supercritical fluid treatment, offer promising recovery rates but face technological and economic as well as environmental compliance limitations. In parallel, the review considers deployment maturity and economics, including an indicative mapping of cost and deployment status to support decision-making. Simultaneously, reuse applications in the construction and infrastructure sectors—such as concrete additives or repurposed structural elements—demonstrate viable low-energy alternatives to full material recovery, although regulatory barriers remain. The study also highlights the importance of systemic approaches, including Extended Producer Responsibility (EPR), Digital Product Passports and EU-aligned policy/finance instruments, and cross-sectoral collaboration. These instruments are essential for enhancing material traceability and fostering industrial symbiosis. In conclusion, there is no universal solution for wind turbine blade recycling. Effective integration of circular principles will require tailored strategies, interdisciplinary research, and bankable policy support. Addressing these challenges is crucial for minimising the environmental footprint of the wind energy sector. Full article

Rail transport is widely regarded as an efficient and environmentally sustainable mode of mobility, although lifecycle emissions from infrastructure can diminish its ecological benefits. This study assesses a novel slab track system design that replaces conventional concrete components with recycled polymeric composite sleepers, supporting circular economy objectives. Analytical calculations (per EN 16432-2 and EN 13230-6) and finite element analysis (FEA) were conducted on a 2.6 m polymeric composite sleeper model under static vertical loading. The results demonstrate that bonded base layers comprising asphalt and hydraulically bound materials reduce bending stresses within the sleeper to 1.307 N/mm², substantially below the 5.50 N/mm² observed without bound layers and well below both characteristic fatigue limits. Laboratory validation via strain-gauge measurements corroborates the numerical model. Despite minor torsional effects from first-batch production, the polymeric composite sleeper design is structurally viable for slab track applications. The methodology is directly transferable to alternative composite designs, allowing material-based adaptation of mechanical performance. These findings support the use of recycled polymeric composite sleepers in slab track systems, combining structural adequacy with enhanced circularity. Further research can base itself on the findings and should incorporate long-term durability testing. Full article

The galvanic industry requires considerable amounts of water and produces significant quantities of wastewater. Two types of wastewater are created in the processes of the galvanic application of metal coatings: used galvanic baths and wastewater generated while rinsing coated elements. The composition and amount of wastewater depend on the type of process, the plant’s operational system, and the quantity of water utilised to rinse the coated elements. In this article, the possibilities of using different techniques, such as chemical precipitation, coagulation and flocculation, ion exchange, adsorption, and membrane filtration, to remove heavy metals from galvanic wastewater were analysed and assessed. It was determined that the use of physicochemical methods (i.e., chemical precipitation, coagulation, and flocculation) to remove heavy metals has significant disadvantages, including operational costs connected with the purchase of chemical reagents and the emergence of metal complexes requiring management/utilisation. On the other hand, the processes of ion exchange and adsorption can be used only for wastewater characterised by a low heavy metal concentration, with organic matter preliminarily removed. In addition, waste polluted with heavy metals in the form of used regenerative baths and used sorbents is generated during these processes. In turn, the advanced techniques of membrane filtration allow for the removal of different types of organic pollutants and heavy metals. The processes of membrane wastewater treatment exhibit a range of advantages compared to traditional technologies, including the complete, environmentally friendly removal of permanent organic pollution, easy integration into conventional technologies, a limited amount of residue, a high level of separation, and a shorter process time. The efficiency of membrane wastewater treatment depends on many parameters, including, most of all, the composition, pH, and type of membrane, as well as process conditions. The possibility of using new types of membranes to remove heavy metals from spent galvanic baths was analysed, and the possibility of using the processes in wastewater treatment systems according to the circular economy model was assessed. The assessment of the efficiency of heavy metal removal in hybrid systems combining specific individual processes and the development of state-of-the-art material solutions to realise these processes may be an interesting direction of research in this field. Full article

Hazelnut cultivation is a strategic agricultural sector in Italy, with Calabria contributing through the native “Tonda Calabrese” cultivar, valued for its biodiversity. Despite its importance, data on the nutritional and compositional characteristics of this cultivar remain limited. In this study, hazelnuts from three different Calabrian producers were analyzed for morphological traits, proximate composition, and elemental content, using both conventional and non-destructive techniques such as CIELab color profiling and ATR-FTIR spectroscopy. The nuts showed high levels of essential micro-elements (Fe, Cu, Zn), aligning with previous findings on other cultivars, and showed no detectable pesticide residues, confirming their nutritional quality. Moreover, this study also aims to explore sustainable valorization strategies for hazelnut by-products, embracing circular economy principles in a “zero waste” approach, including oils and defatted flours. The extracted oils were evaluated for oxidative stability (peroxide value, p-anisidine, TOTOX index) and acidity, meeting Codex Alimentarius quality standards. The residual defatted flour was upcycled through eco-friendly methods, such as Ultrasound-Assisted Extraction (UAE) and Enzyme-Assisted Extraction (EAE), to isolate the polyphenol and protein fractions, respectively. Both extracts exhibited notable antioxidant activity (34.7–35.3 mmol Fe²⁺ eq/100 g and 64.3–82.2 mmol Fe²⁺ eq/100 g, respectively), suggesting their potential use as valuable ingredients for dietetic and nutraceutical applications. Full article

In line with circular economy principles and the reduction of primary material exploitation, waste-to-energy (WtE) by-products such as bottom ash (BA) are increasingly being used as raw materials in cement and ceramics manufacturing. However, it is critical to verify that the final product presents not only adequate technical properties but also that it does not pose negative impacts to the environment and human health during its use. This study investigates the environmental compatibility of the use of ceramic porcelain stoneware tiles manufactured with BA as partial replacement of traditional raw materials, with a particular focus on the leaching behavior of the tiles during their use, and also after crushing to simulate their characteristics at their end of life. To evaluate the latter aspect, compliance leaching tests were performed on crushed samples and compared with Italian End-of-Waste (EoW) thresholds for the use of construction and demolition waste as recycled aggregates. Whereas, to assess the environmental compatibility of the tiles during the utilization phase, a methodology based on the application of monolithic leaching tests to intact tiles, and the evaluation of the results through multi-scenario human health risk assessment and the analysis of the main mechanisms governing leaching at different stages, was employed. The results of the study indicate that the analyzed BA-based tiles showed no significant increase in the release of potential contaminants compared to traditional formulations and fully complied with End-of-Waste criteria. The results of the monolith tests used as input for site-specific risk assessment, simulating worst-case scenarios involving the potential contamination of the groundwater, indicated negligible risks to human health for both types of tiles, even considering very conservative assumptions. As for differences in the release mechanisms, tiles containing BA exhibited a shift toward depletion-controlled leaching and some differences in early element release compared to the ones with a traditional formulation. Full article

This study investigates the utilization of phosphogypsum (PG), an industrial byproduct, as a sustainable additive in reinforced truss concrete slabs to promote eco-friendly construction practices. Through static loading tests (monotonic/cyclic) under mixed boundary conditions (simply supported fixed), four slabs—including 2% PG-modified and ordinary concrete—were evaluated for mechanical performance, stress strain response, deflection, and crack propagation. The results demonstrated that PG enhanced slabs achieved comparable strength to conventional counterparts while exhibiting superior structural integrity at failure, highlighting PG’s potential to reduce environmental waste without compromising performance. Finite element analysis (ABAQUS2023) closely aligned with experimental data (<5% error), validating the model’s reliability in predicting failure modes. The study underscores PG’s viability as a circular economy solution for green building materials, offering dual benefits of waste valorization and resource efficiency. These findings advance sustainable construction by providing actionable insights for integrating industrial byproducts into high-performance structural systems, aligning with global decarbonization goals. Full article

For the successful commercialization of cocoa in the global market, ensuring product quality and compliance with regulations—such as EU regulation, which established maximum cadmium (Cd) levels for cocoa products—is essential. Moreover, cocoa cultivation in Colombian soils, an alternative to coca cultivation, is in many cases an unsustainable practice due to soil degradation, which is accompanied by a drastic decrease in soil organic carbon content. This study evaluated the use of a nature-based solution for cadmium remediation in cocoa cultivation soils by applying three organic amendments: biochar derived from cocoa pod shells (Cocoachar), spent coffee grounds (SCGs), and SCG-derived biochar (SCGchar). The effects of these organic amendments, applied at rates of 5, 10, and 15% (w/w), were evaluated in an in vitro incubation experiment (climate chamber) using soil samples collected from Zulia (mountain soils) and Tibú (alluvial soils), located in the Catatumbo region of Norte de Santander (Colombia). Soil analyses included available Cd concentrations (by atomic absorption spectroscopy), physicochemical properties (pH, organic matter, electrical conductivity), and other mineral elements. The results showed that Cocoachar significantly reduced Cd concentrations while enhancing soil quality, particularly by increasing pH and improving soil organic matter content. The application of 15% Cocoachar reduced Cd levels from 0.056 to 0.012 mg kg⁻¹ and increased soil pH from 6.3 to 7.0 in Zulia. In Tibú, the addition of 15% Cocoachar lowered Cd levels from 0.12 to 0.05 mg kg⁻¹ and raised the pH from 5.0 to 6.1. SCGchar primarily enhanced soil organic carbon, increasing its content from 1.87% to 2.35% in Zulia and from 0.66% to 1.53% in Tibú, thereby supporting ecological balance and sustainable soil fertility. Overall, the recycling of cocoa and coffee by-products into biochar offers a solution within the circular economy and a sustainable way to cultivate cocoa. This in vitro exploratory study must be confirmed with field trials and Cd analyses in cocoa beans. Full article

Modern production systems face the challenges of increasing personalization of products, growing structural complexity, and the need for sustainability. In this context, it is necessary to include the human dimension in the optimization of production processes, especially in line with the principles of Industry 5.0 and the circular economy. In this paper, a complexity index is proposed that integrates the objective characteristics of the product and the subjectively perceived workload of the operator during assembly. The proposed index was used in the assembly line optimization process using linear programming to find a compromise solution between two often-conflicting objectives: maximizing output and minimizing complexity. In the analysis, two approaches to the initial balance of the assembly line were considered—by assembly time and by complexity of work elements—which were used as inputs to the optimization model. The results show that an approach that considers complexity from the operator’s point of view contributes to a more even load distribution but also can lead to higher overall performance. Such an approach confirms the importance of integrating the human factor into optimization processes and thus contributes to the creation of efficient, sustainable, and human-centric production systems of the future. Full article

Lithium is classified as a critical element and is widely used in a variety of high-tech applications. Within the framework of a circular economy, demand is rising for technologies capable of recovering high-tech metals from waste materials and industrial byproducts. Coal fly ash (CFA) has attracted significant attention as a promising secondary resource for this purpose. Effective recovery requires the assessment of both metal enrichment levels and the underlying binding and leaching characteristics. The present study aims to contribute to advancing lithium recovery technology using coal fly ash as a secondary resource, thereby promoting waste valorization. Fourteen samples of coal fly ash from different power plants were collected and their mineralogy was studied by X-ray powder diffraction (XRD), their major constituents were analyzed by X-ray fluorescence spectroscopy (XRF), and their Li content was determined by inductively coupled plasma mass spectrometry (ICP-MS). Leaching experiments were conducted for selected samples using mineral acids (HCl and HF) and citric acid. Lithium concentrations in the analyzed samples ranged from 80 to 256 mg/kg, indicating enrichment relative to both global ash averages (enrichment factor > 1) and the Earth’s crust (enrichment factor > 2). Li in the samples, could be mainly associated with the amorphous fraction present in the samples. Leaching behavior across the samples follows a consistent trend, with hydrofluoric acid exhibiting the highest lithium extraction efficiency—reaching up to 79.9%. Full article

Remanufacturing, a key element of the circular economy, enables products and parts to have new life cycles through a systematic process. Initially, used products (cores) are visually inspected and categorized according to their manufacturer and variant before being disassembled and cleaned. Subsequently, parts are manually classified as directly reusable, reusable after reconditioning, or recyclable. As demand for remanufactured parts increases, automated classification becomes crucial. However, current Deep Learning (DL) methods, constrained by the scarcity of unique parts, often suffer from insufficient datasets, leading to overfitting. This research explores the effectiveness of Data-Efficient Generative Adversarial Network (DE-GAN) optimization approaches like FastGAN, APA, and InsGen in enhancing dataset diversity. These methods were evaluated against the State-of-the-Art (SOTA) Deep Convolutional Generative Adversarial Network (DCGAN) using metrics such as the Inception Score (IS), Fréchet Inception Distance (FID), and the classification accuracy of ResNet18 models trained with partially synthetic data. FastGAN achieved the lowest FID values among all models and led to a statistically significant improvement in ResNet18 classification accuracy. At a [1:1] real-to-synthetic ratio, the mean accuracy increased from 72% ± 4% (real-data-only) to 87% ± 3% (p < 0.001), and reached 94% ± 3% after hyperparameter optimization. In contrast, synthetic data generated by the SOTA DCGAN did not yield statistically significant improvements. Full article

Nepal, like its South Asian neighbours, is exploring Circular Economy (CE) as a pathway to Green Economy and Net Zero commitments. Current studies focus primarily on sector-specific 3R (Reduce, Reuse, Recycle) waste management strategies. However, these approaches overlook the broader sustainability transformation implied by a Sustainable Circular Economy (SCE). This study examines whether a locally relevant SCE model is feasible for Nepal. We conducted thematic analysis of interviews with thirteen representatives from nine CE organizations, supplemented by a literature review. Our findings reveal that while most SCE elements exist individually in Nepal’s context, integration into a comprehensive socially inclusive framework remains underdeveloped. We propose a Nepal-specific SCE framework that could challenge conventional industrial development trajectories focused solely on growth. The authors believe that this Nepal case study has valuable lessons for other developing countries pursuing CE as a strategy, as it suggests that a wider SCE scope is necessary to achieve inclusive development. Full article

Riverbank erosion poses a significant threat to livelihoods and infrastructure in the Vietnamese Mekong Delta (VMD), necessitating innovative and sustainable solutions. This study explores the use of old tyres as a material for embankment construction to stabilize riverbanks, combining physical reinforcement with bioengineering techniques. A pilot project was conducted in Dinh My commune, An Giang Province, where an embankment was constructed using old tyres, geotextile, riprap, and vegetation. Field measurements using the Leica TS02 Plus Total Station and Finite Element Method (FEM) modeling were employed to assess the embankment’s performance. Results indicate that the embankment effectively stabilized the riverbank, with a maximum displacement of 18 mm observed after one year. The FEM predictions closely aligned with the measured data, achieving an accuracy of 68% or higher, validating the model’s accuracy. The integration of vegetation further enhanced stability, demonstrating the potential of this approach as a sustainable and cost-effective solution for riverbank protection. This study highlights the dual benefits of erosion control and waste management, offering a replicable strategy for addressing riverbank erosion across deltaic and lowland regions. The pilot offers a scalable model for climate-resilient infrastructure in deltaic regions globally, linking erosion control with circular economy strategies. Full article

Over the last few decades, polymer composites have been rapidly making inroads in critical applications of electrical storage devices such as batteries and supercapacitors. Structural supercapacitor composites (SSCs) have emerged as multifunctional materials capable of storing energy while bearing mechanical loads, offering lightweight and compact solutions for energy systems. This study investigates the functionalization of Bisphenol A-based thermosetting polymers with ionic liquids, aiming to synthesize dual-functional structural electrolytes for SSC fabrication. A multifunctional sandwich structure was subsequently fabricated, in which the fabricated SSC served as the core layer, bonded between two structurally robust outer skins. The core layer was fabricated using carbon fibre layers coated with 10% graphene nanoplatelets (GNPs), while the skin layers contained 0.25% GNPs dispersed in the resin matrix. The developed device demonstrated stable operation up to 85 °C, achieving a specific capacitance of 57.28 mFcm⁻² and an energy density of 179 mWhm⁻² at room temperature. The performance doubled at 85 °C, maintaining excellent capacitance retentions across all experimented temperatures. The flexural strength of the developed sandwich SSC at elevated temperature (at 85 °C) was 71 MPa, which exceeds the minimum requirement for roofing sheets as specified in Australian building standard AS 4040.1 (Methods of testing sheet roof and wall cladding, Method 1: Resistance to concentrated loads). Finite element analysis (FEA) was performed using Abaqus CAE to evaluate structural integrity under mechanical loading and predict damage initiation zones under service conditions. The simulation was based on Hashin’s failure criteria and demonstrated reasonable accuracy. This research highlights the potential of multifunctional polymer composite systems in renewable energy infrastructure, offering a robust and energy-efficient material solution aligned with circular economy and sustainability goals. Full article