Search Results (2,574)

Waste tyre rubber (TR) from end-of-life tyres poses a major environmental challenge. Therefore, recycling this waste into useful applications contributes to sustainable waste management strategies and supports a circular economy. Rubber possesses properties that can enhance the flexibility and ductility of pavements, making it a feasible material for use in road infrastructure. This study investigates the mechanical and fatigue performance of recycled concrete aggregates (RCA) mixed with waste TR. RCA was partially replaced at three different levels: 5%, 10% and 15% by weight. To mitigate the loss in mechanical strength associated with rubber inclusion, the TR + RCA mixes were stabilised through geopolymerisation using slag as a precursor. The unconfined compressive strength (UCS) increased with higher binder content. For instance, the mix containing 15% TR and stabilised with 5% slag geopolymer achieved a UCS of only 0.7 MPa, whereas increasing the binder content to 15% raised the UCS to 2.2 MPa. Similarly, resilient modulus improved with increasing slag content. Results from the four-point bending fatigue test showed that replacing RCA with rubber particles enhanced the fatigue performance of the mixes. The initial fatigue modulus of 100% RCA mix stabilised with 15% binder was 13,690 MPa, which reduced to 9740 MPa when 10% TR was introduced. In contrast, the number of cycles to reach half the initial modulus increased by four times when the TR content was raised from 0% to 15%. Microstructural observations of the slag-stabilised TR + RCA mixes showed improved microstructure due to geopolymerisation. Only insignificant traces of arsenic (<0.0008 mg/L) and barium (<0.000208 mg/L) were present in the TR + RCA mixes, while all other concerning heavy metals, including mercury and lead, were not detected in the leaching test. This indicates that there is no potential risk of soil or groundwater contamination, confirming the environmental safety of using slag geopolymer-stabilised TR + RCA mixes in subbase applications. Full article

The increasing emphasis on environmental protection, climate change mitigation, and the transition to a circular economy requires industries, including the wood-processing sector, to integrate sustainability into strategic and operational management. Green growth indicators represent essential tools for evaluating the environmental, economic, and social impacts of business activities, while also contributing to the sustainable economics and responsible management of forest resources and products. This study applies a qualitative research design using structured interviews with 10 executives from medium and large woodworking enterprises in Slovakia. The interviews examined company strategies, practices, and challenges in sustainable development and forest resource utilization. The findings reveal that while many companies actively manage waste, invest in green technologies, and conduct internal audits, the broader implementation of environmental management systems and the uptake of public sustainability funding remain limited. Notably, 90% of respondents emphasized waste volume and recovery rates as critical indicators. Based on the results, a set of green growth indicators was developed and categorized across key thematic areas including waste management, energy efficiency, stakeholder communication, certification, and strategic planning. These indicators not only support the assessment of corporate sustainability but also strengthen efficient forest resource management, responsible use of raw materials, and the long-term economic viability of the sector. The study highlights the importance of systematically designed and practically applicable indicators for guiding companies toward sustainable competitiveness and emphasizes the need for stronger institutional support, improved access to reliable data, and integration of sustainability metrics into core business decision-making. Full article

The revalorization of agro-industrial by-products is a key strategy for promoting sustainability and the circular economy. This study assessed the photoprotective potential of underutilized carob (Ceratonia siliqua L.) fractions, including unripe and mature pods, leaves, and seed tissues, through chemical characterization, in vitro assays, and in vivo validation. Extracts showed high polyphenol contents (up to 4.8 g GAE/100 g) and strong antioxidant activity (up to 45 g TE/100 g). Photoprotective properties were confirmed by a solar protection factor of up to 17 and erythema transmission values of 3–6, indicating efficient UV absorption and anti-inflammatory potential, which together support overall skin protection. To validate these effects under physiological conditions, Caenorhabditis elegans was used as an in vivo model under three exposure modalities: complete exposure (contact and ingestion), the barrier effect (UV shielding by the medium), and the physiological effect (systemic protection after ingestion). Seed episperm and unripe pods showed the highest efficacy. Notably, complete exposure reduced UV-induced lethality from 98% to below 50%, mainly due to the barrier effect. This is the first report demonstrating the photoprotective activity of carob by-products in C. elegans, supporting their potential as natural ingredients for cosmetic and nutraceutical applications, and contributing to the sustainable revalorization of local agricultural residues. Full article

In recent years, European cities have implemented numerous initiatives to reduce the use of resources and improve the resilience of climate change by promoting shifts toward the circular economy (CE). This comparative case study investigated the results of the applications of the CE model in the built environment from two different national approaches and perspectives of strategic planning in capitals that represent the “old” (Copenhagen) and “new” (Ljubljana) European Union (EU) member states. This paper introduces the original methodology to assess the implementation of the strategic approaches in the adaptation of the CE in architecture and urban design using a set of 10 selecting indicators. Although both cities have ambitious strategic goals and are undertaking actions aimed at shifting to the CE, they are driven by different motivations (climate crisis vs. urban revitalization and zero waste policy) and exhibit different implementation patterns (top-down systemic/institutional vs. gradual/sectoral). The results highlight the key role of a comprehensive approach to CE implementation, particularly the development of institutional frameworks and dedicated infrastructure and digital tools for transition management, the involvement of external stakeholders in the circular vision, wide-range educational activities, and the promotion of CE initiatives. However, limitations resulting from the lack of a comprehensive and standardized measurement framework pose a challenge to effectively accelerate progress in the shift toward a CE in the built environment. The main contributions of this study are: (1) to identify and verify the methods and strategies undertaken by European cities for the adaptation of a CE in the built environment and (2) demonstrate the different dimensions, levels, and the most relevant factors in the strategic management of the processes of transformation toward the CE. In addition, recommendations for future implementations based on CE systems are indicated. Full article

The circular economy represents one of the key pillars of European Union strategies aiming to decouple growth from resource utilization. The circular economy has emerged as a key flagship for European policies related to sustainable agri-food systems, potentially decreasing pressures on resources and the environment while ensuring economic competitiveness. In this context, this study proposed to measure the circularity performance of the Romanian agri-food system compared with average European Union performance, based on Eurostat data indicators for the years 2014 and 2022 and a normalized composite index composed of the economic, environmental, and social pillars. Indicator scores were categorized by higher-is-better or lower-is-better, constrained in the interval [0, 5] and then aggregated with equal weights. The composite index for Romania exhibited values ranging from 3.14 in 2014 to 3.45 in 2022, showing moderate progress. The results indicate a fragmentary transition where areas of strength for Romania were material resilience and trade. At the same time, areas of weakness were the economic integration of circularity practices. The study’s main limitations arise from the limited agri-food specificity of available indicators and the sensitivity of results to weighting choices. Overall, the findings highlight the need for stronger institutional mechanisms and targeted investments to accelerate Romania’s transition toward a circular agri-food economy. Full article

Feed and water scarcity are major challenges for the sustainability of livestock production, particularly in semi-arid regions with structural limitations in resource availability. In this context, the valorization of agro-industrial by-products contributes to circular agriculture, reduces waste, and promotes more efficient resource use, in line with the United Nations Sustainable Development Goals. This study evaluated the inclusion of partial mixed tomato residue (PMR) silage in sheep diets and its effects on productive performance, total water intake, and meat quality. Eighteen ewe lambs were assigned to two groups: control (concentrate and deferred pasture) and PMR (tomato residue silage and deferred pasture). The PMR silage had a pH of 3.97 and was mainly characterized by lactic and acetic acids, with minor amounts of propionic and butyric acids. The butyric acid concentration (8.9 g kg⁻¹ DM) slightly exceeded the recommended threshold (0.5% DM), suggesting some clostridial activity but remaining below levels associated with severe deterioration. Animals fed PMR silage showed a 36% higher dry matter intake (p = 0.001), with greater intake of total digestible nutrients and fiber. This translated into a 54% higher average daily gain (p = 0.02) and an 11% greater final body weight compared with the control group (p = 0.02). Dietary water intake was also higher in the PMR group, reducing direct water consumption from drinkers by 38% (p < 0.001). Meat quality parameters were unaffected by the diet. Pesticide residue screening by LC-MS/MS revealed no detectable levels of abamectin, cymoxanil, chlorothalonil, difenoconazole, or mancozeb in silage. In meat samples, only chlorothalonil was tested and it was not detected. However, the use of PMR silage increased direct energy demand due to transport and compaction, while feeding costs per unit of weight gain were reduced. Overall, PMR silage proved to be a safe, fermentatively stable, and effective feeding alternative that enhances performance, reduces direct water intake, and maintains meat quality, representing a viable strategy for small ruminant production in water-limited regions. Full article

Lithium-ion batteries are extensively used for energy storage in renewable, electronic, and automotive applications. However, once their electrical capacity is exhausted, they become hazardous waste that requires energy-intensive recycling processes. This study investigates the thermodynamic and exergetic behavior of LiMn₂O₄-based lithium-ion batteries subjected to controlled electrical overvoltage from renewable energy sources, aiming to quantify their potential for thermal energy generation and recovery. A detailed mathematical model was developed to describe the coupled heat transfer and electrochemical phenomena occurring during overvoltage conditions, and experimental validation was performed under various voltage levels and charging states. Energy and exergy analyses were applied to determine the configuration yielding the highest conversion efficiency for both new and aged cells. The maximum thermal energy efficiency reached 81% for new batteries and 4% for used batteries, while the corresponding exergetic efficiencies were 5% and 1.6%, respectively. Although this study does not propose the immediate large-scale reuse of spent batteries as thermal devices, the results provide quantitative insight into irreversible energy conversion processes and highlight their potential contribution to waste heat recovery and energy optimization strategies in sustainable industrial systems. This thermodynamic framework offers a novel approach for valorizing end-of-life batteries within circular energy models, reducing environmental impact, and advancing the integration of renewable energy-driven heat recovery technologies. Full article

Coagulation–flocculation, historically reliant on simple inorganic salts, has evolved into a technically sophisticated process that is central to the removal of turbidity, suspended solids, organic matter, and an expanding array of micropollutants from complex wastewaters. This review synthesizes six decades of research, charting the transition from classical aluminum and iron salts to high-performance polymeric, biosourced, and hybrid coagulants, and examines their comparative efficiency across multiple performance indicators—turbidity removal (>95%), COD/BOD reduction (up to 90%), and heavy metal abatement (>90%). Emphasis is placed on recent innovations, including magnetic composites, bio–mineral hybrids, and functionalized nanostructures, which integrate multiple mechanisms—charge neutralization, sweep flocculation, polymer bridging, and targeted adsorption—within a single formulation. Beyond performance, the review highlights persistent scientific gaps: incomplete understanding of molecular-scale interactions between coagulants and emerging contaminants such as microplastics, per- and polyfluoroalkyl substances (PFAS), and engineered nanoparticles; limited real-time analysis of flocculation kinetics and floc structural evolution; and the absence of predictive, mechanistically grounded models linking influent chemistry, coagulant properties, and operational parameters. Addressing these knowledge gaps is essential for transitioning from empirical dosing strategies to fully optimized, data-driven control. The integration of advanced coagulation into modular treatment trains, coupled with IoT-enabled sensors, zeta potential monitoring, and AI-based control algorithms, offers the potential to create “Coagulation 4.0” systems—adaptive, efficient, and embedded within circular economy frameworks. In this paradigm, treatment objectives extend beyond regulatory compliance to include resource recovery from coagulation sludge (nutrients, rare metals, construction materials) and substantial reductions in chemical and energy footprints. By uniting advances in material science, process engineering, and real-time control, coagulation–flocculation can retain its central role in water treatment while redefining its contribution to sustainability. In the systems envisioned here, every floc becomes both a vehicle for contaminant removal and a functional carrier in the broader water–energy–resource nexus. Full article

The growing global demand for mined commodities has intensified the environmental challenges associated with mine tailings. Currently, an estimated 62,381 mining properties impact approximately 50 million square kilometers of the Earth’s land surface. Annual tailings production exceeds 10 billion tonnes and is projected to reach 19 billion tonnes by 2025. This review examines phytoremediation strategies and the associated legal framework in South Africa, highlighting a critical disconnect between existing remediation approaches, environmental legislation, and the broader sustainable development agenda. To address these gaps, a fundamental shift towards a circular economy paradigm is essential—one that aligns research, policy, and practice to foster innovative, sustainable solutions. Phytoremediation using bioenergy crops such as Vetiver grass (Chrysopogon zizanioides) offers a holistic approach that integrates environmental restoration with circularity and economic viability, while avoiding competition with food crops for arable land. Full article

The SARS-CoV-2 pandemic has driven the emergence of many viral variants carrying multiple mutations, particularly in the spike glycoprotein, which enhance viral adaptability and may alter the structure and functionality of the protein. Here, we present, to the best of our knowledge, the first systematic and comparative structural analysis of monomeric spike protein subunit 1 from three distinct SARS-CoV-2 variants at physiological pH (7.4). A multimodal approach was employed, integrating experimental techniques, including Attenuated Total Reflection Infrared and circular dichroism spectroscopies, with computational methods such as molecular dynamics simulations and surface polarity analyses. This combined approach allowed us to characterize the secondary structure composition, three-dimensional conformational organization, and solvent interaction profiles of each variant. Our findings reveal how the structural and functional properties of the spike protein subunit 1 are influenced by specific amino acid mutations. Indeed, the observed conformational changes and variations in solvent interactions have significant implications for viral infectivity and immune evasion. These findings contribute to the broader understanding of the evolution of SARS-CoV-2 variants and offer valuable insights for drug development, targeted prevention strategies, and biosensor design. Full article

Agricultural straw, a massive lignocellulosic by-product, requires high-value utilization strategies, and larvae of Protaetia brevitarsis (a resource insect) can convert straw into two valuable products: insect protein and frass rich in humic acid (HA). In this study, we investigated the interactions among multiple parameters affecting HA extraction efficiency and optimized the extraction process. The resulting extract was characterized by elemental analysis to determine nutrient elements, trace elements, and heavy metals; by ¹³C nuclear magnetic resonance (¹³C NMR) spectroscopy to identify the main categories of bioactive molecules; and by pot experiments to evaluate its effects on plant growth and quality. The optimized extraction conditions yielded extracts with a total organic carbon (TOC) concentration of 46.8 g/L, meeting the Chinese standard for water-soluble humic acid fertilizers (NY 1106-2010). Elemental analysis indicated that the extract was rich in trace elements, and heavy metal contents met the limitation requirements of toxic and harmful substances in fertilizers (GB 38400-2019). ¹³C NMR analysis revealed that the extract was enriched in aliphatic and methoxyl carbons, while pot experiments with cherry radish demonstrated that application of the extract at appropriate dosages significantly promoted plant growth and improved crop quality. These findings provide scientific support for circular agriculture and arable land protection, highlighting both their academic significance and broad application prospects. Full article

The Circular Economy (CE) has become a foundation of the European Union’s sustainability strategy, aiming to dissociate economic growth from resource use. This article examines the legislative and monitoring frameworks underpinning the European Union’s CE transition, with a particular focus on Slovenia. A systematic review conducted in accordance with the PRISMA 2020 guidelines, EU-level policy analysis, and national indicator evaluation, this article explores the alignment between Slovenia’s national strategies and EU objectives. While Slovenia has demonstrated policy ambition and performs well in municipal recycling, it underperforms in circular material use and domestic material consumption. Governance fragmentation, limited sectoral integration, and monitoring challenges are key barriers. The study contributes to CE research by offering a country-level perspective on policy translation and performance. Recommendations are proposed to strengthen governance, data systems, and sector-specific roadmaps. These conclusions offer valuable insights for scholars and policymakers involved in implementing CE across multi-level governance systems. Full article

The representation of visual hierarchy remains a central concern in contemporary design research and practice. Current design guidelines advocate establishing hierarchical relationships through dimensions such as size or distance, yet concrete and effective integration strategies remain elusive. This study, grounded in Gestalt principles, investigates the impact of design layouts on hierarchical perception under the interaction of proximity and similarity. This experiment systematically controls the size (1:1, 1:3/4 and 1:1/2, respectively) and distance (namely 1/4 R, 1/2 R, 3/4 R, 1 R, 5/4 R and 3/2 R) of two circular objects, employing a 3 × 6 two-way ANOVA. The results indicate that the interaction between size and distance can exert a significant influence on the perception of hierarchy. Among these factors, structural type emerges as the dominant element shaping hierarchical perception, with overlapping structures showing pronounced hierarchical suggestive characteristics that significantly outperform tangential and separated structures. Size can partially regulate this effect. When dimensions are equal, tangential and separated structures show no significant difference in perceived hierarchy. However, with the aid of size disparity, the hierarchical sense of separated structures can be markedly enhanced, yielding an effect stronger than that produced by shared edges. Full article

The valorization of volcanic ash as a raw material for advanced functional materials offers dual benefits for both the environment and technology. Firstly, it diverts waste from landfills, thereby reducing the environmental footprint of volcanic deposits. Secondly, it contributes to the circular economy by transforming an abundant natural residue into a high-value product. In this study, zeolites were synthesized from the ash of the Ubinas volcano via the hydrothermal method in an alkaline medium. A systematic investigation was conducted to ascertain the influence of NaOH concentration and reaction temperature on synthesis efficiency and final material properties. The crystalline phases and morphology of the products were characterized using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM), while textural and thermal properties were evaluated through the Brunauer–Emmett–Teller (BET) method and Thermogravimetric Analysis (TGA). The results revealed that both temperature and NaOH concentration significantly affected the physicochemical properties of the zeolites. Four zeolite types were obtained; among them, Zeolite Z4 (synthesized with 3 M NaOH at 150 °C) exhibited the highest adsorption capacity, with a specific surface area of 35.60 m²/g, while Zeolite Z1 (synthesized at 120 °C with 1.5 M NaOH and 27.85 m²/g) displayed superior thermal stability and crystallinity. These variations in thermal and textural properties were reflected in the catalytic pyrolysis performance of polypropylene (PP). Zeolite Z3 (synthesized at 150 °C with 1.5 M NaOH) achieved the highest gaseous product yield (80.2%), despite lacking the expected zeolitic crystalline phases. In contrast, Zeolite Z2 (synthesized at 120 °C with 3 M NaOH) yielded 57.7% gaseous products and stood out for its predominant analcime phase, characteristic of zeolitic materials. In summary, this study demonstrates that volcanic ash-derived zeolites not only enhance synthesis efficiency and functional performance but also represent a sustainable strategy for waste valorization, closing material loops and enabling the recovery of high-calorific gaseous products from plastic waste. Full article

Wind turbines are reaching end-of-life in increasing volumes, presenting a growing sustainability challenge. In the United States, prevailing waste management practices, primarily landfilling, undermine circular economy objectives by discarding recoverable materials and energy. This study applies life cycle assessment (LCA) to quantify 16 midpoint environmental impacts across three end-of-life pathways—landfilling, recycling, and repurposing—of major turbine components (steel, concrete, and composite blades). An avoided burden approach is used to quantify environmental credits from substituting recovered materials for virgin equivalents. Results show that nearly all recycling and repurposing pathways outperform landfilling across most impact categories. Mechanical recycling of both glass and carbon fiber blades performed better than landfilling in all 16 categories, while pyrolysis and solvolysis improved outcomes in 14–15 of 16 categories (CO₂ eq emissions were higher for pyrolysis and solvolysis than for the landfilling option). Repurposing blades likewise showed broad advantages (15 of 16 categories; ozone depletion was slightly higher), extending material lifetimes before waste treatment. For conventional materials, steel and concrete recycling reduced impacts in most categories, with concrete outperforming landfilling in 15 of 16 categories (marine eutrophication was nearly equal to the landfilling option). The only mixed pathway was cement co-processing of GFRP, which split evenly between benefits and burdens. Sensitivity analysis underscores that improving the quality of recovered materials is critical to maximizing environmental benefits. Overall, both recycling and repurposing offer substantial environmental advantages over landfilling, reinforcing the importance of circular end-of-life strategies in sustaining wind energy across its full life cycle. Full article