Search Results (2,287)

The recycling of technical textile waste represents a major challenge due to the complex and multilayered structure of these materials. Firefighter protective clothing, mainly composed of high-performance aramid fibers combined with polymeric membranes and auxiliary textile components, is commonly landfilled or incinerated at the end of its service life, resulting in a significant environmental impact. This work utilized recycled aramid-rich textile waste obtained from end-of-life firefighter protective clothing as reinforcement for polyamide 6 to develop high-performance thermoplastic composites within a circular economy framework. Composites containing 15, 30, 45, and 60 wt.% of recycled textile waste were manufactured by melt compounding followed by injection molding. In addition, a selected formulation containing 30 wt.% reinforcement was compatibilized using an amino-functional silane to improve interfacial adhesion. The materials were systematically characterized in terms of tensile properties, thermal behavior, thermomechanical performance, water uptake, flammability, colorimetric properties, and fracture morphology by field emission scanning electron microscopy. The results revealed a pronounced increase in stiffness and thermomechanical stability, with tensile strength increasing from approximately 65 MPa for neat PA6 up to 78 MPa at 30 wt.% reinforcement, and elastic modulus exceeding 5000 MPa at high reinforcement contents. An optimal balance between mechanical performance and ductility was achieved at 30 wt.% reinforcement, while higher contents enabled a substantial extension of the service temperature range, with HDT values increasing from 55 °C for neat PA6 up to 173 °C for highly reinforced systems. FESEM analysis confirmed improved interfacial adhesion in silane-compatibilized systems, explaining the enhanced mechanical and thermomechanical behavior. Furthermore, the incorporation of recycled aramid-rich textile waste led to a significant improvement in flame retardancy, enabling UL-94 V-0 classification at 30 wt.% reinforcement and above, without the use of additional flame-retardant additives, enabling UL-94 V-0 classification without additional flame-retardant additives. Overall, this study demonstrates the technical feasibility and high added-value potential of valorizing firefighter protective clothing waste into advanced PA6-based composites with enhanced mechanical, thermal, and fire-resistant properties, providing a sustainable route for the valorization of high-performance textile waste. Full article

The generation of agro-industrial residues represents an environmental challenge and an opportunity for their valorization within a circular economy framework. In this study, Agave salmiana bagasse residues were evaluated as a reinforcing material for developing bioplastics made from maize starch (polymer matrix). Maguey bagasse was collected, ground and sieved to particle sizes below 200 μm and incorporated into bioplastic formulations at different content levels. Five bioplastic films (M1–M5) were obtained and characterized regarding their physical, chemical, mechanical, thermal, and morphological properties. The evaluated parameters included density, color (CIE Lab*), moisture content, water absorption, FTIR analysis, tensile properties, thermal behavior, and surface morphology via SEM. The results showed significant differences among the bioplastic formulations. The moisture content ranged from 7.15% to 10.57%, while water absorption after 24 h reached values of up to 65% for the formulation with the highest bagasse content. Mechanical and thermal analyses indicated that the incorporation of maguey bagasse influenced the structural performance of the bioplastics, while SEM observations revealed changes in surface morphology associated with fiber incorporation. These findings demonstrate the potential of A. salmiana bagasse as a reinforcing agent in starch-based bioplastics, contributing to the development of sustainable materials. The results support their potential as a biodegradable material with exploratory application in an agricultural system. Full article

In karst tunnel engineering, water-filled cavities located above the tunnel crown, under the combined effects of excavation disturbance and hydraulic pressure, are prone to triggering water and mud inrush disasters. The thickness of the water-resisting rock layer is therefore a key factor controlling the stability of the surrounding rock. To address the difficulty in accurately characterizing the mechanical behavior of the crown of horseshoe-shaped tunnels using conventional circular plate or beam models, this study innovatively develops an explicit analytical model for the minimum safe thickness of the water-resisting rock layer based on clamped elliptical thin plate theory and Kirchhoff plate theory, incorporating the influence of cross-sectional geometry. Parametric sensitivity analysis indicates that both karst water pressure and tunnel crown height significantly amplify the required minimum safe thickness, whereas an increase in the tensile strength of the surrounding rock effectively reduces the thickness demand. Specifically, when the karst water pressure increases from 2.5 MPa to 4.5 MPa, the minimum safe thickness rises from 7.5 m to 10.0 m, showing an approximately linear growth trend. The analytical model is further validated through numerical simulations under different “water pressure–thickness” conditions. The results demonstrate that at the calculated recommended thickness, the surrounding rock achieves stable convergence after excavation. High tensile stress and elevated pore pressure zones are mainly concentrated near the tunnel crown, without the formation of through-going tensile failure. Engineering application indicates that the proposed model can provide a quantitative basis for the design of water-resisting rock layer thickness and the assessment of water inrush risk in karst tunnels. Full article

Global poultry production continues to expand rapidly to meet the growing demand for affordable and high-quality animal protein. However, this growth raises pressing concerns about environmental sustainability, natural resource use, and public health. Although current initiatives, such as improved housing systems, optimized feeding practices, and partial soybean meal substitution, have helped mitigate some impacts, comprehensive integrated solutions remain underexplored. This review synthesizes emerging nutritional and management innovations that enhance the sustainability of poultry production while maintaining profitability. It addresses three central research questions: (1) Which alternative feed ingredients most effectively preserve animal performance while minimizing environmental burdens? (2) How can environmental management practices enhance resource efficiency and waste valorization? (3) What roles do life cycle assessment methodologies and policy frameworks play in advancing sustainable poultry systems? Evidence from 100 peer-reviewed studies, industrial data, and field analyses reveals that incorporating insect meals, algae, and agro-industrial by-products can reduce dependence on soybean meal by 20–40% and improve feed efficiency by 5–12% across various poultry production systems. Furthermore, integrating environmental management strategies, such as manure valorization, efficient water and energy use, and the adoption of renewable energy, substantially reduces greenhouse gas emissions and promotes circular economic principles. Life cycle assessment studies confirm that combined dietary and management interventions yield greater reductions in carbon footprint than isolated measures. Future research should focus on optimizing interactions among feed strategies, environmental management, and policy frameworks through digital technologies, nanomaterial-based feed additives, and region-specific sustainability plans to accelerate the transition toward resilient, climate-smart poultry production systems. Full article

The aim of this study was to comprehensively characterize lavender pellets produced from post-distillation residues and evaluate their multifunctional valorization potential. Physicochemical properties, including moisture, ash, heating value, organic matter, total and organic carbon, macro- and micronutrients, potentially toxic heavy metals, polyphenols, microbiological safety, and nutritive composition, were assessed. The pellets demonstrated an energy content comparable to other agricultural residues, with a higher heating value of 18,900 kJ/kg and a lower heating value of 16,603 kJ/kg. High organic matter (87%) and a slightly acidic pH support soil moisture retention, while favorable macronutrient levels enhance their suitability as a soil amendment. Water-based extractions (infusion and decoction) achieved higher yields (15.60–21.66%) than ethanol (13.04%) and more effectively recovered bioactive polyphenols, particularly rosmarinic and chlorogenic acids. Low moisture and water activity ensured storage stability and minimal microbial growth, which was confirmed by microbiological safety tests. Nutritionally, pellets contained moderate protein (9.38%), high cellulose (33.38%), and low fat (2.18%), with total amino acids of 8.91 g/100 g and 36.7% essential amino acids, along with a favorable fatty acid profile rich in polyunsaturated fractions. Overall, these findings highlight lavender pellets as a sustainable resource for energy, soil improvement, bioactive compound recovery, and complementary animal feed within circular economy frameworks. However, future research should focus on investigating whether residual compounds remain in lavender residues that could exert antifeedant or phytotoxic effects. Additionally, the potential for the sequential valorization of lavender residues should be explored, initially through the extraction of bioactive phenols, followed by pellet production for use as fuel or soil amendments. This approach would enable multiple cascading uses and maximize their contribution to comprehensive circular economy strategies. Full article

Industrial food processing generates substantial byproducts, resulting in environmental challenges and economic losses. This study explores the biovalorization of sugar-rich barbecue sauce waste streams through fermentation to create value-added ingredients for sauce production and promote circular economy practices. The barbecue stream was diluted with water at 25 and 50% incorporation levels and fermented at room temperature for 12 days using a microbial consortium comprising three lactic acid bacteria (Lactiplantibacillus plantarum, Lacticaseibacillus rhamnosus, and Weissella confusa) and one yeast (Saccharomyces boulardii). Laboratory-scale fermentation was monitored by measuring pH, total soluble solids, titratable acidity, sugar consumption, and metabolite production. The consortium demonstrated effective performance, reducing pH and TSS and increasing titratable acidity for both incorporation levels over 12 days. The fermented samples were characterized by their antioxidant capacity, color, protein content, humidity, and viscosity. The total phenolic content and antioxidant activity (DPPH) increased significantly (p < 0.05), and the viscosity increased by 254.3% and 48.3% for the fermented streams with 25% and 50% incorporation, respectively. Antimicrobial assays revealed that the fermented samples inhibited typical spoilage bacteria and yeast. This work highlights the potential of fermentation to upcycle barbecue waste, with antimicrobial characteristics contributing to extended shelf life, sustainable food production, and circular economic practices. Full article

This study presents a comprehensive multi-objective optimization of sewage wastewater treatment using bio-based coagulants, guided by the Grey Wolf Optimizer (GWO) and its multi-objective variant (MOGWO). Experimental coagulation data, employing Citrullus lanatus and Cucumis melo as natural coagulants, were modeled using multivariate regression techniques, yielding high coefficients of determination (R² > 0.95) across key water quality parameters. The optimization process targeted maximal reductions in turbidity, total suspended solids (TSS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) through strategic manipulation of pH and coagulant dosage. The single-objective GWO achieved significant outcomes, including a 96.68% turbidity reduction at pH 5 and 50 mg/L dosage. The MOGWO algorithm identified Pareto-optimal solutions, such as a 94.2% turbidity reduction at pH 5 and 72 mg/L dosage, and a balanced BOD reduction of 52.7% at pH 7. The predictive models indicated that optimal treatment conditions could reduce chemical usage by up to 90% compared to conventional coagulants, resulting in potential cost savings of up to 30%. Moreover, the algorithms demonstrated rapid convergence, averaging 200 iterations, highlighting their computational efficiency and robustness. These findings illustrate that integrating bio-based coagulants with advanced optimization techniques can achieve high treatment efficiency while reducing chemical inputs, thus directly supporting environmental sustainability by minimizing sludge and secondary pollution. In this situation, the wastewater treatment plant will focus on resource-recovery systems with less or no waste at the end of the treatment process. This approach aligns with circular economy principles by promoting eco-friendly, cost-effective wastewater treatment solutions suitable for resource-limited settings. The study offers a forward-looking pathway for environmentally responsible wastewater management practices that significantly reduce chemical dependency and contribute to pollution mitigation efforts. Full article

This study aims to investigate the static performance of water-lubricated rubber bearings (WLRBs) with axial grooves. To achieve this objective, an analytical approach is employed that combines a modified Reynolds equation, accounting for surface groove effects and rubber deformation, with a Winkler model and finite element analysis of pressure distribution. By developing a fluid–structure interaction model that incorporates rubber liner deformation, this research reveals the interaction between WLRB geometry and steady-state performance parameters. The investigation evaluates the influence of geometric characteristics, including groove shape, number, and size, on the performance of elastomeric liner WLRBs, while assessing optimal groove depths under various conditions. The study analyzes five distinct groove geometries, including semi-cylindrical, rectangular prism, and three pyramidal types with different apex positions, in a six-groove bearing configuration, presenting their qualitative effects on the behavior of the examined bearings. The key findings indicate that increasing groove size or quantity reduces maximum pressure and load-carrying capacity while elevating friction coefficients. As groove count rises, supporting surfaces diminish, causing pressure distribution to intensify and minimum film thickness to decrease under a specified external load. A notable result reveals that when groove depth exceeds film thickness, performance becomes geometry-independent; however, shallower grooves exhibit significant geometric effects. Additionally, the study identifies groove ends as critical functional zones where film thickness reduction substantially enhances pressure distribution and static performance. Comparative analysis shows that longitudinal grooves with triangular cross sections outperform semi-circular and rectangular variants, with the backward triangular configuration demonstrating superior characteristics due to optimal end-film properties. In conclusion, this research provides a detailed understanding of how groove geometry influences the static performance of WLRBs, highlighting the importance of groove design, particularly at the groove ends, in optimizing bearing functionality. The findings offer valuable insights for the design and selection of groove configurations in water-lubricated rubber bearing applications. Full article

The large quantities of agri-food waste produced worldwide by the tomato processing industry require recovery. This study evaluated the efficiency of the by-product resulting from tomato juice preparation as an innovative biomaterial for removing lead from water. The pomace was dried and tested in two forms: raw (RT) and after extraction of soluble compounds (ET). The extracts obtained from the preparation of ET, could be reintroduced into the food industry (as colorants, etc.) according to the “zero waste” principle, but further studies are needed. No other chemical pre-treatment was applied to improve the lead-adsorption capacity. The pH influence, biosorbent dosage, kinetics and equilibrium were evaluated. Analytical methods, such as atomic absorption spectrometry, elemental chemical analysis, FTIR, scanning electron microscopy, and predictive models, were applied. The outcomes demonstrated a lead-adsorption efficiency of 99.22% for ET and 89.83% for RT, an optimum pH of 4.0 ± 0.5, and an initial solution containing 20 mg Pb²⁺/L. The Langmuir model predicted high removal capacities: 142.18 mg/g for ET and 90.91 mg/g for RT. Both forms of tomato pomace were efficient for sustainable and cost-effective water remediation, but an improvement was noticed after the extraction of soluble components that could be valorized in other products within the circular economy. Full article

The invasive brown macroalga Rugulopteryx okamurae has rapidly expanded across the Mediterranean–Atlantic region, generating severe ecological impacts. Nevertheless, the considerable amount of biomass available creates opportunities for valorisation within circular bioeconomy frameworks. This study provides an integrated characterization of the chemical profile and bioactivities of freshly collected floating biomass of R. okamurae from southern Portugal. Proximate composition was determined, and lipophilic (hexane) and hydrophilic (water) extracts were analyzed by GC–MS and spectrophotometric methods. Antioxidant activity was assessed using complementary radical-scavenging, reducing power, and metal-chelation assays, and enzyme inhibition was evaluated against targets associated with neurodegenerative, metabolic, and dermatological disorders. The lipophilic fraction was dominated by long-chain alkanes (≈101 mg/g extract) and sterols, particularly fucosterol (≈43 mg/g extract), but exhibited low radical-scavenging capacity (no EC₅₀ reached in DPPH or ABTS assays), and no relevant enzyme inhibition. In contrast, the water extract contained measurable phlorotannins (6.61 mg PGE/g extract) and showed moderate antioxidant (ABTS: EC₅₀ = 5.17 mg/mL; FRAP: EC₅₀ = 0.78 mg/mL) and enzyme inhibition activities (BChE: IC₅₀ = 5.17 mg/mL; tyrosinase: IC₅₀ = 0.78 mg/mL). Compared with previous studies on R. okamurae, this work applies a systematic fractionation of biomass from southern Portugal into polar and non-polar fractions and, for the first time, correlates the resulting detailed chemical profiles with multiple bioactivities. This approach revealed a clear functional differentiation between fractions, with bioactivity being mainly associated with polar metabolites. Overall, these findings highlight the value of structured extraction strategies for biomass valorisation and support the sustainable management of R. okamurae. Full article

The growing demand for sustainable agriculture requires strategies that simultaneously recover soil quality, improve crop yield, and add value to food products. This study evaluates walnut shell biochar (450 °C) as a circular amendment applied at 0, 10, and 20 t ha⁻¹ to an arid soil cultivated with pea (Pisum sativum L. cv. Onward) in San Juan, Argentina. Biochar enhanced soil porosity, respiration, organic carbon, and cation exchange capacity, resulting in higher plant biomass and a 30.9% increase in pod yield for the 20 t ha⁻¹ treatment. Pea grains were dehydrated by far-infrared drying at 70 °C, producing flour with improved lipid content, water absorption, and swelling capacity, which increased from 0.21 to 0.26 mL g⁻¹ under the 20 t ha⁻¹ treatment. The combined use of biochar and controlled drying highlights a viable pathway to close the soil–plant–food loop through resource valorization. This work contributes practical evidence of biochar’s multifunctional role in sustainable agri-food systems, aligned with circular economy principles. Full article

Sewage sludge management remains a critical challenge in Greece, where increasing regulatory pressure, environmental constraints, and limited stakeholder participation complicate regional decision-making. In particular, the revision of regional Waste Management Plans requires decision-support approaches that are both technically robust and socially legitimate. This study develops and applies a participatory, data-driven multi-criteria decision analysis framework to evaluate sustainable sewage sludge management strategies in the Region of Eastern Macedonia and Thrace. The framework combines structured stakeholder participation with quantitative performance assessment, enabling transparent, reproducible, and systematic comparison of alternative sewage sludge management options. Four realistic sludge management alternatives—composting fr agriculture, forestry use, land restoration, and thermal drying with energy recovery were assessed against fifteen economic, environmental, and social sub-criteria. Data were collected through structured questionnaires administered to forty-four representatives from five stakeholder groups: utilities (water and sewerage service providers), local authorities, scientists/experts, end-users, and citizens. Group preferences were aggregated using equal group weighting to ensure balanced representation. The results show that environmental and economic criteria outweigh social aspects. The highest mean weights were assigned to compliance with environmental requirements for products derived from the disposal method (0.105) and compliance with stricter national environmental legislation (0.104), followed by energy intensity (0.097), installation cost (0.065), and operation and maintenance (O&M) cost (0.061). Overall rankings identified composting and thermal drying as the most preferred options, followed by land restoration and forestry use; sensitivity analysis (±10% variation in sub-criterion weights) confirmed ranking stability. The proposed framework enhances decision transparency by embedding measurable criteria and stakeholder inputs within a structured analytical process. From a policy perspective, it addresses participation gaps in Greek waste planning and offers a transferable decision-support tool for future regional planning. Further extensions may include integration with life cycle assessment and cost–benefit analysis to support adaptive updates under circular economy objectives. Full article

This study presents a comparative evaluation of four drying methods for carrot, red beet, and pumpkin pomace to produce natural functional food ingredients. The work addresses the valorization of 35–45% vegetable processing waste—a rich source of bioactive compounds—aligning with circular bioeconomy principles and Kazakhstan’s goals for deep processing of agricultural raw materials. The compared methods were convective drying (CD), ultrasound pretreatment + convective drying (US + CD), vacuum-microwave drying (VMD), and ultrasound pretreatment + vacuum-microwave drying (US + VMD). Drying kinetics, water activity, physicochemical and functional properties of powders, retention of bioactive compounds, color characteristics, thermal stability, and sensory attributes were assessed. Kinetics were fitted using Midilli et al., Page, and Weibull models. US + VMD provided the highest drying acceleration (6–11 times faster than CD), reaching final moisture of 5.1–5.9%, water activity a_w 0.27–0.31 in 80–170 min, and bioactive compound retention of 90–95% (carotenoids 92–95%, betalains 90–94%). It also delivered superior flowability (Carr’s index 22.5–30.4%), dispersibility (80–88% in 30 s), and thermal stability (75–85% at 200 °C). Acceleration varied by raw material: maximum for beet (up to 11×) due to soluble sugars and nitrates, minimum for pumpkin (5.5–8×) due to dietary fibers and pectins, and intermediate for carrot (6–9×) influenced by carotenoids’ dielectric properties. The results highlight US + VMD’s strong potential for producing functional powders to replace synthetic additives in food systems. Effective method selection and parameter optimization require consideration of raw material type and rheological characteristics. Full article

Although urban resilience is a complex concept, several initiatives have made it more tangible. Urban public authorities and policymakers are of utmost importance, as they influence multiple neighbourhoods, stakeholders and aspects of urban resilience. Nevertheless, the role of individual facilities—such as sports fields—should not be overlooked. While their impacts are smaller in scale, they can significantly enhance local resilience and serve as inspirational pilots for broader initiatives. To assess resilience at the facility scale, an existing assessment framework was adapted, aligned with ESG (environmental, social and governance) criteria and climate action pillars and valuing ecosystem services. In the sports field case study, stormwater was reframed from a burden into a resource and integrated with other scheduled resilience-enhancing interventions: water conservation, installation of photovoltaic panels, enhanced tree shading, and circularity through sports equipment reuse. Together, these interventions strengthen urban sustainability, resilience, and climate adaptation while delivering ecological and social benefits. The stormwater drainage system was modelled to simulate naturalization actions. The assessment framework is described, and its application at both neighbourhood and facility scales is discussed. Comparisons between the existing and improved situations show clear resilience gains, and opportunities for extending these measures to the city scale are explored. Full article

This research evaluated the efficacy of using two types of biochar (non-modified and acidified) from date palm residues (fronds, leaves, pits) as soil amendments for enhancing soil fertility and maize growth. These biochars were produced through slow pyrolysis under oxygen-limited conditions at 500 °C. Our innovative approach was to minimize gas emissions by converting smoke into liquid fertilizer (LS), which was expected to improve seed germination and early plant growth stages. To assess this aim, a completely randomized experiment was conducted under lab conditions, in which 10 maize seeds were placed on double filter papers in Petri dishes and then exposed to seven concentrations of LS (0.0, 0.01, 0.10, 1.0, 10 and 100%, using distilled water for dilution v/v). The LS contains nutrients and bioactive compounds that may enhance seed germination and early plant growth at low concentrations, whereas higher concentrations may cause phytotoxic effects. Results showed that liquefied smoke at 0.1% increased the absolute percentage of maize germination from 75% (control) to 100% and achieved the highest root length of 9.80 cm. Acidified biochars at 5% reduced soil pH from 8.87 to 8.12 and enhanced potassium availability to 87.93 mg kg⁻¹. Conversely, the non-modified biochars contributed to further increases in soil organic matter (up to 1.02%), nitrogen, and phosphorus. In addition, the application of acidified leaf biochar (5%) enhanced maize shoot growth by 133%, chlorophyll content by 39%, and potassium uptake by 110%. This research establishes a scalable approach for converting agricultural waste into climate-resilient resources, effectively addressing soil degradation in arid environments, boosting crop resilience, and furthering the objectives of a circular bioeconomy. Full article