Search Results (523)

Agricultural and food-processing residues, as well as fruit by-products, represent widely available but still underutilised resources. Although numerous laboratory-scale studies have demonstrated their ability to remove heavy metals from contaminated water, their practical implementation remains limited by incomplete understanding of long-term stability, regeneration efficiency, and end-of-life environmental safety. This review critically evaluates the current state of biosorbent research, with particular emphasis on the full life cycle of these materials, including adsorption performance, regeneration strategies, repeated-use potential, and post-exhaustion management. While focusing primarily on agricultural residues, the review also integrates key findings from alternative materials such as algae, microbial biomass, and industrial sludge to provide a comprehensive evaluation. Particular attention is given to the distinction between desorption and regeneration, metal recovery from desorption streams, and the associated environmental burden of secondary waste generation. In addition to commonly proposed valorisation routes, such as incorporation into construction materials, thermal conversion, and reuse in energy or catalytic applications, the review highlights that most end-of-life pathways remain partial solutions rather than true closed-loop systems. In many cases, only a small fraction of spent biosorbents can be effectively incorporated into secondary products, while remaining residues still require further treatment or disposal. The lack of standardised criteria for defining biosorbent exhaustion and performance thresholds further limits comparability across studies and hinders scale-up. Overall, current evidence suggests that biosorbent-based wastewater treatment should be considered a promising but still partially circular system, where full material closure has not yet been achieved. Addressing these gaps is essential for advancing toward more robust and environmentally sustainable implementation and for improving the circularity of biosorbent-based wastewater treatment systems. Full article

Electrochemical CO₂ reduction to ethanol is a promising route for circular carbon fuel and chemical production, but practical implementation remains limited by coupled membrane, catalyst, transport, and system integration constraints. This Communication reassesses anion-exchange membranes (AEMs) and bipolar membranes (BPMs) for CO₂-to-ethanol electroreduction by integrating recent 2024–2026 advances with foundational membrane and CO₂RR literature. The central argument is that membrane selection is not a passive separation choice; instead, it actively controls local pH, charge carriers, CO₂ availability, carbonate formation, water activity, proton/cation delivery, product crossover, and downstream techno-economic assessment (TEA) and life-cycle assessment (LCA) burdens. AEM operation can create alkaline cathodic microenvironments that favor C–C coupling, but bicarbonate/carbonate formation imposes carbon-loss, salt-management, and CO₂-recovery penalties. BPM operation can improve pH separation and carbon management through water dissociation and bicarbonate acidification, but its viability depends on water-dissociation efficiency, co-ion exclusion, junction stability, hydration management, and voltage control. Recent ethanol-selective catalyst studies further show that copper oxidation state, grain boundaries, subsurface dopants, ionomers, interfacial wettability, and dynamic operation interact strongly with membrane-imposed microenvironments. This Communication proposes a membrane-centered decision framework linking AEM/BPM selection with ethanol selectivity, single-pass carbon utilization, energy efficiency, durability, TEA/LCA boundaries, and future reactor design. Full article

The use of European Sustainability Reporting Standards (ESRS) under the Corporate Sustainability Reporting Directive (CSRD) represents a major change in corporate sustainability reporting, particularly through the formalisation of the double materiality principle. Despite its regulatory relevance, empirical evidence on how organisations disclose double materiality remains limited, especially during the first reporting cycle. This study provides early empirical indicative evidence on the application of double materiality in disclosure following the initial ESRS reporting. It examines how leading European water-sector companies and environmental service providers with urban water activities integrated this approach into their 2024 sustainability disclosures. A mixed-methods design is applied, combining qualitative content analysis with descriptive quantitative checks of sustainability, ESG, and integrated reports. The disclosed material topics are assessed against the ESRS thematic framework. The findings indicate a strong convergence on the key environmental issues reported, notably climate change, water management, and circular economy-disclosed practices, including companies not yet fully subject to ESRS requirements. In contrast, social and governance disclosures suggest greater heterogeneity. Overall, the results suggest that broader material coverage does not necessarily imply higher information quality, as this reflects the breadth of disclosure rather than its quality, reinforcing double materiality as a sector-driven prioritisation mechanism. Full article

Saltworks are anthropogenic environments providing important ecosystem services ranging from biodiversity support to ecotourism. The traditional management of small Mediterranean coastal saltworks is slowly declining. Consequently, there is a need to deepen the study of these active evaporitic basins and valorize the byproducts of the production cycle. In accordance with circular economy principles, these byproducts are traditionally reused as essential ingredients for the purification of edible salt. The study area is a small Mediterranean saltwork, “Chiusicella,” located within the Trapani–Paceco Saltworks Nature Reserve (Sicily, Italy). Sediments from various ponds and a waste material used by salt workers, locally known as “mamma caura”, were analyzed using X-ray diffraction (XRD) and Scanning Electron Microscopy coupled with Energy-Dispersive X-Ray Spectroscopy (SEM-EDS). Additionally, brines from high-salinity ponds were used to analyze the precipitation sequence following total evaporation. Results demonstrate a clear relationship between the stability fields of mineral phases typical of evaporitic environments and the pond typologies. Furthermore, the interaction and synergy between bacterial activity in the water and the precipitating mineral phases appear more evident, thus outlining a clearer profile of the role of byproduct reuse within the saltwork’s annual production cycle. Full article

Cross-flow micro heat exchangers enable compact thermal management for high-density electronics, but their design is traditionally constrained by a strict trade-off between heat transfer and hydraulic resistance. To mitigate this limitation, we investigate the influence of mixed-geometry channel designs on the coupled thermal and hydraulic performance using a three-dimensional conjugate heat transfer model of water flowing through a stainless-steel micro-matrix with a 40-micrometer hydraulic diameter. Numerical simulations show that at low Reynolds numbers (100 to 200), corner-induced steady three-dimensional flow redistribution modifies the thermal boundary layer, causing convective and hydraulic performance to deviate from standard macroscale predictions. By expanding the transverse microchannel spacing from 10 to 60 μm, the Nusselt number increases from 1.15 to 2.07 while maintaining a nearly constant pressure gradient. These results provide geometric guidelines for designing high-efficiency microfluidic cooling systems by mitigating the traditional trade-off between heat-transfer enhancement and hydraulic resistance. Among the geometries evaluated, pure square channels maximize heat transfer, hybrid circular-square configurations optimize hydraulic efficiency, and triangular designs perform poorly due to high viscous drag. These results provide geometric guidelines for mitigating the traditional trade-off between heat-transfer enhancement and hydraulic resistance in microfluidic cooling systems. Full article

The increasing demand for lithium-ion batteries (LIBs) raises concerns about the security of critical raw material supply and the management of hazardous waste. Efficient recycling can alleviate these issues by transforming spent batteries into high-value secondary materials for the circular economy. Industrial recycling has traditionally focused on the recovery of nickel (Ni) and cobalt (Co), whereas lithium (Li) recovery has often been sidelined due to technical complexities and fluctuating economic incentives. To meet the European Union (EU) Batteries Regulation target of 80% lithium recovery by the end of 2031, technically effective and economically viable lithium recovery strategies are required. This study investigates the use of food-grade sucrose as an organic reductant for the targeted recovery of lithium from NMC622 and NCA battery materials. The process combines sucrose-assisted reductive roasting with selective water leaching. The effects of roasting temperature, holding time, sucrose dosage, and heating rate were systematically evaluated and optimised. Under the best conditions of 600 °C, 15 min, 15 wt% sucrose, and a heating rate of 20 °C/min, lithium leaching efficiencies of 93.2% and 87.6% were achieved for separated NMC622 cathode material and NMC622-derived black mass, respectively. The method was also applicable to NCA-based black mass, reaching 83.7% lithium recovery under the same conditions. Mechanistic analysis revealed that lithium release was strongly controlled by the extent of transition metal reduction. Cobalt was fully reduced to its metallic state under all tested conditions. However, maximum lithium recovery required nickel to be reduced to metallic Ni and manganese-containing phases to be converted to MnO. The sucrose-assisted roasting process was rapid and holding times longer than 15 min decreased lithium recovery. This decrease was caused by the formation of poorly soluble lithium-containing phases, such as LiF and Li₃PO₄. F composition analysis showed the black mass (1.06 wt%) and anode fractions (2.26 wt%) to contain significantly more F than the cathode fraction (0.46 wt%), hence leading to the 5% Li leaching efficiency difference between cathode and black mass fractions under most conditions tested. Overall, these results demonstrate that sucrose-assisted reductive roasting, followed by selective water leaching, provides a rapid and effective route for high-efficiency lithium recovery from NMC- and NCA-based battery materials. Full article

Waste lubricating oils (WLOs) represent a major stream of hazardous petroleum-based residues, with global generation exceeding 24 million tons annually. Improper disposal of WLOs poses risks to soil, water, and air quality, while their chemical composition makes them a potential secondary resource within circular economy frameworks. This review summarizes conventional, advanced, and emerging technologies reported for the recycling and valorization of WLOs into high-value petrochemicals and carbon-based materials. Established processes such as acid–clay treatment, solvent extraction, and vacuum distillation are discussed together with more recent approaches, including catalytic upgrading, hydrotreatment, membrane separation, and thermochemical conversion methods such as pyrolysis and catalytic cracking. Reported data on process performance, environmental considerations, techno-economic indicators, and life cycle assessment outcomes are comparatively analyzed to outline current trends, technical challenges, and future development directions in WLO recycling. Particular attention is given to thermochemical pathways capable of generating carbonaceous materials, including carbon black, porous carbons, and functional carbon nanostructures with potential applications in adsorption, catalysis, electrochemical systems, and tribological formulations. Hybrid and integrated process configurations described in the literature are highlighted for their potential to improve recovery efficiency, enhance product quality, and reduce environmental burdens. In addition, recent life cycle assessment (LCA) and techno-economic analysis (TEA) studies are reviewed to provide insight into the environmental and economic implications of advanced re-refining systems. Overall, the reviewed literature indicates that WLO recycling represents not only an important element of sustainable lubricant management but also a promising waste-to-carbon strategy for the production of value-added carbon-based materials and petrochemical products. Full article

Transitioning from conventional wastewater treatment to circular wastewater management requires novel technologies that enable resource recovery, energy efficiency, and resilience under variable conditions. Within the NAMOR project, hybrid microalgae–bacteria Membrane PhotoBioReactors (MPBRs) are assessed as a sustainable solution for decentralized wastewater treatment and reuse. This study focuses on screening and optimizing mixed microalgae–bacterial consortia to treat municipal wastewater streams in the Mediterranean region, with an emphasis on achieving high nutrient removal, biomass productivity and robustness. A diverse set of strains will be evaluated under controlled temperature, light and nutrient regimes to enhance the symbiotic synergy between photosynthetic microalgae and heterotrophic bacteria, while minimizing aeration demand. Based on these results, a pilot demo in Lagadas, Greece, will integrate the optimized consortia into a moving-bed PBR equipped with polymeric carriers and membrane filtration for advanced effluent polishing, intended to produce reclaimed water for irrigation and biomass for valorisation into fertilizers or biogas. Full article

The introduction of sustainable practices into waste management can have a favorable environmental impact, increase resource value, and yield economic gains. Hydrothermal technologies have strong potential for the production of up-cycled ingredients from biowaste (amino acids, sugars, phenols, pharmacologically active compounds, etc.), enabling high energy recovery (50–80%) from biowaste with net-negative carbon emissions. This review discusses the use of subcritical and supercritical water technologies for sustainable valorization of biowaste and conversion of biomass into high-value chemicals and biofuels. The potential for the extraction/generation of bioactive compounds from plant and animal waste is presented, emphasizing the efficiency, compound stability, and bioactivity of the fractions obtained. The possibilities of simultaneous extraction of added-value compounds and hydrolysis of feedstock biopolymers by these technologies are elaborated. The review further addresses the production of biofuels through hydrothermal carbonization for solid fuels, hydrothermal waste liquefaction for liquid fuels, and supercritical water gasification for gaseous fuels. The paper highlights the environmental and economic advantages of technologies based on sub- and supercritical water over conventional chemical and fermentative routes, emphasizing their contribution to a circular bioeconomy by converting biowaste into value-added products and sustainable energy sources. Full article

Aquatic ecosystems are under severe stress from a diverse combination of contaminants, including heavy metals, pesticides, pharmaceuticals, and microplastics, driven by rapid industrialization, intensive agriculture, and urbanization. Globally, 80% of wastewater remains untreated, and conventional systems often fail to address emerging contaminants. Consequently, toxic heavy metals like lead and mercury can persist in water sources for decades. In response, phytoremediation has emerged as a scalable, eco-friendly, nature-based alternative. Among phytoremediation agents, duckweeds are increasingly recognized for their rapid growth, simple morphology, and continuous water-column contact. This review outlines the landscape of duckweed-based remediation, detailing molecular detoxification pathways and the synergistic role of associated microbiomes in enhancing environmental cleanup. Evidence indicates that contaminant removal is often supported by plant-microbe interactions. Despite extensive laboratory validation, field-scale implementation remains constrained by environmental complexity, pollutant mixtures, and variable climatic conditions. Furthermore, while duckweed systems hold promise within circular bioeconomy frameworks, converting wastewater into nutrient-rich biomass, contaminant accumulation in plant tissues raises concerns about biomass utilization and contaminant carryover. Addressing these challenges requires an integrative approach that links molecular detoxification, ecological interactions, and engineered system design to realize the full potential of duckweeds for sustainable aquatic pollution management. Full article

Apple pomace is a widely available food processing by-product that has attracted increasing attention in circular and resource-efficient food systems for its potential in value-added food applications. The use of apple pomace in ready-to-eat (RTE) plant-based meat analogs represents a promising pathway. Unlike plant-based meats intended for cooking, RTE systems impose stricter constraints on structural stability, water retention, flavor integrity, and safety under cold chain conditions. Within this framework, apple pomace represents a compositionally complex material with both opportunities and constraints. This review examines how apple pomace and its derived ingredients can be utilized in RTE plant-based meat analogs, with particular attention to the distinct structural and functional requirements of minced-type and whole-cut products. Current evidence indicates that direct incorporation is more feasible for minced systems, where apple pomace fiber and pectin can support water retention, binding, and refrigerated slice stability when particle size, hydration, and sensory limits are controlled. By contrast, whole-cut applications are more likely to require fractionation, selective extraction, or additional structuring because particulate heterogeneity may disrupt continuous phase integrity and anisotropic structure formation. The review further identifies the main barriers to industrial translation, including water management under refrigerated conditions, flavor and color deviations, challenges in raw material standardization, and techno-economic constraints related to dewatering, processing intensity, and quality control. Overall, this review indicates that apple pomace can function as a technically relevant ingredient in RTE plant-based meat analogs. Its successful implementation depends on converting compositional complexity into predictable functionality through raw material standardization, controlled fraction use, food safety verification, and economically viable processing. In this way, sustainability-driven valorization can be better aligned with the practical requirements of industrial food production. Full article

The increasing generation of agro-industrial residues like nejayote (maize lime-cooking wastewater from the maize nixtamalization process) poses significant environmental challenges in Mexico due to its elevated chemical oxygen demand (COD) and organic load. This study evaluates the physical separation of nejayote via membranes and its use as a low-cost substrate for producing lipids and carotenoids using Rhodotorula glutinis. A batch culture followed by pulse-feeding achieved a COD removal efficiency of 53.6% (0.22 g COD/(L h)) and a biomass concentration of 3.72 ± 0.45 g COD/L within 48 h. The yeast demonstrated a high specific metabolic efficiency, yielding 0.457 g of lipids and 0.0049 g of carotenoids per gram of biomass, with an oleaginous fraction of 46.21% in dry weight. Experimental data calibrated a process model in SuperPro Designer, simulating full-scale processes treating 100, 1000, and 10,000 m³ of nejayote per batch, producing up to 2137.11 MT of lipids and 22.90 MT of carotenoids annually. A techno-economic analysis estimated the investment, operating costs, and financial indicators for all scenarios. Strategies like evaporation and reverse osmosis to concentrate nejayote significantly improved profitability by reducing equipment size. Additionally, a circular economy approach was modeled, recovering process water and nutrient-rich side streams. These findings confirm that integrated physical and biological treatment, coupled with resource recovery, transforms this particularly agro-industrial residue into a technically robust and economically viable biorefinery feedstock, aligning industrial production with sustainable waste management. Full article

Tourism destinations consume vast quantities of energy, water, food, and materials, yet these resource flows remain largely invisible in destination planning practice. The aim of this paper is to develop a conceptual framework that reconceptualises tourism destinations as industrial ecosystems and makes their material and energy flows visible, quantifiable, and amenable to destination-scale planning. Existing frameworks prioritise governance and demand management, leaving the material dimension of sustainability unaddressed. To this end, the paper proposes a multi-scale resource-flow framework grounded in industrial ecology. This is a conceptual framework paper: it develops analytical architecture for destination-scale resource accounting rather than reporting empirical measurements. The framework organises four analytical components—actors, flows, structural configurations, and feedback mechanisms—across macro, meso, and micro scales. Three planning capabilities are advanced: supply-chain-complete environmental accounting, resource hotspot detection, and policy design along the full causal chain from structural arrangement to environmental outcome. Material flow analysis, life cycle assessment, and industrial symbiosis mapping are presented as operational tools, illustrated through reference to high-intensity coastal tourism systems. Industrial symbiosis is positioned as a structural mechanism through which by-product valorisation reduces destination-level resource throughput. The study contributes a bridging framework between governance-oriented tourism planning and the material accounting rigour of industrial ecology, distinguishing it from circular economy models that supply a design principle but no material accounting, from urban metabolism approaches that assume temporally stable flows, and from regenerative development that is values-based rather than quantitative. The framework offers a foundation for more integrated and resource-efficient destination sustainability planning. Full article

The Atlantic blue crab (Callinectes sapidus) is an invasive species widely distributed in the Mediterranean Sea, causing significant ecological and economic impacts. Despite its low commercial value and the limited utilization of undersized and non-marketable specimens, whole blue crab biomass represents a promising resource for the production of value-added compounds within a circular bioeconomy framework. In this study, whole blue crab biomass, including undersized individuals and non-marketable fractions, was directly valorized through enzymatic hydrolysis for the production of protein hydrolysates. Three commercial proteases (Alcalase, Neutrase, and Papain) were comparatively evaluated for protein hydrolysate production, and the hydrolysis conditions were assessed based on soluble matter yield. The evaluation of hydrolysis conditions identified pH 8, 50 °C, enzyme-to-substrate ratio of 2500 U g⁻¹, a solid-to-liquid ratio of 1:4, and a reaction time of 8 h as the most effective conditions for protein solubilization. Under these conditions, maximum soluble matter yields of 57.69% for Alcalase, 51.64% for Neutrase, and 48.44% for Papain were obtained. The obtained hydrolysates were subsequently characterized in terms of protein content and degree of hydrolysis (DH), both of which were significantly affected by enzyme type, following the order Alcalase (64.59 ± 0.75%) > Neutrase (62.29 ± 0.82%) > Papain (58.88 ± 0.65%). A similar trend was observed for degrees of hydrolysis (DH) of the products (43.20 ± 1.24%, 40.29 ± 1.05%, 37.26 ± 1.13%) respectively. Techno-functional properties of the hydrolysates were also enzyme-dependent and closely related to the extent of hydrolysis. Alcalase produced hydrolysates with higher DH, favoring the formation of smaller and more hydrophilic peptides, which enhanced water solubility (98.18 ± 0.51%) and antioxidant activity (77.08 ± 1.06%). In contrast, Papain-derived hydrolysates showed lower hydrolysis extent, likely preserving larger peptide structures and hydrophobic domains associated with higher emulsifying activity (16.10 ± 0.46 m² g⁻¹) and foaming capacity (30.47 ± 1.40%). Neutrase displayed intermediate behavior across most parameters. Overall, the results demonstrate that enzymatic hydrolysis of whole blue crab biomass is an effective valorization strategy, and that enzyme selection plays a key role in modulating hydrolysis efficiency and techno-functional properties. This approach provides a sustainable pathway for the management of invasive species while generating functional ingredients for food and nutraceutical applications. Full article

Green roofs offer significant potential for urban stormwater management, yet their capacity to improve runoff water quality is constrained by the limited pollutant retention of conventional substrates and inherent nutrient leaching risks. This critical review synthesizes recent advances in substrate engineering and phytoremediation to establish an integrated framework for transforming green roofs into active bio-filtration systems. Our analysis reveals that amending conventional substrates with waste-derived biosorbents substantially enhances heavy metal and nutrient retention through complementary mechanisms of surface complexation, ion exchange, and microprecipitation. When strategically coupled with hyperaccumulator plant species and rhizospheric microbial communities, these amended substrates significantly reduce contaminant loads in urban runoff while maintaining hydraulic functionality. We critically evaluate standard growing media versus substrates amended with targeted biosorbents: biochar, which enhances heavy metal retention and hydraulic conductivity via surface complexation; seaweed biomass, which provides superior water retention and cation exchange while reducing synthetic fertilizer dependence; and chitin-rich crab shell waste, which promotes microprecipitation of metals and phosphates while valorizing marine waste. The novelty resides not in the materials themselves, but in their synergistic combination and the systematic comparative analysis of their retention mechanisms under green roof hydrological conditions. This review further identifies critical engineering trade-offs, including biosorbent-induced hydraulic conductivity reductions and long-term adsorption site saturation, and provides actionable design thresholds for amendment dosing, substrate depth, and species selection. Ultimately, this work establishes a mechanistic and practical roadmap for next-generation green roofs that simultaneously optimize stormwater retention, runoff quality, and circular economy valorization, highlighting priority research directions for long-term field validation and climate-adaptive standardization. Full article