Search Results (525)

Hydrothermal carbonization (HTC) is a promising thermochemical process for valorizing wet biomass and organic waste streams, generating hydrochar, gas, and a liquid phase commonly referred to as HTC process liquid or the aqueous phase. Depending on feedstock type and process severity, hydrochar typically accounts for approximately 40–70 wt.% of the initial dry feedstock, the liquid phase for about 30–60 wt.% in lignocellulosic and agricultural residues, and the gas phase for about 1–10 wt.%, while highly hydrated waste streams may generate even higher liquid-phase shares. Although hydrochar has traditionally been considered the main energy product, the liquid phase may retain approximately 20–65% of the initial feedstock carbon and around 15–25% of the initial energy content. However, its high chemical oxygen demand, elevated organic carbon content, variable biodegradability, toxicity, and inhibitory compounds often lead to its classification as a wastewater stream requiring treatment. The crucial novelty of this review is its system-oriented evaluation of HTC process liquid as an energy-bearing and system-integrating stream rather than merely as a wastewater by-product or as a substrate for isolated valorization routes. Therefore, this review evaluates the role of HTC process liquid in energy systems, focusing on its formation mechanisms, chemical composition, energy potential, valorization pathways, integration strategies, and environmental implications. The reviewed evidence shows that HTC process liquid contains a complex mixture of dissolved organic compounds, including volatile fatty acids, sugars, furans, phenols, ketones, aldehydes, amino acids, ammonia, and nitrogen-containing heterocycles. These compounds may support anaerobic digestion, dark fermentation, aqueous phase reforming, electrochemical conversion, nutrient recovery, and process-water recirculation. Among these routes, anaerobic digestion is currently the most mature, although its efficiency depends strongly on HTC severity, feedstock type, inhibitor formation, and microbial adaptation. Hydrogen-oriented and electrochemical pathways offer additional opportunities but still require further validation using real HTC liquids, standardized yield reporting, and long-term stability assessment. Overall, HTC process liquid should not be regarded solely as an environmental burden, but as a chemically complex and energy-rich stream that may improve the performance of integrated HTC-based bioenergy systems. Future research should focus on standardized liquid-phase energy metrics, long-term process integration, toxicity control, and experimentally validated techno-economic and life-cycle assessments. Full article

Palm fruits are produced extensively in tropical and subtropical regions and consumed worldwide. However, over 20% of the total yield is discarded due to inferior quality, resulting in significant agricultural waste and economic loss. To mitigate this challenge and enable the safe valorization of discarded dates (DD) in animal feeding systems, this study employed solid-state fermentation (SSF) to upgrade the nutritional quality of DD and evaluated its potential as a functional feed ingredient for goats. Twenty-four male goats (6 months old; initial body weight 25.86 ± 0.25 kg) were randomly assigned to one of three dietary treatments: a basal diet (control), a diet containing 10% raw DD (D1), and a diet containing 10% solid-state fermented DD (D2). Inclusion of DD in the diet significantly increased average daily gain (ADG), final body weight (BW), and feed efficiency, with the highest values recorded for D2 (p < 0.05). Feeding of DD altered (p < 0.001) all measured rumen fermentation parameters, except pH, with higher levels (p < 0.05) of total volatile fatty acids, propionate, microbial crude protein, and ammonia nitrogen recorded for D1 and D2, as compared to control. Similarly, blood biochemistry revealed elevated total protein, albumin, and globulin in both supplemented groups (p < 0.05), whereas higher glucose and cholesterol levels were recorded for the D1 group (p < 0.05). Notably, systemic antioxidant status improved with the inclusion of SSF fermented DD, as evidenced by increased superoxide dismutase, glutathione peroxidase, and catalase activities, alongside reduced malondialdehyde levels (p < 0.05). The inclusion of DD in the diet decreased cooking and drip losses, and decreased shear force (indicating enhanced tenderness) and water-holding capacity (p < 0.05), with better values recorded for D2. Carcass protein and fat contents increased with the inclusion of DD in the diet, with higher values recorded for D2 (p < 0.05). Fatty acid analysis revealed higher (p < 0.05) contents of rumenic acid and octadecenoic acid in D2, as compared to D1 and control. The concentrations of lysine, methionine, threonine, leucine, and valine in meat were also higher in D2-fed goats (p < 0.05). In conclusion, incorporating solid-state-fermented discarded dates into goat diets represents a promising and sustainable strategy to valorize agricultural waste while concurrently improving growth performance, antioxidant status, meat quality, and selected nutrient profiles of goat meat. These preliminary findings warrant validation in larger-scale production. Full article

This work presents a sustainable strategy for the fabrication of multifunctional silver nanoparticles (Ag-NPs) and Ag/jute nanocomposites using Erythroxylum coca tea waste extract as a bioreducing and stabilizing agent, combined with picosecond pulsed laser irradiation. UV–Vis spectroscopy and transmission electron microscopy revealed the formation of Ag-NPs with diverse morphologies and broad size distributions, which became significantly more uniform after laser post-treatment without the need for additional chemical reagents. Following laser irradiation, the initially broad Ag surface plasmon resonance (SPR) peak transformed into a symmetric Gaussian-shaped band, centered at 407 ± 3 nm for all the Ag-NPs systems. The catalytic performance of unsupported Ag-NPs and Ag-NPs supported on jute fibers was comparatively evaluated by degrading Congo red (CR) dye, revealing that the supported nanocomposites exhibited enhanced catalytic stability, higher pollutant removal efficiency, and improved catalyst recovery. Furthermore, multicomponent catalytic reduction experiments involving CR and 4-nitrophenol (4-NP) in the presence of NaBH₄ revealed simultaneous degradation and reduction pathways mediated by the Ag/jute nanocomposites, as evidenced by the emergence of new absorption bands during the reaction. In parallel, the synthesized Ag-NPs demonstrated pronounced antimicrobial activity against Escherichia coli, generating well-defined inhibition zones. Beyond conventional approaches centered on nanoparticle synthesis and morphology optimization, this study establishes a platform that combines agricultural waste valorization, laser-assisted nanoparticle engineering, and natural-fiber-supported nanocomposite fabrication, enabling efficient remediation of both single- and multicomponent pollutant systems while promoting catalyst reusability and environmental sustainability. These findings demonstrate the Ag/jute nanocomposites as sustainable and scalable catalytic materials for wastewater remediation and antimicrobial applications. Full article

Waste management presents a major environmental and public health challenge, creating an urgent need for strategies that convert discarded materials into higher-value products. Waste-derived nanoparticles (WDNPs) have gained increasing attention because they integrate waste valorization with the production of functional nanomaterials for environmental, biomedical, agricultural, packaging, sensing, catalytic and energy-related applications. This review critically evaluates WDNP synthesis from five major waste streams, including agricultural residues, animal-derived waste, plastic waste, electronic waste and industrial by-products. Across these categories, precursor composition strongly influences nanoparticle size, morphology, surface chemistry, stability and functional performance, making feedstock selection and processing conditions central to reproducible production. Evidence from recent studies indicates that WDNPs have broad functional potential across environmental remediation, biomedical delivery, antimicrobial systems, sustainable packaging, agriculture, energy storage and catalysis. However, translation beyond laboratory-scale studies remains limited by feedstock variability, limited reproducibility, complex purification requirements, potential toxicity, insufficient standardization and limited pilot-scale validation. By comparing synthesis approaches, application outcomes and translational barriers across waste categories, this review provides a critical overview of the opportunities and limitations of WDNPs and identifies the key requirements for their responsible development within a circular-economy framework. Full article

Trihalomethanes (THMs) are priority disinfection by-products in drinking water, and their effective removal remains a persistent challenge for sustainable treatment. Here, olive mill solid waste (OMSW) was valorized into biochar (BC) and evaluated as a low-cost adsorbent for chloroform, bromodichloromethane (BDCM), chlorodibromomethane (CDBM), and bromoform under environmentally relevant conditions. Among the prepared materials, thermally activated BC (BC-T) performed best, achieving equilibrium removals of 74.7 ± 6.6% for chloroform, 91.1 ± 0.8% for BDCM, 87.2 ± 1.9% for CDBM, and 93.8 ± 0.3% for bromoform at 3000 mg/L. Adsorption increased with bromine substitution, following the order of bromoform > CDBM ≈ BDCM > chloroform, consistent with rising hydrophobicity. In contrast, KOH and Zn/Fe activation increased the BET surface area but did not improve THM removal, suggesting that adsorption was controlled by surface chemistry and site accessibility rather than surface area alone. Persulfate (PSF) addition reduced THM removal, indicating that oxidant activation did not compensate for the loss of adsorption capacity. Adsorption data were well described by the Freundlich isotherm and pseudo-second-order kinetics. BC-T also maintained high removal efficiency in drinking water, demonstrating its promise as a practical polishing adsorbent for THM control and as a route for high-value valorization of an abundant agricultural residue. Full article

The global agricultural sector faces the dual challenge of increasing productivity while mitigating environmental impacts caused by synthetic agrochemicals and massive agro-industrial waste. This review examines the transition to “Biostimulants 4.0,” a circular economy paradigm driven by the valorization of biomass residues into high-value biological inputs through nanotechnology and Artificial Intelligence (AI). Our analysis highlights that green extraction methods, specifically enzymatic hydrolysis, preserve bioactive integrity and reduce carbon emissions by up to 23.2 times compared to synthetic nitrogen production. Furthermore, waste-derived formulations and nanoscale smart-delivery systems dramatically enhance crop performance; for instance, chitosan nanoparticles can achieve up to a 471% increase in specific growth metrics through sustained-release pathways. To move the industry beyond empirical trial-and-error, the integration of AI-driven predictive models now achieves up to 87% accuracy in forecasting biostimulant efficacy. Finally, we contrast global regulatory frameworks and evaluate the monetization of biostimulant-driven carbon sequestration, capable of generating high-integrity credits priced up to $35 per tonne, as a critical economic pathway to accelerate commercial adoption and incentivize a resilient, decarbonized agricultural system. Full article

The integration of biochar into asphalt binders represents a significant advancement toward global sustainability in pavement engineering. Produced through biomass pyrolysis, biochar enables the valorization of agricultural and industrial waste while reducing dependence on petroleum-derived binder constituents. This review critically synthesizes current research regarding the impact of biochar on the physical, rheological, and aging performance of bitumen. The evidence consistently shows that biochar improves binder stiffness, raises softening points, and strengthens rutting resistance at elevated temperatures, largely due to its porous microstructure and high carbon content. Biochar-modified binders also exhibit enhanced aging resistance through the adsorption of volatile light fractions. These improvements are primarily ascribed to the carbonaceous composition and high porosity of the biochar particles. However, systemic challenges, including phase stability at high concentrations, long-term oxidative aging, and a lack of standardized characterization protocols, hinder widespread implementation. By identifying consistent findings, contradictions, and critical research gaps across the literature, this review provides a consolidated foundation to guide the transition of biochar-modified bitumen from laboratory investigation to large-scale pavement infrastructure applications. Full article

Bio-based and biodegradable polymer composites based on polylactic acid (PLA) and polybutylene succinate-co-adipate (PBSA) were developed for rigid food packaging applications. Agro-industrial residues consisting of ground leaves and branches derived from tangerine tree cultivation (pruning) were used as fillers at high loading (30 wt%) before (PRE) or after (POST) extraction of bioactive compounds. The influence of blend composition (PLA/PBSA 60/40 and 30/70), filler extraction, and the addition of antioxidants (0.5 wt%) on material properties was systematically investigated. Composites were processed via extrusion and injection molding and characterized through FTIR, SEM, tensile testing and thermal analysis. The results show that polymer blend morphology affects mechanical behavior, with co-continuous structures (60/40) exhibiting improved ductility compared to dispersed systems (30/70). The incorporation of lignocellulosic residues increased stiffness but reduced elongation at break. Extraction treatment significantly modified filler morphology and interfacial interactions, slightly improving dispersion and processability. The effect of the extracted bioactive compounds on the thermal stabilization of biocomposites was also investigated. Overall, the findings demonstrate the potential of combining biodegradable polymer blends with treated agricultural residues to produce sustainable rigid packaging materials while supporting a bio-circular approach. In fact, preliminary extraction of valuable compounds from tangerine pruning waste appears to be a convenient strategy for its efficient cascade valorization. Full article

Background: The residues of Camphora officinarum c.t. borneol after essential oil extraction are often discarded, causing resource waste and environmental pollution, while the edible fungi industry is facing a shortage of traditional cultivation substrates. Methods: This study integrated UPLC-MS/MS and GC-MS to comprehensively profile volatile and non-volatile metabolites. Samples included fresh branches and leaves (ZSXY) and residues after steam distillation (ZSZL), boiling combined with distillation (ZSSZ), and sun-drying after distillation (ZSSG). Results: In total, 2454 metabolites across 25 categories were detected. PCA revealed clear separation between fresh samples and all processed samples, with ZSZL and ZSSZ exhibiting similar metabolic profiles that were distinctly separated from ZSSG. Compared with ZSXY, most metabolites decreased after processing. ZSSG exhibited the strongest degradation, with 1408 down-regulated and only 146 up-regulated metabolites, and total terpenoid content decreased by 92.27%. ZSZL retained the highest levels of nutrients (e.g., amino acids and nucleotides) and bioactive compounds (e.g., phenolic acids, flavonoids, terpenoids), with 322 up-regulated metabolites. Among the specific comparisons, 113, 212, and 487 differentially accumulated metabolites were identified in ZSXY vs. ZSZL, ZSXY vs. ZSSZ, and ZSXY vs. ZSSG, respectively. KEGG enrichment revealed distinct pathway alterations: monoterpenoid degradation and biosynthesis pathways were activated in ZSZL, nitrogen metabolism-related pathways were disturbed in ZSSZ, and both limonene and pinene degradation and aminoacyl-tRNA biosynthesis pathways were enriched in ZSSG. Conclusions: Based on metabolomic profiling, steam distillation residues exhibited favorable retention of nutrients and bioactive compounds, whereas sun-drying led to excessive metabolite loss. These findings support the valorization of processing residues and promote circular agriculture. However, whether these residues can serve as effective substrates for edible fungi cultivation remains to be tested in dedicated cultivation trials. Full article

Anaerobic digestion is a viable pathway to mitigate environmental impacts from swine manure in tropical regions while contributing to circular economy strategies. However, no standardized or integrated framework currently exists that simultaneously quantifies the closure of energy, material, carbon, nutrient, and water loops at the farm scale. This research presents the techno-economic design and environmental assessment of a covered, mechanically agitated lagoon biodigester for a 10,000-head swine fattening module located in Matanzas, Cuba. The system is sized by integrating hydraulic, thermal, and structural parameters, and its economic viability is assessed through Net Present Value (NPV = $1.09 million), Internal Rate of Return (IRR = 32%), and a payback period of approximately three years. A comparative screening-level life cycle assessment shows that biogas-based electricity generation substantially reduces impacts on climate change, air quality, and fossil fuel scarcity compared with conventional diesel-based generation, with trade-offs in eutrophication and ecotoxicity. As a key methodological contribution, five quantitative circular economy indicators are proposed and calculated: the Energy Self-Sufficiency Ratio (ESSR = 1.71), the Waste Valorization Index (WVI = 0.91), the Decarbonization Index (DCI = 6.7), the Fertilizer Substitution Rate (FSR = 16.3 t N year⁻¹), and the Water Closure Factor (WCF = 1.30). These indicators show that the system achieves a 71% net energy surplus, valorizes over 90% of the input mass, avoids 6.7 times more emissions than it generates, replaces synthetic fertilizers, and returns more water than it consumes. The findings provide quantitative evidence that the convergence of mesophilic operation without auxiliary heating, high carbon intensity of the power grid, and availability of agricultural land enhances circularity performance in tropical covered lagoon bioreactors, and the proposed integrated indicator framework, aligned with ISO 59020:2024, provides a reproducible and transferable methodological basis for the comparative assessment of anaerobic digestion systems for livestock waste. Full article

Valorization of agro-industrial waste into functional materials is fundamental to the circular economy, especially for addressing the persistent contamination by anionic azo dyes in textile wastewater. This study evaluates guava seeds modified with hexadecyltrimethylammonium bromide (GS-M) as low-cost biosorbents for the removal of Direct Blue 71 (DB71), comparing their performance with that of natural seeds (GS-N) in batch systems and fixed-bed columns. Characterization by infrared spectroscopy (FTIR) and electron microscopy (SEM-EDS) confirmed successful surfactant immobilization, thereby creating a cationic surface with strong electrostatic affinity for anionic dye molecules. Batch experiments showed that GS-M achieved 98% DB71 removal within 120 min, whereas GS-N reached only 58% after 300 min. For GS-M, both pseudo-first-order and pseudo-second-order models fit the kinetic data well, consistent with concurrent electrostatic and hydrophobic interactions; GS-N was best described by the Elovich model, indicating rate limitation by electrostatic repulsion. GS-M maintained removal efficiency above 84% across pH 3–9, whereas GS-N was effective under acidic conditions. Langmuir maximum adsorption capacity (Q_o) values for GS-M were 6.02 mg/g at pH 4 and 7.87 mg/g at pH 8, a 1.5- to 2.2-fold increase over GS-N under matched conditions. Three adsorption–desorption cycles retained ~49% of the initial GS-M capacity, supporting a short-cycle reuse profile rather than indefinite multi-cycle operation. Fixed-bed column performance was highly sensitive to the hydraulic loading rate (v_c), with breakthrough times increasing nearly eightfold as v_c decreased. The Bed Depth Service Time (BDST), Thomas, and Yoon–Nelson models described the dynamic data consistently, yielding a maximum dynamic capacity of 165.6 mg/L under optimal conditions and providing a quantitative basis for scale-up. These results establish surfactant-modified guava seeds as a low-cost, pH-resilient biosorbent system aligned with circular-economy principles for the sustainable remediation of textile wastewater. Full article

The valorization of agro-industrial residues and sewage sludge into value-added products through vermicomposting represents a promising strategy for nutrient recycling and waste reduction. This study evaluated the effects of aqueous extracts obtained from five vermicomposts (VC1-VC5) produced from different mixtures of vineyard and winery residues and sewage sludge on cucumber (Cucumis sativus L.) seedlings grown under in vitro conditions. The aqueous extracts (10%, w/v) were characterized in terms of pH, electrical conductivity, and total polyphenolic content, and applied to cucumber seedlings cultivated for 30 days under sterile and controlled in vitro conditions using commercially available peat pellets (Jiffy-7^®). Seedling development was monitored throughout the experiment, and morphological and biochemical parameters were assessed at the end of the 30-day assay. All extracts supported seedling development, with no evidence of phytotoxicity. The application of VC2 and VC4 extracts resulted in significant increases in fresh and dry weight, while VC2 led to higher chlorophyll and carotenoid contents. Conversely, VC3 and VC5 extracts were associated with slight reductions in growth parameters and photosynthetic pigment content. Correlation analysis suggested positive associations between biomass accumulation and chlorophyll content, and negative association between total polyphenolic content and stem growth. Overall, the results indicate that aqueous vermicompost extracts were not phytotoxic under the tested conditions, although their effects appear to depend on extract composition, highlighting the importance of feedstock selection for sustainable horticultural applications. Full article

Propolis is a resinous bee product rich in bioactive compounds and widely recognized for its antimicrobial and antioxidant properties, but its effects on plants remain poorly explored, which could prove particularly relevant for applications in sustainable agriculture, namely in weed control. This in vitro study evaluated the phytotoxicity of propolis extracts obtained from materials considered waste, aiming for their valorization as natural bioherbicides. Two hydroalcoholic extracts produced from raw propolis—mPN.EE₇₀ (from mixed leftover samples) and Cr18.EE₇₀ (from a sample rejected by the pharmaceutical industry)—and one aqueous extract (RE23.WE) obtained from the residues of a previous ethanolic extraction were analyzed. All extracts exhibited antioxidant activity (DPPH assay), with mPN.EE₇₀ showing the lowest EC50 and RE23.WE the highest. Significant differences were observed in total phenolic and flavonoid contents, with Cr18.EE₇₀ presenting the highest values and RE23.WE the lowest. In vitro germination and early growth assays revealed pronounced species-, extract- and dose-dependent effects. White mustard (Sinapis alba) and lettuce (Lactuca sativa) were particularly sensitive to RE23.WE, which severely inhibited root growth. Interestingly, the spontaneous weeds Plantago lanceolata and Dactylis glomerata were sensitive to all the extracts, P. lanceolata being the most sensitive of all species. This species was particularly affected in root growth by mPN.EE₇₀, and in epicotyl development by Cr18.EE₇₀. Dactylis glomerata was specifically root-responsive, where RE23.WE, like in P. lanceolata, was the only extract causing significant inhibitions in both root and leaf growth at all concentrations. Although experiments at larger scales are needed for validation before agricultural applications, overall these findings demonstrate the potential of unused propolis samples and extraction residues as a source of bioherbicides for a more sustainable and circular agriculture. In particular, the remarkable effectiveness of the aqueous extract RE23.WE against all tested species promises an effective, environmentally safer, less costly, and therefore more economically viable approach for a weed control strategy. Full article

Wine production is one of the most important agricultural activities worldwide, and generates significant amounts of organic by-products, particularly grape pomace. Traditionally, this was seen as waste, but currently, this residue has been reanalyzed from the perspective of the principles of the bioeconomy and circular economy, demonstrating its potential as a rich source of bioactive compounds with great potential for valorization. Its heterogeneous composition accumulates a variety of polyphenols, dietary fibers, flavonoids, phenolic acids, and other secondary metabolites that confer important biological properties, including antioxidant, anti-inflammatory, and antimicrobial activities. The chemical composition of grape pomace varies substantially according to variety, winemaking method, and extraction conditions, directly impacting its potential application. Extraction methods have progressed from traditional procedures to more advanced techniques such as ultrasound, supercritical fluids, and natural solvents, enabling the selective separation of high-value compounds. This review provides a comprehensive and critical overview of grape pomace valorization, emphasising its composition, green extraction and current industrial applications. In addition, regulatory frameworks and sustainability strategies supporting the integration of grape pomace into value-added production chains are discussed. Overall, grape pomace valorization supports waste reduction and the production of new functional products that balance economic efficiency and environmental responsibility. Full article

Babassu (Attalea speciosa) is one of the most abundant palm species in the Brazilian Amazon and an important unconventional crop, playing a key socioeconomic role due to the commercial exploitation of its oil-rich almonds. However, approximately 90–93% of the fruit biomass—mainly mesocarp, epicarp, and endocarp—is generated as underutilized residue. This systematic review aims to analyze extraction methods, phytochemical composition, and antioxidant capacity of bioactive compounds derived from different babassu fractions. Following PRISMA guidelines, searches of five databases (Embase, ScienceDirect, Scopus, PubMed, and Web of Science) retrieved 410 records, of which 23 met the inclusion criteria. The results show that, although research has predominantly focused on the almond fraction, non-edible parts contain significant levels of phenolic compounds, flavonoids, phytosterols, and other bioactive metabolites with antioxidant properties. Green and non-thermal extraction technologies, such as ultrasound-assisted extraction (UAE), supercritical CO₂ extraction (SC-CO₂), and pressurized liquid extraction (PLE), demonstrated advantages in improving extraction efficiency while reducing solvent consumption and thermal degradation. Overall, the available evidence indicates that babassu residues represent a promising and still underexplored source of bioactive compounds. Their valorization may contribute to sustainable extraction strategies, waste reduction, and the development of value-added products within agricultural and bioeconomic systems. Full article