Search Results (1,207)

2,5-bis(hydroxymethy)lfuran (BHMF), a renewable compound with extensive industrial applications, can be obtained by selective hydrogenation of the C=O group of 5-hydroxymethylfurfural (HMF), a platform molecule derived from lignocellulosic biomass. In this work, we perform kinetic modeling of the selective liquid-phase hydrogenation of HMF to BHMF over a Cu/SiO₂ catalyst prepared by precipitation–deposition (PD) at a constant pH. Physicochemical characterization, using different techniques, confirms that the Cu/SiO₂–PD catalyst is formed by copper metallic nanoparticles of 3–5 nm in size highly dispersed on the SiO₂ surface. Before the kinetic study, the Cu/SiO₂-PD catalyst was evaluated in three solvents: tetrahydrofuran (THF), 2-propanol (2-POH), and water. The pattern of catalytic activity and BHMF yield for the different solvents was THF > 2-POH > H₂O. In addition, selectivity to BHF was the highest in THF. Thus, THF was chosen for further kinetic study. Several experiments were carried out by varying the initial HMF concentration (C⁰_HMF) between 0.02 and 0.26 M and the hydrogen pressure (P_H2) between 200 and 1500 kPa. In all experiments, BHMF selectivity was 97–99%. By pseudo-homogeneous modeling, an apparent reaction order with respect to HFM close to 1 was estimated for a C⁰_HMF between 0.02 M and 0.065 M, while when higher than 0.065 M, the apparent reaction order changed to 0. The apparent reaction order with respect to H₂ was nearly 0 when C⁰_HMF = 0.13 M, while for C⁰_HMF = 0.04 M, it was close to 1. The reaction orders estimated suggest that HMF is strongly absorbed on the catalyst surface, and thus total active site coverage is reached when the C⁰_HMF is higher than 0.065 M. Several Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetic models were proposed, tested against experimental data, and statistically compared. The best fitting of the experimental data was obtained with an LHHW model that considered non-competitive H₂ and HMF chemisorption and strong chemisorption of reactant and product molecules on copper metallic active sites. This model predicts both the catalytic performance of Cu/SiO₂-PD and its deactivation during liquid-phase HMF hydrogenation. Full article

This study evaluated biomass accumulation and phenolic compound production in seven Hypericum species (H. androsaemum, H. calycinum, H. hirsutum, H. kalmianum, H. olympicum, H. perforatum, and H. triquetrifolium) cultivated in vitro under varying growth regulator treatments and culture periods. Shoots were grown on Murashige and Skoog (MS) medium supplemented with benzyladenine (BA) or meta-topoline (mT) and analyzed after 40 and 60 days. MS medium supplemented with 0.2 mg/L BA was the most effective condition for promoting biomass across all species, with shoot fresh weight increasing significantly at 60 days, particularly in H. olympicum, H. perforatum, and H. triquetrifolium. High-performance liquid chromatography coupled with diode array detection and electrospray ionization mass spectrometry (HPLC-DAD-ESI-MS) identified 13 phenolic compounds, including flavonols, hydroxycinnamic acids, anthocyanins, phloroglucinols, and naphthodianthrones. Phenolic profiles were species-specific and influenced by culture period. H. kalmianum accumulated the highest total phenolic content (37.6 mg/g DW), while H. olympicum was the top producer of hypericin and pseudohypericin. These results highlight the crucial role of culture conditions in regulating both biomass and phytochemical production and provide a promising approach for producing bioactive metabolites in Hypericum species through in vitro systems. Full article

Catalytic upgrading of pyrolysis oils is an important step for producing replacement hydrocarbon-rich liquid biofuels from biomass and can help to advance pyrolysis technology. Catalysts play a pivotal role in influencing the selectivity of chemical reactions leading to the formation of main compounds in the final upgraded liquid products. The present work involved a systematic study of solvent-free catalytic reactions of cyclohexanone in the presence of hydrogen gas at 160 °C for 3 h in a batch reactor. Cyclohexanone can be produced from biomass through the selective hydrogenation of lignin-derived phenolics. Three types of catalysts comprising undoped NbOPO₄, 10 wt% NiO/NbOPO₄, and 30 wt% NiO/NbOPO₄ were studied. Undoped NbOPO₄ promoted both aldol condensation and the dehydration of cyclohexanol, producing fused ring aromatic hydrocarbons and hard char. With 30 wt% NiO/NbOPO₄, extensive competitive hydrogenation of cyclohexanone to cyclohexanol was observed, along with the formation of C₆ cyclic hydrocarbons. When compared to NbOPO₄ and 30 wt% NiO/NbOPO₄, the use of 10 wt% NiO/NbOPO₄ produced superior selectivity towards bi-cycloalkanones (i.e., C₁₂) at cyclohexanone conversion of 66.8 ± 1.82%. Overall, the 10 wt% NiO/NbOPO₄ catalyst exhibited the best performance towards the production of precursor compounds that can be further hydrodeoxygenated into energy-dense aviation fuel hydrocarbons. Hence, the presence and loading of NiO was able to tune the activity and selectivity of NbOPO₄, thereby influencing the final products obtained from the same cyclohexanone feedstock. This study underscores the potential of lignin-derived pyrolysis oils as important renewable feedstocks for producing replacement hydrocarbon solvents or feedstocks and high-density sustainable liquid hydrocarbon fuels via sequential and selective catalytic upgrading. Full article

Birch (Betula sp.) bark is a well-known natural source of betulin (Bet) and betulinic acid (BAc), both of which have several bioactive properties. The evaluation of the extraction performance, relative to these lupane-type triterpenoids, provided by different biosolvents requires the development of a high-resolution and high-sensitivity liquid chromatography-mass spectrometry (LC-MS) approach that is also compatible with challenging extractants such as natural deep eutectic solvents (NADESs). In this work, an LC-MS method was developed and analytically characterized prior to its application for the quantitation of Bet and BAc in birch bark extracts obtained using conventional solvents (methanol and acetone) and biosolvents (limonene and NADESs). High precision (RSD < 3.3%), sensitivity (LOD: 23 ng mL⁻¹ and 29 ng mL⁻¹ for Bet and BAc, respectively), and accuracy (95–102% recovery) were found for this optimized method, using an acidulated water–methanol mixture as the mobile phase and sodium acetate as an additive. Extraction experiments conducted at 55 °C revealed that the NADESs, particularly thymol:1-octanol (1:1 molar ratio), outperformed the other solvents and were highly effective for the recovery of both triterpenoids (17.50 mg g⁻¹ and 0.92 mg g⁻¹ of Bet and BAc, respectively). This method can also be applied to similar extracts obtained from other biomasses. Full article

The growing environmental concerns associated with petroleum-based plastics require the development of sustainable, biodegradable alternatives. Polyhydroxyalkanoates (PHAs), a family of biodegradable bioplastics, offer a promising potential as eco-friendly substitutes due to their renewable origin and favorable degradation properties. This research investigates the use of synthetic condensate, mimicking the liquid fraction from drying and shredding of household food waste, as a viable substrate for PHA production using mixed microbial cultures. Two draw-fill reactors (DFRs) were operated under different feed organic concentrations (2.0 ± 0.5 and 3.8 ± 0.6 g COD/L), maintaining a consistent carbon-to-nitrogen ratio to selectively enrich microorganisms capable of accumulating PHAs through alternating nutrient availability and deficiency. Both reactors achieved efficient organic pollutant removal (>95% soluble COD removal), stable biomass growth, and optimal pH levels. Notably, the reactor with the higher organic load (DFR-2) demonstrated a modest increase in PHA accumulation (19.05 ± 7.18%) compared to the lower-loaded reactor (DFR-1; 15.19 ± 6.00%), alongside significantly enhanced biomass productivity. Polymer characterization revealed the formation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), influenced by the substrate composition. Microbial community analysis showed an adaptive shift towards Proteobacteria dominance, signifying successful enrichment of effective PHA producers. Full article

The development of slow-release fertilizers (SRFs) based on production residues is a promising strategy to improve nutrient use efficiency and promote circular economy practices in agriculture. In this study, a series of experimental formulations were designed and tested using pumice scraps, liquid and dried blood, and bone meal, aiming at producing sustainable and low-cost N-P-K SRFs. These were processed through mixing and granulation, both in the laboratory and on a semi-industrial scale. The formulations were evaluated through release tests in 2% citric acid solution simulating the acidic conditions of the rhizosphere, and in acetic acid to assess potential nutrient leaching under acid rain conditions. The results showed a progressive cumulative release of macronutrients (NPKs), ranging from approximately 8% at 24 h to 73% after 90 days for the most effective formulation (WBF6). Agronomic trials on lettuce confirmed the effectiveness of WBF6, resulting in significant biomass increases compared with both the untreated control and a conventional fertilizer. The use of livestock waste and minerals facilitated the development of a scalable product aligned with the principles of sustainable agriculture. The observed release behavior, combined with the simplicity of production, positions these formulations as a promising alternative to conventional slow-release fertilizers. Full article

Olive tree branches (OB) and leaves (OL) from the Viseu region (Portugal) were studied for their chemical composition and liquefaction behavior using polyalcohols. Chemical analysis revealed that OL contained higher ash content (4.08%) and extractives, indicating more bioactive compounds, while OB had greater α-cellulose (30.47%) and hemicellulose (27.88%). Lignin content was higher in OL (21.64%) than OB (16.40%). Liquefaction experiments showed that increasing the temperature from 140 °C to 180 °C improved conversion, with OB showing a larger increase (52.5% to 80.9%) compared to OL (66% to 72%). OB reached peak conversion faster, and the optimal particle size for OB was 40–60 mesh, while OL performed better at finer sizes. OL benefited more from higher solvent ratios, whereas OB achieved high conversion with less solvent. FTIR analysis confirmed that acid-catalyzed liquefaction breaks down lignocellulosic structures, depolymerizes cellulose and hemicellulose, and modifies lignin, forming hydroxyl, aliphatic, and carbonyl groups. These changes reflect progressive biomass degradation and the incorporation of polyalcohol components, converting solid biomass into a reactive, polyol-rich liquid. The study highlights the distinct chemical and processing characteristics of olive branches and leaves, informing their potential industrial applications. Full article

Isobaric vapor-liquid equilibrium (VLE) data for binary mixtures of biomass–derived ethyl levulinate and ethanol were measured using an apparatus comprising a modified Rose-Williams still and a condensation system. Measurements were taken at temperatures ranging from 329.58 K to 470.00 K and pressures of 40.0, 60.0 and 80.0 kPa. The thermodynamic consistency of the VLE data was evaluated using the Redlich-Kister area test, the Fredenslund test and the Van Ness point-to-point test. The data was correlated using three activity coefficient models: Wilson, NRTL and UNIQUAC. The Gibbs energy of mixing of the VLE data was analyzed to verify the suitability of the binary interaction parameters of these models. The activity coefficients and excess Gibbs free energy, calculated from the VLE experimental data and model correlation results, were analyzed to evaluate the models’ fit and the non–ideality of the binary system. The accuracy of the regression results was also assessed based on the root mean square deviation (RMSD) and average absolute deviation (AAD) for both temperature and the vapor phase mole fraction of ethyl levulinate. The results indicate that the NRTL model provided the best fit to the experimental data. Notably, the experimental data showed strong correlation with the predictions of all three models, suggesting their reliability for practical application. Full article

To achieve energy transition, hydrogen and carboxylic acids have attracted much attention due to their cleanliness and renewability. Anaerobic fermentation technology is an effective combination of waste biomass resource utilization and renewable energy development. Therefore, the utilization of anaerobic fermentation technology is expected to achieve efficient co-production of hydrogen and carboxylic acids. However, this process is fundamentally affected by gas–liquid mass transfer kinetics, bubble behaviors, and system partial pressure. Moreover, the related studies are few and unfocused, and no systematic research has been developed yet. This review systematically summarizes and discusses the basic mathematical models used for gas–liquid mass transfer kinetics, the relationship between gas solubility and mass transfer, and the liquid-phase product composition. The review analyzes the roles of the headspace gas composition and partial pressure of the reaction system in regulating co-production. Additionally, we discuss strategies to optimize the metabolic pathways by modulating the gas composition and partial pressure. Finally, the feasibility of and prospects for the realization of hydrogen and carboxylic acid co-production in anaerobic fermentation systems are outlined. By exploring information related to gas mass transfer and system pressure, this review will surely provide an important reference for promoting cleaner production of sustainable energy. Full article

The Adiabatic Sonic Evaporation and Crystallization (ASEC) technology was developed as a disruptive zero-liquid discharge system to treat contaminated mining effluents. This study evaluates its ecotoxicological efficacy using Lemna minor, a freshwater macrophyte, as a sensitive bioindicator. Acute growth inhibition tests were conducted using OECD Guideline 221. Lemna minor was exposed for 7 days to untreated and treated effluents from the Tharsis mine and the Tinto River in southern Spain. The results revealed 100% inhibition of frond growth and biomass in untreated samples (pH < 2.6), indicating acute toxicity. In contrast, effluents treated with ASEC showed growth and biomass accumulation statistically indistinguishable from the control, confirming the system’s efficiency in reducing toxicity and restoring water quality. These findings support the environmental viability of ASEC technology for mine and port effluent treatment. Full article

The biomass-to-liquid process is a promising alternative for sustainably meeting the growing demand for liquid fuels. This study focuses on the fabrication, characterization, and performance of a structured iron catalyst for producing hydrocarbons through Fischer–Tropsch synthesis (FTS). The catalyst was designed to address some drawbacks of conventional supported catalysts, such as low utilization, poor activity, and instability. The experimental investigation involved the manufacturing and characterization of both promoted and unpromoted iron-based catalysts. The performance of the structured iron catalyst was assessed in a fixed-bed reactor under relevant industrial conditions. Notably, the best results were achieved with a syngas ratio typical of the gasification of lignocellulosic biomass, where the catalyst exhibited superior catalytic activity and selectivity toward desired hydrocarbon products, including light olefins and long-chain paraffins. The resulting structured catalyst achieved up to 95% CO conversion in a single pass with 5% selectivity for CH₄. The results indicate that the developed structured iron catalyst has considerable potential for efficient and sustainable hydrocarbon production via the Fischer–Tropsch synthesis. The catalyst’s performance, enhanced stability, and selectivity present promising opportunities for its application in large-scale hydrocarbon synthesis processes. Full article

As the global demand for eco-friendly food ingredients grows, marine macroalgae emerge as a valuable resource for multiple applications using a circular bioeconomy approach. In this study, green macroalgae Ulva flexuosa, naturally accumulated in aquaculture ponds as a residual biomass (by-product) of shrimp and oyster farming, were investigated regarding their bioactivity, chemical composition, and antioxidant properties. The use of aquaculture by-products as raw materials not only reduces waste accumulation but also makes better use of natural resources and adds value to underutilized biomass, contributing to sustainable production systems. For this, a comprehensive approach including the evaluation of its composition and environmentally friendly extraction of bioactive compounds was conducted and discussed. Green macroalgae exhibited high fiber (37.63% dry weight, DW) and mineral (30.45% DW) contents. Among the identified compounds, palmitic acid and linoleic acid (ω-6) were identified in the highest concentrations. Pigment analysis revealed a high concentration of chlorophylls (73.95 mg/g) and carotenoids (17.75 mg/g). To evaluate the bioactivity of Ulva flexuosa, ultrasound-assisted solid–liquid extraction was performed using water, ethanol, and methanol. Methanolic extracts showed the highest flavonoid content (59.33 mg QE/100 g), while aqueous extracts had the highest total phenolic content (41.50 mg GAE/100 g). Ethanolic and methanolic extracts had the most potent DPPH scavenging activity, whereas aqueous and ethanolic extracts performed best at the ABTS assay. Overall, we show the upcycling of Ulva flexuosa, an underexplored aquaculture by-product, as a sustainable and sensible strategy for multiple value-added applications. Full article

Sustainable aviation fuels (SAFs) are currently considered a key element in the decarbonization of the aviation sector, offering a feasible solution to reduce life cycle greenhouse gas emissions without requiring fundamental changes in aircraft or infrastructure. This article provides a comprehensive overview of the current state of SAFs, including their classification, production technologies, economic aspects, and environmental performance. The analysis covers both currently certified SAF pathways, such as HEFA and FT-SPK, and emerging technologies like alcohol-to-jet and power-to-liquid, assessing their technological maturity, feedstock availability, and scalability. Economic challenges related to high production costs, investment risks, and policy dependencies are discussed, alongside potential mechanisms to support market deployment. Furthermore, the article reviews SAFs’ emission performance, including CO₂ and non-CO₂ effects, based on existing life cycle assessment (LCA) studies, with an emphasis on variability caused by feedstock type and production method. The findings highlight that, while SAFs can significantly reduce aviation-related emissions compared to fossil jet fuels, the magnitude of benefits depends strongly on supply chain design and sustainability criteria. There are various certified pathways for SAF production, as well as new technologies that can further contribute to the development of the industry. Properly selected biomass sources and production technologies can reduce greenhouse gas emissions by more than 70% compared to conventional fuels. The implementation of SAFs faces obstacles related to cost, infrastructure, and regulations, which hinder its widespread adoption. The study concludes that although SAFs represent a promising pathway for aviation climate mitigation, substantial scaling efforts, regulatory support, and continued technological innovation are essential to achieve their full potential. Full article

Climate change resulting from human development necessitates increased land use, food, and energy consumption, underscoring the need for sustainable development. Incorporating various feedstocks into value-added liquid fuels and bioproducts is essential for achieving sustainability. Most biomass consists of cell walls, which serve as a primary carbon source for bioenergy and biorefinery processes. This structure contains a cellulose core, where lignin and hemicelluloses are crosslinked and embedded in a pectin matrix, forming diverse polysaccharide architectures across different species and tissues. Nineteen agro-industrial waste products were analyzed for their potential use in a circular economy. The analysis included cell wall composition, saccharification, and calorific potential. Thermal capacity and degradation were similar among the evaluated wastes. The feedstocks of corn cob, corn straw, soybean husk, and industry paper residue exhibited a higher saccharification capacity despite having lower lignin and uronic acid contents, with cell walls comprising 30% glucose and 60% xylose. Therefore, corn, soybeans, industrial paper residue, and sugarcane are more promising for bioethanol production. Additionally, duckweed, barley, sorghum, wheat, rice, bean, and coffee residues could serve as feedstocks for other by-products in green chemistry, generating valuable products. Our findings show that agro-industrial residues display a variety of polymers that are functional for various applications in different industry sectors. Full article

Microcystis, a potentially toxigenic cyanobacterium known to form extensive blooms in eutrophic lakes globally, was investigated in the cold oligotrophic Lake Baikal. We report the isolation of two Microcystis strains, Microcystis aeruginosa and M. novacekii, and document the presence of the latter species in Lake Baikal for the first time. In M. aeruginosa strain BN23, we detected the microcystin synthetase gene mcyE. Liquid chromatography-mass spectrometry revealed the presence of two microcystin variants in BN23, with microcystin-LR, a highly potent toxin, being the dominant form. The concentration of MC-LR reached 540 µg/g dry weight. In contrast, M. novacekii strain BT23 lacked both microcystin synthesis genes and detectable toxins. The habitat waters were characterized as oligotrophic with minor elements of mesotrophy, exhibiting low phytoplankton biomass dominated by the chrysophyte Dinobryon cylindricum (76–77% of biomass), with cyanobacteria contributing 8–10%. The contribution of Microcystis spp. to the total phytoplankton biomass could not be quantified as they were exclusively found in net samples. The water temperature at both sampling stations was ~19 °C, which is considerably lower than optimal for Microcystis spp. and potentially conducive to enhanced microcystin production in toxigenic genotypes. Full article