Search Results (2,232)

Aquaculture sustainability requires a reduction in the reliance on marine-derived raw materials such as fish oil in aquafeeds while maintaining fish health and product quality. This study investigated the effects of replacing fish oil with plant oils supplemented with DHA-rich Schizochytrium limacinum biomass on the gut microbiota of European sea bass (Dicentrarchus labrax). S. limacinum SR21—an oleaginous microalga naturally rich in omega-3 fatty acids—was produced through heterotrophic fermentation using crude glycerol, a waste stream from biodiesel production, within a circular economy framework. A 21-week feeding trial was conducted in an indoor recirculating aquaculture system using 280 fish distributed across eight tanks. Four experimental diets were tested: fish oil-based (FO), plant oil-based without microalga (VO + 0), and plant oil-based supplemented with 5% (VO + 5) or 10% (VO + 10) microalgal biomass. Gut microbiota was analyzed in 22 fish per group using 16S rRNA gene sequencing. While alpha and beta diversity analyses of gut microbiota revealed modest structural shifts at phylum and class ranks, genus-rank differences were evident, with Lactobacillus and Clostridium sensu stricto associated with FO and VO + 0 diets, and Pseudomonas and Staphylococcus enriched in microalga-supplemented groups. Functional inference highlighted enhanced bile acid biosynthesis and carbohydrate metabolism in VO + 0, whereas antioxidant-related pathways, including ubiquinone and carotenoid biosynthesis, were stimulated in VO + 5 and VO + 10 groups. These results demonstrate that S. limacinum biomass modulates microbiota functional capacity, potentially contributing to oxidative stress mitigation and host resilience. The findings support microbiota-informed feed formulation strategies to advance sustainable aquaculture. Full article

Hydrodynamic cavitation (HC) is an efficient technique for biodiesel production. The main contribution of this study is the development of a modular reactor with a universal stainless steel joint, whose design facilitates the installation, replacement, and maintenance of the orifice plate by eliminating flanges and bolts during assembly. Using this reactor, the study evaluated the synergistic interaction between feed pressure and methanol:oil molar ratio in the transesterification of soybean oil, employing a 3² factorial design. The orifice plate was 3 mm thick and had 19 holes with a diameter of 1.0 mm, installed downstream of the pump. The process was carried out for 45 min, using NaOH at 1 wt% relative to the oil and at 60 ± 5 °C. Feed pressures of 1.72, 2.41, and 3.10 bar and methanol:oil molar ratios of 6:1, 8:1, and 10:1 were evaluated, reaching a maximum yield of 92.98% at 3.10 bar and 8:1. Analysis of variance (ANOVA) confirmed a significant interaction (p < 0.0001) and allowed a second-order polynomial model to be fitted (R² = 0.9981). In contrast, conventional mechanical agitation required 90 min to achieve 95% yield. The biodiesel produced met most American Society for Testing and Materials (ASTM) D6751 requirements, confirming the potential of HC as a viable alternative for intensifying biodiesel production. Full article

Biodiesel is a promising, sustainable alternative to fossil fuels such as petrol and diesel. Currently, biodiesel can be produced from edible plant oils and non-edible sources and wastes. Notably, fish waste oil is a sustainable resource for transesterification reactions to produce biodiesel. This research proposes a general process design methodology to investigate the potential of biodiesel production from fish waste oil as a pathway for waste-to-energy. The methodology integrates Pinch Analysis principles and process simulation to optimize the energy efficiency of a process design. Real data are collected on fish waste from fish industries in Egypt, focusing on three regions in northern Egypt with a total capacity of 7.5 tons per day (t/d). The research methodology is applied to the design of a biodiesel production plant with a fish waste oil capacity of 547.5 tons/year. The production process involves a transesterification reaction using methanol and NaOH as catalysts. The annual expected yields are 495.2 tons of biodiesel and 51.4 tons of glycerol. The base design indicates total heating and cooling energies of 6889.6 kW and 11,470.1 kW, respectively, and CO₂ emissions of 19,343 tons/year. An improved design using Pinch Analysis achieves substantial energy savings of 47% in heating, 69% in cooling, and, 9202 tons of CO₂ cut. The novelty of the work lies in developing and applying an integrated process design and energy minimization methodology. The work provides a transferable methodology that can be applied to other wastes. Full article

Biochar-based catalysts have emerged as sustainable alternatives for biodiesel production, achieving high yields (up to 99%) from various feedstocks. This study aimed to utilize Spirulina-derived biochar as a bifunctional green catalyst for biodiesel synthesis from waste cooking oil (WCO) through transesterification and assess its green performance metrics. Biochar synthesized by carbonization (324 °C) was modified with calcium and sulfuric acid, featuring dual acid-base sites. Energy dispersive spectra revealed impregnation of calcium (11.11%) compared to the raw biomass (2.34%), followed by peaks of methoxy group and methylene group, and with methylene and β-carbonyl protons shown by nuclear magnetic spectroscopy. Thus, the biochar catalyst tested on WCO achieved a 93.27% yield under optimized conditions (65 °C, 1:15 methanol-to-oil ratio, 3% catalyst, 3.5 h) via central composite design. Catalyst reusability was maintained over four cycles with an average biodiesel yield (90%). Further, green metrics validate their eco-friendliness with a single-cycle reaction mass efficiency (RME) of 60.8%. When the initial catalyst mass is amortized over four cycles, the cumulative biodiesel yield per initial catalyst input reaches the equivalent of 243% of a single-batch theoretical yield (catalyst productivity = 3.12 g FAME/g catalyst). E-Factor at 0.67 (reduced to 0.17) and mass intensity at 1.68 (down to 0.42), contrasting with business-as-usual scenarios such as sulfuric acid catalysis (RME 70.0%, E-Factor 0.25) using 8.85 g H₂SO₄ vs. ~5 g H₂SO₄/kg biochar. Our results demonstrate that bio-based catalysts minimize non-benign inputs, supporting a circular economy from algal waste. Full article

Biodiesel production can be improved using new microdevice technologies that increase reaction efficiency and yield. Biodiesel synthesis from palm oil was conducted through transesterification using a sodium hydroxide catalyst, and a compact polytetrafluoroethylene microreactor with a 1 mm diameter was used. The effect of methanol-to-oil ratio, temperature, and catalyst concentration was explored to determine the optimal conditions for producing fatty acid methyl esters (FAME). The highest FAME yield reached 90.30%, with a short residence time of 10.85 min. The final product had a density of 0.848 to 0.909 g/mL and a viscosity of 4.038 to 24.987 CSt, showing the method’s effectiveness. Full article

The conversion of low-cost, widely available, and renewable agricultural and forestry biomass waste into high-performance electrode materials for supercapacitors has attracted significant research interest. In this study, bamboo was used as a raw material to prepare bamboo-derived activated carbon (BAC) and nitrogen-doped biomass activated carbon (N-BAC) via a two-step process involving carbonization and KOH activation. The obtained materials were subsequently evaluated as electrode materials for supercapacitors. The effects of carbonization temperature and time, activation temperature and time, and impregnation ratio on the structural properties and iodine adsorption capacity of the activated carbons were systematically examined. The results revealed that all process parameters influenced the iodine adsorption value of the samples in a volcano-type trend. The BAC prepared under optimized conditions (carbonization at 600 °C for 60 min, activation at 850 °C for 60 min, and an impregnation ratio of 6:1) exhibited the highest specific surface area (3013.30 m²/g), a total pore volume of 1.5813 cm³/g, and an average pore diameter of 2.0992 nm. Although nitrogen doping slightly reduced the specific surface area and pore volume of BAC, the introduced nitrogen-containing functional groups participated in redox reactions with the electrolyte, leading to a significant enhancement in the electrochemical performance of N-BAC. In a 6.0 M KOH electrolyte at a scan rate of 0.01 V/s, the specific capacitance of N-BAC reached 288.8 F/g, exceeding that of the optimized BAC (180.85 F/g). The supercapacitor assembled with N-BAC demonstrated a high energy density of 14.4 Wh/kg at a power density of 73.1 W/kg in aqueous electrolyte, the specific capacitance retention rate is about 90.3% after 5000 cycles between −1.2 V and 0 V at a scan rate of 10 mV/s. Overall, this work successfully developed high-performance supercapacitor electrode materials, providing a promising approach for the high-value utilization of biomass resources. Full article

In this paper, batch stirred-tank alcoholysis reactions of used and refined sunflower oils were performed with n-octyl, myristyl, cetyl, oleyl, and stearyl alcohols using immobilized lipases Novozym 435 and Lipozyme IM as catalysts. Alcohol conversions ranged from 74% to 94%, with slight differences between used frying sunflower oil and refined sunflower oil. The resulting wax esters were purified via stepwise column chromatography. The different regioselectivity of the biocatalysts led to distinct reaction pathways, and Novozym 435 proved to be the most effective enzyme, providing higher conversions and no detectable by-products. This study demonstrates the valorization of waste frying oils into high-value wax esters through enzymatic alcoholysis, comparing two industrially relevant immobilized lipases and achieving high conversion across multiple long-chain alcohols. The results highlight a sustainable alternative to conventional chemical catalysis and extend biocatalytic applications beyond traditional biodiesel production. By incorporating waste lipids into value-added products, the overall sustainability and circularity of the system are improved, contributing to green and sustainable chemistry. Full article

Biodiesel is a promising, renewable, and environmentally friendly alternative fuel. Numerous studies have focused on improving the biodiesel production process from various feedstocks using different activation methods and catalysts. However, the reaction times typically range from tens of minutes to hours. This study presents, for one of the first systematic studies exploring time, the potential of using millimeter-wave electromagnetic radiation generated by a gyrotron as an activation method for biodiesel production reactions. Esterification was carried out using free fatty acids and fatty waste, specifically brown grease (BG), in the presence of the Lewis acid catalyst AlCl₃. Complete conversion of oleic acid was achieved after only 0.4 s of exposure to millimeter waves. When BG was used as the feedstock, a biodiesel yield of 73–76% was obtained within only 3.0 s. Gyrotron-based electromagnetic activation was benchmarked against conventional thermal and sonication-assisted methods, demonstrating high effectiveness. This study presents an efficient and novel process that reduces reaction times while utilizing fatty waste as a feedstock, aligning with the principles of green chemistry, the circular economy, and sustainable development. Full article

Biodiesel’s application in compression–ignition engines is mostly limited by the type of methyl esters it contains rather than the total amount of feedstocks. In order to modify the fatty acid methyl ester (FAME) profile for better combustion and emissions, cottonseed (CSOME), neem (NOME), and orange peel oil methyl esters (OPOMEs) were carefully mixed. Fuel chemistry was examined using Gas Chromatography–Mass Spectrometry (GC-MS) and Fourier Transform Infrared (FTIR), which confirmed variations in oxygenated functional groups, saturation levels, and volatility. In a single-cylinder CI engine, diesel, single, binary, and ternary biodiesel mixes were tested over 25–100% load at compression ratios of 17 and 18, both with and without 10% EGR. The ester-optimized ternary blend HBO70 delivered the best overall performance at CR 18 with EGR, exhibiting only a 0.61% reduction in BTE while achieving significant reductions in smoke (44%), PM (51%), NO_x (30%), HC (11%), CO (10%), and specific fuel consumption (SFC) (6.8%). Regression analysis confirmed a temperature- and oxygen-controlled NO_x–PM trade-off, demonstrating that ester-profile optimization is an excellent way to achieve cleaner and more efficient CI engine operation. Full article

Wastewater-based microalgal cultivation enables coupling environmental remediation with the production of sustainable, value-added biomass. In this study, Euglena gracilis was cultivated under non-axenic conditions in a 2% anaerobically digested livestock wastewater (LSWW)-based medium to enhance biomass accumulation, paramylon storage, and biodiesel precursor production, while simultaneously removing residual nitrogen and phosphorus. The LSWW medium was strongly phosphate-limited relative to ammoniacal nitrogen (N:P mass ratio ~39:1), which constrained growth. Adjustment of the N:P ratio to ~10:1 by NaH₂PO₄ supplementation, together with MgSO₄·7H₂O addition, significantly enhanced biomass production, whereas trace metals and CaCl₂ provided minimal benefit. Cultivation at an initial pH of 3 resulted in substantially higher biomass accumulation than at pH 7 under xenic conditions. Under these optimized conditions, total phosphate and ammonia were efficiently removed, decreasing from 5.27 to 0.009 mg/L (99.8%) and from 57.40 to 2.11 mg/L (96.3%), respectively. Although paramylon accumulation was low in LSWW alone (~4% dry weight), short-term ethanol supplementation (0.095%, v/v, 24 h) enhanced paramylon content to ~20% dry weight. Subsequent anaerobic treatment further enhanced lipid conversion, increasing fatty acid methyl ester (FAME) content to ~45% dry weight. Collectively, low-pH non-axenic cultivation of E. gracilis in LSWW, combined with minimal nutrient supplementation, provides an integrated platform for enhanced biomass, paramylon, and biodiesel precursor production with efficient nutrient removal. Full article

The rising global production of biodiesel has led to a surplus of crude glycerol, a byproduct accounting for about 10% of biodiesel’s weight. Crude glycerol contains various impurities, including unreacted alcohol, soap, free fatty acids, water, and leftover reagents, which are often considered waste. Several methods have been explored to utilise this surplus, such as combustion for energy recovery, composting, animal feed, and purification. However, purification can be expensive and is often not economically viable. While there is growing interest in hydrogen production via the steam reforming of glycerol, there is a significant lack of detailed information and research on simulating this process using ChemCAD 8.1.0 software. This study aimed to simulate glycerol steam reforming (GSR) using ChemCAD, a process that converts crude glycerol from biodiesel into hydrogen. The process operates on a Gibbs free energy reactor, simulating GSR using the UNIFAC thermodynamic model under various conditions: temperatures ranging from 200 °C to 1000 °C, steam-to-glycerol mass ratios from 2:1 to 12:1, and a nickel catalyst maintained at 1 wt.%. The results demonstrate maximum glycerol consumption at temperatures above 600 °C and at a steam-to-glycerol mass ratio of 6:1. The optimum conditions for achieving a hydrogen yield of 65.23% occur at 800 °C and a ratio of 8:1 while minimising the formation of byproducts such as CO₂, CO, and CH₄. These findings provide valuable insights for optimising GSR processes and promoting the sustainable utilisation of renewable energy sources, thereby contributing to the circular economy and supporting the United Nations Sustainable Development Goal 7 (Affordable and Clean Energy). Full article

Quaternary Ni-Zn-Mg-Al metallic mixed oxide (MMO) catalysts were synthesized by co-precipitation from layered double hydroxide precursors. The effect of varying Zn content on physicochemical properties and catalytic performance was evaluated. Mg-Al and ternary Ni-Mg-Al and Zn-Mg-Al catalysts were synthetized for comparative purposes. XRD, N₂ sorption, MP-AES, CO₂-TPD, NH₃-TPD, SEM, and EDS characterized the materials’ physicochemical properties. The tested reaction was the transesterification between glycerol and dimethyl carbonate to obtain glycerol carbonate to improve the biodiesel industry. The catalyst containing both Ni and Zn showed the highest glycerol conversion among the evaluated materials. This was related to the increased number and strength of surface basic and acid active sites. Specifically, a high density of strong basic sites and acid ones in the quaternary catalysts was required for the reaction mechanism. The catalyst with 20 at% of Zn (MMO-Ni₁₅Zn₂₀) achieved the highest glycerol carbonate yield (89.6%) under mild reaction conditions and was solvent-free. MMO-Ni₁₅Zn₂₀ catalytic performance was associated with its high total basicity and predominance of strong basic sites and a moderate amount of acid sites. The differences observed between catalytic performances suggest that these results depend on the influence of structural, textural, acid, and basic properties. Reuse tests of the MMO-Ni₁₅Zn₂₀ catalyst showed moderate stability, with a progressive decrease in activity due to the loss of strong basic sites and the formation of agglomerated regions. Nevertheless, MMO-Ni₁₅Zn₂₀ maintained a GC selectivity of 100% in the successive cycles. Full article

The quantity of waste produced by the food industry is on the rise annually. Among the most prevalent types of waste classified as Class I hazardous substances, posing a significant threat to the environment, is used cooking oils, necessitating proper disposal methods. Concurrently, the combustion of petroleum resources generates substantial greenhouse gas emissions, acting as a primary driver of global warming and associated climatic disruptions. To address the issues mentioned above, food industry waste has been processed into biodiesel fuel. The production involved transformation of sunflower and waste cooking oils with ethanol, with the reaction duration incrementally adjusted between 2 and 7 h in 30 min intervals to determine its effect on biofuel yield. The analysis revealed a pronounced disparity in ester yield between the feedstocks, with the primary component derived from sunflower oil exhibiting a yield 5,81% lower than that obtained from waste oil. For the waste oil substrate, the total ester yield varied from 77.45% (at a 3 h reaction duration) to a maximum of 95.49% (observed at 6.5 h). The temporal evolution of ester release demonstrated a complex, non-monotonic trend, characterized by periodic oscillations superimposed upon a parabolic profile. The confidence interval for the temporal yield data was determined to be ±10%. Full article

In this study, the corrosion behavior of pure aluminum in methyl esters with different degrees of unsaturation and chain lengths, as found in biodiesel, was investigated using electrochemical techniques. The methyl esters evaluated included methyl acrylate (C₄H₆O₂) and methyl linoleate (C₁₉H₃₄O₂), which were added to methyl propionate (C₄H₈O₂) and methyl oleate (C₁₉H₃₆O₂), respectively. The electrochemical techniques employed were electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN), complemented by detailed scanning electron microscopy (SEM) analyses. The results indicated that both the corrosion rate and the susceptibility to localized corrosion, such as pitting, increased with higher degrees of unsaturation and longer alkyl chain lengths. The corrosion process remained under charge transfer control and was not directly influenced by these factors. However, the charge transfer resistance decreased with increasing unsaturation and chain length, consistent with the observed increase in corrosion rate. Full article

Biodiesel is a promising alternative to conventional diesel, but its widespread use is inhibited by oxidative stability issues. To address this problem, various strategies have been tested, and among them, the partial hydrogenation of biodiesel FAMEs has shown promising results. Within the framework of the present study, a comprehensive review and an experimental study on biodiesel upgrading through selective partial catalytic hydrogenation have been conducted. The literature indicates that biphasic aqueous/organic catalytic systems have great potential for biodiesel catalytic upgrade, offering high reaction rates, good selectivity and convenient catalyst separation. In this context, an aqueous/organic biphasic system with a Ru/TPPTS catalyst was tested for the partial hydrogenation of biodiesel derived from WCOs. The results were comparable to those reported in the literature, indicating the potential of this process and contributing to the scarce body of research on these systems. Full article