Search Results (2,202)

Soapstock (SS), a by-product of vegetable oil refining, is a promising source of a mixture of mono-, di-, triglycerides, and free fatty acids (MDTG-FFA), a valuable feedstock for biodiesel production. In this study, the selective extraction of MDTG-FFA from SS using green solvents (ethyl acetate, ethyl formate, methyl acetate, isopropyl acetate, and isobutanol) was investigated. Ethyl acetate showed the highest efficiency, allowing the elimination of the phosphatide (PL) precipitation step with acetone. The process optimization was carried out by response surface methodology with central composite design. Statistical analysis confirmed the significance of the obtained models: F-values were 4.55 (p = 0.013) for MDTG-FFA and 9.62 (p = 0.00074) for PL. Regression analysis revealed a good fit of the experimental data with quadratic models for MDTG-FFA and PL, with coefficients of determination (R²) of 0.804 and 0.897, respectively. The optimum extraction parameters were a solvent-to-dry-matter-of-SS ratio 5:1, time 10.2 min, and initial extraction temperature 21.7 °C. Under these conditions, maximum MDTG-FFA yields of 12.6% and 13.4% were achieved for the two batches of SS, respectively, with minimum PL yields of 0.02% and 0.1%. The obtained MDTG-FFA extracts rich in free fatty acids represent a promising feedstock for biodiesel production. The proposed method provides a rational, resource-efficient, and environmentally preferable extraction of valuable components from SS. Full article

Biodiesel, which is a blend of fatty acid methyl esters (FAME), has garnered significant attention as a promising alternative to petroleum-based diesel fuel. Nevertheless, the commercial production of biodiesel faces challenges due to the high costs associated with feedstock and the non-recyclable homogeneous catalyst system. To address these issues, a solid catalyst derived from construction industry waste cement was synthesized and utilized for biodiesel production from waste cooking oil (WCO). The catalyst’s surface and physical characteristics were analyzed through various techniques, including Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier Transform Infrared Spectroscopy (FTIR). The waste-cement catalyst demonstrated remarkable catalytic performance and reusability in the transesterification of WCO with methanol for biodiesel synthesis. A maximum biodiesel yield of 98.1% was obtained under the optimal reaction conditions of reaction temperature 65 °C; methanol/WCO molar ratio 16:1; calcined cement dosage 3 g; and reaction time 8 h. The apparent activation energy (Ea) from the reaction kinetic study is 35.78 KJ·mol⁻¹, suggesting that the transesterification reaction is governed by kinetic control rather than diffusion. The biodiesel produced exhibited high-quality properties and can be utilized in existing diesel engines without any modifications. This research presents a scalable, environmentally benign pathway for WCO transesterification, thereby contributing significantly to the economic viability and long-term sustainability of the global biodiesel industry. Full article

The growing demand for renewable fuels has renewed interest in biodiesel production, prompting exploration beyond conventional reactors. This review assesses three-dimensional (3D) printed microreactors for biodiesel synthesis via transesterification, with a focus on their potential for enhanced process efficiency, sustainability, and modular deployment. Compared with conventional batch and stirred-tank reactors, 3D-printed microstructured systems often offer superior mass and heat transfer, enabling biodiesel yields up to ~99% in some studies, with critically short residence times (e.g., as low as ~5 s) and reported energy reductions of 60% to 90% under optimal conditions. Optimized configurations in recent work achieved energy requirements as low as ~0.05 to 0.12 kWh L⁻¹, substantially lower than the typical 0.25 to 0.60 kWh L⁻¹ for conventional setups. However, existing studies remain limited in number and scope: issues such as catalyst leaching, chemical and thermal stability of printing materials, dimensional inaccuracies, and scalability of microreactor networks remain under-investigated. Long-term durability, real-world feedstock variation (e.g., high-FFA waste oils), and comprehensive lifecycle assessments are often lacking, limiting confident extrapolation to industrial scale. Despite these challenges, the emerging evidence suggests significant promise for 3D-printed microreactors as a pathway toward modular, energy-efficient, and potentially low-carbon biodiesel production, provided that future work addresses their practical limitations and validates performance under industrially realistic conditions. Full article

The massive influx of pelagic Sargassum in the Caribbean poses a serious environmental, social, and economic problem, as the stranded biomass is often treated as waste and deposited in landfills. This literature review synthesizes recent research highlighting its potential for valorization in various industries, turning this challenge into an opportunity. Sargassum has low levels of protein and lipids. Still, it is particularly rich in carbohydrates, such as alginates, fucoidans, mannitol, and cellulose, as well as secondary metabolites, including phenolic compounds, flavonoids, pigments, and phytosterols with antioxidant and bioactive properties. These biochemical characteristics allow for its application in renewable energy (bioethanol, biogas, biodiesel, and combustion), agriculture (fertilizers and biostimulants), construction (composite materials, cement additives, and insulation), bioremediation (adsorption of heavy metals and dyes), and in the health sector (antioxidants, anti-inflammatories, and pharmacological uses). A major limitation is its high bioaccumulation capacity for heavy metals, particularly arsenic, which increases environmental and health risks and limits its direct use in food and feed. Therefore, innovative pretreatment and bioprocessing are essential to mitigate these risks. The most promising approach for its utilization is a biorefinery model, which allows for the sequential extraction of multiple high-value compounds and energy products to maximize benefits, reduce costs, and sustainably transform Sargassum from a coastal pest into a valuable industrial resource. Full article

The valorization of agro-industrial waste could be a strategy to improve organic waste management. The production of activated carbon (AC) is a path to use for this waste, with the aim of reducing its negative effects. AC is characterized by a high internal surface area, chemical stability, and oxygen-containing functional groups in its structure. This work is focused on the valorization of agro-industrial waste such as pineapple peel and coconut shells. These are made up of sucrose, glucose, fructose, and other essential nutrients, as well as cellulose, hemicellulose, and lignin. Activated Carbon was obtained with slow pyrolysis at 400 °C, for 4 h in a stainless-steel tubular reactor with physical activation. The obtained samples were analyzed using SEM, TGA, FTIR, and BET to verify the morphology, thermal degradation, functional groups and pores ratio of the AC, highlighting the presence of materials pore >10 µm. The TGA residual materials gave 16.3% of pineapple peel AC ashes and 0.2% of coconut AC. A C=C, C-H_X, CO, and OH stretching were observed in 400–4000 cm⁻¹. The peak intensity decreased once the biodiesel was treated with AC, because the traces of water and functional groups interacted actively, resulting a high content of bases. Activated carbon was used for dry cleaning of the obtained biodiesel from residual oil, which was effective in reducing pH and moisture levels in the biodiesel samples. Pore distribution was determined by BET, 5.6 nm for pineapple peel and 39.8243 nm for coconut shells. The obtained activated carbon offers a sustainable alternative to traditional carbon sources and contributes to the circular economy by recycling waste biomass. Full article

Microalgae are an evolutionarily ancient and morphologically diverse group of photosynthetic eukaryotes, with taxonomic resolution complicated by environmentally driven phenotypic plasticity. This study merges deep learning and explainable artificial intelligence (XAI) to establish a transparent, reliable, and biologically meaningful framework for green microalgae (Chlorophyta) classification. Microscope images from three morphologically distinct algal species—Desmodesmus flavescens, Desmodesmus subspicatus, and Tetradesmus dimorphus representing the genera Desmodesmus and Tetradesmus within Chlorophyta—were analyzed using twelve convolutional neural networks, including EfficientNet-B0–B7, DenseNet201, NASNetLarge, Xception, and ResNet152V2. A curated dataset comprising 3624 microscopic images from three Chlorophyta species was used, split into training, validation, and test subsets. All models were trained using standardized preprocessing and data augmentation procedures, including grayscale conversion, CLAHE-based contrast enhancement, rotation, flipping, and brightness normalization. The model’s performance was assessed using accuracy and loss metrics on independent test datasets, while interpretability was evaluated through saliency maps and Gradient-weighted Class Activation Mapping (Grad-CAM) visualizations. ResNet152V2 achieved the highest overall performance among all evaluated architectures, outperforming EfficientNet variants, NASNetLarge, and Xception in terms of macro F1-score. Visualization analysis showed that both Grad-CAM and saliency mapping consistently highlighted biologically relevant regions—including cell walls, surface ornamentation, and colony structures—confirming that the models relied on taxonomically meaningful features rather than background artifacts. The findings indicate that the integration of deep learning and XAI can attain consistently high test accuracy for microalgal species, even with constrained datasets. This approach enables automated taxonomy and supports biodiversity monitoring, ecological assessment, biomass optimization, and biodiesel production by integrating interpretability with high predictive accuracy. Full article

The development of sustainable catalysts from renewable resources is a key challenge for reducing the cost of industrial catalytic processes and waste valorization. In this work, low-cost heterogeneous active catalysts were prepared based on pyrolyzed forest residues, forming valuable porous support materials (Biochar) able to efficiently accommodate the highly active heteropolyacid HPW₁₂. Further, magnetic functionality was incorporated in the novel catalytic materials by the impregnation of NiFe₂O₄. The resulting magnetic composites were characterized by FTIR-ATR, SEM-EDS, ICP-OES, BET, XRD, potentiometric titration and magnetometry. The novel HPW₁₂@NiFe₂O₄@Biochar composites were able to valorize the glycerol to produce the fuel additive solketal with high conversion and high selectivity after only 3 h of reaction via acetalization reaction with acetone. The biochar catalytic composite prepared from cork presented higher pore size than the same prepared from forest biomass. This property was crucial to achieve the best conversion (89%) and the highest solketal selectivity (96%). Additionally, reusability capacity was verified, supporting the potential of the cork-pyrolyzed-based composites as potential low-cost catalytic material to produce fuel additives, such as solketal, under sustainable conditions. This may contribute one step further toward a future with greener energy, increasing the viability of biodiesel industry waste. Full article

Concentrated wastewater streams, like vacuum blackwater (VBW), pose significant management challenges due to their high organic strength and pathogen loads. This review evaluates an integrated biorefinery model employing sequential black soldier fly larvae (BSFL) bioconversion and thermophilic anaerobic digestion (TAD) as a circular solution for effective VBW management. The BSFL pretreatment facilitates bio-stabilization, mitigates ammonia inhibition via nitrogen assimilation, and initiates contaminant degradation. However, this stage alone does not achieve complete hygienization, as it fails to inactivate resilient pathogens, including helminth eggs and spore-forming bacteria, thus precluding the safe direct use of frass as fertilizer. By directing the frass into TAD, the system addresses this limitation while enhancing bioenergy recovery: the frass serves as an optimized, nutrient-balanced substrate that increases biomethane yields, while the sustained thermophilic conditions ensure comprehensive pathogen destruction, resulting in the generation of a sterile digestate. Additionally, the harvested larval biomass offers significant valorization flexibility, making it suitable for use as high-protein animal feed or for conversion into biodiesel through lipid transesterification or co-digestion in TAD to yield high biomethane. Consequently, the BSFL-TAD synergy enables net-positive bioenergy production, achieves significant greenhouse gas mitigation, and co-generates digestate as sanitized organic biofertilizer. This cascading approach transforms hazardous waste into multiple renewable resources, advancing both process sustainability and economic viability within a circular bioeconomy framework. Full article

Greenhouse gas (GHG) emissions from maritime transport account for nearly 3% of global totals, making the decarbonisation of this sector a critical priority. In response, the International Maritime Organization (IMO) adopted the GHG Strategy, targeting the full decarbonisation of international shipping by 2050, with interim milestones in 2030 and 2040. This study evaluates the greenhouse gas fuel intensity of three representative vessel types, an oil tanker, a container ship, and a bulk carrier, using one-year operational fuel consumption data in line with the Regulations of the IMO Net-Zero Framework. Both conventional fuels, including conventional marine fuels, and alternative options, encompassing liquefied natural gas (LNG), e-hydrogen, e-ammonia, e-methanol, and biodiesel, are assessed for compliance during 2028–2035. The findings reveal that conventional fuels are unable to meet future targets, resulting in significant compliance deficits and balancing costs of remedial units. LNG provides short-term benefits but is limited by methane slip. In contrast, e-hydrogen and e-ammonia enable long-term compliance and generate surplus units. E-methanol shows a partial potential, while biodiesel delivers only modest improvements. The results underscore the need for a transition toward near-zero-well-to-wake-emission fuels. This study contributes by combining life cycle assessments with regulatory compliance analysis, offering insights for policymakers and industry stakeholders. Full article

As a widely sourced solid waste rich in metallic elements such as Fe, Zn, Mn and Ca, electric furnace dust serves as a crucial raw material for preparing catalytic materials. This study employed a three-step process—“acid/alkali modification–impregnation–calcination”—to synthesise an electric furnace dust-based magnetic heterogeneous catalyst for biodiesel production. The catalyst prepared via CH₃ONa modification combined with Na₂CO₃ impregnation achieved stable cycling performance at low temperatures, with 14 cycles yielding a consistent conversion exceeding 93.44 wt%, demonstrating exceptional catalytic activity. The CH₃ONa modification generates abundant reactive oxygen species on the furnace dust surface, facilitating the binding of hydroxyl oxygen from the active component (Na⁺) to the modified surface (EFD/CH₃ONa) and thereby anchoring the active species. However, the decline in catalytic performance of the Na₂CO₃&(EFD/CH₃ONa) catalyst after calcination at 600 °C (yield decreasing to 69.77 wt% after 11 stable cycles) was attributed to the detachment and agglomeration of the active component sodium at elevated temperatures. This paper employed electric furnace dust as feedstock to synthesise highly active and stable magnetic multiphase catalysts, thereby not only providing an environmentally sound pathway for industrial solid waste recycling but also offering novel insights for the industrial-scale production of biodiesel. Full article

Valorization of environmental waste into sustainable energy and value-added products offers a strategic pathway for advancing circular economic development and resource sustainability. In this study, waste cooking oil was converted into biodiesel using biogenically generated CaO, prepared thermally at 900 °C. The reaction process was modeled and optimized with a Taguchi orthogonal array L9(3⁴), considering four factors at three levels to yield nine experimental conditions. The model reliability was statistically validated through analysis of variance (ANOVA) at 95% confidence level (p < 0.05), achieving a high determination coefficient (R²) of 0.9965. The maximum biodiesel yield of 91.08% was obtained under the optimal conditions of the methanol to oil ratio of 15:1, a catalyst loading of 4.5 wt%, a reaction time of 90 min, a temperature of 65 °C, and a constant stirring speed of 650 rpm. The fuel property analysis confirmed compliance with international biodiesel and diesel standards). Economic evaluation of the process showed that integrating waste cooking oil with reusable seashell-derived catalysts enabled the production of high-quality biodiesel at R23.20 (~USD 1.39)/L, highlighting a sustainable and cost-competitive alternative to conventional feedstock. The study contributes to advancing waste-to-energy technologies and supports the transition towards a circular and sustainable energy future. Full article

Biofuels represent a viable alternative to fossil fuels due to their lower greenhouse gas emissions, potential for large-scale production, and renewable nature. Orange oil, turpentine, and their hydrogenated derivatives have emerged as promising candidates for biofuel components. Efficient design and operation of internal combustion engines require knowledge of biofuel density and viscosity as functions of temperature; however, experimental data on these properties remain limited. In this work, the densities and viscosities of turpentine, orange oil, hydrogenated turpentine, and hydrogenated orange oil were measured at atmospheric pressure over the temperature range (293.15–373.15) K. The measurements were performed with uncertainties below 0.05 kg·m⁻³ for density and 0.3 mPa·s for viscosity. The experimental data were correlated as a function of temperature using a quadratic function for density and the Andrade equation for viscosity, with absolute average relative deviations of 0.01% for density and 0.5% for viscosity. For all substances, both viscosity and density decrease with increasing temperature, and they are lower than the values for biodiesel. Orange oil and turpentine exhibited higher densities but lower viscosities than their hydrogenated counterparts, which can be attributed to differences in molecular size and packing efficiency. Finally, the measured density and viscosity values are compared with the limit values specified in the European and American biodiesel standards. The analysis shows that blending these essential oils with conventional biodiesel could result in biofuel mixtures that meet both standards. Full article

Biofuels, such as biodiesel, bioethanol, and biohydrogen produced from organic waste, constitute a sustainable alternative to non-renewable fuels and drive the energy transition. In this work, the inherent safety methodology was implemented to quantify and evaluate the intrinsic risks of obtaining hydrogen from African palm stems through direct gasification with Selexol. The methodology indicators were calculated with reference to databases, the literature, and safety data sheets, considering critical stages of the process. The total inherent safety index (I_SI) was 38, classifying the process as intrinsically unsafe, with the chemical component scoring 21 points, with hydrogen being the main chemical risk (8 points), along with hazards generated by chemical reactions. Likewise, high temperature and pressure conditions indicate the presence of potentially unsafe equipment such as reactors and heat exchangers, giving the process index 17 points. Based on the results, it is recommended to reduce raw material inventories and optimize operating conditions to reduce the potential for hazardous events and improve overall inherent safety. Full article

Biofuels offer potential to mitigate climate change, increase energy security, and economically support farmers around the world. Licuri (Syagrus coronata) could be an important biofuel feedstock because its kernel (edible seed) has high energy content. This research investigates the optimal reaction conditions to convert fatty acids (FAs) and fatty acid methyl esters (FAMEs) (including licuri biodiesel) to hydrocarbons via deoxygenation in a trickle-bed reactor over granular Pd/C catalysts. Our results indicate that a 20 wt.% palmitic acid (PA) feed is optimum for continuous deoxygenation at 300 °C and 15 bar in 5% H₂/He because of decarboxylation inhibition at higher concentrations. Deoxygenation rates are higher for PA than for methyl palmitate (MP) because of the slow initial hydrogenolysis of the methoxy bond over Pd/C. The hydrocarbon product distributions from deoxygenation of licuri biodiesel were fully consistent with FA decarboxylation and decarbonylation. A lab-prepared 5 wt.% Pd/C catalyst with higher metal dispersion provided modestly higher hydrocarbon yields from licuri biodiesel than a commercial 1 wt.% Pd/C catalyst. Full article