Search Results (77)

The objective of this study was to evaluate the catalytic performance of commercial Nb₂O₅, supplied by CBMM, in the production of biodiesel by transesterification and esterification, using different feedstocks (soybean, corn, sunflower, and waste oils) and both methyl and ethyl routes. For this, the catalyst was characterized in terms of its crystal structure by X-ray diffraction (XRD), specific surface area using the Brunauer–Emmett–Teller (BET) technique, thermal stability by thermogravimetric analysis (TGA), morphology by scanning electron microscopy (SEM), acidity by ammonia desorption at programmed temperature (TPD-NH₃), and catalytic activity by gas chromatography. The results from the structural analyses indicated that Nb₂O₅ has a single monoclinic phase and a morphology consisting of irregular agglomerates. The specific surface area was 1.3 m²/g, and its density was 4.639 g/cm³. The thermogravimetric analysis showed that the material has thermal stability, maintaining its structural integrity up to temperatures as high as 1000 °C. The total acidity reached 301 μmol NH₃/g, indicating the presence of Brønsted and Lewis acidic sites. In catalytic tests, Nb₂O₅ showed higher efficiency in the methyl route, achieving an initial conversion of 96.43% in esters with soybean oil, outperforming other feedstocks. However, catalyst reuse over five cycles revealed a progressive decrease in catalytic activity, possibly due to blocking active sites by adsorbed products, as confirmed by FTIR and XRD analyses conducted on the catalyst. Despite decreased activity after the cycles, the catalyst maintained its crystal structure, indicating structural stability. These results demonstrate the potential of Nb₂O₅ as a heterogeneous catalyst for biodiesel production, particularly with the methyl route and high-quality oils. This study highlights the relevance of Nb₂O₅ in biodiesel synthesis, contributing to sustainable practices and technological advancement in the renewable energy sector. Full article

The rising global energy demand, alongside concerns regarding environmental deterioration due to the use of fossil fuels, has spurred extensive investigation into renewable energy alternatives. Biomass-derived biodiesel, especially from lesser-known oil sources, emerges as a promising option. This research focuses on analyzing the fatty acid methyl esters (FAMEs) derived from Kariya (Hildegardia barteri (Mast.) Kosterm) seed oil through basic catalytic transesterification using gas chromatography–flame ionization detector (GC–FID) analysis, assessing its potential as a biodiesel feedstock. Oil extraction from Kariya seeds was carried out using three solvents (n-hexane, ethanol, and a 1:1 blend of hexane and ethanol), followed by transesterification with methanol. Gas chromatography–mass spectrometry (GC–MS) and GC–FID analyses were utilized to identify and quantify FAMEs in the resulting biodiesel. The results revealed various FAMEs, including methyl myristate, methyl palmitate, methyl stearate, methyl oleate, methyl linoleate, and methyl linolenate. Significant differences in FAME composition were observed among the samples, with hexane–ethanol Kariya oil biodiesel (HE-KOB) showing the highest FAME content (76.1%). This combination of solvents exhibited synergistic effects on the composition of HE-KOB, suggesting potential optimization strategies for biodiesel production. Fourier transform infrared spectroscopy (FTIR) provided additional insights into the molecular composition of the biodiesel samples, confirming their biodiesel nature through the identified functional groups such as methyl, methylene, hydrocarbon, ester, aldehyde, and alkene. Thermogravimetric analysis (TGA) for thermal decomposition also gave an insight into FAME composition and its contribution to the degree of conversion of biodiesel to energy. These findings highlight the feasibility of utilizing Kariya seed oil as a biodiesel feedstock, emphasizing the importance of solvent selection and transesterification conditions in optimizing FAME yield and composition. This research contributes to the exploration of underutilized oil sources for sustainable biodiesel production, aligning with the global shift towards cleaner and renewable energy sources. Full article

The Chlorophyceae algae, specifically Chlorella spp., have been extensively researched for biodiesel production. This study focused on the alga Chlorella variabilis RSM09, which was isolated from a brackish-water environment at Raksamae Bridge in Klaeng District, Rayong Province, Thailand. The effects of the carbon dioxide gas (CO₂) concentration (0.03%, 10%, 20%, 30%, 40%, and 50% v/v), light intensity (3000, 5000, and 7000 Lux), and photoperiod (12:12, 18:6, and 24:0 h L/D) on algal growth and lipid production were investigated. The results indicated that C. variabilis RSM09 achieved optimal growth under 20% v/v CO₂ aeration, with an optical density of approximately 2.91 ± 0.27, a biomass concentration of 1.32 ± 0.14 g/L, and a lipid content of 21.96 ± 0.29% (wt.). Among the three different light intensities, higher optical density (4.20 ± 0.14), biomass (1.79 ± 0.25 g/L), and lipid content (20.75 ± 2.0% wt.) were at the 5000 Lux of light intensity. Additionally, the photoperiod of 24:0 h (L/D) produced the highest biomass at 1.86 ± 0.21 g/L, followed by the 18:6 h light/dark photoperiod with a biomass of 1.65 ± 0.17 g/L, and the 12:12 h light/dark photoperiod with 1.35 ± 0.43 g/L. In contrast, the 18:6 h L/D photoperiod yielded a higher lipid concentration of 25.22 ± 2.06% (wt.) compared to the others. All cultured microalgae showed significant effects on fatty acid composition. Palmitic (16:0), linoleic (C18:2), and linolenic (C18:3) acids were predominant in C. variabilis RSM09 under all photoperiods. This study exhibited that the microalga C. variabilis RSM09 has great potential as a feedstock for biodiesel production. Full article

In this study, an upflow anaerobic packed-bed reactor (UAPB) produced biobutanol from the main byproduct of biodiesel plants, commonly known as glycerol. Currently, butanol production is mostly limited to pure cultures and sterilized feedstocks. Using glycerol wastes from biodiesel production demands a new paradigm because sterilization is not economically feasible for the elevated amount of glycerol generated by the biodiesel industry. Different microbial consortia were evaluated as inoculum sources to convert glycerol to butanol. In the first stage, operations were carried out with an average organic loading rate (OLR) of 13 g COD L⁻¹ d⁻¹. Kefir grains, sucrose auto-fermentation consortium, and heat-treated anaerobic sludge produced 16.7, 48.5, and 12.8 mg of butanol per gram of chemical oxygen demand (COD), respectively. Besides butanol production, a significant amount of ethanol (241.5 mg g⁻¹ COD), acetate (30.3 mg g⁻¹ COD), and butyrate (183.4 mg g⁻¹ COD) were generated with glycerol processed by sucrose auto-fermentation consortium. In the second stage, the organic loading rates of 6.5, 13.0, and 26.0 g COD L⁻¹ d⁻¹ were applied to the UAPB reactor inoculated with sucrose auto-fermentation consortium. The OLR of 13.0 g COD L⁻¹ d⁻¹ yielded the highest production of butanol (41.5 mg g⁻¹ COD) and generated other valuable co-products such as butyrate (246.1 mg g⁻¹ COD), acetate (37.3 mg g⁻¹ COD), and propionate (19.6 mg g⁻¹ COD). Full article

Poly-γ-glutamic acid (γ-PGA) is an attractive biopolymer for medical, agri-food, and environmental applications. Although microbial synthesis by Bacilli fed on waste streams has been widely adopted, the obtainment of efficient sustainable production processes is still under investigation by bioprocess and metabolic engineering approaches. The abundant glycerol-rich waste generated in the biodiesel industry can be used as a carbon source for γ-PGA production. Here, we studied fermentation performance in different engineered Bacillus subtilis strains in glycerol-based media, considering a swrA⁺ degU32^Hy mutant as the initial producer strain and glucose-based media for comparison. Modifications included engineering the biosynthetic pgs operon regulation (replacing its native promoter with P_hyspank), precursor accumulation (sucCD or odhAB deletion), and enhanced glutamate racemization (racE overexpression), predicted as crucial reactions by genome-scale model simulations. All interventions increased productivity in glucose-based media, with P_hyspank-pgs ∆sucCD showing the highest γ-PGA titer (52 g/L). Weaker effects were observed in glycerol-based media: ∆sucCD and P_hyspank-pgs led to slight improvements under low- and high-glutamate conditions, respectively, reaching ~22 g/L γ-PGA (26% increase). No performance decrease was detected by replacing pure glycerol with crude glycerol waste from a biodiesel plant, and by a 30-fold scale-up. These results may be relevant for improving industrial γ-PGA production efficiency and process sustainability using waste feedstock. The performance differences observed between glucose and glycerol media also motivate additional computational and experimental studies to design metabolically optimized strains. Full article

Biodiesel is a mixture of fatty acid alkyl esters (FAAEs) mainly produced via transesterification reactions among triglycerides and short-chain alcohols catalyzed by chemical catalysts (e.g., KOH, NaOH). Lipase-assisted enzymatic transesterification has been proposed to overcome the drawbacks of chemical synthesis, such as high energy consumption, expensive separation of the catalyst from the reaction mixture and production of large amounts of wastewater during product separation and purification. However, one of the main drawbacks of this process is the enzyme cost. In recent years, nano-immobilized lipases have received extensive attention in the design of robust industrial biocatalysts for biodiesel production. To improve lipase catalytic efficiency, magnetic nanoparticles (MNPs) have attracted growing interest as versatile lipase carriers, owing to their unique properties, such as high surface-to-volume ratio and high enzyme loading capacity, low cost and inertness against chemical and microbial degradation, biocompatibility and eco-friendliness, standard synthetic methods for large-scale production and, most importantly, magnetic properties, which provide the possibility for the immobilized lipase to be easily separated at the end of the process by applying an external magnetic field. For the preparation of such effective magnetic nano-supports, various surface functionalization approaches have been developed to immobilize a broad range of industrially important lipases. Immobilization generally improves lipase chemical-thermal stability in a wide pH and temperature range and may also modify its catalytic performance. Additionally, different lipases can be co-immobilized onto the same nano-carrier, which is a highly effective strategy to enhance biodiesel yield, specifically for those feedstocks containing heterogeneous free fatty acids (FFAs). This review will present an update on the use of magnetic iron oxide nanostructures (MNPs) for lipase immobilization to catalyze transesterification reactions for biodiesel production. The following aspects will be covered: (1) common organic modifiers for magnetic nanoparticle support and (2) recent studies on modified MNPs-lipase catalysts for biodiesel production. Aspects concerning immobilization procedures and surface functionalization of the nano-supports will be highlighted. Additionally, the main features that characterize these nano-biocatalysts, such as enzymatic activity, reusability, resistance to heat and pH, will be discussed. Perspectives and key considerations for optimizing biodiesel production in terms of sustainability are also provided for future studies. Full article

Bioenergy productions from microalgae have received wide attention recently and have a high potential to replace fossil fuels. Moreover, due to the high photosynthetic efficiency, microalgae mass cultivation and scale-up are believed to efficiently reduce the impact of greenhouse gas emissions. This review article explores the potential of microalgae as a reliable and sustainable source of bioenergy feedstock. The current review article contains an in-depth discussion of the various methods of producing energy using microalgae, viz. algal fuel cell (AFC), microbial fuel cell (MFC), bioethanol and biodiesel, and various other applications. This article discussed the different aspects of AFC and MFC, such as fuel cell configurations, reaction mechanisms at electrodes, reactor design factors affecting the efficiencies, and strategies to enhance the efficiencies. Moreover, microalgae cultivation, value-added compounds (pigments, polysaccharides, unsaturated fatty acids), liquid fuel production, limitations, the global scenario of microalgae biomass-based energy, and significant advancements in this field. In a nutshell, this review serves as a valuable resource for identifying, developing, and harnessing the potential of microalgae as a promising biofuel source. Full article

Renewable hydrogen production by aqueous phase reforming (APR) over Ni/Al-Ca catalysts was studied using pure or refined crude glycerol as feedstock. The APR was carried out in a fixed bed reactor at 238 °C, 37 absolute bar for 3 h, using a solution of 5 wt.% of glycerol, obtaining gas and liquid products. The catalysts were prepared by the co-precipitation method, calcined at different temperatures, and characterized before and after their use by several techniques (XRD, ICP-OES, H₂-TPR, NH₃-TPD, CO₂-TPD, FESEM, and N₂-physisorption). Increasing the calcination temperature and adding Ca decreased the surface area from 256 to 188 m²/g, and its value after the APR changed depending on the feedstock used. The properties of the acid and basic sites of the catalysts influenced the H₂ yield also depending on the feed used. The Ni crystallite was between 6 and 20 nm. In general, the incorporation of Ca into Ni-based catalysts and the increase of the calcination temperature improved H₂ production, obtaining 188 mg H₂/mol C fed during the APR of refined crude glycerol over Ni/AlCa-675 catalyst, which was calcined at 675 °C. This is a promising result from the point of view of enhancing the economic viability of biodiesel. Full article

The paper investigates the potential of biomass pyrolysis as a sustainable and renewable energy solution. The study focuses on three biomass types: corn cob, vine rod, and sunflower, which are abundant agricultural residues with potential for biofuel production. The pyrolytic gas, oil, and char produced during pyrolysis at a heating rate of 10 °C/min were analyzed. At the pyrolysis temperature of 500 °C, the corn cob showed the smallest final residual mass of 24%, while the vine rod exhibited the largest mass loss of 40%. Gas analysis revealed the concentrations of CO₂, CO, H₂, and CH₄ in the pyrolytic gas, indicating its energy potential. Sunflower presented the largest calorific value of the produced biogas, while corn cob was the lowest. The chemical composition of the bio-oils was determined, with aliphatic acids identified as the dominant compounds, suggesting their potential for biodiesel production. Fourier Transform–Infrared Spectroscopy (FT-IR) analysis of raw biomass and char products demonstrated varying extents of decomposition among the biomass samples. A multicriteria assessment approach was employed to evaluate the differences between the selected three biomass feedstock and determined that sunflower biomass ranked the highest among the three, although the overall difference was small, confirming the suitability of all three biomass samples for pyrolysis conversion to higher-value-added fuels. Full article

According to the EU Directive, the so-called RED II, there is increasing significance for biofuels produced from biomass with low indirect land use change (ILUC) risk. Such an alternative and sustainable feedstock could be microalgae, among others, used for biodiesel production. This is due to the high lipid content of their cells and their potential ability to accumulate significant amounts of carbon dioxide in their biomass, which has a positive effect on the carbon footprint of the product. The aim of this study was to determine the effect of adding algal biodiesel to conventional diesel fuel on selected performance parameters of a diesel engine, taking into account the composition of the emitted exhaust gas. Energy-related engine performance parameters such as power, hourly and specific fuel consumption, engine thermal efficiency, and indicated efficiency were determined. No significant differences were found in the energy parameters of engine operation with the fuels tested. In terms of carbon monoxide and NOx emissions, at the highest engine torque, more favorable parameters were obtained for fuel with biodiesel produced from rapeseed oil (B/RME). Under the same conditions, carbon dioxide emissions for the fuel with the addition of biodiesel from microalgae (B/Algae) were 8.1% lower. Full article

Presently, the use of fossil fuels is not ecologically sustainable, which results in the need for new alternative energies such as biodiesel. This work presents a review of the classification of the lipidic feedstocks and the catalysts for biodiesel production. It also presents the pros and cons of the different processes and feedstocks through which biodiesel is obtained. In this context, cooking oil (WCO) has emerged as an alternative with a high potential for making the process sustainable. A detected limitation to achieving this is the high content of free fatty acids (FFA) and existing problems related to homogeneous and heterogeneous catalysts. To overcome this, the use of bifunctional catalysts is being evaluated by the scientific community. Thus, this work also explores the advances in the study of bifunctional catalysts, which are capable of simultaneously carrying out the esterification of free fatty acids (FFA) and the triglycerides present in the WCO. For the sake of an improved understanding of biodiesel production, flow diagrams and the mechanisms implied by each type of process (enzymatic, homogenous, and heterogeneous) are provided. This article also highlights some of the challenges in catalyst development for sustainable biodiesel production from low-grade raw materials. Full article

Production of biodiesel from edible vegetable oils using homogenous catalysts negatively impacts food availability and cost while generating significant amounts of caustic wastewater during purification. Thus, there is an urgent need to utilize low-cost, non-food feedstocks for the production of biodiesel using sustainable heterogeneous catalysis. The objective of this study was to synthesize a novel supported nano-magnetic catalyst (CaO/Fe₂O₃/feldspar) for the production of biodiesel (fatty acid methyl esters) from waste and low-cost plant seed oils, including Sinapis arvensis (wild mustard), Carthamus oxyacantha (wild safflower) and Pongamia pinnata (karanja). The structure, morphology, surface area, porosity, crystallinity, and magnetization of the nano-magnetic catalyst was confirmed using XRD, FESEM/EDX, BET, and VSM. The maximum biodiesel yield (93.6–99.9%) was achieved at 1.0 or 1.5 wt.% catalyst with methanol-to-oil molar ratios of 5:1 or 10:1 at 40 °C for 2 h. The CaO/Fe₂O₃/feldspar catalyst retained high activity for four consecutive cycles for conversion of karanja, wild mustard, and wild safflower oils. The effective separation of the catalyst from biodiesel was achieved using an external magnet. Various different physico-chemical parameters, such as pour point, density, cloud point, iodine value, acid value, and cetane number, were also determined for the optimized fuels and found to be within the ranges specified in ASTM D6751 and EN 14214, where applicable. Full article

Over the last few years and with increasing global climatic change, the international energy crisis and shortage of freshwater resources have raised many inquiries about global water security and energy. Therefore, finding out alternative and sustainable energy sources has become an important universal requirement. Here, we assessed the viability of exploiting municipal wastewater (WW) as a nutrient-rich growth medium for cultivating the pollution-tolerant coccoid green microalga Chlorococcum sp. (Chlorophyceae) to simultaneously remove nutrients and produce biodiesel. Chlorococcum sp. was isolated from municipal wastewater sampled from Menoufia Governorate, Egypt. Under the standard growth conditions and until reaching the late exponential growth phase, it was cultivated at different concentrations (25%, 50%, 75%, and 100%) of the secondary treated WW, and the findings were compared to the control (grown in BBM). The study results revealed that the 50% WW treatment was the most suitable approach for removing NO₃⁻, NH₄⁺, and TP with percentages of 96.9%, 98.4%, and 90.1%, respectively. Moreover, the 50% WW treatment produced the highest algal biomass (1.97 g L⁻¹) and productivity (82 mg L⁻¹ day⁻¹). In addition, it showed the highest lipid production (600 mg L⁻¹), with 25 mg L⁻¹ day⁻¹ lipid productivity and lipid yield with 30.5% of the cell dry weight (CDW). The gas chromatography–mass spectrometry (GC-MS) technique was applied to characterize fatty acid profiling, and it was found that oleic (C18:1) and palmitic (C16:0) fatty acids were present in much higher concentrations in Chlorococcum sp. cells grown in 50% WW as compared to the control, i.e., 44.43% and 27.38% vs. 36.75% and 21.36%, respectively. No big difference was present in linoleic (C18:2) fatty acid concentrations. Importantly, the biodiesel properties of our Chlorococcum sp. grown in 50% WW were consistent with the international biodiesel standards. In light of our findings, Chlorococcum sp. has a great potential for utilization as a biodiesel feedstock and for bioremediation of wastewater. Full article

Biodiesel production through transesterification results in a large quantity of crude glycerol as a byproduct, the utilization of which is technically and economically challenging. Because of the ability to efficiently process wet feedstocks, supercritical water gasification (SCWG) is utilized in this study to convert crude glycerol into hydrogen-rich syngas. A significant challenge addressed through this study is the decomposition routes of different heterogeneous components of crude glycerol during SCWG. Pure glycerol, methanol and oleic acid were investigated for SCWG as the model compounds of crude glycerol. SCWG of model compounds at temperature, pressure, feedstock concentration and reaction time of 500 °C, 23–25 MPa, 10 wt% and 1 h, respectively, revealed methanol to exhibit the highest H₂ yield of 7.7 mmol/g, followed by pure glycerol (4.4 mmol/g) and oleic acid (1.1 mmol/g). The effects of feedstock concentration from 30 wt% to 10 wt% increased H₂ yield from all model compounds. Response surface methodology (RSM) was used to develop a response curve to visualize the interactive behavior and develop model equations for the prediction of H₂-rich gas yields as a function of the composition of model compounds in the crude glycerol mixture. Predictive models showed a good agreement with experimental results, demonstrating high accuracy and robustness of the model. These findings demonstrated a strong potential of crude glycerol for SCWG to generate H₂-rich syngas. Full article

Compared to fossil fuels, biodiesel is a clean fuel, does not pollute the environment, and can be produced from inexhaustible natural sources. The objectives of our research are to study how increasing doses of complex fertilizers, applied to rapeseed oil culture, affect the production of rapeseeds and oil; the comparative study between the quality parameters of refined rapeseed oil (RRO) and fatty acids (FA); and the analysis of the quality of the biodiesel obtained from them (BRO and BFA). The experimental field is set-up in a Latin rectangle format and is placed on a total area of 400 m² divided into 16 parcels, randomized for uniformity with four replications and four fertilizer graduations (N₀P₀K₀—Control, N₁₆₀P₁₆₀K₁₆₀, N₃₂₀P₃₂₀K₃₂₀, N₄₈₀P₄₈₀K₄₈₀). To obtain biodiesel form oil (BRO) and fatty acids (BFA), the processes of esterification, transesterification, refining, washing, sedimentation, and drying were applied. A comparison between biodiesel quality parameters from RRO and FAs were made, and we highlighted the differences in quality compared to samples from the experimental field. The use of large amounts of complex fertilizers leads to high yields of rapeseed (13.3–47.0 q ha⁻¹) and oil (629.8–2130.8 L ha⁻¹), which are statistically significant only for high doses (N₃₂₀P₃₂₀K₃₂₀ and N₄₈₀P₄₈₀K₄₈₀). For most of the qualitative parameters studied, the differences in values between BFA and BRO have positive values, which means a higher quality for BRO. Both BRO and BFA generally fall within the quality parameters imposed by European standards (ES). Although the quality of BRO is superior to BFA, it is produced on a smaller scale due to the nutritional importance of refined rapeseed oil. This study is of particular importance in the optimization of rapeseed fertilization, with a view to the efficient conversion of crude oil, a feedstock for chemical fertilizers and an environmentally friendly fuel. Full article