Biodiesel Application Research Articles

Applications of Biodiesel in Drilling Fluids

Biodiesel, referred to as the monoalkyl ester of long-chain fatty acid ester that is synthesized by the complete transesterification of triglycerides, has captured the attention of drilling researchers attributing to its magnificent characteristics such as the high flash point, excellent lubricity, nontoxicity, high biodegradability, and abundant feedstock resources, which make it ecofriendly and technically and economically feasible for a sustainable drilling operation. There are several studies that reported and documented the usage of biodiesel in drilling fluids on laboratory and field scales. In this paper, the production and the key physical and chemical properties of biodiesel are thoroughly reviewed. Moreover, the applications of biodiesel in drilling muds either as base fluids or additives were comprehensively surveyed. The literature review revealed that the challenges of biodiesel applications in drilling mud systems are related to its chemical reactivity and adverse interactions with some additives, along with its performance deficiency at temperature above 120°C. Therefore, further investigation on temperature stability and additive compatibility is recommended. In addition, as a new approach, it is recommended to study the potentiality of using crude waste oils in drilling mud formulations. The lessons learned and recommendations stated in this paper will assist in enhancing the proved use of biodiesel and drilling fluid optimization.

An Indian perspective on biodiesel production from rice By-Products

Growing global warming and climate change shifted energy policy to adopt a cleaner and more sustainable way of energy generation across the world. Biodiesel has emerged as a good alternative fuel due to advantages like diesel-like structure and less emission. However, the cost of biodiesel production makes it ineffective compare to the use of diesel especially in a developing country like India. Waste materials as an alternative can help to reduce the cost. In this review rice by-products like rice bran oil and rice husk have been discussed as a cheap and reliable alternative for feedstock and source of catalyst respectively. The Rice bran oil-based biodiesel and Rice husk-based catalyst are briefly discussed using process variables like reaction temperature, yield, etc. Also, the applicability of rice bran biodiesel using engine performance and emission characteristics of biodiesel from rice bran oil is compared and the potential of by-products in India is investigated. Biodiesel production using rice bran oil as a source of free fatty acid and rice husk as a source of catalyst is discussed thoroughly. In conclusion, the rice by-products as input appeared as a good and sustainable alternative for biodiesel production in India.

Analyses and evaluation of the main chemical components in different tobacco (Nicotiana tabacum L.) genotypes

The nicotine, reducing sugar and ion contents from the threshing of tobacco can re-used from the industry. The crude oil and fatty oil compositions of tobacco seeds can be considered as an alternative source of raw material for biodiesel. In this study, the nicotine, reducing sugar content, crude oil, fatty acid composition and ion content were determined in 29 genotypes and 1 cultivar of tobacco. The genetic diversity was determined among the tobacco cultivar and genotypes base on examined properties. The nicotine content varied between 0.10-0.87%, reducing sugar ranged from 9.70-21.30%, crude oil varied between 24.33-47.00% and fatty acid compositions was found in the range of 77.94-100%. Linoleic (13.92-75.04%) and butyric (0.33-64.98%) acids were the major components. Overall, the BSR-5 (52.56 mg/g) and ESR-5 (44.58 mg/g) genotypes exhibited the highest potassium contents and ESR-7 (6.54 mg/g) and ESR-8 (1.28 mg/g) genotypes had the lowest chlorine contents. As a result of this study, the highest nicotine content, reducing sugar and crude oil of tobacco were found in ESR-4, ESR-11 and BSR-5 genotypes, respectively. The dendrogram analysis divided the tobacco into two main groups and most of the same origin genotypes fell into the same group. The results indicated that the different tobacco leaves and seeds can be evaluated as an alternative source in the industry as cigarettes, biodiesel and different industrial applications such as cosmetic, oil paints and varnishes based on their chemical properties.

Generating Pennycress (Thlaspi arvense) Seed Triacylglycerols and Acetyl-Triacylglycerols Containing Medium-Chain Fatty Acids

Thlaspi arvense L. (pennycress) is a cold-tolerant Brassicaceae that produces large amounts of seeds rich in triacylglycerols and protein, making it an attractive target for domestication into an offseason oilseed cash cover crop. Pennycress is easily genetically transformed, enabling synthetic biology approaches to tailor oil properties for specific biofuel and industrial applications. To test the feasibility in pennycress of producing TAGs and acetyl-TAGs rich in medium-chain fatty acids (MCFAs; C6–C14) for industrial, biojet fuel and improved biodiesel applications, we generated transgenic lines with seed-specific expression of unique acyltransferase (LPAT and diacylglycerol acyltransferase) genes and thioesterase (FatB) genes isolated from Cuphea viscosissima, Cuphea avigera var. pulcherrima, Cuphea hookeriana, Coco nucifera, and Umbellularia californica. Wild-type pennycress seed TAGs accumulate no fatty acids shorter than 16C and less than 5 mol percent C16 as palmitic acid (16:0). Co-expressing UcFatB and CnLPAT produced up to 17 mol% accumulation of lauric acid (12:0) in seed TAGs, whereas CvFatB1 CvLPAT2 CpDGAT1 combinatorial expression produced up to 27 mol% medium chain FAs Medium Chain Fatty Acids mostly in the form of capric acid (10:0). CpFatB2 ChFatB2 combinatorial expression predominantly produced, in equal parts, up to 28 mol% myristic acid (14:0) and palmitic acid. Genetically crossing the combinatorial constructs into a fatty acid elongation1 (fae1) mutant that produced no 22:1 erucic acid, and with an Euonymus alatus diacylglycerol acetyltransferase (EaDAcT)-expressing line that produced 60 mol% acetyl-TAGs, had no or relatively minor effects on MCFAs accumulation, suggesting fluxes to MCFAs were largely unaltered. Seed germination assays revealed no or minor delays in seed germination for most lines, the exception being CpFatB2 ChFatB2-expressing lines, which had substantially slower seed germination rates. Taken together, these data show that pennycress can be engineered to produce seeds accumulating modest amounts of MCFAs of varying carbon-chain length in TAGs and acetyl-TAGs, with rates of seed germination being delayed in only some cases. We hypothesize that increasing MCFAs further may require functional reductions to endogenous transferases and/or other FA elongases.

Effect of Phytohormones Supplementation under Nitrogen Depletion on Biomass and Lipid Production of Nannochloropsis oceanica for Integrated Application in Nutrition and Biodiesel

Economic viability of biodiesel production relies mainly on the productivity of biomass and microalgal lipids. In addition, production of omega fatty acids is favorable for human nutrition. Thus, enhancement of lipid accumulation with high proportion of omega fatty acids could help the dual use of microalgal lipids in human nutrition and biodiesel production through biorefinery. In that context, phytohormones have been identified as a promising factor to increase biomass and lipids production. However, nitrogen limitation has been discussed as a potential tool for lipid accumulation in microalgae, which results in simultaneous growth retardation. The present study aims to investigate the combined effect of N-depletion and 3-Indoleacetic acid (IAA) supplementation on lipid accumulation of the marine eustigmatophyte Nannochloropsis oceanica as one of the promising microalgae for omega fatty acids production. The study confirmed that N-starvation stimulates the lipid content of N. oceanica. IAA enhanced both growth and lipid accumulation due to enhancement of pigments biosynthesis. Therefore, combination effect of IAA and nitrogen depletion showed gradual increase in the dry weight compared to the control. Lipid analysis showed lower quantity of saturated fatty acids (SFA, 26.25%) than the sum of monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA). Under N-depletion, SFA decreased by 12.98% compared to the control, which recorded much reduction by increasing of IAA concentration. Reduction of SFA was in favor of PUFA, mainly omega-6 and omega-3 fatty acids which increased significantly due to IAA combined with N-depletion. Thus, the present study suggests a biorefinery approach for lipids extracted from N. oceanica for dual application in nutrition followed by biodiesel production.

Study on enzymatic activity and lipase catalysis by lipase high-yield strain

In this paper, microorganism for high lipase productivity was screened for immobilization in biodiesel synthesis. Strains with high lipase productivity were analyzed at nucleic acid level with special universal primes. In addition, reaction course, theory of lipase adsorption, lipase specificity on substrate, kinetics, and the application of enzymatic synthesis in biodiesel were investigated. The tests of lipase productivity, lipase purification, lipase immobilization, and lipase application in biodiesel were carried out indicating that lipase from the above micro-organisms was able to catalyze the transesterification reaction of rapeseed oil with moderate oleic aicd content.

Preparation and Characterisation of Biodiesel from Marine Macro-algae Chaetomorpha spp.

The petition for substitute energies has increased in the past numerous years. Several substitutes have come into existence in recent years, and many more are on their way to get established as a sustainable fuel substitute. In the present investigation, we carried out the extraction of total lipids and production of biodiesel from Chetomarpha spp., The algae were collected from the natural habitat of Karwar shoreline region. Different pre-treatment was adopted to dry the collected sample for lipid extraction. The solvent Method was followed to obtain biodiesel at laboratory conditions. GC-MS technique was followed to evaluate the composition of fatty acids in Extracted biodiesel. Quantity of total fatty acid (TFAs) accounted nearly normal in its lipid content composition as in many previous reports. Biofuel experiments have shown promising results towards biodiesel application. The same results have been explained in the appropriate form as given below.

Testing engine lubricants for heavy-duty biodiesel applications

Oxidation, bearing and engine tests demonstrate that Shell Rimula R4 X exceeds the minimum performance requirements for engines running on high biocontent biodiesel fuels.

Novel mutant camelina and jatropha as valuable feedstocks for biodiesel production

Novel mutant camelina has become a crop of interest inspired by its short growing season, low harvesting costs and high oil composition. Despite those advantages, limited research has been done on novel mutant lines to determine applicability for biodiesel production. Jatropha is an extremely hardy, frugal and high oil yielding plant species. The major aim of the present study was not only to compare biodiesel production from jatropha and camelina but was also to test the efficacy of camelina mutant lines (M6 progenies) as superior feedstock. The biodiesel yield from camelina oil and jatropha oil was 96% and 92%, respectively. The gas chromatographic analysis using flame ionization detector (GC-FID) showed that mutant camelina oil biodiesel sample contain major amount of oleic acid (46.54 wt%) followed by linolenic acid (20.41 wt%) and linoleic acid (16.55 wt%). Jatropha biodiesel found to contain major amount of oleic acid (45.03 wt%) followed by linoleic acid (25.07 wt%) and palmitic acid (19.31 wt%). The fuel properties of produced biodiesel were found in good agreement with EN14214 and ASTM D6751 standards. The mutant camelina lines biodiesel have shown comparatively better fuel properties than jatropha. It has shown low saponification value (120.87–149.35), high iodine value (130.2–157.9) and better cetane number (48.53–59.35) compared to jatropha biodiesel which have high saponification value (177.39–198.9), low iodine value (109.7–123.1) and lesser cetane number (47.76–51.26). The results of the present student of utilizing novel mutant camelina lines for biodiesel production are quite promising and are helpful in turning out the outcomes of the previous studies suggesting that C. sativa biodiesel presents serious drawbacks for biodiesel applications.

Enhanced Light-Induced Biosynthesis of Fatty Acids Suitable for Biodiesel Production by the Yellow-Green Alga Eustigmatos magnus

Optimization of the fatty acid profile in microalgae is one of the key strategies for obtaining valuable products and sustainable biofuels. Light intensity and light regimes exert an impact on the growth and metabolic process in microalgae. The objective of the present investigations was to assess the effect of light intensity and continuous light vs. photoperiod conditions on the growth and changes in the biomass composition in Eustigmatos magnus, with a focus on bioactive molecules such as lipids and fatty acids. The highest daily productivity of Eustigmatos magnus biomass and lipid yields were detected at continuous illumination and at the highest intensity of light. The results show that the content and composition of fatty acids was influenced by the culture conditions. The biomass of Eustigmatos magnus contained the highest concentrations of polyunsaturated fatty acids in the pphotoperiod conditions with the highest light intensity. This study shows that Eustigmatos magnus has a capacity for the accumulation of palmitoleic acid. A high intensity of continuous light improves the profile of fatty acids in Eustigmatos magnus, which can be suitable for biodiesel applications. At the high intensity of continuous light, Eustigmatos magnus lipids are characterized by high content of oleic acids and low content of saturated and monounsaturated acids.

Engine performance and emission studies by application of nanoparticles as additive in biodiesel diesel blends

The present paper investigates the effects of different nanoparticles blended with biodiesel on performance and emission characteristics of the diesel engine. However, inherent drawbacks like lower heating value, higher density, and viscosity while increased fuel consumption and NOx emissions limit the biodiesel application in engines. In this way, the additives in the form of nanoparticles of different materials play a prominent role to mitigate the drawbacks of biodiesel. The higher calorific value, thermal conductivity, and surface to volume ratio properties of nanoparticles enhanced the engine performance, combustion and emissions compared to neat biodiesel and biodiesel-diesel blends. This study uses five different Diesel, B20, B20CO, B20TO and B20COTO test fuels to be prepared at a different volume mixing ratio. It was concluded that by B20COTO nanoparticle additive fuel showed high BTE and reduced BSFC, HC and NOx emissions on a diesel engine as correlated to other fuels. B20CO fuel showed lower CO emissions as compared other fuels.

A Comprehensive Review of the Application Characteristics of Biodiesel Blends in Diesel Engines

Since the advent of biodiesel as a renewable alternative fuel, it has attracted wide attention from researchers. The raw materials of biodiesel generally produced by transesterification of animal fats, plants, algae or even waste cooking oil, which makes full use of natural resources and alleviates increasingly problematic oil shortages and environmental pollution. Biodiesel can be directly applied to vehicle engines without any modification and will both improve the combustion quality of the engine and reduce the harmful emissions from the engine. This study mainly summarizes the influence of biodiesel applications on diesel engines, including the impact on engine performance, combustion characteristics, emission characteristics, vibration, noise characteristics, and compatibility. In particular, unregulated emissions such as volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs), which are rarely mentioned in other review articles, are also discussed in this study.

Development and Evaluation of Thermodynamic Models for Predicting Cold Flow Properties of Biodiesel

Biodiesel, especially palm oil-based methyl esters (PME), is steadily increasing in consumption in Indonesia and Malaysia as a petroleum diesel substitute. PME has poor cold flow properties due to the presence of saturated bound glycerols. Bound glycerols, such as monoglycerides (MAGs), diglycerides (DAGs), and triglycerides (TAGs), are impurities in biodiesel as a result of incomplete transesterification, and have high melting points. These minor components often solidify even at temperatures higher than the cloud point and thus cause clogging in fuel filters. It is, therefore, essential to predict the solidification temperature for the application of biodiesel, particularly in high blending levels. This study developed and evaluated thermodynamic models for predicting the solidification of biodiesel. Binary and multicomponent mixtures of fatty acid methyl esters (FAMEs) and bound glycerols were prepared as biodiesel models. The solidification temperature was measured by differential scanning calorimetry and the results were compared with the predicted values. It was discovered that most of the binary mixtures of a FAME and a bound glycerol (MAG, DAG, or TAG) behaved as eutectic systems, in which a solid phase consists of a single component. In the case of the eutectic system, the solidification temperature could be estimated by assuming non-ideal liquid solutions, and the modified UNIFAC (Dortmund) model helped calculate the activity coefficient. However, the mixtures of MAG/MAG differed from the eutectic system, suggesting that the solid compounds of different types of MAGs were formed. Thus, the compound formation model was developed, which was successful in predicting the solidification temperatures of biodiesel model fuels that consist of several kinds of FAMEs and MAGs.

Influence of microalgae-ZnO nanoparticle association on sewage wastewater towards efficient nutrient removal and improved biodiesel application: An integrated approach

Present investigation highlighted the capability of microalgae cultivation in sewage wastewater integrated with nanomaterial, addressing wastewater treatment and consequent improvement in lipid for biodiesel application. Herein, the isolated microalga Chlorosarcinopsis sp. MAS04, was cultured in primary treated wastewater (PTWW) and secondary treated wastewater (STWW) incorporated with Zinc Oxide nanoparticles (ZnO- NPs). The characterizations of ZnO-NPs were performed by analytical technique and cytotoxicity assay of microalga against nanoparticles (NPs) was carried out prior to the experiment. The nutrient reduction rate of Chemical Oxygen Demand (COD), Total Nitrogen (TN), Total Phosphorous (TP), and Total Organic Carbon (TOC) by microalga was found higher in PTWW as compared to the STWW when incorporated with the ZnO-NPs. Maximum biomass of 3.43 g/L and 2.14 g/L along with 1.9 and 1.5 folds increase in cellular lipid was recorded in the presence of PTWW and STWW respectively as compared to control (BG-11). The cellular lipids were converted to fatty acid methyl esters (FAMEs) by the process of transesterification and analyzed by Gas Chromatography-Mass Spectrometry (GC–MS). The cells developed in PTWW and STWW incorporated with ZnO-NPs were recorded with a higher amount of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) with controlled polyunsaturated fatty acids (PUFA). Biofuel properties were found in accordance with American and European guidelines. The present report suggested that the Chlorosarcinopsis sp. MAS04 -ZnO NPs association is capable of better nutrient removal from sewage wastewater. Therefore, the nano-bio hybrid opens a new paradigm for efficient wastewater treatment and consequent quality biodiesel production.

Co-transesterification of waste cooking oil, algal oil and dimethyl carbonate over sustainable nanoparticle catalysts

Key challenges for the application of biodiesel include their high acid value, high viscosity, and low ester content. It is essential to develop later-generation biodiesel from unexploited non-food resources for a more sustainable future. Reuse of biowaste is critically important to address these issues of food safety and sustainability. Thus, the co-transesterification of waste cooking oil (WCO), algal oil (AO) and dimethyl carbonate (DMC) for the synthesis of fatty acid methyl esters (FAMEs) was investigated over a series of nanoparticle catalysts containing calcium, magnesium, potassium or nickel under mild reaction conditions. Nanoparticle catalyst samples were prepared from biowaste sources of chicken manure (CM), water hyacinth (WH) and algal bloom (AB), and characterized using XRD, Raman and FESEM techniques for the heterogeneous production of biodiesel. The catalyst was initially prepared by calcination at 850 °C for 4 h in a major presence of CaxMgyCO3, KCl and K2CO3. The WCO and AO co-conversion of 98% and FAMEs co-selectivity of 95% were obtained over CM nanoparticle catalyst under the reaction conditions of 80 °C, 20 mins and DMC to oil molar ratio of 6:1 with 3% catalyst loading and 3% methanol addition. Under the optimum condition, the density, viscosity, and cetane number of the biodiesel were in the range of diesel standards. Nanoparticle catalysts have been proven as a promising sustainable material in the catalytic transesterification of WCO and AO with the major presence of calcium, magnesium and potassium. This study highlights a sustainable approach via biowaste utilization for the enhancement of biodiesel quality with high ester content, low acid value, high cetane number, and low viscosity.

Numerical and experimental investigation of Y-shaped micromixers with mixing units based on cantor fractal structure for biodiesel applications

The biodiesel synthesis intensification can be easily done with the help of microfluidic devices. In this paper, three novel designs are proposed for evaluating mixing performance required for biodiesel preparation. These designs are investigated numerically and then tested experimentally by fabrication of its chips. The current work is focused on the transesterification of sunflower oil with ethanol at room temperature conditions to elaborate on the application of our micromixer for biodiesel synthesis. The mixing of fluids is analyzed in the range of Reynolds number 0.5–100. The designs are proposed based on split and recombination and cantor fraction structure ideas. These designs are YCMSAR, YSMSAR, and YCSMSAR. All these designs are good for effective mixing. However, the YCSMSAR micromixer demonstrates better mixing index of 99.9% at Reynolds number, Re = 100. The effectiveness of our selected design is supported by various plots and contours simulated by COMSOL and by experimental images and supplementary video.

Swirling atomization characteristics of waste oil biodiesel

ABSTRACT In this study, we investigate the macroscopic structure and atomization characteristics of biodiesel produced by sewage oil in swirl atomizing nozzle through numerical simulations and experiments. The simulation is based on Euler-Lagrange method to solve the coupled equations of discrete and continuous phases. This model can boost the practical application of biodiesel in industrial furnaces. The results reveal that when the fuel injection pressure is 0.5 MPa, the size of the atomized particles ranges between 87 and 158 μm, wherein the droplets of particle size less than 50 μm are concentrated in the center of the flow field, and large droplets with size of nearly 150 μm dominate the tail of the spray. This is because in the dense spray area near the nozzle outlet, the turbulent energy of air and droplets is maximum. Therefore, at the outlet of the nozzle, a violent momentum exchange occurs, and the droplet breaks up again, so the particle size of the droplet in the rear part of the dense zone (center of the flow field) decreases. Then, the atomization momentum gradually weakens along the axial direction, and some droplets aggregate in the tail of the dilute zone and in front of the extremely dilute zone, resulting in an increase in droplet size in the extremely dilute zone (tail of the flow field). As the injection pressure increases, Sauter mean diameter of particles fluctuates more drastically, and as time passes, the size of the droplets decreases stepwise and gradually stabilizes in the range of 25–75 μm, keeping the atomization effect in a stable state.

The Evaluation of Lubricants Performances in Light- and Heavy-Duty Diesel Engines in The Application of Biodiesel (B20).

The use of biodiesel as fuel in light- and heavy-diesel engine vehicles in general will negatively affects the lubricant performance. the changes in lubricants properties during the use of B20 were investigated. Two type of vehicles engines were used, namely heavy duty and light duty diesel engines. The road test wascarried out until 40,000 km, while the lubricant was drained and analysed only for 10,000 km of distances. The laboratory test was conducted to observe both fresh and used lubricants. The results show that the biodiesel dilutions were less than 2% both in light- and heavy-duty diesel engines. The kinematic viscositiesof 4 samples of used lubricants in light-duty diesel engine were decreased in the ranges of 0.58 – 7.5%, while in heavy-duty diesel engines were 4.66-16.04% from the initial values. The decreasing of TBNs were less than 14% in light-duty diesel engine and fewer than 16% in heavy-duty diesel engine fuelled by biodiesel (B20). Meanwhile, the acidity of used engine oil was increased until 173% for light-duty diesel engine and 63% heavy-duty diesel engine compare to the initial values. The results show that the metal additives decreased while wear metal increased. According to this study, the increasing of wear metal (copper) in the used lubricants were less than 23% in light-duty diesel engine and lower than 26% in heavy-duty diesel engine fuelled by biodiesel (B20). Meanwhile, the lead contents of used engine oil were increased to 3.2 ppm in heavy-duty diesel engine and was not detected in light-duty diesel engine. After all, this work found that the lubricants exhibit good performances in the light- and heavy-duty diesel engines fuelled by B20. The changes of some critical properties were still in the acceptable values regarding to the specification as required in the SNI-7069-5 (2021).

Cogongrass (Imperata cylindrica) Leaf Extract Counteracts the Effects of Nitrogen Limitation and Induces Changes in Biomass, Lipid, and Fatty Acid Profile in Chlorella vulgaris UMT-M1 and Scenedesmus sp. KS-2

This study assessed the feasibility of unhydrolyzed cogongrass as a medium fortificant for cultivation of Chlorella vulgaris UMT-M1 and Scenedesmus sp. KS-2. Nitrogen-limited media supplemented with 0.1–0.5% (w/v) cogongrass leaf extract induced changes in lipid content and produced effects that appear to counteract the effects of nitrogen depletion, restoring lipid and fatty acid content to levels similar to nitrogen-replete media while biomass was decreased. While nitrogen-limited media led to an increase in total lipid, oleic acid (C18:1) and monounsaturated fatty acid (MUFA) content and a decrease in palmitic acid (C16:0), polyunsaturated fatty acid (PUFA) and saturated fatty acid (SFA) content, the presence of cogongrass extract evidently cancelled this effect. As a sole ingredient, cogongrass reduced biomass, C16:0, PUFA and SFA, but increased total oil, C18:1 and MUFA to levels similar to N-limited media. Unexpectedly, a 45.8% increase in lipid productivity in Scenedesmus sp. under N-limitation was observed, despite a reduction in biomass. This study demonstrates that the extract from cogongrass and likely from other plant sources could potentially be used as a medium fortificant for microalga cultivation for lipid production. It could also be used as part of a cultivation strategy towards the production of desired fatty acid composition for biodiesel applications. In addition, this study could spark new research for alternative medium fortificants for microalga cultivation from various unutilized or waste plant biomass resources.

The Influence of Light and Nutrient Starvation on Morphology, Biomass and Lipid Content in Seven Strains of Green Microalgae as a Source of Biodiesel

The development of clean and renewable energy sources is currently one of the most important challenges facing the world. Although research interests in algae-based energy have been increasing in the last decade, only a small percentage of the bewildering diversity exhibited by microalgae has been investigated for biodiesel production. In this work, seven strains of green microalgae belonging to the genera Scenedesmus, Tetradesmus and Desmodesmus were grown in liquid medium with or without a nitrogen (N) source—at two different irradiances (120 ± 20 and 200 ± 20 μmol photons m−2 s−1)—to evaluate biomass production and FAME (fatty acid methyl esters) content for biodiesel production. The strains of Tetradesmus obliquus and Desmodesmus abundans grown in N-deprived medium showed the highest FAME content (22.0% and 34.6%, respectively); lipid profile characterization highlighted the abundance of saturated FAME (as C16:0 and C18:0) that favors better viscosity (flow properties) and applicability of biodiesel at low temperatures. Light microscopy and confocal laser scanning microscopy observations were employed as a fast method to monitor the vital status of cells and lipid droplet accumulation after Nile red staining in different culture conditions.