Feedstock For Biodiesel Production Research Articles

Ethanol-Based Transesterification of Rapeseed Oil with CaO Catalyst: Process Optimization and Validation Using Microalgal Lipids

Microalgal oil has been increasingly studied as a feedstock for biodiesel production through transesterification reactions using heterogeneous catalysts. This route offers several benefits, including catalyst reuse, ease of separation, and improved safety, while addressing environmental and technical issues associated with using homogeneous acids and bases. Most studies use methanol for the transesterification, and few studies have investigated the transesterification of microalgal oil using ethanol. Beyond the environmental benefits of microalgae compared to plant-based biomass, replacing methanol with bioethanol is advantageous due to its lower cost and reduced toxicity. If the emulsion issue between the produced biodiesel and ethanol is resolved, ethanol could be a more environmentally friendly alternative for green fuel production. This study evaluated various metal oxides as catalysts for the transesterification of rapeseed oil using ethanol as both reagent and solvent to improve miscibility. From catalyst screening, CaO showed the highest fatty acid ethyl esters yield and this catalyst was then tested at different reaction times in two systems (round-bottom flask and autoclave reactor) for the transesterification of both rapeseed and microalgal (Scenedesmus sp.) oil. The highest reaction yield was 86.0% for rapeseed oil and 81.3% for microalgal oil using 114:1 ethanol: oil molar ratio with CaO in an autoclave reactor. This work addresses the limited studies on ethanol in microalgal oil transesterification, demonstrating the effectiveness of CaO as a catalyst. It highlights the potential of ethanol as a greener, cost-effective alternative to methanol for biodiesel production.Graphical

Biodiesel Production from Animal Fats Using Blast Furnace Geopolymer Heterogeneous Catalyst: Optimisation and Kinetic Study

Abstract Biodiesel is a sustainable fuel alternative that is typically produced through a transesterification process that primarily employs homogeneous catalysts. However, they generate significant amounts of wastewater and are often non-\recyclable. This study aims to investigate the application of heterogeneous blast furnace slag geopolymer catalyst for biodiesel production from animal fat. Central composite design was employed to optimise the transesterification process, considering four key variables: the methanol-to-oil ratio (20–50 wt.%), reaction time (3–7 h), reaction temperature (30–70 °C) and catalyst-to-oil ratio (3–15 wt.%). The heterogeneous geopolymer catalyst was characterised using Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. These analyses confirmed the geopolymerisation of the blast furnace slag and revealed no modifications to the geopolymer structure following the transesterification reaction. RSM optimisation resulted in 97.436% biodiesel yield, which was achieved at a constant stirring rate of 450 RPM, a reaction time of 6.254 h, a catalyst ratio of 9.996 wt.%, a methanol-to-animal fat ratio of 33.435 wt.%, and a reaction temperature of 50.509 °C, which was experimentally validated. The transesterification process followed pseudo-first-order reaction kinetics, with an activation energy of 43.76 kJ/mol. These findings demonstrate the potential of animal fat as a low-cost feedstock for biodiesel production catalysed by blast furnace slag geopolymer, offering a more sustainable and environmentally friendly alternative to traditional homogeneous catalysts.

Studies of biodiesel production using various blends of waste palm cooking oil and castor oil

This study has been conducted using blends of castor oil (CO) and waste palm cooking oil (WPCO) in different proportions to enhance % yield of biodiesel via transesterification. The effects of various blending ratios of WPCO: CO (wt.%), molar ratios of methanol: oil, catalyst concentrations (wt.%), reaction time, reaction temperature and various co-solvents have been investigated to determine the optimal conditions for transesterification reaction. Maximum % yield of biodiesel is obtained at 75:25 (wt.%) of WPCO:CO blend, 9:1 methanol to oil ratio, 1 wt.% KOH catalyst, reaction temperature of 32°C, reaction time of 30 min, using n-hexane as co-solvent. The highest obtained biodiesel yield is 96%. Analysis confirmed 25 FAME components, and the fuel met ASTM standards. Blending non-edible feedstocks for biodiesel production is a sustainable approach to reduce costs and environmental impact.

Enhanced biomass and lipid production of Chlorella vulgaris through the utilization of municipal wastewater as a nutrient source: A sustainable feedstock for biodiesel production

Enhanced biomass and lipid production of Chlorella vulgaris through the utilization of municipal wastewater as a nutrient source: A sustainable feedstock for biodiesel production

Green Gold: Sustainable Biodiesel Production and Bioactive Compounds Extraction from Microalgae

Microalgae have attracted significant interest from both scientific and industrial sectors as a potential source of high-lipid feedstock for biodiesel production. Current research has mainly emphasized on the production of biodiesel from algal biomass, with a focus on collecting, isolating, screening, and characterizing suitable algal species. In this regard, a total of sixty-seven microalgal strains were isolated from both freshwater and marine sources across various regions. The screening for high-lipid microalgae strains was conducted using the Nile Red method to identify neutral lipid droplets. Out of the sixty-seven strains, four promising biodiesel-producing strains Chlorococcum aquaticum, Scenedesmus obliquus, Nannochloropsis oculata, and Chlorella pyrenoidosa were selected based on their high lipid and biomass accumulation, Among the prescreened algal strains, Scenedesmus obliquus exhibited the highest biomass at 1.32±0.023 g/L, while Chlorella pyrenoidosa had a significantly higher lipid content of 15.27%. Further GC-MS (Gas Chromatography-Mass Spectrometry) analysis was conducted to identify the free fatty acids present in the algal oil. The FAME (Fatty Acid Methyl Ester) profile revealed the presence of several key fatty acids, including palmitic acid (16:0), palmitoleic acid (C16:1), stearic acid (C18:0), and oleic acid (C18:1). Together, these fatty acids indicate that the algal strains are rich in both saturated and unsaturated fatty acids, which are key for producing high-quality biodiesel. The combination of these fatty acids suggests that the algal oil could meet the required standards for biodiesel production, offering good energy content, stability, and favorable cold-flow properties. Thus, these micro-algal strains are promising candidates for sustainable biodiesel production.

Catalytic Performance of Newly Synthesized Heterocyclic Hydrazone Derivatives For Production of High Yield Neem Biodiesel

Biodiesel, a sustainable and environmentally friendly substitute for diesel, has attracted growing attention in recent years. The reuse of non-edible neem oil as a feedstock for biodiesel production is affordable and naturally safe. This study aimed to understand the understudied benefits of using heterocyclic organic hydrazone derivatives as catalysts for high yield biodiesel production. The catalysts were characterized using techniques such as EIMS, NMR, CHN and FTIR analysis, which revealed the morphological and functional characteristics of the catalyst. The optimum process conditions were found to be catalyst concentration of 50 mg/10 mL, methanol-to-oil molar ratio of 3:1, reaction temperature of 60 °C, and reaction duration of 60 min; these conditions yielded 95% biodiesel. The produced biodiesel was analyzed using FTIR, and different parameters like moisture content, saponification value, density, acid value, iodine value, and FFA value. The use of neem oil and organic based catalysts for biodiesel production is an economical and environmentally sustainable process.

Process Optimization for Madhuca indica Seed Kernel Oil Extraction and Evaluation of its Potential for Biodiesel Production

The current research aims to optimize the solvent-based oil extraction process from Mahua (Madhuca indica) seed using response surface methodology and biodiesel production using heterogeneous catalysts. The oil extraction was varied through the levels of process parameters including extraction temperature (60 to 80°C), solvent-to-seed ratio (3 to 9 wt/wt), and time (2 to 4 h). The experiments were designed following the Central Composite model. The regression model provided optimal values for the selected process parameters based on the extraction yield percentage. To ensure the model’s reliability, it was experimentally validated. Maximum experimental oil yields of 50.9% were obtained at an optimized extraction scenario of 70 °C extraction temperature, solvent-to-seed ratio of 6 wt/wt, and time 4 h. The extracted oil’s physicochemical properties and fatty acid composition were tested. Also, using copper-coated dolomite as a catalyst, the extracted oil was transformed into biodiesel via transesterification. The FAME (94.31%) content of the prepared biodiesel was determined via gas chromatography. As a result, the findings of this study will be useful in further research into the use of Madhuca indica as a potential feedstock for biodiesel production.

Effects of CO2 Aeration and Light Supply on the Growth and Lipid Production of a Locally Isolated Microalga, Chlorella variabilis RSM09

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.

Taxonomic, Physiological, and Biochemical Characterization of Asterarcys quadricellularis AQYS21 as a Promising Sustainable Feedstock for Biofuels and ω-3 Fatty Acids.

Asterarcys quadricellularis strain AQYS21, a green microalga isolated from the brackish waters near Manseong-ri Black Sand Beach in Korea, shows considerable potential as a source of bioactive compounds and biofuels. Therefore, this study analyzed the morphological, molecular, and biochemical characteristics of this strain; optimized its cultivation conditions; and evaluated its suitability for biodiesel production. Morphological analysis revealed characteristics typical of the Asterarcys genus: spherical to ellipsoidal cells with pyrenoid starch plates and mucilage-embedded coenobia. Additionally, features not previously reported in other A. quadricellularis strains were observed. These included young cells with meridional ribs and an asymmetric spindle-shaped form with one or two pointed ends. Molecular analysis using small-subunit rDNA and tufA sequences confirmed the identification of the strain AQYS21. This strain showed robust growth across a wide temperature range, with optimal conditions at 24 °C and 88 µmol m-2s-1 photon flux density. It was particularly rich in ω-3 α-linolenic acid and palmitic acid. Furthermore, its biodiesel properties indicated its suitability for biodiesel formulations. The biomass of this microalga may serve as a viable feedstock for biodiesel production and a valuable source of ω-3 fatty acids. These findings reveal new morphological characteristics of A. quadricellularis, enhancing our understanding of the species.

Extraction of Avocado Seed Waste as a Potential Feedstock for Biodiesel Production

The rising interest in sustainable energy sources has spotlighted biodiesel as a promising alternative to fossil fuels. Avocado seed waste, rich in vegetable oil, presents a potential feedstock for biodiesel production. However, optimizing the extraction process to maximize oil yield and quality is crucial. This study addresses the knowledge gap concerning the impact of drying time and solvent type on oil extraction efficiency from avocado seeds. Here, we show the effects of varying drying times (2, 3, and 4 hours) and using two solvents (96% ethanol and isopropyl alcohol) on the oil yield and quality using Soxhlet extraction. Results indicate increased drying time correlates with reduced moisture content, with values of 79.94%, 63.17%, and 47.39% for 2, 3, and 4 hours, respectively. Comparatively, isopropyl alcohol exhibited a higher fatty acid content (0.718%) than 96% ethanol. The density of oil extracted with 96% ethanol (1.34 g/ml) after 3 hours of drying surpassed that of isopropyl alcohol. These findings suggest that drying time and solvent type significantly influence the extraction efficiency and quality of oil from avocado seeds, highlighting their potential as a viable biodiesel feedstock.

Optimization of ultrasound-assisted biodiesel production from python fat oil using response surface methodology

Diversification of oil feedstocks for biodiesel production is very necessary to reduce dependence on traditional vegetable oils and animal fats. Therefore, a conventional and ultrasound-assisted single-step transesterification process was optimized using response surface methodology (RSM) for biodiesel production from a novel feedstock python fat oil (PFO). Second-order polynomial models of the conventional (CM) and ultrasound-assisted (USM) methods were used to predict the biodiesel yield, and the coefficient of determination (R2) was found to be at 0.9946, and 0.9873, respectively. The optimal biodiesel yield of USM calculated from the model is 99.12 % with the following reaction conditions: PFO/methanol ratio of 33.77 wt%, PFO/KOH ratio of 1.05 wt%, and reaction time of 128.53 min. Biodiesel yield results under optimal conditions have demonstrated that the regression models are consistent with experimental data. Besides, the biodiesel yield of USM (98.90 %) was significantly higher than that of CM (92.73 %). In particular, the properties of PFO biodiesel produced under optimal conditions were found to agree with EN 14,214 standard specifications. In summary, single-step biodiesel production from the PFO new feedstock with USM can be commendably used to engender and adopt a more sustainable and environmentally friendly energy approach.

Utilization of sterculia foetida oil as a sustainable feedstock for biodiesel production: optimization, performance, and emission analysis

This study examines the feasibility of employing Sterculia foetida oil as a sustainable feedstock for biodiesel production, offering an eco-friendly substitute for conventional diesel fuel without requiring engine alterations. The method employs a two-step catalytic process, first with acid esterification to reduce the free fatty acid (FFA) concentration, followed by alkaline esterification for biodiesel synthesis. Essential process parameters—such as reaction time, temperature, catalyst concentration, and molar ratio—are carefully optimized to improve biodiesel yield. Under optimal conditions, the process achieves an impressive conversion rate of 95.2 %, demonstrating the considerable potential of Sterculia foetida oil for biodiesel production. Furthermore, blends of Sterculia foetida biodiesel (SFB) and diesel demonstrate a notable decrease in harmful emissions, especially a 2.3 % reduction in carbon monoxide (CO), a 4.1 % reduction in hydrocarbons (HC), and a 1.9 % decrease in smoke emissions compared to pure diesel. This study highlights the innovative use of non-edible oil as feedstock, a customized optimization method, and a highly effective catalytic process, all while emphasizing environmental sustainability and reduced emissions.

Quercus ballot as an innovative feedstock for biodiesel production using ZnO nanocatalyst

Selecting non-edible plant seed oil remains the best choice for biodiesel production using an effective nanocatalyst. In this study, the ZnO was prepared as a nanocatalyst using an aqueous extract from the Alhaji marorum plant. Nano ZnO has shown high catalytic activity, is cost-effective, environmentally friendly and converts triglycerides into fatty acid methyl esters. The results indicate that ZnO nanocatalyst exhibit a high specific surface area (146.82 m2 g-1), large pore volume (0.35 cm3 g-1), and an average crystallite size of 42.3 nm. The FESEM analysis shows that the particle size of ZnO lies in the range of 30–50 nm with a rod shape and densely packed morphology. The biodiesel is produced using a transesterification process from novel non-edible Quercus ballot plant seeds. The resulting biodiesel has a 98.06 % yield under a methanol/oil ratio of 6:1 with 0.5 wt% ZnO nanocatalyst at 65 °C for 80 min. It is established that the methanol-to-oil ratio and the catalyst concentration significantly affect the transesterification reaction. The biodiesel produced is characterized by GC–MS to determine its exact composition and FTIR is used to confirm functional groups and is evaluated according to ASTM D6751.

Carbon isotope composition of biomass and water use efficiency in young plants of Jatropha curcas L. under irrigated or water deficit conditions

Jatropha curcas L. is a non-food crop quoted as a promising natural feedstock for biodiesel production in tropical and subtropical regions. Although an efficient mechanism of drought avoidance through stomatal control of transpiration has been demonstrated in this species, low carbon assimilation and growth rates preclude any advantage of such strategy under water limitation. Two greenhouse experiments were conducted with the objective of investigating varietal differences in water use as the trade-off between carbon isotope composition (δ13C) in different tissues and water use efficiency, in young plants of J. curcas. The first experiment was a survey with seven provenances of J. curcas under non-limiting water availability. There were no significant differences among provenances for leaf gas exchange rates, growth and whole-plant transpiration (T). However, significant effects of provenance and tissue (stem bark or leaf) in δ13C were demonstrated. The provenances CNPAE183 and CNPAE222 were selected for the second experiment, as variations in water use traits and δ13C between the two provenances were observed. Soil water deficit, imposed for 18 days, led to significant physiological, biochemical, and morphological changes. An early and sharp response to water deficit in CNPAE183 as compared to CNPAE222 was observed, as indicated by a 44% higher rate of decrease of T in the former. In addition, water deficit led to increase of δ13C, which was more pronounced in CNPAE222 (13% in young leaves) when compared to CNPAE183 (11% in young leaves). In both provenances, δ13C was less negative in young as compared to mature tissues. Significant and direct correlations between stem bark and leaf δ13C and leaf-level intrinsic water use efficiency were observed. Contrasting results, particularly on T and δ13C, suggest the existence of genetic diversity for water relations and metabolic traits linked to drought tolerance in J. curcas. Using stem bark or leaf δ13C measurements as the basis for large-scale screening of water-use efficient genotypes should be considered.

Valorization of Biodiesel-Derived Crude Glycerol for Producing Yeast Oil as an Alternative Biodiesel Production Feedstock: Productivity Improvement in Batch and Repeated Batch Fermentation

Valorization of Biodiesel-Derived Crude Glycerol for Producing Yeast Oil as an Alternative Biodiesel Production Feedstock: Productivity Improvement in Batch and Repeated Batch Fermentation

Fabrication of heterogeneous catalyst for production of biodiesel form municipal sludge

Sewage sludge, a semi-solid byproducts of municipal wastewater treatment processes, offers a sustainable and cost-effective feedstock for biodiesel production through the synthesis of catalytic heterogeneous catalysts. In this study, we developed a novel heterogeneous catalyst by impregnating aluminum nitrate and calcite, obtained from carbon dioxide-sequestering bacteria, onto DigSBiochar (Biochar derived from digested sewage sludge). The produced catalyst was subsequently immobilized with the lipase enzyme isolated from Bacillus sp., creating a bioactive material for the transesterification of lipids in sewage sludge. Comprehensive characterization of the biocatalysts was conducted using Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Field Emission Scanning Electron Microscopy (FE-SEM). Gas Chromatography-Mass Spectrometry (GC-MS) analysis of the resulting fatty acid methyl esters (FAMEs) demonstrated that the highest yield was achieved with the enzyme immobilized on the activated heterogeneous catalyst using methanol (99 %), followed by the activated heterogeneous catalyst with methanol (96 %), and methanol with Sulfuric acid (82 %). This study underscores the potential of utilizing municipal sewage sludge as a valuable resource for producing efficient heterogeneous catalysts, thereby advancing sustainable waste management practices and promoting renewable energy production.

Cultivation of chlorella vulgaris using aquaculture wastewater: Assessing its viability as a promising resource for biodiesel production

This study investigates the viability of utilizing Chlorella vulgaris cultivated in aquaculture wastewater as a feedstock for biodiesel production. The research involved scaling up the algal culture from 10 ml to 10 liters in a photobioreactor, optimizing growth conditions, and analyzing the water parameters of the aquaculture wastewater medium. The results showed successful growth of the algal culture, with the highest growth rate achieved on day 15 in the 10-liter reactor. The harvested biomass was converted into biodiesel through direct transesterification, and the produced biodiesel was characterized using Fourier-transform infrared spectroscopy (FTIR) and fuel property tests. The FTIR analysis confirmed the presence of functional groups indicative of esterification, validating the successful conversion of the wet biomass into biodiesel. The fuel property tests revealed that the algal biodiesel exhibited marginally higher kinematic viscosity but a favourable flash point compared to established standards. Emission tests demonstrated an increase in CO2 and hydrocarbon emissions with higher engine loads, aligning with combustion principles. The findings highlight the potential of utilizing aquaculture wastewater as a sustainable medium for cultivating Chlorella vulgaris and producing biodiesel, contributing to the development of more resource-efficient and environmentally friendly biofuel production methods.

Distribution and Diversity of Phytoplankton in Lake Alau, Maiduguri, Northeast Nigeria

The production of biodiesel from Thevetia peruviana seed oil using two different catalysts (NaOH and KOH) was evaluated. The Physical and chemical properties after extracting the seed oil were determined and the following results were obtained (density; 0.896g/cm3 , pH; 5.6, oil content; 32.5%, moisture content; 1.5%, specific gravity; 1.33, viscosity; 20mm2 /s, and refractive index; 1.48) and (Acid value; 0.3 mg of KOH/g, free fatty acid; 0.45%, iodine value; 38.5gI/100g, saponification value; was 75mg/KOH) respectively. Different catalysts were prepared by dissolving separately (0.18g. 0.20g and 0.21g) w% of NaOH and another 0.18g, 0.20, 0.21g w% of KOH pellets each in 10ml of methanol to produce concentrations of sodium and potassium methoxide respectively. Furthermore, Yellow Oleander Oil (YOO) was divided into 6 portions (25ml each) and poured into 6 different beakers (100ml) and separately placed on a magnetic stirrer. The amount of biodiesel produced at different concentrations of NaOH catalyst was 20.3ml, 20.1ml, and 22.3ml and the amount of biodiesel produced at different concentration of KOH were 24.2ml, 22.1ml, and 21.0ml. The conversion yield of the biodiesel catalysts was 81.2%, 80.4% and 89% for the NaOH catalyst and 96.8%, 88.4% and 84.0 for the KOH catalyst. The properties of the biodiesel such as flash point were 68℃, pour point was 3℃, cloud point was 7℃, cetane number was 98, the acid value was 0.5mg of KOH/g, density was g/cm3 , Iodine value was 3gI/100g, saponification value was 104, viscosity was 1.5mm2 s, the refractive index was 1.49. The results obtained from the study indicate that the physicochemical properties of the synthesized biodiesel are in agreement with the ASTM standard specifications. Both catalysts gave a considerable yield with KOH having a higher yield than NaOH in almost all the concentrations used. Thevetia peruviana can be considered a highly promising feedstock for biodiesel production.

Electrolytic biodiesel production from spent coffee grounds: Optimization through response surface methodology and artificial neural network

BackgroundThe disposal of waste spent coffee grounds (SCG) presents a pressing environmental concern, necessitating effective pre-treatment strategies to mitigate potential damage. Transesterification emerges as a viable solution for converting SCG lipids into biodiesel, offering both environmental and economic benefits. MethodsIn this study, the utilization of SCG as a renewable feedstock for biodiesel production through an innovative electrolysis process has been explored, aiming to address the dual challenges of waste management and sustainable energy production. To obtain maximum conversion of SCG oil to biodiesel, a comprehensive analysis of the fatty acid profile using Gas Chromatography-Mass Spectrometry (GC–MS), was conducted allowing for precise characterization of lipid content. Additionally, Fourier Transform Infrared (FTIR) spectroscopy was employed to categorize functional groups and Nuclear Magnetic Resonance (1H NMR) spectroscopy was utilized to analyze the molecular structure of the SCG oil. Optimization of process parameters namely, catalyst concentration, electrolysis time, and direct current (DC) voltage was performed using Response Surface Methodology (RSM) and Artificial Neural Network (ANN) techniques. The ANN model, with its ability to capture complex nonlinear relationships, was particularly effective in identifying the optimal combination of parameters, thereby maximizing biodiesel yield. Significant findingsThe extracted SCG oil was characterized using FTIR, GC–MS and 1H NMR analysis. The GC- MS analysis of bio-oil has reported 44.6 % Linoleic acid, 31.6 % Palmitic acid. The extracted oil had got significant amount of key saturated and unsaturated fatty acid making it suitable for transesterification process. Through ANN, the optimal combination of parameters for electrolytic transesterification i.e.,0.75 wt% catalyst loading, 2 h electrolysis time, and 40 V DC voltage, yielded the highest biodiesel production (98.32 wt.%). Comparative analysis indicated superior performance of the ANN model (R2 = 0.9931, MAE = 0.123) over RSM (R2 = 0.9636, MAE = 1.546). The artificial neural network (ANN) provided a more accurate forecast of the process yield; however, the RSM model effectively predicted the interactions and significance of the pyrolysis factors. The artificial neural network (ANN) provided a more accurate forecast of the process yield; however, the RSM model effectively predicted the interactions and significance of the pyrolysis factors. Biodiesel characterization via FTIR and 1H NMR analysis showed physiochemical properties within standard limits for SCG biodiesel.

Effects of Temperature and Nitrogen Limitation on Growth and Lipid Production of Oleaginous Microalgae from Hot Springs

Oleaginous microalgae have gained increasing attention as an alternative feedstock for biodiesel production due to the increasing demand of fuel, climate change, and global warming. This study aimed to isolate and screen robust microalgal strains from hot springs for cultivation in subtropical and tropical areas. The newly isolated oleaginous microalgae were cultivated at 30, 35 and 40 °C. Among mesophilic and thermophilic strains tested, Chlamydomonas sp. HP59 is considered the most robust strain as it showed high cell growth in a broad range of temperatures (30 - 40 °C), with the maximum dried cell weight at 40 °C. Un-optimal temperatures for cell growth did improve lipid content by 2 - 4 folds. To increase lipid production, the 2-stage cultivation, in which nitrogen-rich was applied to promote cell growth in the 1st stage and nitrogen-limitation was applied to stimulate lipid accumulation in the 2nd stage, was performed. The high temperature combined with nitrogen-limitation did improve lipid production by all microalgae. With this strategy, Chlamydomonas sp. HP59 showed the highest dried cell weight of 4.33 g/L and lipid production of 1.72 g/L. This study has shown the potential use of the newly isolated oleaginous microalgae from hot springs to be cultivated at high temperatures and under nitrogen-limited conditions for the production of biodiesel feedstocks. HIGHLIGHTS Mesophilic and thermophilic oleaginous microalgae were isolated from hot springs. Un-optimal temperatures for cell growth did improve lipid content by 2 - 4 folds. Combined effect of high temperature and nitrogen limitation effectively increased lipid content. Two-stage cultivation gave high dried cell weight and hence overall high lipid production. GRAPHICAL ABSTRACT