Biofuel Synthesis Research Articles

Bioengineered microbial platforms for biomass-derived biofuel production – A review

Global warming issues, rapid fossil fuel diminution, and increasing worldwide energy demands have diverted accelerated attention in finding alternate sources of biofuels and energy to combat the energy crisis. Bioconversion of lignocellulosic biomass has emerged as a prodigious way to produce various renewable biofuels such as biodiesel, bioethanol, biogas, and biohydrogen. Ideal microbial hosts for biofuel synthesis should be capable of using high substrate quantity, tolerance to inhibiting substances and end-products, fast sugar transportation, and amplified metabolic fluxes to yielding enhanced fermentative bioproduct. Genetic manipulation and microbes' metabolic engineering are fascinating strategies for the economical production of next-generation biofuel from lignocellulosic feedstocks. Metabolic engineering is a rapidly developing approach to construct robust biofuel-producing microbial hosts and an important component for future bioeconomy. This approach has been widely adopted in the last decade for redirecting and revamping the biosynthetic pathways to obtain a high titer of target products. Biotechnologists and metabolic scientists have produced a wide variety of new products with industrial relevance through metabolic pathway engineering or optimizing native metabolic pathways. This review focuses on exploiting metabolically engineered microbes as promising cell factories for the enhanced production of advanced biofuels.

Strategic way for valorization of manure into chemicals and fuels

Animal manure contains a variety of organic materials that can be used for synthesis of value-added biofuels and chemicals. To maximize the carbon recovery from animal manure waste, this study focused on consecutive valorization of horse manure into furfural and syngas (H2 and CO). Acid hydrolysis/dehydration of horse manure was employed to extract furfural, and the residue after furfural extraction was valorized into syngas and bio-oil through CO2-assisted pyrolysis. In acid treatment process, the levulinic acid and furfural were produced from horse manure, and the maximum yield (3.68 wt%) of furfural was achieved at 0.5 M H2SO4 (40 wt% based on hemicellulose content). Horse manure residue was further converted into bio-oil and syngas under N2/CO2 environments. Under CO2 atmosphere, gas phase homogeneous reactions were occurred, which simultaneously reduced CO2 and oxidized bio-oil showing enhanced CO formation (18 times higher comparing to pyrolysis under N2). The homogeneous reaction also resulted in decrease of aromaticity in bio-oil. To enhance the reaction kinetics of the homogeneous reaction and thermal cracking of bio-oil under CO2, catalytic pyrolysis was performed in the presence of Ni/SiO2 catalysts. The catalytic pyrolysis improved syngas (H2 and CO) production more than one order of magnitude higher, comparing to pyrolysis without Ni catalyst. All the experimental findings suggested that horse manure and CO2 could be used as raw materials for production of value-added chemicals and syngas.

Bifunctional crystalline microporous organic polymers: Efficient heterogeneous catalysts for the synthesis of 5-hydroxymethylfurfural

Developing efficient catalysts for the synthesis of 5-hydroxymethylfurfural (HMF) from biomass resources is very demanding as it is an important renewable platform chemical for the synthesis of biofuels, polymers and fine chemicals. Here, we have designed two new crystalline microporous bi-functional porous organic polymers through the extended aromatic substitution reaction under refluxing conditions. Porous polymers containing sulfonic acid and secondary amine groups are two reactive catalytic centres for carrying out the bi-functional heterogeneously catalysed reactions. Bifunctionalized porous polymers POPDS and POPSDS are synthesized through the reaction of 2,2′-benzidinedisulfonic acid and 4,4′-diaminostilbene-2,2′-disulfonic acid with cyanuric chloride, respectively. The materials were characterized thoroughly using powder X-ray diffraction, N2 sorption, FTIR, solid state 13C CP MAS NMR spectroscopy, FE-SEM, HR-TEM, XPS and TG/DTA analysis. These two crystalline porous polymers possesses good surface acidic and basic sites, and having flower-like and spherical particle morphologies. POPDS and POPSDS exhibited superior catalytic activity for the conversion of different small carbohydrates to 5-hydroxymethylfurfural (HMF) under microwave irradiation. Moreover, the recyclability tests of these catalysts revealed good durability up to sixth consecutive reaction cycles, suggesting the future potential of these catalysts in the sustainable synthesis of HMF.

One-dimensional titanate nanotube materials: heterogeneous solid catalysts for sustainable synthesis of biofuel precursors/value-added chemicals-a review.

One-dimensional (1D) titanate nanotubes materials (protonated titanate nanotube (HTNT) and sodium titanate nanotube (NaTNT)) have been reported as low-cost and efficient catalytic materials in chemical syntheses for the production of biofuel precursors with interesting catalytic performance exhibited, even better than some commonly used zeolites, H-MOR, H-β, SO42−/Al2O3, and H-ZSM-5 solid catalysts with environmental benign in focus when compared with homogeneous catalytic materials. This mini-review expressly revealed the significance and potential of using HTNT and NaTNT as sustainable and environmentally benign solid catalysts/supports in various chemical reactions. The critical assessment of biomass valorization and titanate nanostructured materials as catalysts/supports via Green Chemistry approach, #7 (use of renewable feedstocks), #9 (use of catalyst against stoichiometry) and United Nations (UN) Sustainable Development Goals (SDGs), #7 (affordable and clean energy; ensure access to inexpensive, reliable, sustainable, and new energy), is presented as integrated pathways to meet environmental benign technology toward sustainability. Hence, this work follows in the pattern of recent formulated features reported for solid catalysts—‘PYSSVR’ concept, which means P–production cost, Y–yield, S–stability, S–selectivity, V–versatility, and R–reusability.Graphical

Biodiesel Production over Niobium-Containing Catalysts: A Review

Nowadays, the synthesis of biofuels from renewable raw materials is very popular. Among the various challenges involved in improving these processes, environmentally benign catalysts compatible with an inexpensive feedstock have become more important. Herein, we report the recent advances achieved in the development of Niobium-containing heterogeneous catalysts as well as their use in routes to produce biodiesel. The efficiency of different Niobium catalysts in esterification and transesterification reactions of lipids and oleaginous raw materials was evaluated, considering the effect of main reaction parameters such as temperature, time, catalyst load, and oil:alcohol molar ratio on the biodiesel yield. The catalytic performance of Niobium compounds was discussed considering the characterization data obtained by different techniques, including NH3-TPD, BET, and Pyr-FT-IR analysis. The high catalytic activity is attributed to its inherent properties, such as the active sites distribution over a high specific surface area, strength of acidity, nature, amount of acidic sites, and inherent mesoporosity. On top of this, recycling experiments have proven that most Niobium catalysts are stable and can be repeatedly used with consistent catalytic activity.

Photoelectron Photoion Coincidence Spectroscopy Provides Mechanistic Insights in Fuel Synthesis and Conversion

Clean combustion, i.e., the reduction of NOx and soot emissions, and carbon neutrality, achieved in part by biofuel synthesis, are major milestones in the transition to a sustainable future. To overcome empiric and time-consuming process optimization steps, we need detailed reaction mechanistic and chemical insights on these processes. Be it in combustion or in catalysis, highly reactive intermediates, such as radicals, carbenes, and ketenes drive chemical reactions. Knowing the fate of these species helps develop strategies to optimize chemical energy conversion processes. This calls for advanced mass spectrometric tools, which enable the detection of transient species. In this review, we report on the application of state-of-the-art photoelectron photoion coincidence (PEPICO) spectroscopy with vacuum ultraviolet (VUV) synchrotron radiation as advanced diagnostic tools in catalysis and combustion research. We discuss reaction mechanisms in biomass conversion to sustainable fuels, where we report on the pyrolysis of wood samples probed using VUV photoionization mass spectrometry (PIMS) and obtain deep mechanistic insights in the (non)catalytic pyrolysis of lignin model compounds with PEPICO detection. PEPICO is also shown to contribute to the mechanistic understanding of catalysis by unveiling catalytic alkane valorization mechanisms. We discuss how PEPICO detection advances combustion diagnostics, thanks to the application of photoelectron spectroscopy and velocity map imaging. We report on mechanistic aspects of ignition, such as fuel radical formation and oxidation to peroxy species, and discuss reaction pathways of pollutant formation. In addition, we zoom into the elementary reactions of combustion and discuss isomer-selective kinetics experiments on radical oxidation. Newly revealed reaction pathways to polycyclic aromatic hydrocarbon (PAH) formation are also detailed. Finally, we describe current instrumental developments to improve PEPICO detection and report on innovative sources, reactors, and reaction sampling approaches to be combined with this technique.

MOF-Encapsulating Metal–Acid Interfaces for Efficient Catalytic Hydrogenolysis of Biomass-Derived Aromatic Aldehydes

Developing an efficient and selective catalyst for C–O hydrogenolysis of biomass-derived aromatic aldehydes, such as 5-methylfurfural (MF), 5-hydroxymethylfurfural (HMF), and vanillin (VA), is highly significant for the synthesis of biofuel and fine chemicals. Herein, metal–organic framework (MOF)-encapsulating metal–acid interfaces (Pd@UiO–CH2SO3H, Pd@UiO–PhSO3H) were first reported. Compared with traditionally supported catalysts (Pd/UiO–SO3H, Pd/UiO–NH2), Pd–acid-interface-encapsulated MOFs show much higher activity and selectivity for MF to 2,5-dimethylfuran (DMF), HMF to DMF, and VA to 2-methoxy-4-methylphenol (MMP) reactions. In particular, Pd@UiO–SO3H shows the best catalytic performance with 89.0 and 86.0% DMF yield from MF and HMF and a 99.4% MMP yield from VA based on its suitable hydrophilicity, high hydrogen activation ability, and abundant Pd–SO3H interface active sites. According to the catalytic performance of Pd/UiO–NH2 and the results of an ATR-IR test, the acidic sites on the Pd–acid interface can accelerate the activation of the hydroxyl group for these hydrogenolysis reactions. This work provides an effective design strategy for the preparation of MOF-encapsulating metal–acid interfaces and shows the powerful synergistic effect of hydrogenation and acid catalysis.

Sugarcane bio-refinery products: An efficient one umbrella approach for synthesis of biofuel and value-added compounds using metal-free photo-catalyst

The synchronized transformation of molasses, sugarcane juice, glucose, fructose, and sucrose into water insoluble platform chemicals, has stand up as a resourceful exercise to eradicate the expensive separation steps. On the other hand, the existing processes involve both acid-catalyzed and hydrogenation processes. We report herein, new green approaches for sequential conversion of sugarcane biorefinery products into biofuels using metal free carboxyl acid functionalized ionic liquid entangled porphyrin (CAFILP) photo-catalyst. Both levulinic acid (LA) and hydroxymethyl furfural (HMF) are water soluble and difficult to separate from the reaction mixture. Remarkably, the reaction of mixture containing LA and HMF easily converted to ethyl levulinate that considerably increases the yield of levulinate by affording another transformation technique excluding the hydrogenation step. The photo-catalytic activity of CAFILP affords ethyl levulinate (94%) and HMF (70%) yield that matches the acidic strength articulated by the Hammett acidity function. Photo-catalyst CAFILP exhibited intense absorptions in the visible regions with low band gap (1.49 eV) for visible light absorption is a key step of photocatalytic performance to convert sugarcane bio-refinery products into biofuels. The yield of HMF/LA was the highest from molasses, comprising more fructose that facilitates faster conversion compare to other biomass sources. Other products of sugarcane bio-refinery like sugarcane juice, sucrose, glucose, and fructose also have potential to add value in the bioenergy chain, affording HMF as the main product using optimized reaction conditions in presence of CAFILP photo-catalyst. The reusability of photocatalyst (up to 5 runs) was confirmed by easy filtration with good photo-catalytic activity.

Vegetable oils – raw materials for producing biodiesel

This paper presents the results of a study of the physical and chemical properties of samples of vegetable oils (sunflower, rapeseed, olive). It has been shown that the viscosity of oils varies from 41.4 to 61.7 cSt at a temperature of 40 ° C for olive and sunflower oils, respectively. The acid numbers of the oil samples were also determined, it was found that the lowest indicator is characteristic of sunflower oil. Pour points of oils also range from -3 to -16 ° C for olive and sunflower oils, respectively. Using the method of IR spectroscopy, functional groups in the composition of samples of vegetable oils were studied and it was shown that the composition of oils contains carbonyl and hydroxyl functional groups, indicating the presence of carboxylic acids. Based on studies of the physical and chemical properties of vegetable oils, it was found that sunflower, olive and rapeseed oils can serve as raw materials for the synthesis of biofuels based on them, since they contain free fatty acids. To obtain biodiesel fuel based on vegetable oils, it is planned to use the transesterification method in the presence of various catalysts (alkaline, acidic, and complex).

High-Yielding Terpene-Based Biofuel Production in Rhodobacter capsulatus.

Energy crisis and global climate change have driven an increased effort toward biofuel synthesis from renewable feedstocks. Herein, purple nonsulfur photosynthetic bacterium (PNSB) of Rhodobacter capsulatus was explored as a platform for high-titer production of a terpene-based advanced biofuel-bisabolene. A multilevel engineering strategy such as promoter screening, improving the NADPH availability, strengthening the precursor supply, suppressing the side pathways, and introducing a heterologous mevalonate pathway, was used to improve the bisabolene titer in R. capsulatus. The above strategies enabled a 35-fold higher titer of bisabolene than that of the starting strain, reaching 1089.7 mg/L from glucose in a shake flask. The engineered strain produced 9.8 g/L bisabolene with a yield of >0.196 g/g-glucose under the two-phase fed-batch fermentation, which corresponds to >78% of theoretical maximum. Taken together, our work represents one of the pioneering studies to demonstrate PNSB as a promising platform for terpene-based advanced biofuel production.

Effect of molecular structure of cation and anions of ionic liquids and co-solvents on selectivity of 5-hydroxymethylfurfural from sugars, cellulose and real biomass

The concept of biorefinery still requires advancements in process development for energy and materials. Ionic liquids have been successfully used for several biorefinery applications including high yield synthesis of biofuels and value added platform chemicals. Designing suitable ionic liquid that is efficient in terms of cost as well as product selectivity is still highly needed. This study is carried out to check the effect of different anions of Bronsted acidic ionic liquids (BAILs), Bronsted Lewis acidic ionic liquids (BLAILs), Lewis acidic ionic liquids (LAILs) as well as organic electrolyte solutions (OES) for 5-HMF selectivities from monosaccharides, polysaccharides as well as lignocellulosic composite. Different variables and parameters such as Lewis acidity of anions, alkyl side chain of ionic liquid, metal chloride type and loading, time, temperature, substrate loading, polar protic and aprotic solvents are thoroughly studied for process optimization. Polar protic solvents added in [C1C4SO3HPy] based ionic liquids with CH3COO− and Cl− anions yielded 94 and 80% 5-HMF from fructose and glucose respectively in the presence of AlCl3 as Lewis acid. C4SO3H side chain yielding high from fructose and glucose is inefficient for conversion of cellulose and lignocellulose. High product selectivity from these biopolymers is achieved using butyl side chain with 3-methylpyridinium cation and chlorochromate anion.

High-Grade Biofuel Synthesis from Paired Electrohydrogenation and Electrooxidation of Furfural Using Symmetric Ru/Reduced Graphene Oxide Electrodes.

Electrochemical hydrogenation is a challenging technoeconomic process for sustainable liquid fuel production from biomass-derived compounds. In general, half-cell hydrogenation is paired with water oxidation to generate the low economic value of O2 at the anode. Herein, a new strategy for the rational design of Ru/reduced graphene oxide (Ru/RGO) nanocomposites through a cost-effective and straightforward microwave irradiation technique is reported for the first time. The Ru nanoparticles with an average size of 3.5 nm are well anchored into the RGO frameworks with attractive nanostructures to enhance the furfural’s paired electrohydrogenation (ECH) and electrooxidation (ECO) process to achieve high-grade biofuel. Furfural is used as a reactant with the paired electrolyzer to produce furfuryl alcohol and 2-methylfuran at the cathode side. Simultaneously, 2-furic acid and 5-hydroxyfuroic acid along with plenty of H+ and e– are generated at the anode side. Most impressively, the paired electrolyzer induces an extraordinary ECH and ECO of furfural, with the desired production of 2-methylfuran (yield = 91% and faradic efficiency (FE) of 95%) at XFF = 97%, outperforming the ECH half-cell reaction. The mechanisms of the half-cell reaction and paired cell reaction are discussed. Exquisite control of the reaction parameters, optimized strategies, and the yield of individual products are demonstrated. These results show that the Ru/RuO nanocomposite is a potential candidate for biofuel production in industrial sectors.

Zymomonas diversity and potential for biofuel production

BackgroundZymomonas mobilis is an aerotolerant α-proteobacterium, which has been genetically engineered for industrial purposes for decades. However, a comprehensive comparison of existing strains on the genomic level in conjunction with phenotype analysis has yet to be carried out. We here performed whole-genome comparison of 17 strains including nine that were sequenced in this study. We then compared 15 available Zymomonas strains for their natural abilities to perform under conditions relevant to biofuel synthesis. We tested their growth in anaerobic rich media, as well as growth, ethanol production and xylose utilization in lignocellulosic hydrolysate. We additionally compared their tolerance to isobutanol, flocculation characteristics, and ability to uptake foreign DNA by electroporation and conjugation.ResultsUsing clustering based on 99% average nucleotide identity (ANI), we classified 12 strains into four clusters based on sequence similarity, while five strains did not cluster with any other strain. Strains belonging to the same 99% ANI cluster showed similar performance while significant variation was observed between the clusters. Overall, conjugation and electroporation efficiencies were poor across all strains, which was consistent with our finding of coding potential for several DNA defense mechanisms, such as CRISPR and restriction–modification systems, across all genomes. We found that strain ATCC31821 (ZM4) had a more diverse plasmid profile than other strains, possibly leading to the unique phenotypes observed for this strain. ZM4 also showed the highest growth of any strain in both laboratory media and lignocellulosic hydrolysate and was among the top 3 strains for isobutanol tolerance and electroporation and conjugation efficiency.ConclusionsOur findings suggest that strain ZM4 has a unique combination of genetic and phenotypic traits that are beneficial for biofuel production and propose investing future efforts in further engineering of ZM4 for industrial purposes rather than exploring new Zymomonas isolates.

Towards Valorization of Baobab for the Production of Biofuels

Baobab (Adansonia digitata) is a promising bio-resource distributed across Africa. A variety of biofuels such as biodiesel, bioethanol, bio-oil and biogas can be prepared from feedstock derived from baobab. In this vein, different parts of baobab plant, for instance oil, fruit shells, and seed cakes can be utilized for biofuel synthesis. In this study, novozyme-435 (CAL-B) was used as a biocatalyst for biodiesel production. Oil to biodiesel conversion of 91.8±2.6% was obtained within 6 h reaction time at 50 °C when the molar ratio of oil to methanol was maintained at 1: 3. Biocatalysts are non-toxic and biodegradable, therefore sustainable for the process. The results showed potential use of baobab oil as a feedstock for biodiesel production.

Selective Electrochemical Decarboxylation of n-Octanoic Acid to Hydrocarbons on Pt Nanocrystals

Electrocatalytic synthesis of valuable biofuels and chemicals from biomass-derived acids is a promising approach, but selectively producing deoxygenated hydrocarbons is still a great challenge. In ...

Synthesis of High-Density Aviation Biofuels from Biomass-Derived Cyclopentanone

Herein, we describe a three-step synthesis strategy starting with a chemical kinetics-governed one-pot two-step reaction. A series of biomass-derived molecules have been converted into ring-structured alkanes suitable for use as transportation fuels or jet fuels with high overall isolated yields of 68–90%. Various biomass-derived molecules can be used as starting materials, which include molecules with different functional groups such as carbonyl groups, benzene and furan rings, olefins, and so forth. Efficient and green reactions, including one-pot two-step reactions and solvent-free reactions, with common reagents and catalysts under mild reaction conditions or even under room temperature, were developed to produce bi(cyclopentane)-based biofuels with diversified and selective structures in good to excellent yields. The obtained products exhibit high densities of 0.87–0.94 g/cm3 and high net volumetric heating values of 38.3–41.4 MJ/L. Besides, they also have other fuel properties comparable to some well-known commercial synthetic fuels such as JET A, JET A-1, JET B, JP-10, and RJ-4. Some of the obtained biofuels have low freezing points of −58 and −80 °C. This general synthetic approach could be extended to a range of precursors with different carbon numbers, which allows the selective generation of high-energy content ring-structured alkanes with carbon numbers of C11–C26.

Insights into the physiology of Chlorella vulgaris cultivated in sweet sorghum bagasse hydrolysate for sustainable algal biomass and lipid production

Supplementing cultivation media with exogenous carbon sources enhances biomass and lipid production in microalgae. Utilization of renewable organic carbon from agricultural residues can potentially reduce the cost of algae cultivation, while enhancing sustainability. In the present investigation a medium was developed from sweet sorghum bagasse for cultivation of Chlorella under mixotrophic conditions. Using response surface methodology, the optimal values of critical process parameters were determined, namely inoculum cell density (O.D.750) of 0.786, SSB hydrolysate content of the medium 25% v/v, and zero medium salinity, to achieve maximum lipid productivity of 120 mg/L/d. Enhanced biomass (3.44 g/L) and lipid content (40% of dry cell weight) were observed when the alga was cultivated in SSB hydrolysate under mixotrophic conditions compared to heterotrophic and photoautotrophic conditions. A time course investigation revealed distinct physiological responses in terms of cellular growth and biochemical composition of C. vulgaris cultivated in the various trophic modes. The determined carbohydrate and lipid profiles indicate that sugar addition to the cultivation medium boosts neutral lipid synthesis compared to structural lipids, suggesting that carbon flux is channeled towards triacylglycerol synthesis in the cells. Furthermore, the fatty acid profile of lipids extracted from mixotrophically grown cultures contained more saturated and monosaturated fatty acids, which are suitable for biofuel manufacturing. Scale-up studies in a photobioreactor using SSB hydrolysate achieved a biomass concentration of 2.83 g/L consisting of 34% lipids and 26% carbohydrates. These results confirmed that SSB hydrolysate is a promising feedstock for mixotrophic cultivation of Chlorella and synthesis of algal bioproducts and biofuels.

Modeling of industrial-scale sorption enhanced gasification process: One-dimensional simulations for the operation of coupled reactor system

Sorption enhanced gasification (SEG) is a promising technology for producing gas derived from renewable feedstock to be used in biofuel synthesis processes. As a response to the growing need for renewable fuels, an SEG reactor design was developed for industrial-scale dimethyl ether (DME) production. A 100MWth scale SEG reactor concept for wood pellets as a feedstock was created by a model-based approach. Thus, a 1D modeling tool for the coupled circulating fluidized beds was developed. The model was used to investigate the dual fluidized bed system’s operation in the gasifier temperature range of 730–790°C. In this range, the optimal producer gas composition without external hydrogen for the downstream DME synthesis was achieved at gasifier temperature 730°C: 63 %vol,dbH2, 11 %vol,dbCO, 13 %vol,dbCO2. The model prediction was successfully compared against experimental data and modeling results from the literature. The developed 1D model enables the investigation of the composition and yield of the producer gas with different operating parameters, such as the part-load operation. This advanced capability can be used to develop new control strategies for the SEG system and investigate the impact of various operating parameters on the producer gas composition and yield.

Graphitic carbon embedded FeNi nanoparticles for efficient deoxygenation of stearic acid without using hydrogen and solvent

Upgrading fatty acids to hydrocarbons via deoxygenation is significant for the synthesis of high-grade biofuels. Developing economic reaction conditions without using noble metal-based catalysts in the absence of hydrogen and solvent has promising application prospects. Herein, carbon-coated bimetallic FeNi nanoparticles were prepared via an in-situ carbonization-reduction strategy using double-metal cyanide at different temperatures for the deoxygenation of stearic acid. The size of the alloy core and the thickness of the carbon shell were found to be easily adjusted by varying temperature. Compared with monometallic Fe/C and Ni/C catalysts, the alloy catalyst exhibits an obvious improvement in both the conversion of stearic acid and the selectivity of heptadecane. ATR-IR spectra show that the insertion of the inert Fe element into Ni nanoparticles can promote carboxylic acid group adsorption but restrain hydrocarbon group adsorption. The synergistic effect of Fe and Ni elements leads to the promotion of direct decarboxylation of stearic acid and suppression of the C–C cracking reaction. Among different alloy catalysts studied, FeNi@C-800 exhibits the greatest catalytic performance with a 99.9% conversion of stearic acid and 76.8% selectivity for heptadecane. Furthermore, the catalyst can still maintain a stable catalytic performance against the leaching and ripening of metal through the protection afforded by the carbon shell. This work not only provides a powerful reaction system for the decarboxylation of stearic acid but also demonstrates an alternative catalyst to noble metals based on a convenient carbonization-reduction strategy.

Characterization of biomass produced by Candida tropicalis ASY2 grown using sago processing wastewater for bioenergy applications and its fuel properties

The cost of biodiesel production and the requirement of raw ingredients are the primary constraints that need to be addressed while searching for viable alternative fuels to petrol and diesel. Oleaginous yeasts are gaining wider acceptance as biofuel candidates among oil-rich crops/microbes. The present investigation aimed to integrate the agro-industrial wastewater stream as a nutrient source for the cultivation of oleaginous yeast and to use the resultant biomass and lipid as a feedstock for biofuel synthesis. The yeast biomass grown in sago processing wastewater contained 7.21% moisture content, 69.01% volatile matter, 12.61% fixed carbon, and 11.16% ash content. The ultimate analysis determined the contents of carbon (40.43%), nitrogen (5.14%), hydrogen (4.62%), sulfur (0.54%), and oxygen (49.27%). The heating value of yeast biomass was 16.54 MJ kg−1. The thermal behavior of yeast biomass also suggests its potential use as an energy source. The FTIR spectrum of biomass had major lipid (3030–2800 cm−1 and 1500–1350 cm−1) and carbohydrate (1250 cm−1 and 1000 cm−1) functional peaks. Further FAME profiling revealed that the yeast biomass is primarily composed of stearic, oleic, linoleic, and linolenic acids, similar to the vegetable oils. The fuel characteristics of yeast biodiesel (SV, 168.87 mg KOH g−1; IV, 120 mg I2 100 g−1; CN, 61.79; and KV, 3.16 mm2 s−1) are also within the ASTM standard limits, suggesting that yeast biomass could be a sustainable and economically viable feedstock for both solid and liquid biofuel production.