Large-scale Biodiesel Production Research Articles

The effects of cultivation depth, areal density, and nutrient level on lipid accumulation of Scenedesmus acutus in outdoor raceway ponds

Lipid accumulation is critical in the production of biodiesel from microalgae. However, little work has been done on the assessment of lipid accumulation during nitrogen stress in large research-scale outdoor raceways during different seasons; most values for lipid accumulation are assumptions based on work completed in laboratory settings or outdoor photobioreactors. This study focused on the use of raceway ponds operated in batch cultivation mode with an area of 30.37 m2 to determine the impacts of nitrate-nitrogen concentration and cultivation depth on the ability of Scenedesmus acutus strain LB 0414 to accumulate lipids. A concentration of less than 60 mg N-NO3− L−1 was required for removal of nitrogen in the cultivation medium within 8 days to stimulate lipid accumulation and increase lipid productivity. When nitrate concentrations were increased to prevent nitrogen depletion, lipid productivity decreased, which demonstrates that stressing is needed to induce lipid accumulation for increased lipid productivity. Additionally, decreasing cultivation depth below 9 cm, compared to raceways operated at a depth of 20–24 cm, increased lipid productivity by 62 % in December 2014 and 38 % in February 2015. More desirable environmental conditions, mainly increased sunlight and temperature, in February, increased biodiesel productivity for all raceways and account for the decrease in productivity differences. This research highlights increased lipid productivity found by reducing cultivation depth and nitrogen concentrations in outdoor raceways and provides insight into the optimal conditions for large-scale biodiesel production.

Experimental and modelling studies on continuous synthesis and refining of biodiesel in a dedicated bench scale unit using centrifugal contactor separator technology

Continuous synthesis and refining of biodiesel (FAME) using a laboratory scale bench scale unit was explored. The unit consists of three major parts: (i) a continuous centrifugal contactor separator (CCCS) to perform the reaction between sunflower oil and methanol; (ii) a washing unit for the crude FAME with water/acetic acid consisting of a mixer and a liquid–liquid separator; and (iii) a FAME drying unit with air. The continuous setup was successfully used for a 4 h runtime without any operational issues. The CCCS was operated at an oil flow rate of 32 mL/min, rotational speed of 35 Hz, 60°C, a catalyst concentration of 1.2% w/w and a methanol flow rate of 10 mL/min. The flow rate of water (containing 1% w/w acetic acid) for the biodiesel washing unit was 10 mL/min (20°C); the air flow rate (5% humidity) was set at 12 L/min. After 4 h runtime, approximately 7 kg of refined FAME was produced from a cumulative sunflower oil feed of 7.07 kg. The ester content of the refined FAME was 98% w/w (GC). Other relevant product properties were also determined and most were shown to meet the ASTM specifications. The refining section was modelled and optimised using ASPEN software.Practical applications: Synthesis and refining of sunflower biodiesel was successfully performed in a dedicated bench scale unit using centrifugal contactor separator technology. Besides for large scale biodiesel production, this technology has particularly potential to be applied in small mobile biodiesel units due to the compact size, robustness, flexibility in operation and high volumetric productivity of the CCCS devices.Schematic representation of the continuous bench scale unit.

Evaluating the effects of biocompatible cholinium ionic liquids on microbial lipid production by Trichosporon fermentans.

BackgroundMicrobial lipid is a potential raw material for large-scale biodiesel production and lignocellulosic hydrolysate has been considered as promising low-cost substrate for lipid fermentation. Lignocellulosic biomass needs to be pretreated before enzymatic hydrolysis, and biocompatible cholinium ionic liquids (ILs) have been demonstrated to be highly efficient for pretreatment. However, the impact of these ILs residues in hydrolysates on downstream biotransformation remains unknown. Therefore, the influence of three typical cholinium ILs on the lipid production by Trichosporon fermentans was first investigated.ResultsThe cell growth of T. fermentans was stimulated in the presence of cholinium lysine ([Ch][Lys]) and cholinium serine ([Ch][Ser]), while the lipid accumulation was inhibited by [Ch][Lys]) and [Ch][Ser]. Both cell growth and lipid accumulation of T. fermentans were inhibited in the presence of cholinium acetate ([Ch][OAc]). Despite the reduction in lipid content, the lipid production by T. fermentans was improved in the presence of low concentrations of [Ch][Lys] (≤30 mM) and [Ch][Ser] (≤20 mM) due to the remarkable increase of biomass. It was found that cholinium cation had minor influence on lipid production. However, the anions of [Ch][Lys] and [Ch][Ser] could be assimilated as nitrogen source by T. fermentans and the reduced C/N ratio accounts for the inhibition of lipid accumulation, which could be alleviated by improving C/N ratio of medium. In addition, the anion of [Ch][OAc] could be metabolized by T. fermentans, leading to a rapid alkaline-pH shift and strong inhibition of lipid production. And this inhibitory effect on lipid production could be significantly reduced by controlling culture pH.ConclusionsThe anions of [Ch][Lys], [Ch][Ser] and [Ch][OAc] play an important role in affecting the cell growth and lipid accumulation of T. fermentans, and the inhibition of these three ILs on lipid production can be alleviated by careful fermentation condition control. Hence, T. fermentans is a promising strain for microbial lipid production from cholinium ILs-pretreated lignocellulosic hydrolysates.

Potentials of Microalgae Biodiesel Production in Nigeria

Bio-energies are renewable, sustainable and environmentally-friendly. Although Nigeria has a lot of various biomass materials, production of bio-fuels in Nigeria is faced with a lot of challenges. It has been argued that large scale production of bio-energies from food crops as replacement or supplements to fossil fuels cannot be realistically achieved because of possible negative effects on food security. There is high potential for largescale production of biodiesel from microalgae in Nigeria. Establishment of biodiesel production industries in Nigeria will have positive effects on socio-economic development of the country. It has been estimated that Nigeria currently needs about 27 thousand barrels of biodiesel per day to be able to replace the entire consumed fossil diesel with B20 blends. There is therefore an urgent need to isolate and develop productive strains that are adapted to non-arable lands in Nigeria, develop appropriate photo bioreactors and culture systems for large scale production of microalgae biodiesel, and develop bioenergy friendly policies and incentives to encourage bio-energy production in Nigeria.Keywords: bio-energy; climatic conditions; fossil fuel; microalgae; production economics

Polypropylene Bundle Attached Multilayered Stigeoclonium Biofilms Cultivated in Untreated Sewage Generate High Biomass and Lipid Productivity.

The potential of microalgae biofuel has not been realized because of the low productivity and high costs associated with the current cultivation systems. In this study, a new low-cost and transparent attachment material was tested for cultivation of a filamentous algal strain, Stigeoclonium sp., isolated from wastewater. Initially, the different materials tested for Stigeoclonium cultivation in untreated wastewater were nylon mesh, polyethylene mesh, polypropylene bundle (PB), polycarbonate plate, and viscose rayon. Among the materials tested, PB led to a firm attachment, high biomass (53.22 g/m(2), dry cell weight), and total lipid yield (5.8 g/m(2)) with no perceivable change in FAME profile. The Stigeoclonium-dominated biofilm consisted of bacteria and extracellular polysaccharide, which helped in biofilm formation and for effective wastewater treatment (viz., removal efficiency of total nitrogen and total phosphorus corresponded to ~38% and ~90%, respectively). PB also demonstrated high yields under multilayered cultivation in a single reactor treating wastewater. Hence, this system has several advantages over traditional suspended and attached systems, with possibility of increasing areal productivity three times using Stigeoclonium sp. Therefore, multilayered attached growth algal cultivation systems seem to be the future cultivation model for large-scale biodiesel production and wastewater treatment.

Catalytic behaviour of four different supported noble metals in the crude glycerol oxidation

The activity of four different noble metals (Ag, Au, Pd and Pt) in the liquid phase oxidation of pure glycerol was confronted with the results obtained with a crude glycerol fraction, received from a large-scale biodiesel production plant. The catalysts were characterized by numerous techniques, giving insight into actual metal loading (elemental analysis by ICP and XRF), surface morphology (nitrogen absorption methods—BET and porosity), chemical state of both the support and the metal (XRD and XPS), and, finally, the metal particle size distribution (TEM microscopy). A good dispersion of totally reduced noble metal particles of a nanometric size (an average metal diameters were equal 3.5nm, 4.2nm, 4.7nm and 21.2nm for respectively Pd, Pt, Au and Ag) was accompanied with a comparable values of total metal loadings on the alumina support (from 0.95 and 0.96wt.% for Pt and Pd, up to 0.98 and 1.13wt.% for Au and Ag supported catalysts, respectively). In terms of initial reaction rate, the most active sample was the Au/Al2O3 catalyst, both using pure (12976molh−1molAu−1) or crude glycerol (1230molh−1molAu−1). However, comparison of the selectivities and conversions after 1–2h shows that the most robust and resistant catalyst – toward the impurities present in crude glycerol – is Pd/Al2O3, with a loss of conversion less than 50% (in respect to analogous reaction using pure glycerol) and almost unchanged high selectivity to glyceric acid (close to 80–90%). Ag/Al2O3 also showed a relatively high resistance to impurities in terms of glycerol conversion, but with a drastic modification of its selectivity. The activity of the two other catalysts was dramatically affected with a conversion divided by ca. 4 and even 10 for the Pt and the Au catalysts, respectively, when using crude glycerol instead of pure glycerol. Finally, the effect of each main impurity (MONG-NM, i.e., matter organic non-glycerol and non-methanol; ash; methanol; sulphur compounds) was independently studied. In any case, the sulphur compounds and MONG-NM were the impurities the most detrimental for the performances of catalysts. Thus, they should be removed in priority from crude glycerol fractions before reaction, while ashes and methanol should not be considered as completely undesirable.

Large-scale biodiesel production using flue gas from coal-fired power plants with Nannochloropsis microalgal biomass in open raceway ponds

The potential use of microalgal biomass as a biofuel source has raised broad interest. Highly effective and economically feasible biomass generating techniques are essential to realize such potential. Flue gas from coal-fired power plants may serve as an inexpensive carbon source for microalgal culture, and it may also facilitate improvement of the environment once the gas is fixed in biomass. In this study, three strains of the genus Nannochloropsis (4-38, KA2 and 75B1) survived this type of culture and bloomed using flue gas from coal-fired power plants in 8000-L open raceway ponds. Lower temperatures and solar irradiation reduced the biomass yield and lipid productivities of these strains. Strain 4-38 performed better than the other two as it contained higher amounts of triacylglycerols and fatty acids, which are used for biodiesel production. Further optimization of the application of flue gas to microalgal culture should be undertaken.

Manipulation of carbon flux into fatty acid biosynthesis pathway in Dunaliella salina using AccD and ME genes to enhance lipid content and to improve produced biodiesel quality

Advanced generations of biofuels basically revolve around non-agricultural energy crops. Among those, microalgae owing to its unique characteristics i.e. natural tolerance to waste and saline water, sustainable biomass production and high lipid content (LC), is regarded by many as the ultimate choice for the production of various biofuels such as biodiesel. In the present study, manipulation of carbon flux into fatty acid biosynthesis pathway in Dunaliella salina was achieved using pGH plasmid harboring AccD and ME genes to enhance lipid content and to improve produced biodiesel quality. The stability of transformation was confirmed by PCR after several passages. Southern hybridization of AccD probe with genomic DNA revealed stable integration of the cassette in the specific positions in the chloroplast genome with no read through transcription by indigenous promoters. Comparison of the LC and fatty acid profile of the transformed algal cell line and the control revealed the over-expression of the ME/AccD genes in the transformants leading to 12% increase in total LC and significant improvements in biodiesel properties especially by increasing algal oil oxidation stability. The whole process successfully implemented herein for transforming algal cells by genes involved in lipid production pathway could be helpful for large scale biodiesel production from microalgae.

Synthesis and refining of sunflower biodiesel in a cascade of continuous centrifugal contactor separators

The synthesis of fatty acid methyl esters (FAME) from sunflower oil and methanol was studied in a continuous centrifugal contactor separator (CCCS) using sodium methoxide as the catalyst. The effect of relevant process variables like oil and methanol flow rate, rotational speed and catalyst concentration was investigated and modelled using non‐linear regression. Good agreement between experiments and model were obtained. At optimised conditions (oil flow rate of 31 mL/min, rotational speed of 34 Hz, catalyst concentration of 1.2%w/w and a methanol flow rate of 10 mL/min), the FAME yield was 94 mol% at a productivity of 2470 kg FAME/m3reactor.h. Proof of principle for the synthesis and subsequent refining of FAME in a cascade of two CCCS devices was also obtained. Relevant properties of the refined FAME obtained using this technology were determined and were shown to meet the ASTM specifications.Practical application: Synthesis and refining of sunflower biodiesel was successfully performed in a cascade of two CSSS devices. Besides for large scale biodiesel production, this technology has particularly potential to be applied in small mobile biodiesel units due to the compact size, robustness, flexibility in operation, and high volumetric productivity of the CCCS devices.Schematic representation of the process concept for continuous synthesis and refining of sunflower biodiesel synthesis in a cascade of continuous centrifugal contactor separators.

Possible future effects of large-scale algae cultivation for biofuels on coastal eutrophication in Europe

Biodiesel is increasingly considered as an alternative for fossil diesel. Biodiesel can be produced from rapeseed, palm, sunflower, soybean and algae. In this study, the consequences of large-scale production of biodiesel from micro-algae for eutrophication in four large European seas are analysed. To this end, scenarios for the year 2050 are analysed, assuming that in the 27 countries of the European Union fossil diesel will be replaced by biodiesel from algae. Estimates are made for the required fertiliser inputs to algae parks, and how this may increase concentrations of nitrogen and phosphorus in coastal waters, potentially leading to eutrophication. The Global NEWS (Nutrient Export from WaterSheds) model has been used to estimate the transport of nitrogen and phosphorus to the European coastal waters. The results indicate that the amount of nitrogen and phosphorus in the coastal waters may increase considerably in the future as a result of large-scale production of algae for the production of biodiesel, even in scenarios assuming effective waste water treatment and recycling of waste water in algae production. To ensure sustainable production of biodiesel from micro-algae, it is important to develop cultivation systems with low nutrient losses to the environment.

Efficacy of drying and cell disruption techniques on lipid recovery from microalgae for biodiesel production

Downstream processing of microalgal biomass presents a significant challenge to large scale biodiesel production. Scenedesmus sp. which is known to be a potential feedstock for biodiesel production was cultivated in an open circular pond. The biomass productivity peaked at day 21 with a yield of 1.16gL−1. Biomass was harvested by gravitational settling followed by centrifugation. Harvested biomass was dried using the freeze drying, oven drying and sun drying processes followed by lipid extraction which yielded 29.65%, 28.63% and 28.33% lipidg−1 DCW (dry cell weight) respectively. Lipids were extracted from microalgal biomass dried by selected drying techniques using microwave and sonication for cell disruption in the presence of mixture of chloroform and ethanol (1:1). Microwave assisted extraction of sun dried biomass yielded 28.33% lipidg−1 DCW, as compared to 18.9% lipidg−1 DCW achieved by sonication assisted extraction. The saponification and acid values of the lipid obtained from Scenedesmus sp. dried by selected drying techniques showed high saponification and acid value indicating presence of high free fatty acid content. Effect of different drying and cell disruption technique on fatty acid profile of lipids extracted from Scenedesmus sp. biomass was also studied. These values indicate promising potential of the oil produced for conversion into biodiesel.

Tetrahydrofuran-Assisted Base Catalysed Transesterification of Rice Bran Oil for Biodiesel Production

Tetrahydrofuran-assisted base catalysed transesterification of rice bran oil was carried out for biodiesel production. The main problem of conventional base catalysed transesterification reaction is that the reactants are not readily miscible and thus high reaction temperature and longer reaction time is required for the transesterification reaction to complete. The addition of co-solvent such as THF (tetrahydrofuran) enables the reaction to occur in single phase. The base catalysed ethyl ester production aided with tetrahydrofuran as co-solvent was optimised in terms of amount of KOH catalyst, ethanol to oil molar ratio, THF to ethanol ratio, reaction time and reaction temperature. The efficient reaction conditions using tetrahydrofuran as co-solvent were 2% catalyst concentration, 8:1 ethanol to oil molar ratio, THF to ethanol ratio of 0.27, reaction time 45 min and reaction temperature 40 °C. The maximum recovery and conversion of oil into ethyl ester was reported to be 75.8 and 95%. The co-solvent assisted transesterification thus can save time, energy and labour for large scale production of biodiesel.

Chitosan and Its Derivatives Applied in Harvesting Microalgae for Biodiesel Production: An Outlook

Although oil‐accumulating microalgae are a promising feedstock for biodiesel production, large‐scale biodiesel production is not yet economically feasible. As harvesting accounts for an important part of total production cost, mass production of microalgae biodiesel requires an efficient low‐energy harvesting strategy so as to make biodiesel production economically attractive. Chitosan has emerged as a favorable flocculating agent in harvesting of microalgae. The aim of this paper is to review current research on the application of chitosan and chitosan‐derived materials for harvesting microalgae. This offers a starting point for future studies able to invalidate, confirm, or complete the actual findings and to improve knowledge in this field.

Comparative life cycle assessment of biodiesel from algae and jatropha: A case study of India

Algae and jatropha, two types of promising and unconventional biomass, are investigated in this study for large-scale production of biodiesel. The aim is to evaluate the potential advantages and the magnitude of closeness of life cycle balances between these two biodiesel pathways compared to fossil diesel, by taking into account possible uncertainties. The geographical location of this study is India with a prospect of utilizing available wastelands in southern regions. The results indicate that the environmental performance of algal biodiesel is comparable to that of jatropha biodiesel. Both show significant GHG emission and fossil energy depletion reductions which are in the range of 36-40 and 10-25% respectively compared to fossil diesel in the studied geographic context.

Biodiesel synthesis by TiO2–ZnO mixed oxide nanocatalyst catalyzed palm oil transesterification process

Biodiesel is a promising alternating environmentally benign fuel to mineral diesel. For the development of easier transesterification process, stable and active heterogeneous mixed metal oxide of TiO2-ZnO and ZnO nanocatalysts were synthesized and exploited for the palm oil transesterification process. The synthesized catalysts were characterized by XRD, FT-IR, and FE-SEM studies for their structural and morphological characteristics. It was found that TiO2-ZnO nanocatalyst exhibits good catalytic activity and the catalytic performance was greatly depends on (i) catalyst concentration (ii) methanol to oil molar ratio (iii) reaction temperature and (iv) reaction time. A highest 98% of conversion was obtained at the optimum reaction parameters with 200 mg of catalyst loading and the biodiesel was analyzed by TLC and (1)H NMR techniques. The TiO2-ZnO nanocatalyst shows good catalytic performance over the ZnO catalyst, which could be a potential candidate for the large-scale biodiesel production from palm oil at the reduced temperature and time.

Low solvent, low temperature method for extracting biodiesel lipids from concentrated microalgal biomass

An industrially relevant method for disrupting microalgal cells and preferentially extracting neutral lipids for large-scale biodiesel production was demonstrated on pastes (20-25% solids) of Nannochloropsis sp. The highly resistant Nannochloropsis sp. cells. were disrupted by incubation for 15 h at 37°C followed by high pressure homogenization at 1200 ± 100 bar. Lipid extraction was performed by twice contacting concentrated algal paste with minimal hexane (solvent:biomass ratios (w/w) of <2:1 and <1.3:1) in a stirred vessel at 35°C. Cell disruption prior to extraction increased lipid recovery 100-fold, with yields of 30-50% w/w obtained in the first hexane contact, and a further 6.5-20% in the second contact. The hexane preferentially extracted neutral lipids over glyco- and phospholipids, with up to 86% w/w of the neutral lipids recovered. The process was effective on wet concentrated paste, required minimal solvent and moderate temperature, and did not require difficult to recover polar solvents.

Pilot-scale biodegradation of swine manure via Chrysomya megacephala (Fabricius) for biodiesel production

Swine manure may cause environmental pollution and resource waste if not handled properly on pig farms. In this paper, the technology for pig manure biodegradation and biodiesel production using Chrysomya megacephala (Fabricius) is described. About 700kg of fresh pig manure (73% moisture) can be converted within one week into 18.2kg dried larvae biomass containing about 21.11% oil in a pilot plant. The properties of the oil extracted from the larvae meal treated with three different drying methods were compared, indicating that the drying method may affect the properties of feedstock oil. The acid value (1.9mgKOH/g), iodine value (86.3gI/100g), melt point (3.1°C) and peroxide value (0.08meq/kg) of the oil extracted from the larvae treated with both boiling water and oven-drying were superior to the values of the larvae treated with either oven-drying or sun-drying directly. The main fatty acids of the swine manure C. megacephala larvae oil were found to be composed of palmitic acid (36.91%), oleic acid (27.67%), palmitoleic acid (10.89%) and linoleic acid (9.49%). Most of the properties of the biodiesel converted from the feedstock oil by alkaline-catalyst transesterification met the EN 14214 standard in terms of density (0.89g/cm3), viscosity (5.1mm2/s), ester content (96.6%), flash point (138°C), cetane number (56), water content (0.02%) and acid value (0.28mg KOH/g). This study suggests that the swine manure-grown C. megacephala larvae could be a feasible feedstock for a large-scale biodiesel production.

Critical analysis of current Microalgae dewatering techniques

Oil-accumulating Microalgae have the potential to enable large-scale biodiesel production without competing for arable land or biodiverse natural landscapes. However, Microalgae harvesting/dewatering is a major obstruction to industrial-scale processing for biofuel production. The dilute nature of Microalgae in cultivation creates high operational costs for harvesting, thus making microalgal fuel less economical. Within the last decade, significant advances have been made to develop new technologies for dewatering or harvesting of Microalgae. The choice of which harvesting technique to apply depends on the Microalgae cell size and the desired product. Microalgae dewatering processes can broadly be classified as primary and secondary dewatering. This article provides an overview of current dewatering techniques along with a critical analysis of costs and efficiencies, and provides recommendations towards cost-effective dewatering.

Evaluating new isolates of microalgae from Kazakhstan for biodiesel production

New microalgal strains that are native to South-East Kazakhstan were isolated and characterized with a view to identifying suitable candidates for biodiesel production. Six strains of chlorophyte algae (named K1–K6) were recovered from environmental samples as axenic cultures, and molecular analysis revealed that five (K1–K5) are strains of Parachlorella kessleri, whereas K6 is a strain of Chlorella vulgaris. A third isolate from Uzbekistan (termed UZ) was also identified as a separate strain of P. kessleri. All strains show high growth rates and an ability to utilize acetate as an exogenous source of fixed carbon. Furthermore, under conditions of nitrogen depletion, all three strains showed a significant accumulation of neutral lipids (triacylglycerides). P. kessleri K5 and C. vulgaris K6 therefore represent promising autochthon strains for large-scale cultivation and biodiesel production in Kazakhstan.

Microwave energy potential for biodiesel production

Microwave energy based chemical synthesis has several merits and is important from both scientific and engineering standpoints. Microwaves have been applied in numerous inorganic and organic chemical syntheses; perhaps, from the time their ability to work as heat source was discovered. Recent laboratory scale microwave applications in biodiesel production proved the potential of the technology to achieve superior results over conventional techniques. Short reaction time, cleaner reaction products, and reduced separation-purification times are the key observations reported by many researchers. Energy utilization and specific energy requirements for microwave based biodiesel synthesis are reportedly better than conventional techniques. Microwaves can be very well utilized in feedstock preparation, extraction and transesterification stages of the biodiesel production process. Although microwave technology has advanced in other food, pharmaceutical and polymer chemistry related research and industry, it has yet to prove its potential in the biodiesel industry at large scale applications. This paper reviews principles and practices of microwave energy technology as applied in biodiesel feedstock preparation and processing. Analysis of laboratory scale studies, potential design and operation challenges for developing large scale biodiesel production systems are discussed in detail.