Biodiesel production from sediments of a eutrophic reservoir

Sediments from eutrophic reservoir Bugach (Siberia, Russia) were tested for possibility to produce biodiesel. We supposed that the sediments could be a promising biodiesel producer. The major reason of high price of biodiesel fuel is cost of a raw material. The use of dredging sediments for biodiesel production reduces production costs, because the dredging sediments are by-products which originated during lake restoration actions, and are free of cost raw materials. Lipid content in sediments was 0.24% of dry weight. To assess the potential of from sediments as a substitute of diesel fuel, the properties of the biodiesel such as cetane number, iodine number and heat of combustion were calculated. All of this parameters complied with limits established by EN 14214 and EN 14213 related to biodiesel quality.     

Search for new strains of microalgae-producers of lipids from natural sources for biodiesel production

Biomass of high-yielding strains of phototrophic microorganisms actively accumulating lipids is a promising non-traditional raw material for bioenergy including the production of biodiesel. In this study, we present results of searching for new strains of microalgae-producers of lipids from hot springs. Within the framework of research, the primary screening of water for the presence of lipid - accumulative microalgae was carried out with the help of qualitative reaction with lipid-specific dyes, as well as 5 axenic isolates of microalgae with stable growth were identified in the laboratory and their productivity and fatty acid composition were studied. The isolated strains were identified as Chlorella vulgaris sp-1, Ankistrodesmus sp-21, Scеnеdеsmus obliquus sp-21, Chlorella pyrenoidosa sp-13 and Chlamydomonas sp-22. The obtained data showed that the isolated strains determined by biomass in the range 1.3 g/l to 1.81 g/l. As a result of the research, it was established that the highest content of lipids was observed in the strains Chlorella vulgaris sp-1 and Scеnеdеsmus obliquus sp-21, which is 28.7 and 29.8% of the cell dry weight, respectively. The analysis of the fatty acid composition of the cells showed that the largest mass fraction of saturated and monounsaturated fatty acids was found in strain Scеnеdеsmus obliquus sp-21 - 61.9%. In the result, Scеnеdеsmus obliquus sp-21 strain isolated from thermal sources was selected as a promising candidate for biodiesel production.     

Characterization of microalgal species isolated from fresh water bodies as a potential source for biodiesel production

Due to increasing oil prices and climate change concerns, biodiesel has gained attention as an alternative energy source. Biodiesel derived from microalgae is a potentially renewable and carbon–neutral alternative to petroleum fuels. One of the most important decisions in obtaining oil from microalgae is the choice of algal species to use. Eight microalgae from a total of 33 isolated cultures were selected based on their morphology and ease of cultivation. Five cultures were isolated from river and identified as strains of Scenedesmus obliquus YSR01, Nitzschia cf. pusilla YSR02, Chlorella ellipsoidea YSR03, S. obliquus YSR04, and S. obliquus YSR05, and three were isolated from wastewater and identified as S. obliquus YSW06, Micractinium pusillum YSW07, and Ourococcus multisporus YSW08, based on LSU rDNA (D1-D2) and ITS sequence analyses. S. obliquus YSR01 reached a growth rate of 1.68 ± 0.28 day⁻¹ at 680_nm and a biomass concentration of 1.57 ± 0.67 g dwt L⁻¹, with a high lipid content of 58 ± 1.5%. Under similar environmental conditions, M. pusillum reached a growth rate of 2.3 ± 0.55 day⁻¹ and a biomass concentration of 2.28 ± 0.16 g dwt L⁻¹, with a relatively low lipid content of 24 ± 0.5% w/w. The fatty acid compositions of the studied species were mainly myristic, palmitic, palmitoleic, oleic, linoleic, g-linolenic, and linolenic acids. Our results suggest that S. obliquus YSR01 can be a possible candidate species for producing oils for biodiesel, based on its high lipid and oleic acid contents.     

Effects of flocculants on lipid extraction and fatty acid composition of the microalgae Nannochloropsis oculata and Thalassiosira weissflogii

The aim of this study was to investigate the possible interference of anionic and cationic flocculants in the lipid extraction and fatty acid profiles of two species of marine microalgae: Nannochloropsis oculata and Thalassiosira weissflogii. Cells were grown in batch cultures (f/2 medium, salinity of 28, temperature of 20 °C, light intensity of 40 ??mol photons  m^-2 s^-1 and 12/12 h L/D photoperiod) and concentrated using sodium hydroxide (control), sodium hydroxide and the anionic polyacrylamide flocculant Magnafloc^® LT-25 (APF treatment) and sodium hydroxide plus the cationic polyacrylamide flocculant Flopam^® (CPF treatment). There were no statistically significant differences among treatments with respect to lipid extraction for both species. However, N. oculata which presented higher percentages of C16:0, C16:1 and C20:5 fatty acids showed an increase of C14:0 and a decrease of C20:5 with the use of anionic flocculant. Additionally, T. weissflogii which had high percentages of C16:0, C16:1, C16:3 and C20:5, showed a decrease of C18:0 and C18:1n9c when both flocculants were used and a small decrease of C16:0 in the APF treatment. The results indicate that the choice of flocculant should be based on the level of saturation desirable, i.e., if the goal is to produce more stable biodiesel, with low percentage unsaturated fatty acids, then anionic flocculants should be used. On the other hand, if the aim is to produce unsaturated fatty acids for commercial uses in the pharmacy or food industries, then anionic polymers should be avoided.     

Isolation and identification by 18S rDNA sequence of high lipid potential microalgal species for fuel production in Hainan Dao

To exploit indigenous microalgal species with the potential for biodiesel production, 101 algal cultures were isolated from partial waters in Hainan province. Eight cultures were selected based on their high biomass, high lipid content and ease of cultivation, then identified based on morphology and 18S rDNA sequence analysis. These isolates were identified as Tetranephris brasiliensis DL12, Ankistrodesmus gracilis DL25, Ankistrodesmus sp. CJ02, Desmodesmus subspicatus WC01, A. gracilis CJ09, Chlorella vulgaris CJ15, Desmodesmus sp. WC08, Chlorella sorokiniana XS04, respectively. Desmodesmus sp. WC08 reached the highest biomass concentration (2.32 g L⁻¹) with the lipid content of 31.30%. Higher lipid content of 47.90% and 47.39% were gained by A. gracilis CJ09 and C. vulgaris CJ15, respectively. However, C. vulgaris CJ15 and Desmodesmus sp. WC08 had higher lipid productivity (117.37 mg L⁻¹ d⁻¹and 115.73 mg L⁻¹ d⁻¹, respectively) in terms of comprehensive consideration. The fatty acid compositions of these microalgal species were mainly palmitic, palmitoleic, stearic, oleic with GC–MS (gas chromatography–mass spectrometer) analysis. A. gracilis CJ09, T. brasiliensis DL12, A. gracilis DL25 and Desmodesmus sp. WC08 had the higher oleic acid content (over 50% of the total fatty acids) than the others. The results suggest that marine microalgae strain Desmodesmus sp. WC08 can be the most appropriate candidate for producing oil for biodiesel, based on its higher biomass productivity, lipid productivity and fatty acid profile.     

Energy recovery from microalgal biomass via enhanced thermo-chemical process

This work showed that microalgae having low lipid content has high potential for energy recovery via thermo-chemical processes. As an example, Microcystis aeruginosa (M. aeruginosa) was considered and tested. Specifically, this work verified that the growth rate of M. aeruginosa was extremely fast compared to other microalgae (as a factor of ∼10). Moreover, this work investigated the CO₂ co-feed impact on thermo-chemical processes (pyrolysis/gasification) using M. aeruginosa. Introducing CO₂ in the thermo-chemical process as reaction media or feedstock can enhance the efficiency of thermo-chemical processes by expediting the cracking capability of condensable hydrocarbons (tar). The generation of CO was enhanced as a factor of ∼2. Further generation of H₂ could be achieved in the presence of CO₂. Thus, utilizing CO₂ as reaction media or chemical feedstock can modify the end products into environmentally benign and desirable ones. The CO₂ co-feed impact on thermo-chemical processes with lingo-cellulosic biomass can be universally applied.     

Waste-free technology of wastewater treatment to obtain microalgal biomass for biodiesel production

Five axenic cultures of microalgae were isolated from the wastewater of Almaty city and identified as Chlorella vulgaris strain № 1, Chlorella sp. strain № 3, Scenedesmus obliquus, Phormidium foveolarum and Lyngbya limnetica. Among these strains, C. vulgaris strain № 1 was characterized by the maximum growth rate and the highest productivity. Mass cultivation of this strain in wastewater resulted in accumulation of 5 × 10⁷ cells per ml in 16 days, and in the removal of ～95% of pollutants from water. Cells of C. vulgaris consisted of ～35% proteins, 29% carbohydrates, 30% lipids, and 6% ash, as calculated on a dry weight basis. The major fatty-acids of C. vulgaris were represented by palmitic, cis-7,10-hexadecenoic acid, linoleic, and α-linolenic acids. Culturing in wastewater decreased the unsaturation index of FAs. Thus, C. vulgaris cells are suitable for both waste water purification and accumulation of biomass for further biodiesel production.     

Biodiesel production by ultrasound-assisted transesterification: State of the art and the perspectives

In the present paper state-of-the art and perspectives of ultrasound-assisted (UA) biodiesel production from different oil-bearing materials using acid, base and enzyme catalysts are critically discussed. The ultrasound action in biodiesel production is primarily based on the emulsification of the immiscible liquid reactants by microturbulence generated by radial motion of cavitation bubbles and the physical changes on the surface texture of the solid catalysts generating new active surface area. The importance of ultrasound characteristics and other process variables for the biodiesel yield and the reaction rate is focused on. UA transesterification is compared with other techniques for biodiesel production. Several different developing methods reducing the biodiesel production costs such as the optimization of process factors, the development of the process kinetic models, the use of phase transfer catalysts, the application of the continuous process, the design of novel types of ultrasonic reactors and the in situ ultrasound application in transesterification of oily feedstocks are also discussed.     

Investigating the interdependence between cell density,biomass productivity,and lipid productivity to maximize biofuel feedstock production from outdoor microalgal cultures

For biofuel applications, increasing net lipid productivity from continuous flow microalgal cultures is critically important. Parameters that affect net lipid productivity include: cell lipid content, culture flow rate or hydraulic retention time, and biomass concentration. However, these parameters are interlinked and cannot be independently altered. This research is aimed at probing the interdependence between variables and maximizing net lipids from outdoor algal cultures. Three representative algal species for biodiesel production namely, Nannochloris sp., Selenastrum capricornutum, and Scenedesmus dimorphus, were grown in an outdoor continuous-flow system at four different Hydraulic Retention Times (HRT) of 6, 12, 18 and 24 h. The highest biomass cell concentration (250 mg/L) occurred at the longest HRT (24 h) and decreased progressively with shorter HRTs. However, net aerial biomass productivity numbers did not follow a specific pattern. The highest net aerial productivity of 43.4 g/m²/day was achieved with Nannochloris sp. species at 6 h HRT, compared to 32.1 g/m²/day at 24 h HRT by S. capricornutum species. Net lipid productivity was found to be significantly higher at 24 h HRT, achieving 7.9, 9.6 and 10.4 g/m²/day for Nannochloris sp., S. capricornutum, and S. dimorphus respectively. When the media flow was curtailed, the lipid concentrations increased at the expense of protein and carbohydrate contents of the cell.     

Biodiesel from microalgae – Life cycle assessment and recommendations for potential improvements

Microalgae are considered as one of the potential major source of biofuel for the future. However, their environmental benefit is still unclear and many scientific publications provide contradictory results. Here we perform the Life Cycle Assessment of the production and combustion of 1 MJ of algal methylester. The system under consideration uses standard open raceways under greenhouses. Lipid extraction and transesterification are carried out on a humid paste produced by centrifugation. Our environmental and energetic analysis shows that improving the energy balance is clearly the key priority to make microalgal cultivation sustainable and to reduce its greenhouse gas (GHG) emissions. To achieve significant reduction of the GHG emissions, most of the studies of the literature focus on technological breakthroughs, especially at the production step. However, since a large fraction of environmental impacts and especially GHG emissions do not occur directly at the production facility but stem from the production of the electricity required for producing, harvesting and transforming algae, it seems relevant to question the source of electricity as well as algae production technology. We consider a scenario where up to 45% of electricity was produced by a local renewable source and then we compare it to the improvements resulting from technological breakthroughs resulting in higher microalgal productivity or biomass concentration. It turns out that increasing the yield only drastically reduces the climate change for low starting productivity. The climate change is always significantly reduced by the use of local renewable electricity. It is therefore wiser to increase biomass productivity to easily achievable values (10–15 gm⁻² d⁻¹), and then radically change improvements pathways by considering the composition of the electricity mix used for example. At least, it must be underlined that the introduction of renewable electricity also affect energetic efficiency, leading to a positive cumulative energy balance due to better energetic ratios.     

Characterization of fatty acid and carotenoid production in an Acutodesmus microalga isolated from the Algerian Sahara

An Acutodesmus microalga of the Scenedesmaceae family isolated from the Algerian Sahara was characterized for its ability to produce lipids, fatty acids (FA) and carotenoids under nitrate starvation, osmotic stress and a varying level of oxidative stress. The FA produced by this strain isolated from an environment typified by extreme heat showed a lower degree of unsaturation than those of other Scenedesmus which have been isolated from cold or temperate water environments, with no unsaturated C16 FA and more than 92% of the FA profile being comprised of FA with less than three unsaturated bonds. According to the degree of unsaturation and the cetane number, the FA profile from this strain is highly favorable for biofuel production. Lipogenesis and carotenogenesis were easily reversible upon removal of the stress. These results constitute an advance in developing strains suitable for industrial-scale production of biofuels.     

Biodiesel from oilgae,biofixation of carbon dioxide by microalgae: A solution to pollution problems

Algae containing 30–75% of lipid by dry basis can be called oilgae. All microalgae species produce lipid however some species can contain up to 70% of their dry weight. Microalgae appear to be the only source of renewable biodiesel that is capable of meeting the global demand for transport fuels. Biodiesel production by using oilgae is an alternative process in contrast to other procedures not only being degradable and non-toxic but also as a solution to global warming via reducing emission gases. Algae-based technologies could provide a key tool for reducing greenhouse gas emissions from coal-fired power plants and other carbon intensive industrial processes. Because algae are rich in oil and can grow in a wide range of conditions, many companies are betting that it can create fuels or other chemicals cheaper than existing feedstocks. The aim of microalgae biofixation of CO₂ is to operate large-scale systems that are able to convert a significant fraction of the CO₂ outputs from a power plant into biofuels.     

生物柴油及其生产技术的进展

介绍了由可再生油脂原料衍生的环保燃料生物柴油在国内外应用现状,重点介绍了酯交换法制备生物柴油技术研究进展情况,展望了生物柴油产业在我国的发展前景。     

Exploring alkaline pre-treatment of microalgal biomass for bioethanol production

We have investigated, for the first time, the alkaline pre-treatment of microalgal biomass, from the species Chlorococcum infusionum, using NaOH for bioethanol production. This pre-treatment step aims to release and breakdown entrapped polysaccharides in the microalgae cell walls into fermentable subunits. Three parameters were examined here; the concentration of NaOH, temperature and the pre-treatment time. The bioethanol concentration, glucose concentration and the cell size were studied in order to determine the effectiveness of the pre-treatment process. Microscopic analysis was performed to confirm cell rupturing, the highest glucose yield was determined to be 350 mg/g, and the maximum bioethanol yield obtained was 0.26 g ethanol/g algae using 0.75% (w/v) of NaOH and 120 °C for 30 min. Overall, the alkaline pre-treatment method proved to be promising option to pre-treat microalgal biomass for bioethanol production.     

Synergistic carbon metabolism in a fast growing mixotrophic freshwater microalgal species Micractinium inermum

In recent years microalgae have attracted significant interest as a potential source of sustainable biofuel. Mixotrophic microalgae are able to simultaneously photosynthesise while assimilating and metabolising organic carbon. By combining autotrophic and heterotrophic metabolic pathways biomass productivity can be significantly increased. In this study, acetate-fed mixotrophic Micractinium inermum cultures were found to have a specific growth rate 1.74 times the sum of autotrophic and heterotrophic growth. It was hypothesised that gas exchange between the two metabolic pathways within mixotrophic cultures may have prevented growth limitation and enhanced growth. To determine the extent of synergistic gas exchange and its influence on metabolic activity, dissolved inorganic carbon (DIC), dissolved oxygen (DO) and photosynthesis and respiration rates were measured under different trophic conditions. A 32.7 fold and 2.4 fold increase in DIC and DO concentrations, relative to autotrophic and heterotrophic cultures respectively, were coupled with significant increases in rates of photosynthesis and respiration. These data strongly support the hypothesis of mixotrophic gas exchange within M. inermum cultures. In addition to enhanced growth, this phenomenon may provide reductions in aeration and oxygen stripping costs related to microalgae production.     

Biodiesel production over copper vanadium phosphate

In the present study, copper vanadium phosphate (CuVOP) with three-dimensional network structure was synthesized by hydrothermal method, and was characterized by Infrared spectrum (IR), elemental analysis (EA), EDXRF (energy dispersive X ray fluorescence) etc. Moreover, soybean oil was used as feedstock for producing biodiesel, and biodiesel was produced by CuVOP-catalyzed transesterification process. Response surface methodology was employed to statistically evaluate and optimize the conditions for the maximum conversion to biodiesel, and the effects of amount of catalyst, ratio of methanol to oil, reaction time and reaction temperature were investigated by the 2⁴ full-factorial central composite design. The maximum conversion is obtained at amount of catalyst of 1.5%, methanol/oil molar ratio of 6.75, reaction temperature of 65 °C and reaction time of 5 h. Copper vanadium phosphate CuVOP resulted very active in the transesterification reaction for biodiesel production.     

Feasibility of microalgal and macroalgal biomass co-digestion on biomethane production

Algal biomass is a promising candidate for biofuels/chemicals production in recent decades due to their huge availability and ease of cultivation methods when compared to terrestrial crops. Anaerobic digestion (AD) of algal biomass is viable option for green and sustainable biorefinery to produce energy and waste minimization. In this study, the feasibility of microalgal and macroalgal biomass on biomethane production and evaluated for mono-digestion and co-digestion process. The experiments resulted showed that mono-digestion gave relatively lower methane yield (MY) of 102–180 mL/g VS than co-digestion experiments. Co-digestion of microalgae and macroalgae biomass in the ratio of 2:8 provided the peak MY of 256 mL/g VS with an increment in MY over 40–70% than the individual algal biomass. The kinetic analysis showed that synergic effect of co-digestion with proper nutrient balance promoted the methane conversion yield from algal biomass with reduction in lag-phase time and overall improved process performances. Co-digestion of mixed algal strain is a feasible strategy to boost-up the performance of AD with relative easiness in real-field applications.     

Fatty acid methyl ester production from wet microalgal biomass by lipase-catalyzed direct transesterification

The aim of this work was to optimize the production of fatty acid methyl ester (FAME, biodiesel) from wet Nannchloropsis gaditana microalgal biomass by direct enzymatic transesterification. This was done in order to avoid the high cost associated with the prior steps of drying and oil extraction. Saponifiable lipids (SLs) from microalgal biomass were transformed to FAME using the lipase Novozyme 435 (N435) from Candida antarctica as the catalyst, and finally the FAME were extracted with hexane. t-Butanol was used as the reaction medium so as to decrease lipase deactivation and increase mass transfer velocity. A FAME conversion of 99.5% was achieved using wet microalgal biomass homogenized at 140 MPa to enhance cell disruption, a N435:oil mass ratio of 0.32, methanol added in 3 stages to achieve a total of 4.6 cm³ g⁻¹ of oil and 7.1 cm³ g⁻¹ oil of added t-butanol, with a reaction time of 56 h. The FAME conversion decreased to 57% after catalyzing three reactions with the same lipase batch. This work shows the influence of the polar lipids contained in the microalgal biomass both on the reaction velocity and on lipase activity.     

Biodiesel production from mahua (Madhuca indica) oil having high free fatty acids

A technique to produce biodiesel from mahua oil (Madhuca indica) having high free fatty acids (19% FFA) has been developed. The high FFA level of mahua oil was reduced to less than 1% by a two-step pretreatment process. Each step was carried out with 0.30–0.35 v/v methanol-to-oil ratio in the presence of 1% v/v H₂SO₄ as an acid catalyst in 1-hour reaction at 60°C. After the reaction, the mixture was allowed to settle for an hour and methanol–water mixture that separated at the top was removed. The second step product at the bottom was transesterified using 0.25 v/v methanol and 0.7% w/v KOH as alkaline catalyst to produce biodiesel. The fuel properties of mahua biodiesel were found to be comparable to those of diesel and conforming to both the American and European standards.     

Biomass and lipid productivities of marine microalgae isolated from the Persian Gulf and the Qeshm Island

In this work, the screening of 147 microalgal strains from the Persian Gulf and the Qeshm Island (Iran) were done in order to choose the best ones, in terms of growth (biomass) rate and lipid content for biodiesel production. A methodology, combining experiments in lab-scale and pilot plant (open pond) used to produce and evaluate biomass and lipid productivity is presented for the systematic investigation of the potential of different microalgae species. The culture conditions, including photo flux (180 ??E m⁻² s⁻¹), photoperiod (12 h light/dark), temperature (25 °C), pH (≈8), air (carbon dioxide) and growth medium, were kept constant for all experiments. Microalgae were screened in two stages using optical density (for evaluation of biomass concentration) and Nile red and gas chromatography (for determination of lipid content and fatty acid fractions). In general, maximum specific growth rate and the maximum biomass productivity were obtained after 8-12-day culture. Nannochloropsis sp. and Neochloris sp. were selected from the marine microalgal culture collection, due to their high biomass (50 and 21.7 g L⁻¹, respectively) and oil content (52% and 46%, respectively). If the purpose is to produce biodiesel only from one species, Nannochloropsis sp. presented the most adequate fatty acid profile, namely linolenic and other polyunsaturated fatty acids. However, the microalgae Chlorella sp. can also be used if associated with other microalgal oils. In addition, selected strains could be potent candidates for commercial production in the open pond culture.