Microalgae Biodiesel Research Articles

Esterification of free fatty acids with methanol to biodiesel using heterogeneous catalysts: From model acid oil to microalgae lipids

One of the main problems of microalgae lipids is their high content of free fatty acids (FFAs), which creates problems of soap formation during homogeneous alkali transesterification. The main purpose of this study was to test heterogeneous catalysts to transform the FFAs from a oil (oleic acid+canola oil) used as a model and from microalgae lipids (Scenedesmus obliquus and Chlorella protothecoides) into biodiesel. Under the conditions tested (temperature: 120°C, autogenous pressure, reaction time: 60min, methanol to lipid ratio: 0.57mL/g and 2.5wt% Amberlyst-15 relative to microalgae lipids), Chlorella protothecoides lipids allowed to reach a higher conversion (84%) compared to Scenedesmus obliquus lipids (34%). However, the study showed that both microalgae lipids suffered from mass transfer limitations, due to impurities, because FFAs conversions higher than 90% were obtained with the model oils (20–33wt% FFAs in canola oil). Despite the fact that the FFAs from both microalgae were suitable to produce biodiesel, further studies must be made on alkali transesterification of the remaining lipids still present in microalgae biodiesel and on crude lipid purification in order to limit the mass transfer problems.

A CFD study on spray characteristics of heavy fuel oil-based microalgae biodiesel blends under ultra-high injection pressures

Blended fuels have intrinsic potential for substitution with petro fuel for the purpose of emission control and fuel efficiency improvement. Therefore, in the current study, non-reacting spray characteristics of heavy fuel oil (HFO) combined with microalgal biodiesel as blended fuel under ultra-high injection pressure is numerically investigated. To accomplish this task with spray morphology, the characteristics of spray penetration, spray cone angle, spray volume and Sauter Mean Diameter (SMD) are studied. The OpenFOAM CFD toolbox is employed with Eulerian–Lagrangian multiphase formulation for fuel discrete phase interacting with gaseous continuous phase modeling. Lagrangian particle tracking (LPT) method is applied for the fuel droplet tracking by Lagrangian scheme. Moreover, hybrid breakup model of KH-RT and k − ϵ as the standard model in Reynolds Averaged Navier–Stokes (RANS) are used for liquid fuel core breakup and turbulence modeling, respectively. Computational results are validated against existing experimental data for HFO and good agreements are displayed. Longer spray penetration length with sharper tip, wider spray cone angle, more obese spray volume and lower SMD are obtained for the blended fuels. Overall, it is concluded that HFO-microalgal biodiesel blended fuels present a better fuel–air mixture and improves atomization procedure under high and ultra high injection pressures.

Intensification of microalgae drying and oil extraction process by vapor recompression and heat integration

Reducing energy penalty caused by drying and oil extraction is the most critical challenge in microalgae biodiesel production. In this study, vapor recompression and heat integration are utilized to optimize the performance of wet microalgae drying and oil extraction. In the microalgae drying stage, the hot exhaust stream is recompressed and coupled with wet microalgae to recover the condensate heat. In the oil extraction stage, the exergy rate of recovered solvent is also elevated by compressor and then exchanged heat with feed and bottom stream in the distillation column. Energy and mass balance of the intensified process is investigated and compared with the conventional microalgae drying-extraction process. The simulation results indicated that the total energy consumption of the intensified process can be saved by 52.4% of the conventional route.

Microalgae consortia cultivation in dairy wastewater to improve the potential of nutrient removal and biodiesel feedstock production.

The potential of microalgae consortia used in dairy wastewater treatment combined with microalgae biodiesel feedstock production was evaluated by comparing the nutrient removal of dairy wastewater, the growth of cells, and the lipid content and composition of biomass between monoalgae and microalgae consortia cultivation system. Our results showed that higher chemical oxygen demand (COD) removal (maximum, 57.01-62.86%) and total phosphorus (TP) removal (maximum, 91.16-95.96%) were achieved in almost microalgae consortia cultivation system than those in Chlorella sp. monoalgae cultivation system (maximum, 44.76 and 86.74%, respectively). In addition, microalgae consortia cultivation except the mixture of Chlorella sp. and Scenedesmus spp. reached higher biomass concentration (5.11-5.41gL(-1)), biomass productivity (730.4-773.2mgL(-1)day(-1)), and lipid productivity (143.7-150.6mgL(-1)day(-1)) than those of monoalgae cultivation (4.72gL(-1), 674.3, and 142.2mgL(-1)day(-1), respectively) on the seventh day. Furthermore, the fatty acid methyl ester (FAME) profiles indicated the lipids produced from microalgae consortia cultivation system were more suitable for biodiesel production. The microalgae consortia display superiority in dairy wastewater treatment and the getting feedstock for biodiesel production.

Biodiesel Production and Unsaponified Lipids Extraction from Microalgae: an Experimental Study

Background: Microalgae are a promising feedstock to produce biofuels such as biodiesel, since their culture does not compete with food crops. In order to make a microalgae biodiesel process cost effective, a biodiesel production process, which consists in separating the microalgae unsaponified lipids (such as carotenoids) from the biodiesel produced, has been tested. Methods: In this process, the 1st step is an alkali reaction (saponification) between microalgae lipids and potassium hydroxide (KOH) (1.26 mmol OH-/g methanol), followed by a 2nd acid reaction step (esterification) using sulphuric acid (H2SO4) (1.65 mmol H+/g methanol) with a total methanol to lipid ratio of 13 mL/g. Between these 2 steps, a solvent extraction (hexane) separates the unsaponified lipids from the reaction mixture. Results: This 2-step process resulted in a FAME yield of 91 g FAME/kg dry biomass, a biodiesel purity of 260 mmol FAME/100 g biodiesel and an unsaponified lipid yield of 170 g lipid/kg dry biomass. The 2-step process (with a hexane separation between both steps) tested in this study achieved a higher FAME yield and a higher biodiesel purity compared to a lipid crystallization separation. When crystallization with hexane at 0°C was tested at the same biodiesel production conditions as the 2-step process, a maximum FAME yield of 35 g FAME/kg dry biomass with a biodiesel purity of 52 mmol FAME/100 g biodiesel were obtained. Conclusion: Despite the fact that this 2-step process produces an important amount of salt (4.8 kg K2SO4/kg FAME), for the best operating conditions tested, in comparison to a conventional vegetable oil-based biodiesel obtained by 1-step alkali homogeneous catalytic processes (0.03 kg K2SO4/kg FAME), it is effective and simple, and could help biodiesel from microalgae be cost effective. Keywords: Biodiesel, crystallization, solvent extraction, lipids, microalgae, purification.

Optimization of Nitrogen, Phosphorus and Salt for Lipid Accumulation of Microalgae: Towards the Viability of Microalgae Biodiesel

In recent years, microalgae biodiesel has attracted expressive attention and investment, once it was considered a potential resource for energy. Although the wide use of microalgae biodiesel is restricted by its high production cost. For cost-efficient and sustainable production of biodiesel from microalgae, a proper understanding of the variables and their impacts on physiology of the strains is required. In this study, a simple factorial design 23 was used to find optimal conditions for the cultivation of Ankistrodesmus sp. and Chlamydomonas sp. in batch culture. The three components considered were nitrate, phosphate and sodium chloride, used to assess the metabolic versatility of the strains in brackish conditions. The results showed that culture medium with 0.04 g·L?1 nitrate, 0.01 g·L?1 phosphate and 5.0 g·L?1 sodium chloride resulted to be the most effective condition to growth and fatty acids accumulation. Using this optimal condition, Ankistrodesmus sp. and Chlamydomonas sp. increased in 2.1 and 2.4 folds their fatty acids yield, respectively. Importantly, this protocol reduced 75% of the nitrate and phosphate concentrations of the original medium (ASM-1). Additionally, fatty acids analysis found that these strains were mainly constituted of C16-C18, in accordance with the requirements for biodiesel production. The simple factorial design applied here proved to be an important tool towards a better understanding of synergistic effects of tested factors on microalgae metabolism, and the resulting information could be used effectively to improve microalgae cultivation.

Evaluation of Five Nannocfhloropsis Sp. Strains for Biodiesel and Poly-Unsaturated Fatty Acids (PUFAs) Production

In this study, five Nannochloropsis sp. strains recently isolated from China’s coastal waters were evaluated for their biodiesel and poly-unsaturated fatty acids (PUFAs) production potential. The results shown, Nannochloropsis sp. 628 achieved the highest biomass accumulation of 7.05 ± 0.21 g L-1, and Nannochloropsis sp. 1049 was the most promising lipid producer, with lipid content of 61.16 ± 0.03% dry cell weight (DCW) and lipid productivity of 235.89 ± 7.58 mg L-1 d-1. For all the strains, neutral lipid was the predominant component of total lipid which counted for percentages ranging from 69.25 ± 1.06% to 87.31 ± 0.26% total lipid. The favorable fatty acids (FAs) of saturated FAs, monounsaturated FAs and C16-C18 components of total FAs of the strains were all preferable attained. Suitable biodiesel properties within the prescribed limits were also revealed. High production ability of PUFAs (89.27 ± 7.79 mg L-1 to 134.94 ± 9.84 mg L-1) meant PUFAs could be considered as co-products of microalgae biodiesel production. The present study shown the Nannochloropsis sp. strains could be consider as valuable feedstock candidates for biodiesel production.

Life cycle value analysis for sustainability evaluation of bioenergy products

Bioenergy products appear to be practical, effective, and environmentally sustainable renewable energy resources which simultaneously reduce fuel-associated environmental impacts and increase economic value of the products. The use of bioproducts may not always have a net positive environmental or economic attributes, therefore, an adequate sustainability evaluation tool for the products which incorporates life-cycle approach is generally desired. This paper presents an informative value analysis which couples concepts of life cycle energy efficiency and production cost ratios, for a feasible assessment of function value for bioenergy products. Bioenergy products that are selected for the value assessment in this study include biodiesel, bioethanol and biocharcoal. This study is divided into two parts: value factor development along with discussions on the results of value analysis for bioenergy products, and, a sensitivity analysis in determining influential factors for value factor estimations. The results showed that microalgae biodiesel and biochar had the lowest and the highest function values, respectively, among assessed bioenergy systems. This was mainly due to the significant difference in energy input in manufacturing design and production cost. Future improvements in bioenergy production can be anticipated for developing bioenergy products with high value factors which demonstrate high economic viability, environmental performance and social acceptability. This analysis can be of interest to bioenergy production planners for sustainable product development.

Greenhouse gas emissions and energy balance of biodiesel production from microalgae cultivated in photobioreactors in Denmark: a life-cycle modeling

The current use of fossil fuels is problematic for both environmental and economic reasons and biofuels are regarded as a potential solution to current energy issues. This study analyzes the energy balances and greenhouse gas emissions of 24 different technology scenarios for the production of algal biodiesel from Nannochloropsis cultivated at industrial scale in photobioreactors in Denmark. Both consolidated and pioneering technologies are analyzed focusing on strengths and weaknesses which influence the performance. Based on literature data, energy balance and greenhouse gas emissions are determined in a comparative ‘well-to-tank’ Life Cycle Assessment against fossil diesel. Use of by-products from biodiesel production such as glycerol obtained from transesterification and anaerobic digestion of residual biomass are included. Different technologies and methods are considered in cultivation stage (freshwater vs. wastewater; synthetic CO2 vs. waste CO2), harvesting stage (flocculation vs. centrifugation) and oil extraction stage (hexane extraction vs. supercritical CO2 extraction). The choices affecting environmental performance of the scenarios are evaluated. Results show that algal biodiesel produced through current conventional technologies has higher energy demand and greenhouse gas emissions than fossil diesel. However, greenhouse gas emissions of algal biodiesel can be significantly reduced through the use of ‘waste’ flows (nutrients and CO2) but there are still technical difficulties with both microalgae cultivation in wastewater as well as transportation and injection of waste CO2. In any way, a positive energy balance is still far from being achieved. Considerable improvements must be made to develop an environmentally beneficial microalgae biodiesel production on an industrial scale. In particular, different aspects of cultivation need to be enhanced, such as the use of wastewater and CO2-rich flue gas from industrial power plants.

A Review on Microalgae Biodiesel Production and its Usage in Direct Injection Diesel Engines as Alternate Fuel

Biodiesel is one of the promising alternative fuels for automotive engines due to the depletion of fossil fuel resources, increasing energy demands and environmental concerns. The biodiesel can be obtained from various bio energy resources such as edible and non-edible vegetable oils and animal fats. However, the use of biodiesel derived from edible oils such as palm oil, sunflower oil and soybean oil has negative impact on global food market. Biodiesel from microalgae is considered as a third generation biofuel derived from non-edible resources and best suited for internal combustion engines. Microalgae have the potential to provide sufficient fuel for global consumption due to its high oil content and fast growing ability. This paper provides a brief overview of biodiesel production from microalgae biomass and its suitability as alternate fuel in diesel engines. This review highlights the selection of suitable algae species for oil production, fuel properties in comparison with standard diesel and other biodiesel fuels, performance, combustion and emission characteristics when used in engines, and the economical aspects. Further, the research and development aspects of biodiesel from microalgae as fuel for automobile diesel engines are also reviewed.

Effect of diethyl aminoethyl hexanoate on the accumulation of high-value biocompounds produced by two novel isolated microalgae

The low productivity of microalgae has restricted scale-up application of microalgae-based biodiesel processes. Diethyl aminoethyl hexanoate (DA-6) was investigated to enhance the biomass and metabolite productivity. At a very low concentration (10−7M) DA-6 made Chlorella ellipsoidea SDEC-11 and Scenedesmus quadricauda SDEC-13 obtain enlarged cell size, 114mgL−1d−1, 101mgL−1d−1 biomass productivity and 39.13mgL−1d−1, 32.69mgL−1d−1 lipid productivity, respectively. Biomass and lipid productivity of SDEC-11 and SDEC-13 were 100mgL−1d−1 and 30.05mgL−1d−1, 94mgL−1d−1 and 28.43mgL−1d−1, respectively, without DA-6. Twice hormone dose in 10−6M DA-6 medium resulted in higher biomass productivity (106mgL−1d−1) and longer exponential growth of SDEC-13. DA-6 also ensured the property of microalgae biodiesel to meet the EN 14214 standard. The current investigation demonstrated that DA-6 accelerated the microalgae growth and simultaneously improved the quality and quantity of lipid for biodiesel production.

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

Biodiesel production by direct transesterification of microalgal biomass with co-solvent

In this study, a direct transesterification process using 75% ethanol and co-solvent was studied to reduce the energy consumption of lipid extraction process and improve the conversion yield of the microalgae biodiesel. The addition of a certain amount of co-solvent (n-hexane is most preferable) was required for the direct transesterification of microalgae biomass. With the optimal reaction condition of n-hexane to 75% ethanol volume ratio 1:2, mixed solvent dosage 6.0mL, reaction temperature 90°C, reaction time 2.0h and catalyst volume 0.6mL, the direct transesterification process of microalgal biomass resulted in a high conversion yield up to 90.02±0.55wt.%.

ENERGY ANALYSIS OF LIPID EXTRACTION OF Scenedesmus sp. PRODUCED IN PILOT SCALE

he production of biodiesel from lipids extracted from microalgae biomass is a promising approach to biofuels. However, this approach is still not commercialized because of the high costs of processes associated with, for example, time consumption and / or biomass drying with intense energy usage. However, it was not possible to show extraction methods among the lipids existing in the literature, which could be applied specifically to the extraction of lipids from the microalgae Scenedesmus sp. from the large-scale wet biomass, which is the current challenge faced by the Center for Research and Development of Sustainable Energy Auto (NPDEAS). Therefore, in this study, the possibility of avoiding the drying process, and extracting lipids directly from humid biomass, using the saponification method, was tested and compared with conventional Bligh and Dyer extraction (B & D). This study introduced the cultivation of microalgae Scenedesmus sp. compact tubular photobioreactors 12 m3 in area 10 m2 (8 x 5 x 2 m). The classical method of lipid extraction from microalgae - B & D - brings many pigments and polar lipids that exist in the biomass and the conversion rate was only 65-66%, whereas the recovery of fatty material in the wet biomass by the saponification method showed high conversion rate (90-95%). Therefore, the saponification process showed a high recovery of fatty acids that can be easily converted into biodiesel by esterification, and it was shown that the stage of drying the biomass can be removed without losing the fatty acids. In relation to the energy usage in the process, it was shown that drying the biomass for extraction of fatty acids uses more energy than that produced in the final product, biodiesel, showing that the removal of fatty acids of the wet biomass is of strategic importance to the viability of microalgae biodiesel.

Dynamic metabolic profiling of the marine microalga Chlamydomonas sp. JSC4 and enhancing its oil production by optimizing light intensity

BackgroundMarine microalgae are among the most promising lipid sources for biodiesel production because they can be grown on nonarable land without the use of potable water. Marine microalgae also harvest solar energy efficiently with a high growth rate, converting CO2 into lipids stored in the cells. Both light intensity and nitrogen availability strongly affect the growth, lipid accumulation, and fatty acid composition of oleaginous microalgae. However, very few studies have systematically examined how to optimize lipid productivity by adjusting irradiance intensity, and the metabolic dynamics that may lead to improved lipid accumulation in microalgae have not been elucidated. Little is known about the mechanism of lipid synthesis regulation in microalgae. Moreover, few studies have assessed the potential of using marine microalgae as oil producers.ResultsIn this work, a newly isolated marine microalga, Chlamydomonas sp. JSC4, was selected as a potential lipid producer, and the effect of photobioreactor operations on cell growth and lipid production was investigated. The combined effects of light intensity and nitrogen depletion stresses on growth and lipid accumulation were further explored in an effort to markedly improve lipid production and quality. The optimal lipid productivity and content attained were 312 mg L−1 d−1 and 43.1% per unit dry cell weight, respectively. This lipid productivity is the highest ever reported for marine microalgae. Metabolic intermediates were profiled over time to observe transient changes during lipid accumulation triggered by combined stresses. Finally, metabolite turnover was also assessed using an in vivo13C-labeling technique to directly measure the flow of carbon during lipid biosynthesis under stress associated with light intensity and nitrogen deficiency.ConclusionsThis work demonstrates the synergistic integration of cultivation and dynamic metabolic profiling technologies to develop a simple and effective strategy for enhancing oil production in a marine microalga. The knowledge obtained from this study could be useful in assessing the feasibility of marine microalgae biodiesel production and for understanding the links between dynamic metabolic profiles and lipid biosynthesis during the course of microalgal cultivation.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0226-y) contains supplementary material, which is available to authorized users.

Valorisation of biodiesel production wastes: Anaerobic digestion of residual Tetraselmis suecica biomass and co-digestion with glycerol.

One of the principal opportunity areas in the development of the microalgal biodiesel industry is the energy recovery from the solid microalgal biomass residues to optimise the fuel production. This work reports the cumulative methane yields reached from the anaerobic digestion of the solid microalgal biomass residues using different types of inocula, reporting also the improvement of biogas production using the co-digestion of microalgal biomass with glycerol. Results demonstrate that the solid microalgal biomass residues showed better biogas production using a mesophilic inoculum, reaching almost two-fold higher methane production than under thermophilic conditions. Furthermore, the solid microalgal biomass residues methane production rate showed an increase from 173.78 ± 9.57 to 438.46 ± 40.50 mL of methane per gram of volatile solids, when the co-digestion with glycerol was performed. These results are crucial to improve the energy balance of the biodiesel production from Tetraselmis suecica, as well as proposing an alternative way to treat the wastes derived from the microalgae biodiesel production.

Microalgae Oil: Algae Cultivation and Harvest, Algae Residue Torrefaction and Diesel Engine Emissions Tests

Microalgae can be used as a biological photocatalyst to reduce the CO2 levels in the atmosphere, with the advantage of not competing with food crops for arable land, and thus offer a potential method for limiting climate change. Microalgae have also been proposed as a sustainable fuel source. This study investigated the microalgae harvest yields, the thermogravimetric behavior of both microalgae oil and microalgae residue, the torrefaction of microalgae residue, and diesel engine tests using diesel-microalgae biodiesel blends. The mean annual harvest rate of microalgae oil in open ponds was found to be 4355 kg per 10000 m 2 . Compared with conventional diesel, the fuel blends - B2 (2% microalgae biodiesel + 98% conventional diesel), B2-But20 (B2 + 20% Butanol) and B2-But20-W0.5 (B2-But20 + 0.5% water) showed a reduction of 22.0%, 57.2%, and 59.5% in PM emissions, and a decrease of 17.7%, 31.4% and 40.7% in BaPeq emissions, while B2-But20 and B2-But20-W0.5 had reduced NOx emissions, of approximately 25.0% and 28.2%, respectively, but B2 showed a 2.0% increase in NOx emissions. Conversely, the addition of water and butanol fractions in diesel increases HC and CO emissions, although these can be easily removed using tailpipe catalysts and absorbers. In addition, torrefaction of microalgae residue results in solid, liquid and gas products. This study is the first of its kind to report the liquid compositions from the torrefaction of microalgae residue. The condensate liquid products contained glucose molecules like 1,4:3,6-Dianhydro-α-d-glucopyranose, and furfural, limonene, pyridine, levoglucosan, and aziridine, among others. These compounds can be utilized as microalgae value added products, and applied in specialty industries as pharmaceutical, cosmetic, or solvent raw materials. Briefly, microalgae not only offer benefits in reducing CO2 from the atmosphere or providing raw materials for biodiesel production, but microalgae residue can also be treated via torrefaction to produce biochar. Based on the results of this study, more research is recommended on the economic potential of using both solid and liquid products from microalgae torrefaction.

Emission Reductions of Nitrogen Oxides, Particulate Matter and Polycyclic Aromatic Hydrocarbons by Using Microalgae Biodiesel, Butanol and Water in Diesel Engine

The transport sector is a major consumer of fossil fuels especially petroleum diesel, which is used to power diesel engines used on-road and off-road in trucks, tractors, passenger cars as well as marine vessels. This is because the diesel engine offers various benefits compared to the spark ignition engine. The advantages include superior fuel efficiency, higher thermal efficiency, greater power output, better fuel saving, lower carbon dioxide (CO2) emission, larger torque and greater durability. Conversely, the diesel engine is a major source of both criteria and non-criteria air pollutants, which contribute to the deteriorating air quality thereby putting the health of mankind at risk. The objective of this study was to investigate the performance of butanol- microalgae biodiesel-diesel blends in terms of energy performances and pollutants’ emission reductions by comparing the brake specific fuel consumption (BSFC), brake thermal efficiency (BTE) and exhaust gases temperatures as well as the nitrogen oxides (NOx), particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), carbon monoxide (CO) and hydrocarbons (HC) of various diesel blends and against the baseline performance of regular petroleum diesel. All diesel blends showed higher BSFCs and BTEs compared to regular petroleum diesel, whereby BT20W0.5 had the highest BSFC and BT15B2 had the best performance in terms of BTE. Among the diesel blends, only 2% microalgae added to diesel blends increased the NOx emissions by about 2%, while for the addition of 10–20% butanol fractions and 0.5% water fractions resulted in lower NOx emissions by about 12–28%, when compared to petroleum diesel. All the diesel blends considered in this study showed PM reductions ranging between 22.4% for B2 and 60.4% for BT15W0.5%, while reductions of PAH emissions were ranging from 6.5% for B2 to 22.76% for BT20W0.5. On the other hand, only the use of 2% microalgae biodiesel showed reductions in CO emissions of about 0.34% and 1.01% for B2 and BT20B2 blends, respectively, while other diesel blends showed increased CO emissions of about 1.72–2.94% in comparison to CO emissions of diesel fuel emissions. The addition of higher butanol fractions of 20% increased the HC emission factors by approximately 18% and 70%, while the HC emission factors for biodiesel, 10–15% butanol fractions and 0.5% water additions lead to reductions in emission by about 8–50%. According to the results of this study, more research is recommended on the economic potential of using of oxygenated additives in diesel engine especially water addition, higher alcohols and dieselhols blends to evaluate the possibility of synergetic properties of these kinds of fuels to achieve simultaneous reductions in the emissions of NOx, PM, CO, HC, PAHs and other persistent organic pollutants (POPs).

Microalgae Lipid and Biodiesel Production: A Brazilian Challenge

Global increases in atmospheric CO2 and climate change are drawing considerable attention to identify sources of energy with lower environmental impact than those currently in use. Biodiesel production from microalgae lipids can, in the future, occupy a prominent place in energy generation because it represents a sustainable alternative to petroleum-based fuels. Several species of microalgae produce large amounts of lipids per biomass unit. Triacylglycerol is the fatty acid used for biodiesel production and the main source of energy reserves in microalgae. The current literature indicates that nutrient limitations can lead to triacylglycerol accumulation in different species of microalgae. Further efforts in microalgae screening for biodiesel production are needed to discover a native microalgae that will be feasible for biodiesel production in terms of biomass productivity and oil. This revision focuses in the biotechnological potential and viability of biodiesel production from microalgae. Brazil is located in a tropical region with high light rates and adequate average temperatures for the growth of microalgae. The wide availability of bodies of water and land will allow the country to produce renewable energy from microalgae.

Microalgae as sustainable renewable energy feedstock for biofuel production.

The world energy crisis and increased greenhouse gas emissions have driven the search for alternative and environmentally friendly renewable energy sources. According to life cycle analysis, microalgae biofuel is identified as one of the major renewable energy sources for sustainable development, with potential to replace the fossil-based fuels. Microalgae biofuel was devoid of the major drawbacks associated with oil crops and lignocelluloses-based biofuels. Algae-based biofuels are technically and economically viable and cost competitive, require no additional lands, require minimal water use, and mitigate atmospheric CO2. However, commercial production of microalgae biodiesel is still not feasible due to the low biomass concentration and costly downstream processes. The viability of microalgae biodiesel production can be achieved by designing advanced photobioreactors, developing low cost technologies for biomass harvesting, drying, and oil extraction. Commercial production can also be accomplished by improving the genetic engineering strategies to control environmental stress conditions and by engineering metabolic pathways for high lipid production. In addition, new emerging technologies such as algal-bacterial interactions for enhancement of microalgae growth and lipid production are also explored. This review focuses mainly on the problems encountered in the commercial production of microalgae biofuels and the possible techniques to overcome these difficulties.