Algae as a promising resource for biofuel industry: facts and challenges

Energy is the main driving force of society today that should be handled as a whole starting from production to consumption. With the rapid increase in the energy necessity, alternative methods and sources are becoming a crucial topic that should be scientifically highlighted with all their pros and cons. Especially the problems related to the fossil sources of energy triggered the search on the renewable alternatives like algae. In order to reach the desired amounts of energy with the satisfactory quality and quantity, understanding the algae as a living thing with the biological mechanism and existing production technologies are the key points to have a projection for commercialization. In this regard, technical facts and challenges on algal biofuel production should be evaluated. Keeping in mind the specifications and possible advantages related to their taxonomy, algae can serve as a promising source to reduce fossil fuel consumption. With the progress in the modern technology, reaching an effective production process will be possible, and this will help the algal biofuels to prove their maturity as a sustainable source for future. Within this context, the aim of this review is to point out the crucial technical challenges about algal fuels comprising both the macroalgae and microalgae as a reliable source of renewable energy. Copyright © 2016 John Wiley & Sons, Ltd.     

Microalgae for biodiesel production and other applications: A review

Sustainable production of renewable energy is being hotly debated globally since it is increasingly understood that first generation biofuels, primarily produced from food crops and mostly oil seeds are limited in their ability to achieve targets for biofuel production, climate change mitigation and economic growth. These concerns have increased the interest in developing second generation biofuels produced from non-food feedstocks such as microalgae, which potentially offer greatest opportunities in the longer term. This paper reviews the current status of microalgae use for biodiesel production, including their cultivation, harvesting, and processing. The microalgae species most used for biodiesel production are presented and their main advantages described in comparison with other available biodiesel feedstocks. The various aspects associated with the design of microalgae production units are described, giving an overview of the current state of development of algae cultivation systems (photo-bioreactors and open ponds). Other potential applications and products from microalgae are also presented such as for biological sequestration of CO₂, wastewater treatment, in human health, as food additive, and for aquaculture.     

纤维藻培养及制备生物柴油的研究

探讨了纤维藻(Ankistudesmus sp)的低成本培养模式,考察了氮源和碳源以及反应器形式对纤维藻生物量、油脂积累以及油脂组成的影响。户外培养纤维藻在氮饥饿条件下油脂产率较高;通过槽式反应器和管式反应器的比较发现:槽式反应器更适合微藻的大规模培养;混养培养时能显著增加纤维藻的生物量和油脂含量,最佳添加条件下藻的生物量和油脂含量分别高达1.64 g/L和15.9%,1.41 g/L和11.9%。藻油经酸催化甲酯化制备生物柴油,经气相色谱分析,藻油主要成分为棕榈酸、油酸和亚油酸。氮缺陷、流加葡萄糖培养得到的纤维藻油含有25.32%的棕榈酸、44.74%的油酸,其制备得到的生物柴油具有更好的氧化稳定性和低温流动性。     

Investigation of silicates as a catalyst in biodiesel production: A review

Hiking of crude oil prices and diesel fuel shortage is incentive for the researchers to develop bioenergy sources. Biodiesel has environmental beneficial attributes, and its production processes are worthy of continued studies. Many biodiesel production processes are available but, most of them are not on a commercial scale. Biodiesel production using solid catalysts involved fewer unit operations compared with homogeneous catalyzed processes. Many heterogeneous catalysts have been extensively investigated in the recent years and well established. Researchers' focus is how to obtain active and more stable silicates catalyst that can be recycled for several times in the process. Silicates catalyst activity and stability are critically discussed in this work to assess their industrial application, as excessive purification steps could be avoided. This review provides a brief overview on semi‐novel heterogeneous catalyst types ‘silicates’ used in the transesterification of vegetable oils for biodiesel production. Process conditions and leaching out of catalyst active sites are also highlighted. Product quality analysis is presented, in addition to concluded remarks regarding silicates as a selected catalyst. A preliminary economic assessment of biodiesel production catalyzed by the suggested catalyst ‘silicates’ compared with potassium hydroxide (KOH) and lime (CaO) is performed. Copyright © 2016 John Wiley & Sons, Ltd.     

Two Mychonastes isolated from freshwater bodies are novel potential feedstocks for biodiesel production

Microalgae have been considered as ideal feedstocks for biodiesel production but the potential application is still under investigations. Here, eight kinds of microalgae were identified from water samples based on the morphologic and phylogenetic analyses. Among these eight microalgae, two Mychonastes S4 and S15 exhibited relative faster growth rate in the early culture stage and the highest contents of lipids. The two Mychonastes also showed higher C18:1 contents than the two Chlorella which were traditionally considered to be potential species for biodiesel production. As one kind of less researched microalgae, this study suggests Mychonastes should be a potential feedstock for biodiesel production. The application of the microalgal biodiesel still have some limiting factors, however, it is promising based on better lipid extraction technology and more relevant studies.     

A review on microalgae,a versatile source for sustainable energy and materials

Increasing energy demands, predicted fossil fuels shortage in the near future, and environmental concerns due to the production of greenhouse gas carbon dioxide on their combustion have motivated the search for alternative ‘clean’ energy sources. Among many resources for this, microalgae have been found to be most promising due to their high production capacity of vegetable oils. They possess a high growth rate, need abundantly available solar light and CO₂, and thus are more photosynthetically efficient than oil crops. Also, they tolerate high concentration of salts allowing the use of any type of water for the agriculture and the possibility of production using innovative compact photobioreactors. In addition, microalgae are a potential source of biomass, which may have great biodiversity and consequent variability in their biochemical composition. This paper presents an overview on microalgae with particular emphasis as a source for energy (biofuel/electricity) and new materials. Critical issues involved in production of microalgae and their use, future R & D to overcome these, including the work initiated by the authors at Federal University of Paraná, UFPR, in Brazil are discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

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.     

Comparison of oil extraction methods,energy analysis and biodiesel production from flax seeds

In recent years, the commercial potential of oil extraction and biodiesel production derived from vegetable seed is being realized. The process energy input requirements are important factors in oil extraction and biodiesel production. This research work investigated oil extraction from flax seeds and compared extraction yield with the energy load. The effect of moisture content on the oil yield was compared between a mechanical oil expeller, organic solvent extraction, organic solvent and microwave assisted, organic solvent and ultrasonic assisted, and combined microwave and ultrasonic with organic solvent. The maximum oil yields % wt/wt from these techniques was 22.6%, 36.3%, 10.0%, 42.0% and 27.8%, respectively. The moisture content had a significant effect on oil yield with the mechanical oil expeller, organic solvent method and ultrasonic assisted extraction, whereas no or little effect was found on microwave‐assisted extraction. The microwave‐assisted extraction showed better results compared with the ultrasonic‐assisted and combined treatment methods. The relative energy consumption of these processes was experimentally investigated; energy ratios were calculated based on the amount of energy recovered to the amount of energy supplied to the flax seed for oil extraction. The net energy ratios showed that microwave‐assisted extraction had the highest (25.21%), followed by organic solvent method (14.04%), ultrasonic method (6.33%) and lowest was with combined ultrasonic and microwave assisted treatment (5.73%). These results showed that flax seed oil can be extracted using microwave‐assisted methods efficiently and in an energy feasible manner. In situ ultrasonic transesterification was applied to powdered samples with 4%, 8% and 12% moisture content (on % dry basis) within an ultrasonic bath having an intensity of 0.124 W/cm². The flax seed biodiesel produced showed a highest conversion yield of 93%, and the effect of different moisture content on the yield showed that 4% moisture content sample produced the greatest biodiesel yield. Copyright © 2013 John Wiley & Sons, Ltd.     

Current scenario of biodiesel development in India: prospects and challenges

For a developing nation like India, the current energy portfolio is dominated by fossil fuels such as oil, coal, and petroleum products. Due to the rapid depletion and limited available resources, the price of fossil fuel increases. Also, fossil fuel induces climate change, environmental pollution, and rising global temperature. There is urgent need to shift from conventional energy to renewable energy source for sustainable and economic growth and to enhance a country’s energy security. Biofuel offers an attractive source of energy for the substitution of fossil fuels, and looking at the huge demand for diesel in all sectors of the economy, the biodiesel is being viewed as the best substitute for diesel. The other advantage for biofuel promotion in India is climate change mitigation through reduced greenhouse gas (GHG) emission. This article provides the current status of biodiesel development in India and discusses the role played by the centre and state government in promoting second-generation feedstock (nonedible seeds) and third-generation feedstock (algae) for biodiesel production.     

Conceptual design of a hybrid thin layer cascade photobioreactor for microalgal biodiesel synthesis

Even though microalgae are able to produce various valuable metabolites, microalgal culture on an industrial scale still faces challenging difficulties. Open systems may be cheaper to construct, easier to operate and maintain, and possess greater surface area to volume ratio, but they are also easily contaminated, have high water loss due to evaporation, and suffer from unfavorable weather. On the other hand, closed photobioreactor systems possess higher biomass yields, better control over culture parameters, and lower contamination risks. However, photobioreactors are costlier to construct and maintain. Thus, a hybrid semi-closed thin layer cascade photobioreactor was proposed to cultivate high-density microalgal cultures for biodiesel production. Computational fluid dynamics analysis was carried out to observe fluid behavior in the hybrid photobioreactor design. The simulation results showed satisfactory performance in the improved design, making the photobioreactor a potential candidate for microalgal biodiesel production.     

Transesterification of non-edible seed oil for biodiesel production: characterization and analysis of biodiesel

Evaluation of Radish (Raphanus sativus) seed oil (RSO) as a non-edible feedstock for biodiesel production was the main target of the present study. Extraction by solvent disclosed that radish seeds contains 33.50 wt.% of oil. Therefore, biodiesel production from it could be beneficial. Optimized base-catalyzed transesterification of RSO with methanol, ethanol and mixed methanol/ethanol was performed, to produce fatty acid methyl esters, fatty acid ethyl esters and mixed fatty acid methyl ethyl esters, respectively. The optimal yields of the methyl esters, ethyl esters and mixed methyl ethyl esters, were 95.55wt.%, 90.66 wt.% and 93.33 wt.%, respectively when the optimal reaction conditions were attained. Fuel properties of the parent oil were positively changed as consequence of transesterification reaction such that they fulfilled the standard limits as prescribed by ASTM D6751. Moreover, fuel properties of (biodiesels + petro diesel) blends conformed ASTM D7467-17 standards indicating their suitability as a fuel for diesel engines. Biodiesels form RSO were analyzed by thin layer chromatography and FTIR spectroscopy, and both techniques conformed its conversion into its corresponding alkyl esters.     

Hydrogen-enriched palm biodiesel as a potential alternative fuel for diesel engines: Investigating performance and emission characteristics and mitigation strategies for air pollutants

Palm biodiesel is one of the most suitable alternative fuels due to its capability to replace traditional fossil fuel usage in IC engines. Even as palm biodiesel (POBD) reduces harmful pollutant gases, the engine performance is not on an equal scale with neat diesel. To address this shortcoming, an investigation was carried out to examine the application of palm biodiesel (PBD) and hydrogen induction through the intake air at the flow rates of 6 and 8LPM (Litre Per Minute) in the compression ignition (CI) engine. The experimental study shows that POBD has poor engine performance and moderate pollution reduction compared with neat diesel. When compared to POBD and neat diesel, the higher calorific value and other H₂ characteristics improve combustion properties, resulting in higher engine performance and lower pollutant gases (except NOx). When compared to the palm biodiesel blend (BD 30), the results of BD30+8LPM reduced the Specific fuel consumption (SFC) by 0.0885kg/kWh and improved the brake thermal efficiency (BTE) by 6.67%. The Carbon monoxide (CO), hydro carbon (HC), and smoke opacity were reduced by 0.047% volume, 29.2 ppm, and 6.52% respectively. A marginal increase in NOx was seen as 297.6 ppm.     

A green route for biodiesel production from waste cooking oil over base heterogeneous catalyst

The present work describes the synthesis of porous BaSnO₃ by eco‐friendly sol‐gel method using albumin as a bio‐template agent, and its application as a solid base catalyst in biodiesel production from waste cooking oil. The physico‐chemical, textural, and morphological properties of the catalyst were evaluated by X‐ray diffraction (XRD), Brunauer‐Emmett‐Teller (BET), field emission scanning electron microscopy (FESEM), and temperature programmed desorption (TPD)–CO₂ techniques. The synthesized catalyst showed considerable stability, efficient catalytic activity, and negligible metal leaching. The satisfactory performance of the catalyst could be ascribed to the presence of basic sites of different strength on the surface of the catalyst. The catalyst produced maximum biodiesel yield of 96% at optimum reaction conditions of 90°C reaction temperature, methanol to oil molar ratio of 10:1, catalyst dosage of 6 wt%, and reaction time of 2 hours. Moreover, the catalyst showed substantial reusability up to five reaction cycles without any considerable decrease in transesterification activity.     

Cyprinus carpio fish oil: A novel feedstock for biodiesel production

Biodiesel was developed from a novel nonedible oil source, namely Cyprinus carpio fish oil. The acid value of fish oil was very low (0.70 mg KOH/g oil, 0.35 free fatty acid content). As a result, biodiesel was produced through a one-step transesterifcation process, i.e. alkali-catalyzed transesterification with methanol. The optimal conditions for producing biodiesel from fish oil were investigated. The highest biodiesel yield (97.22% ~ 96.88% w/w ester content) was obtained under optimum conditions of 0.75% KOH w/w, 7:1 methanol to oil molar ratio, 60°C reaction temperature and 60-minute duration. Properties of the produced biodiesel as well as its blends with petro-diesel fulfilled the standard limits as prescribed by ASTM D6751 and EN 14214 indicating its suitability as a fuel for diesel engines.     

Co-production of biodiesel and alpha-linolenic acid (omega-3 fatty acid) from microalgae,Desmodesmus sp. MCC34

Microalgae are a potential source of biofuel and nutraceuticals. In the present study, Desmodesmussp. MCC34 was identified as a promising species for biodiesel and omega-3 fatty acid productions after initial screening since it had displayed the highest lipid productivity of 15.9 mg L^?1 day^?1 and alpha-linolenic acid of 24% of total fatty acids. Using silver ion chromatography, 92% of pure alpha-linolenic acid was selectively removed from total lipid of Desmodesmussp. MCC34, while the residual oil having a higher amount of saturated and monounsaturated fatty acids displayed biodiesel property adhering to international standards, suggesting fuel co-application.

Abbreviations: ALA: alpha-linolenic acid methyl ester; GLAME: gamma-linolenic acid methyl ester; FAME: atty acid methyl ester; SFA: aturated fatty acid; MUFA: monounsaturated fatty acid; PUFA: polyunsaturated fatty acid.     

Production of biodiesel from citrus maxima (Chakotara) seed oil,a potential of non-food feedstock and its blends with n butanol-diesel and purification,utilization of glycerol obtained as by-product from biodiesel

The aim of the study is to enhance the production and performance of biodiesel from non-food feedstock seeds of citrus maxima through base catalyzed transesterification process. The Performance of biodiesel was increased by the blends with butanol-diesel (Biodiesel + Butanol + Diesel) in different proportions. The obtained biodiesel and its blends were characterized by ASTM. In this study, Glycerol was obtained as a by-product of citrus maxima biodiesel. Crude glycerol was purified by the H₃PO₄, H₂SO₄, HCl, and HNO₃. The characterization of glycerol included Flash Point, ash Content, alkalinity, FT-IR, etc..     

Upgrading techniques for transformation of biogas to bio‐CNG: a review

Increasing consumption of fossil fuels and environmental concern has led to increased use of compressed natural gas (CNG) in the transportation sector. Keeping in view limited resources of CNG, biogas is advised as potential fuel to provide continuous supply of CNG in the form of bio‐CNG. Various technologies, that is, physical and chemical absorption (using water and amine solutions, respectively, for the absorption of carbon dioxide), pressure swing adsorption, membrane separation, and cryogenic separation, are available for purifying biogas and thus upgrading it, to bio‐CNG with about 95% methane. Among these, water scrubbing and pressure swing adsorption are the best technologies with respect to various aspects including cost; however, suitability of a technology is decided by various factors including size/quantity of biogas generation, targeted quality of biogas, site of application, and economics of process. Copyright © 2017 John Wiley & Sons, Ltd.     

High free fatty acid coconut oil as a potential feedstock for biodiesel production in Thailand

Coconut oil having 12.8% free fatty acid (FFA) was used as a feedstock to produce biodiesel by a two-step process. In the first step, FFA level of the coconut oil was reduced to 0.6% by acid-catalyzed esterification. In the second step, triglycerides in product from the first step were transesterified with methanol by using an alkaline catalyst to produce methyl esters and glycerol. Effect of parameters related to these processes was studied and optimized, including methanol-to-oil ratio, catalyst concentration, reaction temperature, and reaction time. Methyl ester content of the coconut biodiesel was determined by GC to be 98.4% under the optimum condition. The viscosity of coconut biodiesel product was very close to that of Thai petroleum diesel and other measured properties met the Thai biodiesel (B100) specification.     

Muskmelon (Cucumis melo) seed oil: A potential non-food oil source for biodiesel production

Methanolysis of muskmelon seed oil was optimized employing RSM (response surface methodology). Four process variables were evaluated at two levels: methanol/oil molar ratio (3:1–12:1), catalyst concentration in relation to oil mass (0.25–1.25 wt % KOH), reaction temperature (25–65 °C) and methanolysis reaction time (20–90 min). Multiple regression analysis was employed to get the quadratic polynomial equation for predicting transesterification using RSM. The result indicated that catalyst concentration and reaction temperature were the important factors that significantly affect the yield of MMOMEs (muskmelon oil methyl esters)/biodiesel. The RSM methodology was used to obtain methyl esters yield (89.5%) were found at following reaction conditions; 5.8:1 methanol-to-oil ratio, 0.79% catalyst concentration, 55 °C reaction temperature and 72.5-min reaction time. There was a linear correlation between observed and predicted values. The biodiesel was analyzed using GC/MS (gas chromatography/mass spectrometry) which indicated four FAMEs (fatty acid methyl esters) (linoleic-, oleic-, palmitic- and stearic acids) as its major components. The FT-IR (fourier transform infraRed) spectrum of MMOMEs was also acquired to ensure the confirmation of methyl esters formation. Fuel properties of MMOMEs were determined and found to satisfy the ASTM D 6751 and EU 14214 specifications.