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528 KiB

Open AccessArticle

Use of Anion Exchange Resins for One-Step Processing of Algae from Harvest to Biofuel

by Jessica Jones, Cheng-Han Lee, James Wang and Martin Poenie

Energies 2012, 5(7), 2608-2625; https://doi.org/10.3390/en5072608 - 24 Jul 2012

Cited by 6 | Viewed by 9123

Abstract

Some microalgae are particularly attractive as a renewable feedstock for biodiesel production due to their rapid growth, high content of triacylglycerols, and ability to be grown on non-arable land. Unfortunately, obtaining oil from algae is currently cost prohibitive in part due to the [...] Read more.

Some microalgae are particularly attractive as a renewable feedstock for biodiesel production due to their rapid growth, high content of triacylglycerols, and ability to be grown on non-arable land. Unfortunately, obtaining oil from algae is currently cost prohibitive in part due to the need to pump and process large volumes of dilute algal suspensions. In an effort to circumvent this problem, we have explored the use of anion exchange resins for simplifying the processing of algae to biofuel. Anion exchange resins can bind and accumulate the algal cells out of suspension to form a dewatered concentrate. Treatment of the resin-bound algae with sulfuric acid/methanol elutes the algae and regenerates the resin while converting algal lipids to biodiesel. Hydrophobic polymers can remove biodiesel from the sulfuric acid/methanol, allowing the transesterification reagent to be reused. We show that in situ transesterification of algal lipids can efficiently convert algal lipids to fatty acid methyl esters while allowing the resin and transesterification reagent to be recycled numerous times without loss of effectiveness. Full article

(This article belongs to the Special Issue Algae Fuel)

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821 KiB

Open AccessArticle

Comprehensive Evaluation of Algal Biofuel Production: Experimental and Target Results

by Colin M. Beal, Robert E. Hebner, Michael E. Webber, Rodney S. Ruoff, A. Frank Seibert and Carey W. King

Energies 2012, 5(6), 1943-1981; https://doi.org/10.3390/en5061943 - 20 Jun 2012

Cited by 43 | Viewed by 11434

Abstract

Worldwide, algal biofuel research and development efforts have focused on increasing the competitiveness of algal biofuels by increasing the energy and financial return on investments, reducing water intensity and resource requirements, and increasing algal productivity. In this study, analyses are presented in each [...] Read more.

Worldwide, algal biofuel research and development efforts have focused on increasing the competitiveness of algal biofuels by increasing the energy and financial return on investments, reducing water intensity and resource requirements, and increasing algal productivity. In this study, analyses are presented in each of these areas—costs, resource needs, and productivity—for two cases: (1) an Experimental Case, using mostly measured data for a lab-scale system, and (2) a theorized Highly Productive Case that represents an optimized commercial-scale production system, albeit one that relies on full-price water, nutrients, and carbon dioxide. For both cases, the analysis described herein concludes that the energy and financial return on investments are less than 1, the water intensity is greater than that for conventional fuels, and the amounts of required resources at a meaningful scale of production amount to significant fractions of current consumption (e.g., nitrogen). The analysis and presentation of results highlight critical areas for advancement and innovation that must occur for sustainable and profitable algal biofuel production can occur at a scale that yields significant petroleum displacement. To this end, targets for energy consumption, production cost, water consumption, and nutrient consumption are presented that would promote sustainable algal biofuel production. Furthermore, this work demonstrates a procedure and method by which subsequent advances in technology and biotechnology can be framed to track progress. Full article

(This article belongs to the Special Issue Algae Fuel)

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825 KiB

Open AccessArticle

Microalgae Isolation and Selection for Prospective Biodiesel Production

by Van Thang Duong, Yan Li, Ekaterina Nowak and Peer M. Schenk

Energies 2012, 5(6), 1835-1849; https://doi.org/10.3390/en5061835 - 15 Jun 2012

Cited by 142 | Viewed by 16311

Abstract

Biodiesel production from microalgae is being widely developed at different scales as a potential source of renewable energy with both economic and environmental benefits. Although many microalgae species have been identified and isolated for lipid production, there is currently no consensus as to [...] Read more.

Biodiesel production from microalgae is being widely developed at different scales as a potential source of renewable energy with both economic and environmental benefits. Although many microalgae species have been identified and isolated for lipid production, there is currently no consensus as to which species provide the highest productivity. Different species are expected to function best at different aquatic, geographical and climatic conditions. In addition, other value-added products are now being considered for commercial production which necessitates the selection of the most capable algae strains suitable for multiple-product algae biorefineries. Here we present and review practical issues of several simple and robust methods for microalgae isolation and selection for traits that maybe most relevant for commercial biodiesel production. A combination of conventional and modern techniques is likely to be the most efficient route from isolation to large-scale cultivation. Full article

(This article belongs to the Special Issue Algae Fuel)

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1110 KiB

Open AccessArticle

Seasonal Variation of Lipids and Fatty Acids of the Microalgae Nannochloropsis oculata Grown in Outdoor Large-Scale Photobioreactors

by Martin Olofsson, Teresa Lamela, Emmelie Nilsson, Jean Pascal Bergé, Victória Del Pino, Pauliina Uronen and Catherine Legrand

Energies 2012, 5(5), 1577-1592; https://doi.org/10.3390/en5051577 - 21 May 2012

Cited by 121 | Viewed by 11388

Abstract

While focus in oil-producing microalgae is normally on nutrient deficiency, we addressed the seasonal variations of lipid content and composition in large-scale cultivation. Lipid content, fatty acid profiles and mono- di- and triglycerides (MAGs, DAGs, and TAGs) were analyzed during May 2007–May 2009 [...] Read more.

While focus in oil-producing microalgae is normally on nutrient deficiency, we addressed the seasonal variations of lipid content and composition in large-scale cultivation. Lipid content, fatty acid profiles and mono- di- and triglycerides (MAGs, DAGs, and TAGs) were analyzed during May 2007–May 2009 in Nannochloropsis oculata grown outdoors in closed vertical flat panels photobioreactors. Total lipids (TL) ranged from 11% of dry weight (DW) in winter to 30% of DW in autumn. 50% of the variation in TL could be explained by light and temperature. As the highest lipid content was recorded during autumn indicating an optimal, non-linear, response to light and temperature we hypothesize that enhanced thylakoid stacking under reduced light conditions resulted in more structural lipids, concomitantly with the increase in glycerides due to released photo-oxidative stress. The relative amount of monounsaturated fatty acids (MUFA) increased during autumn. This suggested a synthesis, either of structural fatty acids as MUFA, or a relative increase of C16:1 incorporated into TAGs and DAGs. Our results emphasize the significant role of environmental conditions governing lipid content and composition in microalgae that have to be considered for correct estimation of algal oil yields in biodiesel production. Full article

(This article belongs to the Special Issue Algae Fuel)

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349 KiB

Open AccessArticle

High Lipid Induction in Microalgae for Biodiesel Production

by Kalpesh K. Sharma, Holger Schuhmann and Peer M. Schenk

Energies 2012, 5(5), 1532-1553; https://doi.org/10.3390/en5051532 - 18 May 2012

Cited by 718 | Viewed by 37162

Abstract

Oil-accumulating microalgae have the potential to enable large-scale biodiesel production without competing for arable land or biodiverse natural landscapes. High lipid productivity of dominant, fast-growing algae is a major prerequisite for commercial production of microalgal oil-derived biodiesel. However, under optimal growth conditions, large [...] Read more.

Oil-accumulating microalgae have the potential to enable large-scale biodiesel production without competing for arable land or biodiverse natural landscapes. High lipid productivity of dominant, fast-growing algae is a major prerequisite for commercial production of microalgal oil-derived biodiesel. However, under optimal growth conditions, large amounts of algal biomass are produced, but with relatively low lipid contents, while species with high lipid contents are typically slow growing. Major advances in this area can be made through the induction of lipid biosynthesis, e.g., by environmental stresses. Lipids, in the form of triacylglycerides typically provide a storage function in the cell that enables microalgae to endure adverse environmental conditions. Essentially algal biomass and triacylglycerides compete for photosynthetic assimilate and a reprogramming of physiological pathways is required to stimulate lipid biosynthesis. There has been a wide range of studies carried out to identify and develop efficient lipid induction techniques in microalgae such as nutrients stress (e.g., nitrogen and/or phosphorus starvation), osmotic stress, radiation, pH, temperature, heavy metals and other chemicals. In addition, several genetic strategies for increased triacylglycerides production and inducibility are currently being developed. In this review, we discuss the potential of lipid induction techniques in microalgae and also their application at commercial scale for the production of biodiesel. Full article

(This article belongs to the Special Issue Algae Fuel)

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394 KiB

Open AccessArticle

Microwave-Assisted Transesterification of Macroalgae

by Angeles Cancela, Rocio Maceiras, Santiago Urrejola and Angel Sanchez

Energies 2012, 5(4), 862-871; https://doi.org/10.3390/en5040862 - 26 Mar 2012

Cited by 28 | Viewed by 9763

Abstract

Nowadays microwave radiation is being researched to produce biodiesel from different raw materials due to the many advantages that this technology presents compared to traditional transesterification, such as shorter reaction times and less amount of heat energy to obtain biodiesel. The aim of [...] Read more.

Nowadays microwave radiation is being researched to produce biodiesel from different raw materials due to the many advantages that this technology presents compared to traditional transesterification, such as shorter reaction times and less amount of heat energy to obtain biodiesel. The aim of this research was to explore the possibility of carrying out the microwave-assisted transesterification of macroalgae and compare the results with the traditional transesterification. For that reason, some experiences were conducted using sunflower oil and macroalgae as raw material. Based on the obtained results, the best conditions for microwave-assisted transesteriﬁcation reaction were macroalgae to methanol ratio of 1:15 (wt/vol), sodium hydroxide concentration of 2 wt % and reaction time of 3 min. Full article

(This article belongs to the Special Issue Algae Fuel)

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1157 KiB

Open AccessCommunication

Effects of Light and Temperature on Fatty Acid Production in Nannochloropsis Salina

by Jon Van Wagenen, Tyler W. Miller, Sam Hobbs, Paul Hook, Braden Crowe and Michael Huesemann

Energies 2012, 5(3), 731-740; https://doi.org/10.3390/en5030731 - 12 Mar 2012

Cited by 201 | Viewed by 14713

Abstract

Accurate prediction of algal biofuel yield will require empirical determination of physiological responses to the environment, particularly light and temperature. One strain of interest, Nannochloropsis salina, was subjected to ranges of light intensity (5–850 μmol m⁻² s⁻¹) and temperature [...] Read more.

Accurate prediction of algal biofuel yield will require empirical determination of physiological responses to the environment, particularly light and temperature. One strain of interest, Nannochloropsis salina, was subjected to ranges of light intensity (5–850 μmol m⁻² s⁻¹) and temperature (13–40 °C) and its exponential growth rate, total fatty acids (TFA) and fatty acid composition were measured. The maximum acclimated growth rate was 1.3 day⁻¹ at 23 °C and 250 μmol m⁻² s⁻¹. Fatty acids were detected by gas chromatography with flame ionization detection (GC-FID) after transesterification to corresponding fatty acid methyl esters (FAMEs). A sharp increase in TFA containing elevated palmitic acid (C16:0) and palmitoleic acid (C16:1) during exponential growth at high light was observed, indicating likely triacylglycerol accumulation due to photo-oxidative stress. Lower light resulted in increases in the relative abundance of unsaturated fatty acids; in thin cultures, increases were observed in palmitoleic and eicosapentaenoic acids (C20:5ω3). As cultures aged and the effective light intensity per cell converged to very low levels, fatty acid profiles became more similar and there was a notable increase of oleic acid (C18:1ω9). The amount of unsaturated fatty acids was inversely proportional to temperature, demonstrating physiological adaptations to increase membrane fluidity. These data will improve prediction of fatty acid characteristics and yields relevant to biofuel production. Full article

(This article belongs to the Special Issue Algae Fuel)

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515 KiB

Open AccessArticle

Influence of n-Hexane on in Situ Transesterification of Marine Macroalgae

by Angel Sánchez, Rocio Maceiras, Angeles Cancela and Mónica Rodríguez

Energies 2012, 5(2), 243-257; https://doi.org/10.3390/en5020243 - 6 Feb 2012

Cited by 38 | Viewed by 8802

Abstract

The purpose of this work is to investigate the influence of n-hexane addition on in situ transesterification of a solid raw material for biodiesel production. Extraction and reaction of macroalgae oil has been performed simultaneously in a batch reactor adding n-hexane [...] Read more.

The purpose of this work is to investigate the influence of n-hexane addition on in situ transesterification of a solid raw material for biodiesel production. Extraction and reaction of macroalgae oil has been performed simultaneously in a batch reactor adding n-hexane with the reactants. In order to analyze the influence of n-hexane on the transesterification, the reaction was also carried out with sunflower oil. The results show that the presence of n-hexane does not have an important effect on the transesterification. It was also observed that this method requires large quantities of methanol to carry out the reaction. The best reaction conditions for in situ transesteriﬁcation of marine macroalgae were 300:1 methanol-to-oil molar ratio, 1% catalyst concentration, 60 °C reaction temperature and 11 h reaction time, resulting in a methyl esters yield of 17.1%. Thus, biodiesel production from macroalgae by transesterification in situ could be feasible, using hexane for the extraction and eliminating the previous extraction. This integrated method is thus effective and technically attractive. Full article

(This article belongs to the Special Issue Algae Fuel)

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Review

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197 KiB

Open AccessReview

Current Status and Prospects of Biodiesel Production from Microalgae

by Xiaodan Wu, Rongsheng Ruan, Zhenyi Du and Yuhuan Liu

Energies 2012, 5(8), 2667-2682; https://doi.org/10.3390/en5082667 - 25 Jul 2012

Cited by 64 | Viewed by 10146

Abstract

Microalgae represent a sustainable energy source because of their high biomass productivity and ability to remove air and water born pollutants. This paper reviews the current status of production and conversion of microalgae, including the advantages of microalgae biodiesel, high density cultivation of [...] Read more.

Microalgae represent a sustainable energy source because of their high biomass productivity and ability to remove air and water born pollutants. This paper reviews the current status of production and conversion of microalgae, including the advantages of microalgae biodiesel, high density cultivation of microalgae, high-lipid content microalgae selection and metabolic control, and innovative harvesting and processing technologies. The key barriers to commercial production of microalgae biodiesel and future perspective of the technologies are also discussed. Full article

(This article belongs to the Special Issue Algae Fuel)

324 KiB

Open AccessReview

Achieving a Green Solution: Limitations and Focus Points for Sustainable Algal Fuels

by Douglas Aitken and Blanca Antizar-Ladislao

Energies 2012, 5(5), 1613-1647; https://doi.org/10.3390/en5051613 - 21 May 2012

Cited by 37 | Viewed by 9027

Abstract

Research investigating the potential of producing biofuels from algae has been enjoying a recent revival due to heightened oil prices, uncertain fossil fuel sources and legislative targets aimed at reducing our contribution to climate change. If the concept is to become a reality [...] Read more.

Research investigating the potential of producing biofuels from algae has been enjoying a recent revival due to heightened oil prices, uncertain fossil fuel sources and legislative targets aimed at reducing our contribution to climate change. If the concept is to become a reality however, many obstacles need to be overcome. Recent studies have suggested that open ponds provide the most sustainable means of cultivation infrastructure due to their low energy inputs compared to more energy intensive photobioreactors. Most studies have focused on strains of algae which are capable of yielding high oil concentrations combined with high productivity. Yet it is very difficult to cultivate such strains in open ponds as a result of microbial competition and limited radiation-use efficiency. To improve viability, the use of wastewater has been considered by many researchers as a potential source of nutrients with the added benefit of tertiary water treatment however productivity rates are affected and optimal conditions can be difficult to maintain year round. This paper investigates the process streams which are likely to provide the most viable methods of energy recovery from cultivating and processing algal biomass. The key findings are the importance of a flexible approach which depends upon location of the cultivation ponds and the industry targeted. Additionally this study recommends moving towards technologies producing higher energy recoveries such as pyrolysis or anaerobic digestion as opposed to other studies which focused upon biodiesel production. Full article

(This article belongs to the Special Issue Algae Fuel)

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