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Special Issue "Algae Fuel"

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A special issue of Energies (ISSN 1996-1073).

Deadline for manuscript submissions: closed (28 February 2012)

Special Issue Editor

Guest Editor
Dr. Paul L. Chen

Center for Biorefining, Department of Bioproducts and Biosystems Engineering, University of Minnesota, 1390 Eckles Ave., St. Paul, MN 55108, USA
Website | E-Mail
Phone: 612-625-7721
Interests: pyrolysis; hydrothermal liquefaction; microalgae; food processing

Special Issue Information

Dear Colleagues,

Fast growing, oil producing algae are recognized as one of the most promising biomass feedstock for production of biofuels and bioproducts. Despite the many advances made over several decades, commercialization of algal fuels remains challenging chiefly because of the techno-economic constrains and lack of understanding of life cycle impacts.  This special issue is to solicit high quality, original research contributions on all aspects of algae to fuels technologies, including but not limited to strain selection and development, cultivation techniques and facilities, harvest, downstream processing, product development, techno-economic analysis, and life cycle analysis.

Dr. Paul L. Chen
Guest Editor

Keywords

  • algae
  • microalgae
  • biofuels
  • biodiesel
  • photobioreactor
  • harvest
  • conversion

Related Special Issue

Published Papers (10 papers)

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Research

Jump to: Review

Open AccessArticle Use of Anion Exchange Resins for One-Step Processing of Algae from Harvest to Biofuel
Energies 2012, 5(7), 2608-2625; doi:10.3390/en5072608
Received: 15 March 2012 / Revised: 5 June 2012 / Accepted: 13 July 2012 / Published: 24 July 2012
Cited by 3 | PDF Full-text (528 KB) | HTML Full-text | XML Full-text | Supplementary Files
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)
Open AccessArticle Comprehensive Evaluation of Algal Biofuel Production: Experimental and Target Results
Energies 2012, 5(6), 1943-1981; doi:10.3390/en5061943
Received: 9 March 2012 / Revised: 30 May 2012 / Accepted: 5 June 2012 / Published: 20 June 2012
Cited by 20 | PDF Full-text (821 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle Microalgae Isolation and Selection for Prospective Biodiesel Production
Energies 2012, 5(6), 1835-1849; doi:10.3390/en5061835
Received: 5 April 2012 / Revised: 1 June 2012 / Accepted: 14 June 2012 / Published: 15 June 2012
Cited by 32 | PDF Full-text (825 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle Seasonal Variation of Lipids and Fatty Acids of the Microalgae Nannochloropsis oculata Grown in Outdoor Large-Scale Photobioreactors
Energies 2012, 5(5), 1577-1592; doi:10.3390/en5051577
Received: 12 March 2012 / Revised: 3 May 2012 / Accepted: 9 May 2012 / Published: 21 May 2012
Cited by 45 | PDF Full-text (1110 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle High Lipid Induction in Microalgae for Biodiesel Production
Energies 2012, 5(5), 1532-1553; doi:10.3390/en5051532
Received: 30 March 2012 / Revised: 3 May 2012 / Accepted: 8 May 2012 / Published: 18 May 2012
Cited by 206 | PDF Full-text (349 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle Microwave-Assisted Transesterification of Macroalgae
Energies 2012, 5(4), 862-871; doi:10.3390/en5040862
Received: 22 February 2012 / Revised: 19 March 2012 / Accepted: 22 March 2012 / Published: 26 March 2012
Cited by 8 | PDF Full-text (394 KB) | HTML Full-text | XML Full-text
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)
Open AccessCommunication Effects of Light and Temperature on Fatty Acid Production in Nannochloropsis Salina
Energies 2012, 5(3), 731-740; doi:10.3390/en5030731
Received: 21 January 2012 / Revised: 24 February 2012 / Accepted: 1 March 2012 / Published: 12 March 2012
Cited by 56 | PDF Full-text (1157 KB) | HTML Full-text | XML Full-text
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)
Open AccessArticle Influence of n-Hexane on in Situ Transesterification of Marine Macroalgae
Energies 2012, 5(2), 243-257; doi:10.3390/en5020243
Received: 20 December 2011 / Revised: 13 January 2012 / Accepted: 2 February 2012 / Published: 6 February 2012
Cited by 11 | PDF Full-text (515 KB) | HTML Full-text | XML Full-text
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)

Review

Jump to: Research

Open AccessReview Current Status and Prospects of Biodiesel Production from Microalgae
Energies 2012, 5(8), 2667-2682; doi:10.3390/en5082667
Received: 15 May 2012 / Revised: 13 July 2012 / Accepted: 20 July 2012 / Published: 25 July 2012
Cited by 15 | PDF Full-text (197 KB) | HTML Full-text | XML Full-text
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)
Open AccessReview Achieving a Green Solution: Limitations and Focus Points for Sustainable Algal Fuels
Energies 2012, 5(5), 1613-1647; doi:10.3390/en5051613
Received: 6 March 2012 / Revised: 29 April 2012 / Accepted: 9 May 2012 / Published: 21 May 2012
Cited by 16 | PDF Full-text (324 KB) | HTML Full-text | XML Full-text
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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