Advances and perspectives in using microalgae to produce biodiesel
TL;DR: The state of the art regarding microalgae toward production of biofuels is covered, both from the point of view of the microalgal cell itself and of the supporting bioreactor; and current limitations and promising perspectives in this field are discussed.
About: This article is published in Applied Energy.The article was published on 2011-10-01. It has received 569 citations till now.
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TL;DR: A critical evaluation of the available information suggests that the economic viability of the process in terms of minimizing the operational and maintenance cost along with maximization of oil-rich microalgae production is the key factor, for successful commercialization ofmicroalgae-based fuels.
Abstract: Microalgae feedstocks are gaining interest in the present day energy scenario due to their fast growth potential coupled with relatively high lipid, carbohydrate and nutrients contents. All of these properties render them an excellent source for biofuels such as biodiesel, bioethanol and biomethane; as well as a number of other valuable pharmaceutical and nutraceutical products. The present review is a critical appraisal of the commercialization potential of microalgae biofuels. The available literature on various aspects of microalgae, e.g. its cultivation, life cycle assessment, and conceptualization of an algal biorefinery, has been scanned and a critical analysis has been presented. A critical evaluation of the available information suggests that the economic viability of the process in terms of minimizing the operational and maintenance cost along with maximization of oil-rich microalgae production is the key factor, for successful commercialization of microalgae-based fuels.
912 citations
Journal Article•
TL;DR: In this paper, various technologies currently used for dewatering microalgal cultures along with a comparative study of the performances of the different technologies are reviewed and compared, as well as a comparison of the performance of different technologies.
Abstract: Microalgae dewatering is a major obstruction to industrial-scale processing of microalgae for biofuel prodn. The dil. nature of harvested microalgal cultures creates a huge operational cost during dewatering, thereby, rendering algae-based fuels less economically attractive. Currently there is no superior method of dewatering microalgae. A technique that may result in a greater algal biomass may have drawbacks such as a high capital cost or high energy consumption. The choice of which harvesting technique to apply will depend on the species of microalgae and the final product desired. Algal properties such as a large cell size and the capability of the microalgae to autoflocculate can simplify the dewatering process. This article reviews and addresses the various technologies currently used for dewatering microalgal cultures along with a comparative study of the performances of the different technologies.
851 citations
TL;DR: An empirical and critical analysis on the potential of translating research findings from laboratory scale trials to full scale application and current methods for biomass harvesting and lipid extraction are critically evaluated.
755 citations
Cites background from "Advances and perspectives in using ..."
...The limitations of open pond culture have lead to much research into photobioreactors, as a method of primarily overcoming contamination and low productivity [10,52]....
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...The stability of light intensity and photoperiod provided by artificial light has potential to enhance yearly total oil yields by 25–42% [52]....
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...The most popular photobioreactor configurations are tubular, vertical or column, flat plate and annular reactors [10,52]....
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...Mixing provides a benefit in phototrophic systems in that mixing as well as aeration is accomplished simultaneously [52]....
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...Monocultures are possible in for extended periods of time if they are operated in a sterile manner [10,52]....
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01 Jan 2013
TL;DR: In this article, the authors present an empirical and critical analysis on the potential of translating research findings from laboratory-scale trials to full-scale application in bio-diesel production.
Abstract: The economically significant production of carbon-neutral biodiesel from microalgae has been hailed as the ultimate alternative to depleting resources of petro-diesel due to its high cellular concentration of lipids, resources and economic sustainability and overall potential advantages over other sources of biofuels. Pertinent questions however need to be answered on the commercial viability of large scale production of biodiesel from microalgae. Vital steps need to be critically analysed at each stage. Isolation of microalgae should be based on the question of whether marine or freshwater microalgae, cultures from collections or indigenous wild types are best suited for large scale production. Furthermore, the determination of initial sampling points play a pivotal role in the determination of strain selection as well as strain viability. The screening process should identify, purify and select lipid producing strains. Are natural strains or stressed strains higher in lipid productivity? The synergistic interactions that occur naturally between algae and other microorganisms cannot be ignored. A lot of literature is available on the downstream processing of microalgae but a few reports are available on the upstream processing of microalgae for biomass and lipid production for biodiesel production. We present in this review an empirical and critical analysis on the potential of translating research findings from laboratory scale trials to full scale application. The move from laboratory to large scale microalgal cultivation requires careful planning. It is imperative to do extensive pre-pilot demonstration trials and formulate a suitable trajectory for possible data extrapolation for large scale experimental designs. The pros and cons of the two widely used methods for growing microalgae by photobioreactors or open raceway ponds are discussed in detail. In addition, current methods for biomass harvesting and lipid extraction are critically evaluated. This would be novel approach to economical biodiesel production from microalgae in the near future. Globally, microalgae are largest biomass producers having higher neutral lipid content outcompeting terrestrial plants for biofuel production. However, the viscosities of microalgal oils are usually higher than that of petroleum diesel.
695 citations
TL;DR: In this article, a review of the available literature is presented, analyzing the influence of parameters such as temperature, holding time and catalyst dosage on the yield and properties of the different product fractions.
Abstract: Among the various types of biomass, microalgae have the potential of becoming a significant energy source for biofuel production in the coming years. Currently, research is mainly focusing on optimization of the cultivation methods and the conversion of just a single microalgae fraction (lipids for biodiesel production). Hydrothermal liquefaction is a method for thermochemical conversion of wet microalgae, producing a liquid energy carrier called ‘bio-oil’ or ‘biocrude’, next to gaseous, aqueous and solid by-products. A review of the available literature is presented here, analyzing the influence of parameters such as temperature, holding time and catalyst dosage on the yield and properties of the different product fractions. Also, the strain selection and the status of the technology for hydrothermal processes are analyzed. Finally, based on the findings obtained from the literature review, directions for future research are suggested.
608 citations
References
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TL;DR: As demonstrated here, microalgae appear to be the only source of renewable biodiesel that is capable of meeting the global demand for transport fuels.
9,030 citations
"Advances and perspectives in using ..." refers background in this paper
...83 kg of CO2, which can readily be obtained from industrial flue gases via bio-fixation [9]....
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...The yearly oil yield in outdoor microalgal cultivation systems illuminated by sunlight lies between 100 and 130 m ha 1 [9]....
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...Chisti [9] favoured airlift, tubular photobioreactors – but pointed out that their productivity per unit area may be only slightly larger than that of a pond reactor, although the microalga can be grown to higher densities (thus reducing energy inputs downstream)....
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...Manymicroalgal species can be induced to accumulate substantial contents of lipids [10]; although average lipid contents vary between 1% and 70%, some species may reach 90% (w/wDW) under certain conditions [9,11,12] – see Table 1....
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TL;DR: 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).
Abstract: 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 CO 2 , wastewater treatment, in human health, as food additive, and for aquaculture.
5,158 citations
"Advances and perspectives in using ..." refers background in this paper
...10% (w/wDW), and a concomitant metabolic shift was observed towards carbohydrate synthesis and storage [7]....
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...Chlorella vulgaris, Haematococcus pluvialis and Arthrospira (Spirulina) platensis are examples of species that can grow under photoautotrophic, heterotrophic and mixotrophic conditions [7]....
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...Lipid content and productivity of various marine and freshwater microalga species [7]....
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...braunii [7,14]....
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...Phototrophic cultivation is the most frequently used – and also the easiest to scale-up; it is particularly promising because microalgae may uptake CO2 from flue gas of factories, and convert it to oil – thus upgrading a waste to advantage [7]....
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TL;DR: In this article, the transesterification reaction is aected by molar ratio of glycerides to alcohol, catalysts, reaction temperature, reaction time and free fatty acids and water content of oils or fats.
4,902 citations
"Advances and perspectives in using ..." refers background in this paper
...5–7% in ponds and close photobioreactors [36,37]; in the former case, this translates to a yield of 30– 40 gdry biomass m 2 d 1 [4]....
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TL;DR: In this article, the authors reviewed the technologies underpinning microalgae-to-bio-fuels systems, focusing on the biomass production, harvesting, conversion technologies, and the extraction of useful co-products.
Abstract: Sustainability is a key principle in natural resource management, and it involves operational efficiency, minimisation of environmental impact and socio-economic considerations; all of which are interdependent. It has become increasingly obvious that continued reliance on fossil fuel energy resources is unsustainable, owing to both depleting world reserves and the green house gas emissions associated with their use. Therefore, there are vigorous research initiatives aimed at developing alternative renewable and potentially carbon neutral solid, liquid and gaseous biofuels as alternative energy resources. However, alternate energy resources akin to first generation biofuels derived from terrestrial crops such as sugarcane, sugar beet, maize and rapeseed place an enormous strain on world food markets, contribute to water shortages and precipitate the destruction of the world's forests. Second generation biofuels derived from lignocellulosic agriculture and forest residues and from non-food crop feedstocks address some of the above problems; however there is concern over competing land use or required land use changes. Therefore, based on current knowledge and technology projections, third generation biofuels specifically derived from microalgae are considered to be a technically viable alternative energy resource that is devoid of the major drawbacks associated with first and second generation biofuels. Microalgae are photosynthetic microorganisms with simple growing requirements (light, sugars, CO 2 , N, P, and K) that can produce lipids, proteins and carbohydrates in large amounts over short periods of time. These products can be processed into both biofuels and valuable co-products. This study reviewed the technologies underpinning microalgae-to-biofuels systems, focusing on the biomass production, harvesting, conversion technologies, and the extraction of useful co-products. It also reviewed the synergistic coupling of microalgae propagation with carbon sequestration and wastewater treatment potential for mitigation of environmental impacts associated with energy conversion and utilisation. It was found that, whereas there are outstanding issues related to photosynthetic efficiencies and biomass output, microalgae-derived biofuels could progressively substitute a significant proportion of the fossil fuels required to meet the growing energy demand.
4,432 citations
"Advances and perspectives in using ..." refers background in this paper
...However, the cost of this operation is typically high, because the initial mass fractions are generally low, and the cells normally carry negative charge and excess algogenic organic material that contribute to their stability in a dispersed state [51]....
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TL;DR: A brief summary of the current knowledge on oleaginous algae and their fatty acid and TAG biosynthesis, algal model systems and genomic approaches to a better understanding of TAG production, and a historical perspective and path forward for microalgae-based biofuel research and commercialization are provided.
Abstract: Microalgae represent an exceptionally diverse but highly specialized group of micro-organisms adapted to various ecological habitats. Many microalgae have the ability to produce substantial amounts (e.g. 20-50% dry cell weight) of triacylglycerols (TAG) as a storage lipid under photo-oxidative stress or other adverse environmental conditions. Fatty acids, the building blocks for TAGs and all other cellular lipids, are synthesized in the chloroplast using a single set of enzymes, of which acetyl CoA carboxylase (ACCase) is key in regulating fatty acid synthesis rates. However, the expression of genes involved in fatty acid synthesis is poorly understood in microalgae. Synthesis and sequestration of TAG into cytosolic lipid bodies appear to be a protective mechanism by which algal cells cope with stress conditions, but little is known about regulation of TAG formation at the molecular and cellular level. While the concept of using microalgae as an alternative and renewable source of lipid-rich biomass feedstock for biofuels has been explored over the past few decades, a scalable, commercially viable system has yet to emerge. Today, the production of algal oil is primarily confined to high-value specialty oils with nutritional value, rather than commodity oils for biofuel. This review provides a brief summary of the current knowledge on oleaginous algae and their fatty acid and TAG biosynthesis, algal model systems and genomic approaches to a better understanding of TAG production, and a historical perspective and path forward for microalgae-based biofuel research and commercialization.
3,479 citations
"Advances and perspectives in using ..." refers background in this paper
...At present, one is indeed still far from globally understanding the detailed molecular pathways and forms of regulation of lipid metabolism in microalgae; although bioinformatics applied to already sequenced microalgal genomes has unfolded essentially similar biochemical routes therefor, little experimental validation of putative enzyme activities has so far been reported [18] – with the exception of the recent work by Moellering et al....
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