A Review: Microalgae and Their Applications in CO_2 Capture and Renewable Energy
TL;DR: In this paper, a review of the literature on microalgae that were cultivated using captured CO_2, technologies related to the production of bio-fuels from micro-algae and the possible commercialization of micro-algal-based bio-fuel.
Abstract: Fossil fuels, which are recognized as unsustainable sources of energy, are continuously consumed and decreased with increasing fuel demands. Microalgae have great potential as renewable fuel sources because they possess rapid growth rate and the ability to store high-quality lipids and carbohydrates inside their cells for biofuel production. Microalgae can be cultivated on opened or closed systems and require nutrients and CO_2 that may be supplied from wastewater and fossil fuel combustion. In addition, CO_2 capture via photosynthesis to directly fix carbon into microalgae has also attracted the attention of researchers. The conversion of CO_2 into chemical and fuel (energy) products without pollution via this approach is a promising way to not only reduce CO_2 emissions but also generate more economic value. The harvested microalgal biomass can be converted into biofuel products, such as biohydrogen, biodiesel, biomethanol, bioethanol, biobutanol and biohydrocarbons. Thus, microalgal cultivation can contribute to CO_2 fixation and can be a source of biofuels. This article reviews the literature on microalgae that were cultivated using captured CO_2, technologies related to the production of biofuels from microalgae and the possible commercialization of microalgae-based biofuels to demonstrate the potential of microalgae. In this respect, a number of relevant topics are addressed: the nature of microalgae (e.g., species and composition); CO_2 capture via microalgae; the techniques for microalgal cultivation, harvesting and pretreatment; and the techniques for lipid extraction and biofuel production. The strategies for biofuel commercialization are proposed as well.
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TL;DR: The multifaceted roles of microalgae in wastewater treatment from the extent of micro algal bioremediation function to environmental amelioration with the involvement of microalgal biomass productivity and carbon dioxide fixation are highlighted.
217 citations
TL;DR: A systematically integrated genome sequencing and process-scale engineering approach for the extraction of lipids and co-products is critical in the development of future microalgal biorefineries.
159 citations
TL;DR: In this article, the importance of identifying the type of medium suitable for microalgae cultivation is highlighted along with descriptions and comparison of the medium types that include freshwater, saltwater and wastewater.
Abstract: As the world's natural fuel sources continue to deplete, the search for alternative fuel sources intensifies. A promising fuel source alternative is biofuels from microalgae, due to it being a renewable source, its wide availability, and also its high production rate. This paper reviews recent developments in microalgae culture medium, cultivation systems and growth modes. The importance of identifying the type of medium suitable for microalgae cultivation is highlighted along with descriptions and comparison of the medium types that include freshwater, saltwater and wastewater. The different cultivation systems such as open system, closed system, dark system and offshore cultivation used for cultivating microalgae are discussed, along with a study on the impact of large scale cultivation using these systems. Besides that, various growth modes for microalgae cultivation like phototrophic, heterotrophic, mixotrophic, photoheterotophic modes are reviewed.
159 citations
TL;DR: This critical review presents an overview of new applications of microalgae for bioenergy production, including as a novelty the use of micro algae for electricity generation in microalgai-MFCs and capturing the CO2 emissions of these systems, their advantages, limitations and future prospects.
151 citations
TL;DR: A cradle-to-gate approach was used to provide expedient insights on the effect of different cultivation systems and biomass productivity toward life cycle energy, carbon balance, and economic sustainability of microalgae biodiesel production pathways and a co-production of bioethanol frommicroalgae residue was proposed in order to improve theEconomic sustainability of the overall system.
146 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
"A Review: Microalgae and Their Appl..." refers background in this paper
...Although this reaction requires much alcohol, the methyl ester yield is greater than 98% (Chisti, 2007)....
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...Gas exchange vessels to supply CO2, air and nutrients and to remove O2 are connected to the main reactor (Richmond, 2004; Chisti, 2007)....
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...reactor to prevent the flocculation of microalgal biomass (Chisti, 2007)....
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...Biodiesel is a promising renewable energy that does not require engine modification and reduces CO (by 50%) and CO2 (by 78%) emissions (Chisti, 2007)....
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...The pump also helps to maintain a highly turbulent flow within the reactor to prevent the flocculation of microalgal biomass (Chisti, 2007)....
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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
"A Review: Microalgae and Their Appl..." refers background in this paper
...As a result, CO2 fixation using microalgae can reduce the CO2 emission from power plants, which has the positive environmental impact (Inoue et al., 1995; Yun et al., 1997; Abu-Khader, 2006; Brennan and Owende, 2010)....
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TL;DR: The first use of microalgae by humans dates back 2000 years to the Chinese, who used Nostoc to survive during famine, while future research should focus on the improvement of production systems and the genetic modification of strains.
3,793 citations
"A Review: Microalgae and Their Appl..." refers background in this paper
...…that can convert carbon dioxide (CO2) into raw materials for producing biofuels (e.g., biohydrogen, biodiesel, and bioethanol), animal food chemical feedstocks and high-value bioactive compounds (e.g., Docosahexaenoic acid (DHA)) (Spolaore et al., 2006; Milledge, 2011; Razzak et al., 2013)....
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TL;DR: Amine scrubbing has been used to separate carbon dioxide (CO2) from natural gas and hydrogen since 1930 and is ready to be tested and used on a larger scale for CO2 capture from coal-fired power plants.
Abstract: Amine scrubbing has been used to separate carbon dioxide (CO2) from natural gas and hydrogen since 1930. It is a robust technology and is ready to be tested and used on a larger scale for CO2 capture from coal-fired power plants. The minimum work requirement to separate CO2 from coal-fired flue gas and compress CO2 to 150 bar is 0.11 megawatt-hours per metric ton of CO2. Process and solvent improvements should reduce the energy consumption to 0.2 megawatt-hour per ton of CO2. Other advanced technologies will not provide energy-efficient or timely solutions to CO2 emission from conventional coal-fired power plants.
3,427 citations
TL;DR: Economics of monoseptic production of microalgae in photobioreactors and the downstream recovery of metabolites are discussed using eicosapentaenoic acid (EPA) recovery as a representative case study.
2,220 citations
"A Review: Microalgae and Their Appl..." refers background or methods in this paper
...The Centrifugation is an efficient but energy-intensive method (Molina et al., 2003)....
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...The flocculation mechanism is to neutralize or reduce the negative charge on the microalgal cellular surface to aggregate cells in suspension, which can be collected by adding flocculants such as multivalent cations and cationic polymers (Molina et al., 2003)....
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...Moreover, microfiltration is more cost-effective than centrifugation (Molina et al., 2003)....
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...such as multivalent cations and cationic polymers (Molina et al., 2003)....
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