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Cultivation, photobioreactor design and harvesting of microalgae for biodiesel production: A critical review
Chun-Yen Chen a,b, Kuei-Ling Yeh a, Rifka Aisyah a, Duu-Jong Lee c, Jo-Shu Chang a,b,d,*
Department of ChemicalEngineering, National Cheng Kung University, Tainan, Taiwan Sustainable Environment Research Center, National Cheng Kung University, Tainan, Taiwan c Department of Chemical Engineering, College of Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan d Microalgae Biotechnology and Bioengineering Laboratory, Center for Biosciences and Biotechnology, National Cheng KungUniversity, Tainan, Taiwan
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Microalgae have the ability to mitigate CO2 emission and produce oil with a high productivity, thereby having the potential for applications in producing the third-generation of biofuels. The key technologies for producing microalgal biofuels include identiﬁcation of preferable culture conditions for high oil productivity,development of effective and economical microalgae cultivation systems, as well as separation and harvesting of microalgal biomass and oil. This review presents recent advances in microalgal cultivation, photobioreactor design, and harvesting technologies with a focus on microalgal oil (mainly triglycerides) production. The effects of different microalgal metabolisms (i.e., phototrophic,heterotrophic, mixotrophic, and photoheterotrophic growth), cultivation systems (emphasizing the effect of light sources), and biomass harvesting methods (chemical/physical methods) on microalgal biomass and oil production are compared and critically discussed. This review aims to provide useful information to help future development of efﬁcient and commercially viable technology for microalgae-basedbiodiesel production. Ó 2010 Elsevier Ltd. All rights reserved.
Article history: Received 31 March 2010 Received in revised form 13 June 2010 Accepted 24 June 2010 Available online xxxx Keywords: Microalgae Oil/lipid Light sources Photobioreactor Harvesting
1. Introduction Today about 80% of global energy demand is produced from fossil fuels. However, extensive utilization of fossil fuels has ledto global climate change, environmental pollution, and health problems (Hallenbeck and Benemann, 2002). Many countries are thus turning their attention to the development of new, clean, and sustainable energy sources. Among the various potential sources of renewable energy, biofuels are of most interest and are expected to play a crucial role in the global energy infrastructure in the future.Biodiesel, one of the most commonly used biofuels, is recognized as an ideal recyclable energy carrier, and thus also as a possible primary energy source (Chisti, 2007). Commercial biodiesel is currently produced from animal fat, waste frying oil and vegetable oils (Barnwal and Sharma, 2005), whose competition with edible vegetable oil for agricultural land is still a controversial issue (Mata et al.,2010). Consequently, microalgae that can grow rapidly and convert solar energy to chemical energy via CO2 ﬁxation are
* Corresponding author. Address: Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan. Fax: +886 6 2357146/2344496. E-mail address: firstname.lastname@example.org (J.-S. Chang). 0960-8524/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.doi:10.1016/j.biortech.2010.06.159
now being considered a promising oil source for making biodiesel (Mata et al., 2010). Under suitable culture conditions, some microalgal species are able to accumulate up to 50–70% of oil/lipid per dry weight (Chisti, 2007). The fatty acid proﬁle of microalgal oil is suitable for the synthesis of biodiesel (Gouveia and Oliveira, 2009). The major attraction...