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Extraction of Algal Lipids for Use in Biodiesel ProductionEPA Grant Number: FP917173
Title: Extraction of Algal Lipids for Use in Biodiesel Production
Investigators: Soh, Lindsay
Institution: Yale University
EPA Project Officer: Zambrana, Jose
Project Period: September 1, 2010 through August 31, 2013
Project Amount: $111,000
RFA: STAR Graduate Fellowships (2010) RFA Text | Recipients Lists
Research Category: Fellowship - Science & Technology for Sustainability: Energy , Academic Fellowships
Due to their high lipid content and ease of cultivation, algae are potentially ideal starting materials for the production of biodiesel that may be used to replace non-renewable petroleum based transport fuels. Though algae-based biofuels are promising, limitations in the technology needed to grow and harvest the algae as well as to extract the enclosed lipid have inhibited their implementation. The objective of this research is to contribute to the development of algal lipids into a viable energy source by optimizing lipid extraction techniques for efficiency, sustainability, decreased hazard, and selectivity, focusing on the use of supercritical fluids as alternative, green solvents.
Due to limited fossil fuel supplies and global climate change, alternative energy sources must be found. Biodiesel produced from algae shows great potential to sustainably replace petroleum-based transport fuel, but technological hindrances, including inefficient lipid extraction, have prevented their implementation. This research aims to optimize algal lipid extraction for efficiency, sustainability, and decreased hazard, focusing on using supercritical fluids as alternative, green solvents.
In order to improve upon the current extraction methods, cell disruption, greener solvent systems, selective extraction, and simplified extraction-fuel conversion processes will be evaluated for their ability to increase efficiency and decrease hazard associated with lipid extraction. In particular, supercritical carbon dioxide (scCO2) will be used as a non-polar solvent to solubilize the algal lipid. The supercritical extraction conditions will be modified by varying pressure, temperature, and co-solvent use, in order to find the most effective conditions in terms of efficiency and selectivity. The efficiency of extraction can be evaluated by assessing the fatty acid methyl ester (FAME) content of the lipid extraction and thus the algal biodiesel production potential. Further, the selectivity of each variation can be quantified by also assessing the full lipid profile of the extract, including triglyceride and phospholipid content.
While conventional solvents are effective at almost completely extracting lipids from algal cells, their drawbacks include inherent toxicity, poor selectivity, and difficult separation of the contaminants as well as solvents from the desired product. Due to their sensitivity to changes in pressure and temperature, scCO2 conditions can be tuned to selectively extract the desired triglycerides, eliminating unwanted lipid-like materials such as phospholipids and pigments. Co-solvents can also be used to further enhance solubility and selectivity, raising the efficiency of extraction by scCO2 closer to that of traditional solvents. Further, supercritical conditions may also be tuned to not only extract but also transesterify the algal lipids, found as triglycerides, into FAME that can be directly used as biodiesel, simplifying the multi-step process into one. In addition to triglycerides, the selectivity of supercritical fluid extraction can be used to selectively extract other materials from algae for use in products such as cosmetics, nutraceuticals, and polymers. Subsequent to extraction, the system can simply be brought back to atmospheric conditions to evaporate the carbon dioxide as a gas.
Potential to Further Environmental/Human Health Protection
Upon successful completion of this research, an efficient, green, and sustainable means to extract algal lipid for biofuel will have been developed for implementation as a renewable alternative for transport fuel. Supercritical carbon dioxide extraction has already proven to be an effective and less hazardous means for lipid extraction, and by optimizing its use for lipid extraction, the potential for algal biodiesel as a sustainable alternative to fossil fuels increases. Finally, by using waste products from biodiesel production, environmental and economic impacts will be minimized and an efficient closed-system process implemented.