Extraction of lipids from microalgal slurries with liquid CO2

Abstract

Traditional methods for lipid extraction from microalgae achieve high yields, but at the cost of energy-intensive drying of the microalgae before extraction and the toxicity and price of the extraction solvents. Liquid carbon dioxide (lCO2) is shown to successfully extract lipids from aqueous microalgal slurries. The rate and yield were dependent on the extraction conditions, including lCO2 flow rate, reaction time, lCO2 pressure, microalgae cocentration, and mixing. Higher concentrations of microalgae resulted in a decrease in percent yield, likely due to mass transfer limitations when mixing the lCO2 and algae. However, increasing the flow rate of lCO2 (1.5 to 4 mL/min) or the pressure (7.5 to 17.5 MPa) improved the extraction yield and the rate of extraction. Liquid CO2 does not contaminate the aqueous waste stream, does not require the algae to be completely dried and does not require as much pressure as supercritical CO2.