Comparison of cell disruption techniques prior to lipid extraction from Scenedesmus sp. slurries for biodiesel production using liquid CO2

Abstract

Microalgae have long been considered an ideal potential feedstock for the production of biodiesel because of their fast growth rates, high productivities, and high intracellular lipid content. Conventional extraction methods generally utilize high pressures, halogenated organic solvents, dried algae, or long extraction periods, leading to high energy/capital costs to achieve acceptable microalgal lipid yields. For this reason, liquid CO₂ has emerged as an innovative, greener extraction technique that offers the benefits of utilizing a lower pressure (150 bar) and temperature (25 °C), and lower energy/capital costs than supercritical CO₂. However, obtaining complete access to the lipids contained in microalgal slurries continues to present a significant challenge. This study investigates mechanical and chemical cell disruption techniques, including ultrasonication, microwave radiation, grinding with liquid N₂, osmotic shock, cooling, and freeze-drying, prior to the extraction of neutral lipids (NL) and free fatty acids (FFA) from Scenedesmus sp. slurries. The highest NL/FFA yield obtained was roughly 9.6 wt% when microwave radiation was applied, compared to a total NL/FFA yield of 13.2 wt% obtained by Soxhlet extraction.