Supercritical Fluid CO2 Extraction

Supercritical carbon dioxide extraction is one of the available green technologies that replaces the traditional organic solvent. The extraction and reaction field have new dimensions with the introduction of supercritical fluid technology. The basic principle of this technology is achieving a homogenous phase after the evaporation of the vapor phase and the separation of liquid beyond the critical point. The supercritical phase helps in the transformation of the fluid into a supersolvent, which simultaneously increases the efficiency of extraction.

There are some new supercritical fluids that are currently being explored for the extraction of lipid: ethylene, CO2, ethane, methanol, ethanol, benzene, toluene, and water. According to Halim et al., the wet mass of Chlorococcum sp. was extracted using supercritical CO2 and the lipid yield was found to be around 7.1% at the critical temperature of 60°C, the critical pressure of 30 Mpa, and an extraction time of 80 min. The lipid yield was found to be higher when obtained from wet biomassthan from dry biomass (5.8%), which also significantly reduces the cost and energy involved during the drying of biomass. Soxhlet extraction was found to be less efficient (5.8%) when compared to supercritical extraction. The lipid yield attained from the Bligh and Dyer method was found to be nearly double that of supercritical CO2. Therefore, this indicates that the microalgae strains and culture conditions play a significant role in determining the appropriate lipid extraction methods. Hence, the design of an extraction technique should be done wisely to reduce the total energy involved during the extraction process.