Criteria

Organic solvent extraction

SCCO2 extraction

Lipid selectivity

Selectivity is not easily tuned. Costly post-extraction fractionation step may be needed

SCCO2 tunable selectivity minimizes co-extraction of contaminants, hence reducing cost needed for downstream fractionation

Time

Solute transfer equilibrium limitation results in slow extraction rate and increases time needed for a complete extraction

Due to its intermediate liquid — gaseous properties, SCCO2 extraction is much more rapid and can complete extraction within shorter period of time

Energy

It consumes little energy as extraction is conducted near ambient conditions. However, solvent needs to be removed in energy-intensive evaporation

It is highly energy-intensive as pressurization is needed in order to convert fluid to supercritical state

Installation and

Expensive pure solvent is needed

Installation of large-scale pressure

operating (non-energy and non-time related) cost

for extraction

vessel needed for SCCO2 extraction is extremely expensive. CO2 derived from the flue gas of any power station has to be purified before it can be used for lipid extraction

Reaction to lipid

Solvent may react with lipid, especially during evaporation when it is removed from the lipids

SCCO2 is non-reactive with lipids

Hazard and toxicity

Toxic solvent is used in a large volume

High-pressure hazard is possible though this should be easily avoided with good engineering design