The future of high pressure extraction technologies can be bright, in particular as SFE and SFF are concerned.
There are already significant installations for SFE at world scale, first of all those related to coffee decaffeination in this case the process allows obtaining two high-value products, decaffeinated coffee and caffeine sold to the beverage industry.
SFF starts to be utilized for concentrating omega-3 fatty acid derivatives, in competition with the more common ultra-high vacuum distillation.
It is the authors’ opinion that instead the use of SC-CO2 added with polar co-solvents will not lead to large industrial applications, taking into account that, in this case, one of the major advantages of the technology is lost: downstream of the depressurization step, the solute is not solvent-free but rather dissolved in the liquid phase represented by the polar co-solvent. In addition, when recycling the CO2 after expansion, the presence of some residual co-solvent in the CO2 can cause a non-optimal operation of the CO2 condenser.
Regarding PLE, an important point is to find a cheap and effective method for separating solute and solvent downstream of the PLE operation: the use of appropriate membranes could provide an appropriate solution to the issue.
Finally, worthy of mention is the use of the so-called ‘ultrahigh pressure extraction’ techniques, referred to operations occurring at pressures ranging from 100 to 500 MPa [47]. In principle these techniques allow a significant process intensification, but their actual application on an industrial scale is to be demonstrated.
Notably, for such high pressure operations (SFE, SFF, PLE) the scale-effect regarding the initial investment costs is really significant. The dependence of the investment costs on the plant size can be estimated resorting to Eq