Percolation extraction is a mass-transfer process where a solvent flows through a packed material, dissolving and carrying target compounds as pressure and connectivity increase. In CO₂ systems, crossing the percolation threshold enables rapid penetration, enhanced solubility, and efficient, near-complete extraction with minimal residue.
A percolation extractor is a device used to extract soluble compounds from solid materials (such as herbs, botanicals, coffee, or pharmaceuticals) by continuously passing a solvent through a packed column of the material.
Load the material – Finely ground plant or solid material is packed into a vertical column.
Add solvent – A liquid (water, ethanol, or another solvent) is poured on top.
Controlled flow – The solvent slowly moves downward by gravity.
Collection – As it passes through, it dissolves target compounds and exits the bottom as extract.
Your biomass is packed into an extraction vessel just like a traditional percolation column. It creates a fixed bed through which solvent must travel.
Instead of gravity pulling ethanol downward, pressurized subcritical CO₂ (with dissolved co-solvent) is pumped through the bed.
CO₂ acts as the primary carrier
Co-solvent (e.g., ethanol) modifies polarity
Flow is continuous and controlled
This maintains a strong concentration gradient — the key principle behind percolation efficiency.
In a standard percolator, solvent passes once.
In your system:
Extract-laden CO₂ exits the vessel
Pressure/temperature change causes separation
CO₂ is recompressed and sent back through
This makes it a recirculating percolator, continuously refreshing solvent strength while minimizing solvent consumption.
Subcritical CO₂ (typically lower temperature and moderate pressure) behaves like a nonpolar liquid solvent.
Adding a co-solvent increases solvating power for:
Alkaloids
Polyphenols
Certain polar fractions
So instead of a static ethanol percolation, you have a pressure-tuned, polarity-adjustable percolation system.
