Technology
Carbon dioxide above 73.8 bar and 31.1 °C stops behaving like a gas or a liquid and becomes something in between. It diffuses through plant material like a gas and dissolves oils like a solvent — and when you drop the pressure, it disappears completely.
The principle
Hexane is hexane. Its solvating power is fixed, so it takes what it takes and you separate the rest downstream. Supercritical CO₂ is different: its density — and therefore what it will dissolve — changes continuously with pressure and temperature.
That turns solvent selection into a process variable. At lower pressures CO₂ is relatively non-polar and picks up light volatiles and aroma compounds. Push the pressure up and it starts pulling heavier resins, waxes and pigments. We run between 300 and 600 bar at 35–80 °C, choosing the window per crop and per specification.
Practically, this means we can give you a light, aroma-forward essential oil fraction and a heavy, actives-rich oleoresin fraction from the same botanical — or a single full-spectrum extract if that's what your formulation needs.
The process
Seven steps, one closed loop. The CO₂ that leaves the separator goes back into the extraction vessel.
Incoming material is cleaned, dried to a target moisture and milled to a controlled particle size. Particle size drives extraction kinetics more than almost anything else, so this step is specified per crop, not done by eye.
Prepared material is charged into the extraction vessel and sealed. Bed packing is controlled to avoid channelling, which is the usual cause of inconsistent yield between batches.
CO₂ is compressed past its critical point and brought to the target pressure and temperature for that crop and that fraction.
Supercritical CO₂ flows through the bed, dissolving the target compounds. Contact time and flow rate are set by the recipe for that product.
The loaded CO₂ passes into separators held at stepped pressures. As pressure falls, solvating power falls, and different fractions precipitate out at different stages — this is where a fraction is isolated rather than blended.
Stripped CO₂ is condensed and returned to the storage tank for the next cycle. Over 90% is recovered, which is both an environmental and a cost story.
The extract is filtered, sampled and tested against specification. Once released, it is packed under nitrogen into aluminium-lined bags or HDPE drums with the COA travelling with the consignment.
Plant parameters
| Parameter | Value | Note |
|---|---|---|
| Finished extract capacity | Up to 2 MT/month | 1–2 tonnes per month depending on crop and fraction |
| Production model | Continuous campaign | Two-shift operation, 330 days a year |
| Extraction pressure | 300 – 600 bar | Set per crop and per fraction |
| Extraction temperature | 35 – 80 °C | Low enough to protect thermolabile actives |
| Solvent | 100% food-grade CO₂ | No hexane, ethanol or co-solvent on site |
| CO₂ recovery | >90% | Condensed and returned to the loop each cycle |
| Ginger extract yield | 5.5% | Guaranteed on dried sonth |
| Minimum trial lot | Small-batch | Trial quantities accepted for evaluation |
| Liquid effluent | Nil | Zero liquid discharge |
Comparison
Each method has a place. Here's an honest read on where each one lands.
| Supercritical CO₂ | Steam distillation | Solvent (hexane / ethanol) | |
|---|---|---|---|
| Operating temperature | 35 – 80 °C | 100 °C+ | 60 – 80 °C, plus desolventising heat |
| Solvent residue | None | None | Residual solvent, requires testing and limits |
| Thermolabile actives | Preserved | Often degraded | Partly degraded during desolventising |
| Aroma fidelity | Close to the fresh plant | Top notes lost, cooked character | Variable; solvent character can carry |
| Selectivity | Tunable by pressure and temperature | Volatiles only | Broad, non-selective |
| Heavy / non-volatile actives | Accessible at high pressure | Not extractable | Accessible |
| Effluent | Zero liquid discharge | Condensate to treat | Solvent-laden effluent and emissions |
| Clean-label position | Strong | Strong | Requires declaration |
| Capital cost | High | Low | Moderate |
Steam distillation remains the sensible route for many high-volume, low-value volatile oils. We use CO₂ where the actives are heat-sensitive, where the aroma matters, or where a solvent declaration would cost you the account.
Flexibility
Because the solvent is the same for every product and only the parameters change, the plant switches botanicals without a rebuild. We run in campaigns — a block of days on one crop, then a changeover and cleaning cycle, then the next.
For you, that has two consequences. First, we can take on a botanical we haven't run before without a capital conversation. Second, we can run genuinely small campaigns for a trial — and then scale the same product up to two tonnes a month once it's approved, without changing the process.
Send us the material and the target profile. We'll run a lab-scale assessment and tell you honestly whether CO₂ is the right route for it.