What Is CO2 Extraction?

CO2 extraction is the newest of the three main routes to a natural aromatic material, and in several respects the most capable. It is also the most capital-intensive, which is why it has not displaced the others.

The supercritical state

Above roughly 31 °C and 74 bar, carbon dioxide enters a supercritical state: neither liquid nor gas, but with properties of both. It diffuses through material like a gas while dissolving compounds like a liquid solvent.

Critically, adjusting temperature and pressure changes what it will dissolve. The extraction can be tuned toward lighter volatiles or heavier resinous material.

Why this matters

• Low temperature. Around 31–40 °C rather than 100 °C, so thermally fragile compounds survive.
• No residual solvent. Depressurise and the CO2 becomes gas and leaves entirely.
• Tunable selectivity. The same botanical yields different extracts under different conditions.
• No oxidation during processing. The CO2 atmosphere is inert.

Select versus total extracts

A select extract is produced at lower pressure and recovers mainly the volatile fraction — closer to an essential oil, though generally truer to the living plant. A total extract uses higher pressure and pulls waxes, lipids and pigments as well, giving a fuller, heavier material closer to a resinoid.

The two are different products from the same plant and the same machine. A quotation should say which.

The trade-offs

Equipment operating at 300 bar and above is expensive to build, certify and run. Batch sizes are typically smaller than distillation. Not every botanical benefits enough to justify the cost — for many robust materials, steam distillation gives a perfectly good result far more cheaply.

Where CO2 earns its cost is with delicate, heat-sensitive material, and where residual solvent is unacceptable. Ambrette seed is a good example: its value lies in macrocyclic lactones that survive CO2 extraction well.