Supercritical CO2 extraction: isolating cannabinoids without solvents

Beyond 30.98 °C and 73.77 bar, its critical point, CO2 stops being either a gas or a liquid: it becomes a supercritical fluid, with the density of a liquid and the diffusivity of a gas. That dual property makes it an efficient solvent for extracting apolar molecules such as cannabinoids, without destroying heat-sensitive terpenes. On leaving the vessel the pressure is released: the CO2 vaporises instantly and the extract precipitates out, pure. The gas is then recompressed and returned in a closed loop, with no atmospheric discharge.

Reference industrial installations generally run several extraction units in a closed circuit, able to process several tonnes of dried hemp a month, in a cleaner-chemistry approach with no toxic effluent and with emissions minimised by recirculating the CO2. The exact parameters (pressure, temperature, flow rate) usually stay confidential from one operator to the next, but the principle is unchanged: a cycle at gentle pressure and temperature preserves the terpene profile better than steam distillation or ethanol extraction.

Supercritical CO2 wins on the criterion that matters most for a food or cosmetic extract: zero solvent residue, verifiable by GC-MS on every batch. Pharmaceutical ethanol, a class 3 solvent under the ICH Q3C classification, tolerates up to 5,000 ppm of residue and partly denatures the terpenes. Hydrocarbons such as butane or propane preserve terpenes well but leave residues that must be measured, and are not covered by that same classification. Steam distillation leaves no residue, but partly degrades the aromatic compounds.

A serious extraction line has its own analytical laboratory, co-located with the clean room. There you will generally find high-performance liquid chromatography (HPLC) to assay cannabinoids batch by batch, gas chromatography (GC and GC-MS) for terpenes and volatile residues, sometimes centrifugal counter-current chromatography to separate closely related isomers, and vacuum molecular distillation to purify without thermal degradation. In-line control during production is combined with preparative separations downstream.

Owning analytical equipment is not enough: traceability rests on a documented management system. Four frameworks stack up at the most rigorous operators: ISO 9001 for quality management, HACCP for hazard analysis in production, good manufacturing practice (GMP) and good hygiene practice (GHP). None replaces another: an operator declaring only ISO 9001 has a framework for its documentary process, without on its own guaranteeing the absence of biological contamination.

Beyond the extraction process, the quality guarantee rests on published batch-by-batch analyses, a cannabinoid profile by HPLC, a terpene profile by GC-MS, and screening for heavy metals, pesticides and mycotoxins. Choosing supercritical CO2, or pharmaceutical ethanol under molecular distillation, rather than butane or hexane, remains a reliable indicator of industrial seriousness. The legal threshold, moreover, stays fixed at 0.30 % total THC in the finished product, in accordance with the Conseil d'État decision of 29 December 2022. To understand how these extracts are then formulated, see our article on full-spectrum hemp extract.

Does supercritical CO2 leave traces in the final extract?

No. At atmospheric pressure the CO2 vaporises completely and leaves no residue detectable by standard GC-MS analysis.

Why not use ethanol alone, which is cheaper?

Ethanol remains a valid pharmaceutical option, but it partly denatures the terpenes and leaves a residue tolerated under the ICH Q3C classification, whereas supercritical CO2 leaves none at all.

How can I tell whether an extract was made with supercritical CO2?

The certificate of analysis or the product sheet should say so. If that information is missing, contact the manufacturer: a serious operator discloses its extraction method.

Does CO2 extraction change the legal THC threshold?

No. Whatever the extraction method, the 0.30 % THC threshold in the finished product applies in the same way to every hemp extract sold in France.