What is CO₂ extraction?

Carbon dioxide (CO₂) extraction is a process that uses CO₂ to extract phytochemicals (such as cannabinoids, terpenes, flavonoids, etc.) from a plant. At certain temperatures and pressures, CO₂ acts like a solvent. It is one of the most expensive extraction methods; however, it is widely used due to its effectiveness, safety and environmentally friendly approach to processing plant materials.

What is CO₂ extraction used for?

With its increasing popularity, cannabis has been rapidly entering the worldwide market, and extracts are an essential component of this booming industry.

Supercritical CO₂ extraction is a commonly used method to separate various components from the plant due to it producing a pure, clean, and safe product. It is a process used to obtain extracts and other substances using gases that are under super- or sub-critical conditions. Super-critical gases have all the physical properties of gases, but they are incompressible and possess the same dissolving power as liquids.

Extraction Equipment and Method

The size of the extraction system will vary depending on the batch size. Samples can be as small as 10 grams, and as large as hundreds of kilograms. Supercritical CO₂ extraction takes longer to complete than other methods, due to the continuous fluctuations in temperature and pressure.

To perform an extraction, the plant material must be ground and placed into an extraction vessel. The CO₂ gas is then subjected to a high temperature and pressure. A pump then forces the super-critical CO₂ into the extraction vessel, where it meets the plant and breaks the trichomes, allowing it to dissolve part of the plant material. A pressure-release valve then allows the material to flow into a separate vessel, where an internal compressor and heater are used to adjust the pressure and temperature.

By changing the temperature and pressure as well as the flow rate, certain molecules will bond to the CO₂, allowing them to be separated from the plant. Many systems will reroute the CO₂ back into the tank to be used during the next batch. The extract is then moved to a collection jar, such as a beaker.

Advantages of CO₂ extraction

Purer:  CO₂-extracted material is free of residual solvents. Nothing is left behind once the extraction is over, since the CO₂ bubbles away, leaving no trace in the end product.

Safer: Comparing CO₂ cannabis extraction with butane or propane? Don’t forget to include the facility costs for processing with a compressed flammable gas.

Tunable: CO₂ has a very low boiling temperature and wants to be a gas at room temperature, so it naturally separates from the extracted oil, without any additional distillation or purging.

Cold: CO₂ extraction can be carried out at temperatures native to the plant, minimizing the thermal degradation of the plant material and the extracted oil.

Cost Efficient: CO₂ is readily available and widely used in a number of industries. Super-critical CO₂ extraction systems recirculate and subsequently recover 95% of the CO₂ used in each extraction.

Conclusion

This method is considered environmentally friendly, as it doesn’t create any unwanted or harmful side products. It is best known for its use in the production of hemp paste, as well as decaffeinated coffee and tea.

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