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CO2 Extraction Equipment: Basics, Principles, Features, Tips

In terms of efficiency and safety in biomass extraction, supercritical CO2 (carbon dioxide) extraction stands out as one of the best methods for separating active ingredients(essential oils, cannabinoids, and terpenes) from plant biomass material. While ethanol and hydrocarbon technology exist, this eco-friendly and safer solvent can be used for plant biomass material processing at any scale.

In terms of infrastructure costs, CO2 extraction is known for its high entry price relative to alcohol and hydrogen-based extractors. Although the initial up-front cost is relatively high, in the later use cost and safety facility investment, carbon dioxide occupies a great advantage. And in some special plant extractions, CO2 seems to be the only solution, such as the removal of caffeine from tea and coffee or the extraction of hops, and even in the synthesis of medicinal materials, such as nano-scale pharmaceutical production.

What is supercritical CO2?

Carbon dioxide (CO2) is a naturally occurring compound consisting of one carbon atom and two oxygen atoms held together by a covalent double bond. Carbon dioxide is the most important long-lasting greenhouse gas in the Earth’s atmosphere and a key element of the carbon cycle. Natural sources of carbon dioxide emissions include decomposition, ocean release, and respiration. Natural sinks of carbon dioxide include photosynthesis by terrestrial plants and uptake by the ocean through physicochemical and biological processes.

In layman’s terms, carbon dioxide is a substance that animals breathe out, and a gas that is produced by biomass at high temperatures (burning). Plants, in contrast to animals, absorb carbon dioxide and expel oxygen.

At standard temperature and pressure, carbon dioxide can exist in the atmosphere as a colorless, odorless, and nonflammable gas. It is called solid dry ice.

Carbon dioxide becomes a liquid at pressures above 73 psi. Its critical points are 1060psi and 87.8º F. If the temperature and pressure exceed the critical point, carbon dioxide will become a supercritical fluid with liquid and gas properties.

6 features of supercritical CO2 fluid

  1. In the supercritical state, carbon dioxide fills the container like gas and has the density of a liquid. These properties help it to fully soak the plant biomass material and remove the active ingredients of the plant, so as to achieve the purpose of extraction of active ingredients. Unlike alcohol and hydrogen-based solvent extraction, supercritical CO2 extraction does not leave any residual solvent in the final product.
  2. In addition, supercritical CO2 has a distinct feature that it can be recaptured and recycled in closed-loop operating systems, making them an environmentally friendly production option.
  3. For botanical extraction companies, carbon dioxide is highly efficient at extracting valuable therapeutic compounds from plants. The operator can adjust the temperature, pressure, and flow rate in the system to extract the desired compound.
  4. Compared to steam extraction, supercritical CO2 extraction has higher extraction efficiency, and at the right temperature, pressure and time, it can even fully extract the target extract.
  5. Of course, there is a higher advantage: supercritical CO2 is extracted at close to room temperature so that the composition of the extract will not be destroyed. Terpenes, for example, decompose at high temperatures, but they are well retained in supercritical CO2 fluids at low temperatures and low pressures.

6 Benefits of CO2 extraction

  1. Economy
  2. Full spectrum extraction
  3. No chemical solvents
  4. Non-flammable
  5. Eco-friendly
  6. Multistage separation and extraction

Subcritical and Supercritical CO2 Extraction

Most often we hear about supercritical CO2 extractions, but that’s actually only one method of CO2 extraction. There are two ways of CO2 extraction: supercritical CO2 extraction and subcritical CO2 extraction:

Subcritical CO2 Extraction

Subcritical CO2 extraction happens at temperatures and pressures below CO2’s critical point. The process is longer and less efficient, and the typical yield is smaller.

In subcritical extractions, the pressure is maintained while the temperature is taken below the supercritical threshold, causing it to become a (non-supercritical) liquid. It still maintains some hydrophobic extraction properties, but the lower temperatures protect fragile constituents from denaturing. As a liquid, the CO2’s solvent efficiency lowers but allows extraction technicians to carefully select the compounds like terpenes they want from the biomass.

While it takes much longer to complete runs, this technique is perfect for the extraction of terpenes, particularly because it uses lower temperatures.

Subcritical vs Supercritical CO2

  • Subcritical (low temp, low pressure) CO2 extractions take more time and produce much smaller yields than supercritical, but they retain the essential oils, terpenes, and other sensitive chemicals within the plant.
  • Supercritical is a high-pressure and high-temperature process that damages most terpenes and heat-sensitive chemicals but can extract much larger molecules such as lipids (omega 3 and 6), chlorophyll, and waxes.

Which is better?

Up until recently, supercritical CO2 extraction was the most commonly acknowledged method of CO2 extraction, but as more emphasis is placed on full-spectrum plant products and the role of terpenes in cannabis products, subcritical CO2 extractions have challenged common thought and practice.

The argument is that the medicinal impact of the whole plant is greater than the sum of its parts—or what scientists refer to as the “entourage effect,” a hotly debated topic in the cannabis industry.

Full-spectrum CO2 Total Extract

Truly full-spectrum CO2 hemp extracts include first performing a subcritical extraction, separating the extracted oil, then extracting the same plant material using supercritical pressure, and finally homogenizing both oil extracts into one.

CO2 Extraction Process

CO2 extraction machine
CO2 extraction machine

Supercritical carbon dioxide is a widely used extraction method in the essential oils industry due to it effectively purifies the crude plant material. When CO2 is used in a supercritical state, it allows the producer to always be in control of the process by manipulating its physical properties to isolate certain molecules.

The supercritical CO2 extraction method has many benefits including the ability to produce clean and pure concentrates. It is known for its safety as a solvent since it is non-flammable and has a significantly lower risk of leaving residual solvents in the end product. In fact, it is commonly used in the decaffeination of coffee and the extraction of essential oils from plants.

CO2 does not leave behind any residual solvents, this lack of residual chemicals in the end product is very important since many consumers use these products for medicinal and wellness purposes. Medical users may turn to CO2 extracts primarily for their relative safety and purity.

More importantly, CO2 is known as an efficient solvent in extracting the plant’s temperature-sensitive terpenes. It can create a full-spectrum product that contains the plant’s original flavor and aromatic profile.

9 Steps of CO2 Extraction

Supercritical CO2 extraction takes longer to complete than other methods, due to the continuous fluctuations in temperature and pressure. For example, the extraction of one batch, of plant material can take 1 to2 hours.
  1. Before creating any new CO2 extraction protocol, it is important to consider reasonably expected results. The goal is that all desirable compounds can be extracted from biomass with CO2 fluids. This is very important, CO2 extraction is not a panacea, such as extracting nicotine from tobacco is an impossible task.
  2. Biomass drying, (usually biomass is dried by farms), the moisture content is less than 10%;
  3. Grinding biomass, in general, the particle size of biomass grinding is between 40-80 mesh. It is difficult to extract the extract with too large particles, and it is difficult for the supercritical CO2 fluid to pass through if the particles are too small; (Why do you need to grind?)
  4. In some laboratories, there will be many CO2 extraction subjects, so we must also consider the cleaning of the machine before the formal extraction, so as to prevent other extracts from being mixed in the experiments or production to be carried out. For example, after extracting chili or ginger, pigments, not just grease, will be left in the pipes, extraction containers, and separation containers of the machine, and the cleaning of the machine will be very important.
  5. Grinding the plant material and putting it into the extraction container contains a lot of information in this small step: we need to prevent the crushed biomass from flowing into the CO2 extraction machine, then both ends of the biomass basket must be installed Filter paper, sometimes with additional medical cotton.
  6. The CO2 liquid is forced into the machine by a high-pressure pump, pressurized and heated up to a supercritical state, and enters the extraction vessel, where it meets the plant and breaks the trichomes, causing it to dissolve part of the plant material.
  7. By changing the temperature and pressure, as well as the flow rate, certain molecules will bind to the carbon dioxide, separating them from the plant.
  8. The material is then allowed to flow into a separate vessel through special valves, where pressure and temperature are regulated, where the extract is separated.
  9. After the full extraction process, the extract crude extract is separated and collected while the CO2 is condensed and converted back into a liquid, ready for use again.

How to extract terpenes?

CO2 is known as a tunable solvent. During the extraction process, operators can manipulate the temperature and pressure to turn carbon dioxide into its supercritical state. It is able to extract terpenes under high pressure and low temperatures.

When in the supercritical state, the solvent can pass through the biomass and release the oils contained inside. Many processors may perform multiple runs to remove different compounds at different temperatures and pressures.

Seasoned operators may do an initial run where they remove the terpenes first under a subcritical extraction environment. In the subcritical environment, operators use low pressure and low temperatures to retain the most fragile compounds from the plant.

Then, the operators do a supercritical run with high pressures and high temperatures to remove as many of the target extract as possible.

CO2 may pull out undesirable plant material, which may require additional post-processing to remove the fats, lipids, and waxes from the extract.

FAQ about CO2 extraction

The answers to the most common questions about CO2 extraction.

What is CO2 extraction called?

CO2 extraction, aka Supercritical CO2 extraction or Supercritical CO2 fluid extraction, is a relatively modern technology for the production of lipophilic plant extracts. Lipophilic means the ability of a chemical compound to dissolve in fats, oils, lipids, and some solvents such as hexane or toluene.

  • Is CO2 extraction safe?
  • Is CO2 extraction better than other methods?
  • Is CO2 extraction better than butane?
  • Is CO2 extraction better than cold pressed?
  • How much is a CO2 extractor?
  • How Do You Extract CBD with CO2?
  • How is CO2 extracted at home?
  • Is CO2 extraction healthy?
  • Why is CO2 extraction better than steam distillation?
  • Does CO2 extraction remove terpenes?
  • Is CO2 extraction full spectrum?
  • Is distillate better than CO2?


  2. CO2 Extraction: Supercritical vs. Subcritical

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