Make supercritical CO2 fluid extraction simple and easy to understand

What is supercritical CO2 extraction?

Among several supercritical fluid (abbreviated SCF) technologies, the earliest developed, most researched and industrialized product technology is undoubtedly the supercritical fluid extraction (abbreviated SFE) technology.

Supercritical fluid extraction (SFE) is the process of separating one component (the extractant) from another (the matrix) using supercritical fluids as the extracting solvent.

Supercritical CO2 extraction (SCFE) is used particularly in the food, beverage, cosmetics and pharmaceutical industry for extracting natural substances, aromas, fats, oils, waxes, polymers, enzymes and colourants in their supercritical physical state.

CO2 is a natural and environmentally-friendly solvent which has advantages over synthetic and harmful media such as n-hexane when it comes to sustainability.

Supercritical CO2 coffee essential oil extraction machine
supercritical CO2 extraction machine

Why use carbon dioxide extraction?

Carbon dioxide is the most common compound used in high-pressure extraction. It boasts a number of benefits compared to other solvents used for botanical extraction.

For starters, carbon dioxide is a non-toxic substance that is readily available commercially for lower costs than other chemical alternatives. In addition, carbon dioxide is environmentally safe, straightforward to work with, and it creates a superior product typically free of any by-products or residue. Temperature, time, flow rate, and pressure can be manipulated to enable the precise extraction of specific plant compounds.

Principle of CO2 extraction

Supercritical extraction uses a supercritical fluid as the separation medium (extractant), and uses the fluid to have a highly enhanced dissolving ability in a supercritical state to achieve effective extraction of certain components (solutes) in the raw material, and then pass the temperature and The continuous adjustment of the pressure can reduce the density of the extractant, that is, reduce its solubility to the solute, so as to achieve high-efficiency separation of specific components in the raw material.

CO2 Extraction Process
CO2 Extraction Process Diagram

What is supercritical fluid extraction
What is supercritical fluid extraction

Advantages of CO2 Extraction: Key Takeaway

Because supercritical fluid has excellent mass transfer characteristics of gas and solvation ability equivalent to liquid solvents, supercritical extraction using it as a separation medium is considered to integrate the two unit operations of distillation and liquid-liquid extraction to a certain extent.
The advantages of this form a unique separation technology.The basis of the theory is the phase equilibrium relationship of the fluid mixture in the supercritical state, which operates in the mass transfer process.
Purer
CO2 extracted material is free of residual solvents.
Nothing is left behind once the extraction is over since the carbon dioxide bubbles away, leaving no trace in the end product.
Safer
Comparing CO2 cannabis extraction to butane or propane? Don’t forget to include the facility costs for processing with a compressed flammable gas.
CO2 extraction is often used in the extraction of plant essential oils

Extraction process

The most commonly used supercritical fluid in the supercritical extraction process is SC-CO2, and the products obtained by supercritical CO2 are mostly a mixture of volatile oils, greases, alcohols, ethers, esters, resins and other lipophilic chemical components; 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. Some systems have the option to be automated, so the producer does not need to be present during the batch. Supercritical CO2 extraction takes longer to complete than other methods, due to the continuous fluctuations in temperature and pressure. For example, the extraction of 20 lbs. of plant material can take 4 to6 hours.

To perform an extraction, the plant material must be ground and placed into an extraction vessel. CO2 gas undergoes high temperature and pressure. A pump then forces supercritical 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 pressure and temperature. By changing the temperature and pressure as well as flow rate, certain molecules will bond to CO2, allowing them to be separated from the plant. Many systems will reroute 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.

Star Anise Oil Supercritical CO2 Extraction Machine
300L Star Anise Oil Supercritical CO2 Extraction Machine
Co-solvent pump
Co-solvent pump

Cosolvent

For substances with greater polarity (such as flavonoids, saponins, alkaloids, etc.), a small amount of polar entrainer (or co-solvent, modifier, co-solvent) is often added to increase the CO2 polarity. The ability to dissolve sexual substances.

The addition of a small amount of co-solvents (such as water, methanol, ethanol, acetone, ethyl acetate, etc.) can not only increase the density of the supercritical fluid, but more importantly, it can form a new strong intermolecular force with some solute molecules , Thereby improving the selectivity of the process.

Further reading

5 advantages of CO2 extraction of essential oils

5 advantages of CO2 extraction of essential oils

There are innumerable advantages of CO2 extracted essential oils whereby they have gained huge popularity.
Some of them are listed below:

  • 100% Pure & Natural: For the purpose of obtaining the purest form of CO2 grade essential oils, the extraction process is carried out at a lower temperature by using carbon dioxide which is not only nontoxic but odorless too.
  • Free from Leftover Residues: There is no serious concern about leftover residues in CO2 grade essential oils since only supercritical carbon dioxide is utilized for their extraction process under the ambient temperature.
  • Therapeutic Properties: The extraction process of CO2 possesses the great ability to obtain the maximum level of therapeutic components from the botanical materials like plants and herbs.
  • Pleasurable Natural Aroma: CO2 grade essential oils are widely cherished for their natural fragrance which resembles the original plant material as they are extracted without solvent & heat.
  • Free From Adulteration: CO2 extraction method is the perfect choice for the preparation of 100% natural essential oils as they are not extracted from any petroleum derivatives-based products like hexane or butane.

Differences between: Cold-pressed method, CO2 extraction method, Hydro-distillation method and Solvent extraction method.

Cold Pressed methodCO2 Extraction methodHydro-Distillation methodSolvent extraction method
Utilized for the extraction of Carrier and Base Oils.Utilized for the extraction of premium-quality Essential Oils.Utilized for the extraction of Attars.Utilized for the extraction of Absolutes.
Usually, oily nuts and fruits are taken for the extraction of Carrier & Base Oils.The aromatic parts of the plants like Leaves, Flowers, Stems, etc. are used for the extraction of Essential Oils.Floral parts, petals and leaves are taken from the plants & herbs for the extraction of Attars.Any desired part of the plant can be utilized for the extraction of Absolutes.
Without any involvement of carrier, only compression of botanical material works to obtain Carrier & Base Oil.CO2 is used as a carrier to obtain the oil from the parts of the plant.Water is used as a carrier for the purpose of extracting the oil content from the fragrant parts of plants.Hexane, ethanol, methanol or petroleum ether is used for the extraction of oil content from botanical materials.
Mechanical pressure and usual temperature are used to obtain Carrier or Base Oils.For the extraction of Essential Oils, the only high pressure is required. CO2 extraction process occurs at moderate temperature.In order to obtain the final product, high heat is used to evaporate the water content from the mixture.Only mild heat is used to enhance the evaporation rate of the solvent. Also, cooling may be required at last.

Is CO2 extraction safe?

When done by trained professionals in properly equipped labs, CO2 is among the safest extraction techniques available. From an environmental and health perspective, it is less toxic than petroleum-based hydrocarbons such as butane or propane.

CO2 boasts another feature that also adds to its safety. Any residual CO2 which remains in the extract evaporates, so there is no residual solvent left in the product.

Is CO2 extraction better than other methods?

The relative safety and non-toxicity of CO2 extraction generally renders it a more appealing option than other extraction methods. The versatility of the technology also offers an edge over other methods. Modification of the temperature and pressure allows different terpenes, and other compounds to be targeted, allowing the extraction process to be customized for different formulations. Most importantly, the nature of the CO2 extraction process itself tends to result in a superior product.

Benefits of Supercritical CO2 Extraction

By using supercritical CO2, the producer has total control over the procedure, CO2 can be recycled, making this method more environmentally friendly compared to others. Further, the Federal Drug Administration (FDA) has labeled CO2 safe for industrial extractions. CO2 acts as a cleaning agent, so microbial bacteria, molds, and mildews are killed during the process. The yield using supercritical CO2 is higher than other extraction methods; however, the yield and quality of product can easily be varied by adjusting the physical properties.
If there is residue on the extract, it will evaporate, as CO2 is a gas at room temperature. Extracts obtained from supercritical CO2 extraction are appealing to the food and beverage and medical industries, because it is guaranteed there is no residual solvent present on the product. Because there is no residual solvent on the product, the extract will be purer than many solvent-based extraction methods. Additionally, the plant is not subjected to extreme temperatures, so it does not experience degradation as it does during other extraction methods.

How Does CO2 Extraction Work?

While terms like “supercritical” can sound pretty complex and hard to grasp, the CO2 extraction is actually a pretty simple and straightforward process. There are two basic steps in the carbon dioxide extraction method.

extractor of supercritical CO2 extraction machine
extractor of supercritical CO2 extraction machine

Steps to CO2 Extraction

First, the ground plant solids (Our recommended particle size is 60-80 mesh) are placed in the extraction chamber.

Pressurize liquid CO2 to a supercritical state and into the chamber, where thanks to its properties, CO2 acts as a solvent and dissolves the oils while capturing the essential active compounds at the same time and separates compounds such as terpenes.

In the second step, the supercritical fluid is moved into a “separation vessel,” where heat and pressure encourage the active compounds to separate from the carbon dioxide, where it becomes an immiscible fluid thanks to temperature and pressure gradients. The final step includes the extraction of CO2 by letting it stabilize back to its gaseous state, this enables it to restabilize as a gas and flow back into the CO2 tank, leaving behind amber-colored cannabis oil.

Bear in mind; this is a rather oversimplified version of the extraction process as there are many more nuances involved.

What’s the difference between subcritical and supercritical CO2 extraction?

CO2 extraction is available in two forms: supercritical CO2 extraction and subcritical CO2 extraction. They’re similar extraction methods with two key differences: temperature and pressure.

Supercritical CO2 extraction

CO2 reaches a supercritical temperature at slightly above room temperature, which means it can be converted to a liquid, allowing the safe extraction of volatile active compounds that may be degraded by heat. Supercritical fluid extraction (SFE) utilizes CO2 in this state where it exhibits both gas and liquid properties. In this supercritical phase, it moves through the plant material like a gas but dissolves trichomes like a liquid.

The compound-rich solvent is then delivered into a vessel which lowers the pressure and temperature, separating the active compounds and terpenes.

Subcritical CO2 extraction

Subcritical CO2 extraction involves a similar process but with a lower temperature and less pressure.

Supercritical CO2 extraction is the most common CO2 extraction technique used for cannabis because it offers a higher yield more rapidly.

Is CO2 extraction better than cold pressed?

COLD-PRESSED

Cold-pressed oil is obtained through pressing and grinding fruit or seeds with the use of stainless steel presses.

The raw plant material is placed between horizontal plates which are drawn together by a rotating screw (the ‘expeller’), and the oil is squeezed out.

Despite the name, a certain amount of heat is produced during the process due to friction, averaging at about 40˚C. To be marketed as cold-pressed, the temperature must stay below a rather toasty 49˚C.

Just like if we were subjected to these temperatures, delicate ingredients can end up less than ‘fresh’ and many of their therapeutic properties are lost.

CO2 EXTRACTION VS COLD-PRESSED

CO2 extraction is best because oxygen-free environments and low temperatures are particularly important when extracting fragile oils like Rosehip.

By keeping temperatures low and extracting all the ‘active’ components, we’re able to preserve and protect the complete botanical, skin-loving properties of the Rosehip.

This process delivers twice the regenerative sterols and five times more of those carotenoids than your average Rosehip seed oil. It also means it lasts four times longer in your bathroom cabinet!

This includes the incredible natural colour and smell. You only have to see how orange, concentrated and herbaceously-scented Rosehip BioRegenerate is to witness CO2 extracts at their best!

CO2 extraction also leaves absolutely no solvent residues, so the final oil is impeccably pure. The low temperature and lack of waste streams/emissions make it an extremely environmentally friendly process, too!

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Parts identification drawing of supercritical carbon dioxide extraction machine

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Entrainer system of supercritical CO2 extraction machine

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Entrainer system of supercritical CO2 extraction machine

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