CO2 Extraction

December 11, 2010

in MMJ Articles

What is Co2 extraction?

CO2 extraction is the process of removing the beneficial compounds from herbal material. A mixture of heat (or cold), solvents, pressure and time are typically employed in the quest for the gold hidden within nature’s herbal treasures. Herbs have a variety of health promoting compounds that can support health and well being if they can be consumed in sufficient concentrations.

This is an important issue: if you don’t consume the “active” dose of the herbal material, it doesn’t convey it’s health promoting properties. The study and practice of extraction has arisen to solve this problem–by extracting these valuable substances without a. degrading them and b. in high enough concentrations, these life-enhancing chemicals can work wonders within the human body.

Forms of extraction

Herbs have been an important part of human life from the time early humans began eating them. Over time, humans have experimented with a variety of herbal extraction methods including cooking them with water, smoking them, soaking them in alcohol, cooking them with butter or oil, pressing the oil out, distilling them, extracting them with chemicals and pressure extracting them with a variety of gases.

Cup of Tea

Among the very first methods of extraction is the simple cup of tea. Heat is one of the key properties of herbal extraction, and water is very good solvent for extracting certain compounds. Thus, the method of water extraction was born.

Soak and Press (Tincture)

As humans evolved they began soaking their herbs in alcohol. Alcohol is also a powerful solvent. One of the main draw backs to this method is that tinctures tend to have low concentrations of the desired compounds.

Cooking in Butter or Oil

This method works well for fat soluble materials. However, for health promoting purposes, this delivery method is less than desirable. Add something simple about why its health promoting

Cold Press

This method employes a large press to press out the desired compounds. This method can work well for certain compounds, but tends to highly impractical for most herbs.

Distillation (concentrated liquid extract)

Distillation can be extremely powerful because it can use low heat to achieve an extremely concentrated final product. This (The) main strength of this method is also the main draw back–it extracts a broad spectrum of beneficial compounds.

Chemical Extraction

A variety of chemicals can be used for extraction, however this is typically highly undesirable as a result of the harmful nature of the chemicals used.  Impossible to get all of the solvent chemical out of the end product

Super Critical CO2

A process that uses a pressure system for circulating pure CO2 through herbal material. This method is extremely powerful in that is the purest method of extraction and among the most precise.

Why is CO2 the Extraction Method of Choice?

CO2 extraction is simply the purest form of extraction–all the stuff you want and none of the stuff you don’t. In fact, it is the only extraction method accepted by the exceptionally stringent European Union and it leaves no trace of solvent residue in the end product.

Super-critical Fluid Extraction (SFE) is the process of separating one component (the extract) from another (the matrix) using super-critical fluids as the extracting solvent. Extraction is usually from a solid matrix, but can also be from liquids. SFE can be used as a sample preparation step for analytical purposes, or on a larger scale to either strip unwanted material from a product (e.g. decaffeinate) or collect a desired product (e.g. essential oils). Carbon dioxide (CO2) is the most used super-critical fluid, sometimes modified by co-solvents such as ethanol or methanol. Extraction conditions for super-critical CO2 are above the critical temperature of 31°C and critical pressure of 74 bar.

The advantages of super-critical fluid extraction (compared with liquid extraction) are that it is relatively rapid because of the low viscosity and high diffusivity associated with super-critical fluids. The extraction can be selective to some extent by controlling the density of the medium and the extracted material is easily recovered by simply depressurizing, allowing the super-critical fluid to return to gas phase and evaporate leaving no or little solvent residues. Carbon dioxide is the most common super-critical solvent. It is used on a large scale for the decaffeinate of green coffee beans, the extraction of hops for beer production, and the production of essential oils and pharmaceutical products from plants.


In 1822, Baron Charles Cagniard de la Tour discovered the critical point of a substance in his famous cannon barrel experiments. Listening to discontinuities in the sound of a rolling flint ball in a sealed cannon filled with fluids at various temperatures, he observed the critical temperature. Above this temperature, the densities of the liquid and gas phases become equal and the distinction between them disappears, resulting in a single super-critical fluid phase.

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