There are many techniques that are applied to separate all the different components of cannabis. Using these extraction techniques, the many different parts of cannabis – all containing different chemicals – can be isolated. This helps in bringing out the more desirable compounds present in cannabis so that they can be used for a wide variety of applications.
There are over 113 cannabinoids that can be separated from the cannabis plant. Of these, the more popular ones are cannabidiol (CBD) and tetrahydrocannabinol (THC). In addition to these, there are many cannabis compounds that include more than one of these cannabinoids and have been referred to as whole plant extracts.
The process isn’t simple. It is an exact science and cannot be likened to cooking. In addition to specific knowledge about the plant, this process requires laboratory equipment and proper safety measures. The process needs to be carried out with great care so that the final product is safe for use by human beings.
Supercritical CO2 extraction is one of the many techniques applied to the extraction of cannabis. Before delving into more details about this form of extraction, it is important to briefly understand the other techniques that are popularly used for cannabis extraction.
Types of Cannabis Extraction Methods
There are many different methods that are commonly used for cannabis extraction. They differ in the type of solvent used, the laboratory conditions, equipment used and so on. Some of the more popular cannabis extraction methods are mentioned below.
In this technique, the plant material is first soaked in a solvent, most commonly ethanol, before it is removed to filter the liquid.
Once the filtration process is carried out, the alcohol is removed using evaporation. It is important to get rid of the chlorophyll in the plant extract as it can be dissolved by the solvents, giving the remaining product a bitter taste.
The process is carried out under strict monitoring as ethanol – or whichever form of alcohol is used – is extremely flammable. One of the reasons why this method is popular is because the final extract doesn’t have any toxic residual chemicals.
Butane or Propane Extraction
In this method of extraction, solvents like butane or propane are used. If the former is being used, cannabis and liquid butane is placed in a controlled system (both heated and pressurized) where evaporation removes the butane solvent by first turning it into vapor. There are some safety concerns when this method is being used.
For example, butane is highly flammable even in its gaseous phase. If adequate care isn’t taken with regards to the temperature, there can be an explosion. Also, if some butane or propane is left in the extract, it can be very harmful if consumed by humans.
These are more basic techniques when it comes to cannabis extraction, as they don’t utilize any solvents for extracting some of the desirable plant components. Instead, the kief is separated from the cannabis by simply grinding the product and running it through sieves.
Another basic extract of cannabis is hash, also known as hashish. This involves the separation of the trichomes from the rest of the plant material.
This is done because the most amount of desirable compounds are actually in this part. Finally, rosin is another solvent-free extract of cannabis that has become popular over the past few years.
The final technique of extraction to be discussed here, which will be discussed in greater detail throughout the article, is CO2 extractions. Instead of using forms of alcohol, as in the case of other solvent-based extraction techniques, this uses carbon dioxide.
This process of extraction is preferred to others as the yield is higher and less of the desirable compounds are lost through this process. The main issue with this form of extraction is the cost of putting together all the equipment that this technique requires.
What Exactly Is Supercritical CO2?
There are specialized extraction machines that are able to freeze CO2 gas and compress it into a “supercritical” state. In this state, the CO2 takes a cold liquid form.
In order to get the CO2 to this supercritical stage, the compound – which acts as a gas at room temperature and pressure – is turned into liquid after placing it in a machine with the pressure increased to 75 pounds per square inch and the temperature under -69 degrees Fahrenheit.
After the CO2 is in liquid form, the temperature and pressure are increased to make the fluid reach the supercritical stage.
As CO2 is referred to as a “tunable solvent” it can help in the creation of a wide variety of end products, each at a different phase of the process.
As the solubility of CO2 differs at different pressures, the supercritical CO2 allows for the extraction of different compounds at different levels. These levels are the result of small adjustments in the nature of CO2.
This process ensures that you don’t end up with a combination of the different extracts. In addition to this, it is gentler than the other commonly used solvents that can affect the quality of the final product.
Why Is CO2 Used?
Using solvents like ethanol, butane or propane can affect the final product that you achieve at the end of the extraction. With carbon dioxide, however, this is not a problem that you will face. CO2 is known for giving the purest quality of compounds without the presence of any harmful toxins that could be left behind in the final product if any of the other solvents were used for extraction.
In addition to this, industries are investing in the commercial processing abilities of CO2 as it works out to be cheaper in the long run because of the relatively safe processing and low number of post-processing steps. When other solvents are used, the post-processing takes a lot of time and effort.
CO2 works in a more efficient manner. While there is a good amount of initial investment required for the equipment, CO2 extractions work out to be inexpensive in the long run. Most importantly, CO2 is considered as a solvent that can be tuned to fit your requirements. It works to separate the different constituents of cannabis in the process of extraction.
Finally, CO2 acts like a sanitizing agent, which will keep the resulting cannabis compounds clean. It can also be used for extracting other plants like hops or organic crops.
Difference between Supercritical and Subcritical CO2 Extraction
The prerequisites for the CO2 to be considered supercritical have been mentioned earlier. While extractions using supercritical CO2 are the more popular ones, it isn’t the only method to carry out extractions using CO2. The other type of CO2 extraction utilizes subcritical CO2, which will be discussed in greater detail below.
Supercritical CO2 Extractions
The more popular type of CO2 extraction is the one that uses supercritical CO2. Here, the pressure is very high and the temperature is kept at 88 degrees Fahrenheit. These high pressure and high temperature conditions affect the process of extraction by damaging most of the terpenes and heat sensitive chemicals that are a part of the plant matrix.
This method, however, is popular as it is faster and can extract the larger molecules of lipids, waxes, as well as the chlorophyll from the plant.
Subcritical CO2 Extractions
From the supercritical stage, if the temperature and pressure are both lowered, the CO2 will reach a subcritical stage. Extractions can be carried out even in this stage but the amount of time that it takes will increase by quite a bit. In addition to this, the yield is also lesser than supercritical extractions. The advantage of subcritical CO2 extractions, however, is that they hold on to the more sensitive chemicals in the plant, in addition to terpenes and essential oils.
There are also mid-critical extractions that take place between the range of supercritical and subcritical but they will not be discussed here.
How Is Supercritical CO2 Used for Cannabis Extraction?
The process starts with liquid CO2, which has to be converted to its supercritical form for the best results. In order to facilitate this, the temperature of the CO2 is increased using a heater and the pressure is increased using a compressor. The increase in pressure and temperature converts the liquid CO2 into its supercritical form, which is then passed through good quality cannabis.
This cannabis is stored in an extractor and on coming in contact with the CO2, all the trichomes, terpene oils and waxes are removed from the plant material. The solution – with all the desirable compounds of cannabis – is moved through a separator. In this step of the process, compounds like trichomes, terpenes and others are pulled apart to be placed in a collection vessel.
The supercritical CO2 moves through a specialized condenser, which turns it into a liquid again. This liquid moves back into the storage tank where the process was started so that the cycle can be repeated again and again.
The best part about using supercritical CO2 for this method of extraction is that you don’t have to worry about any remaining CO2 that could have been left behind in the final extract that you have collected. Once the pressure is removed, the liquid CO2 converts into the gaseous form and evaporates without leaving a trace.
This means that you can get rid of any residual CO2 by just leaving the extract at room temperature for a brief amount of time. The CO2, in its gaseous form, will just evaporate into the atmosphere. If the supercritical CO2 extraction machine is more sophisticated – as is the case with industrial-level machinery – it will be able to recapture the residual CO2 and reuse it at the end of the extraction process.
CO2 System Considerations for Cannabis Extraction
Supercritical CO2 extraction is one of the best methods of extracting chemical compounds from the plant matrix. In order to conduct the entire process with greater efficiency, the machinery that is being used is of critical importance. The most important factors that control this efficiency are the pressure conditions, the temperature considerations and maintenance of these factors throughout the process.
First, the maximum pressure rating will be able to ensure that there is enough pressure in the vessel to push the CO2 into its supercritical format. Pressure is only the first out of two important considerations to keep the CO2 in its supercritical form.
The second factor is temperature. This can be divided into two distinct verticals. First, you will have to ensure that the temperature of the carbon dioxide can be measured. Here, it is important that the temperature of the gas is being monitored and not the temperature of the vessel containing it.
After this, there is a need for high wattage heaters to be present within the machine so that the temperature – which was measured earlier – can be increased or decreased according to the needs of the extraction.
Advantages of Supercritical CO2 Extraction Across Fields
The use of supercritical CO2 extraction isn’t just limited to cannabis. It can be applied to a wide variety of products as it is quite cheap and environment friendly, because of its recyclable nature. As opposed to the other harmful solvents like butane, propane and ethanol, supercritical CO2 will not have a detrimental effect on safety of the entire exercise.
Some of the other processes that utilize supercritical CO2 are the creation of high-quality vanilla, coffee, tea, fruit extracts, nut aromas and extracts, omega-3 oils, fragrances and perfumes, hop extraction for beer, algae based oil extractions and so on.
The process of cannabis extraction can be quite complicated and should not be attempted by people who do not have experience in the field. The more sophisticated techniques, like supercritical CO2 extraction, require a great amount of raw materials – like liquid CO2 – and a sound technological system, which cannot be accessed if you are not professionally involved in this field. While the process can sound complicated, it is the best way to extract the different compounds of cannabis effectively.