The Difference Between Supercritical CO2 and Ethanol Extraction
Posted on November 9, 2020 by Paige Pesko
Multiple methods are available for extracting CBD from hemp plants. When it comes to industrial-scale CBD production, the two most popular methods are supercritical CO2 extraction and ethanol extraction. Knowing the difference between supercritical CO2 and ethanol extraction is essential for your company to decide which method will fit your capabilities, budget, and needs.
What Is Extraction?
In order to understand the difference between supercritical CO2 and ethanol extraction, you must review the logistics of extraction. Extraction is the process of removing valuable cannabinol from the hemp plant. But oil cannot be removed from the plant through purely mechanical processes such as squeezing oil from olives or juice from lemons. Facilities need solvents to remove the oil from the plant matrix and further processing to filter the oil from any remaining plant matter.
Supercritical CO2 Extraction
What Does “Supercritical” Mean?
CO2 (carbon dioxide) is a common gas that naturally exists in the Earth’s atmosphere. However, in the right circumstances, CO2 can take a partly liquid form. To accomplish this, facilities place CO2 in specialized machinery that puts it under immense pressure and heat. This state, when the CO2 is neither liquid nor gas, is called supercritical, and it makes for an effective extraction solvent.
For this process, three tanks are put in a closed-looped system. CO2 is put in one tank, and the plant matter, called trim, is put in another. The third tank remains empty. The CO2 is put under heat and pressure until it reaches its supercritical state, and then it’s allowed to pass through the trim. Because supercritical CO2 has both liquid and gaseous properties, it can dissolve the plant matter as it passes through it. The pressure in the plant matter tank is much higher than the pressure in the empty chamber, so the CBD and cannabis mixture flows into this chamber. The CBD, which has a different density than the CO2, separates from it.
From here, the CBD undergoes further processing. Emulsification occurs, in which CBD is combined with pure alcohol on a molecular level and then crystallized. From here, the substance is filtered, the alcohol is distilled from it, and what remains is quality CBD.
One of the main draws of supercritical CO2 extraction is the fact that, as a solvent, it’s not flammable like ethanol is. This gives operators a greater feeling of ease, especially since they’re working with high temperatures. CO2 is also less toxic than ethanol and leaves behind less residue in the oil. The CO2 also acts as a cleaning agent, killing off mildew and bacteria, making for purer CBD products.
After the CO2 passes through the trim, operators can cycle it back into the original tank to be reused in the process. CO2 itself is also considered a more environmentally safe solvent with a smaller carbon footprint. This gives CO2 extraction an eco-friendly edge over some of the other methods.
Because of the complex, scientific process of changing CO2 from a gas to a supercritical state, facilities need to purchase highly specialized equipment. Because the machinery is so specialized, it also requires facilities to give employees a greater deal of specialized training. This severely drives up the initial cost of CO2 extraction when compared to other methods.
The CO2 process takes longer than solvent-based processes. Along with this, the batches cannot be processed continuously like other extraction methods can. The machinery must be completely cleaned and sterilized between uses. This cuts down on how much CBD a facility can reasonably produce in a day.
The ethanol extraction process begins with chilling a large quantity of ethyl alcohol. The plants are loaded into a centrifuge and washed in the chilled alcohol. This process separates the cannabinoids from the waxes, fats, and other plant matter. The solution then goes through a four-stage filtration system to remove any remaining plant matter, including chlorophyll. From here, what remains undergoes a process known as short-path distillation, in which the CBD distillate is separated from the ethanol. The ethanol is then processed and prepared to be reused in future extraction cycles.
Smaller Initial Cost
As we stated, CO2 extraction units are significantly more expensive to acquire. Even when compared to other solvent-based extraction methods such as those that use butane and propane, ethanol extraction systems are the most cost-effective systems available. They also require far less specialized training, making it easier to get operators ready for production.
Larger Production Rates
Because of the simplicity of the ethanol extraction process, it’s far easier to extract more CBD at a quicker rate. Batches can be produced one after another without as much need to prepare the systems again. Beyond that, the ethanol doesn’t have to undergo as intense of a preparation process as CO2 does, cutting down production time for the process. This allows facilities to produce more CBD in a day.
Most solvents used for CBD extraction are flammable, and ethanol is no exception, though it is far less flammable than other extraction solvents. This forces facilities to take greater fire safety precautions while extracting CBD and storing materials.
In most cases, ethanol is a polar solvent, meaning that on a molecular level it has a slightly negative charge. Because of this, water-soluble materials in the plant, such as chlorophyll, will often remain after being washed in the solvent. This is why plant matter has to undergo the additional step of filtration during ethanol extraction, which it does not have to go through during CO2 extraction.
Making the Choice
Choosing between supercritical CO2 and ethanol extraction comes down to the capabilities of your company. For companies that want the taste of CBD extracted by CO2 and don’t mind a higher cost and lower yield, CO2 extraction is a better choice. However, if you want to get into production more quickly and at a lower cost and produce a greater quantity of CBD, ethanol extraction is the choice for you.