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Hemp Extraction Methods

Updated: Mar 28, 2021


If you are thinking about starting a CBD business or just want to be a better educated consumer, this article will provide you with essential knowledge about different types of CBD extracts and how they are made.


Hemp flowers and potential contaminants

First, female hemp plants are grown until the end of their flowering cycle, producing flowers rich in cannabinoids. These plants are then harvested and dried before they can be processed. The quality and cannabinoid profile of the raw material directly affects the end product.


Hemp and cannabis plants are known to be efficient bio-accumulators of pesticides and heavy metals. This is a fancy way of saying that they pick up chemicals from the environment and concentrate them in the plant alongside the beneficial compounds we want like cannabinoids, terpenes, etc.


For this reason, starting with organically grown hemp flowers is key to producing high quality extract that is safe for human consumption. Equally important is proper testing of the extracts to ensure they are free from pesticides, solvents, heavy metals and microbial contamination.


Extraction Methods

The next step after harvesting and drying the hemp is to extract the cannabinoids from the dried plant matter.


There are several types of extraction methods used today including CO2 extraction, Rosin pressing, Lipid extraction, hydrocarbon extraction (butane/propane) and ethanol (high proof alcohol) extraction. We will look at each of these separately.


CO2 extraction involves using specialized equipment to add pressurized Carbon Dioxide to the dried hemp flower. CO2 extraction is the most expensive way to process hemp as it requires expensive equipment, but is also considered one of the cleanest extraction methods as there is typically no solvent residue in the final product. This process allows the beneficial compounds from the plant to dissolve in the CO2 and separate from the plant fibers. Once this process is complete, the CO2 is then separated from the cannabis oil by adjusting the pressure and the CO2 can be then be recycled and reused.


Subcritical vs Supercritical CO2 extraction

You may have heard the terms Subcritical and Supercritical. In a nutshell, Subcritical extraction occurs when the CO2 remains in a liquid form using lower temperature and pressure, and Supercritical extraction occurs at a higher temperature and pressure where the CO2 becomes a supercritical liquid, with properties of both a liquid and a gas.

Subcritical extraction results in less solvent power which makes for a lower yield. At the same time, subcritical extraction has the advantage of producing a cleaner extract that preserves volatile compounds like terpenes, while at the same time excluding undesirable plant matter like plant waxes and chlorophyll.


In contrast, Supercritical extraction allows the CO2 gas to better penetrate the plant matter resulting in a higher yield, although the supercritical extract will contain more undesirable plant matter and will usually cause the loss of volatile compounds like terpenes. Some processors using Supercritical CO2 extraction use "terpene traps" which allow the collection of terpenes as they evaporate. These terpenes can then be added back to the extracts or to tinctures during the formulation process. Supercritical extracts also will require further processing like winterization to remove waxes, lipids and chlorophyll, while subcritical extracts will not require this process.


Rosin

Rosin is a relatively new form of extraction and first became popular as a DIY hack shared widely on internet cannabis forums. Making Rosin involves extracting the beneficial compounds from cannabis or hemp flowers using only heat and pressure. Rosin extracts are considered to be one of the highest quality concentrates available as they don’t require solvents of any kind and have superior flavor due to high terpene content. Original Rosin pressing was done at home using easily available tools like hair curlers and parchment paper. Today there are commercial Rosin presses that can process large quantities of dried flower. At this time, producing Rosin at scale presents a challenge as it is a time consuming process involving repetitive manual labor but in our opinion, Rosin produces one of the cleanest, highest quality extracts available today.


Lipid Extraction

Lipid extraction is where the dried flowers are gently heated in a plant fat like coconut or olive oil. Care must be taken to control the temperature as cannabinoids can degrade and evaporate at higher temperatures. Pressure can also be added to speed up the process and increase extraction efficiency. The plant compounds like cannabinoids, terpenes, plant fats and antioxidants readily dissolve in the oil, and can then be easily separated from the plant fiber. An advantage of lipid extraction is that no solvents are required.


Ethanol Extraction

Ethanol extraction is an ancient method which involves using high proof food grade alcohol as a solvent. Humans have been using ethanol to create herbal tinctures since alcohol was first distilled. A common ethanol tincture is vanilla extract which is made by soaking vanilla beans in alcohol.


With hemp ethanol extraction, the dried hemp is mixed with ethanol and the active ingredients from the dried flowers dissolve in the alcohol. Then the alcohol is separated from the leftover plant matter and evaporated to leave behind a concentrated extract. This can be done in a cold or hot process and processing times vary based on the equipment used and the desired end result. Longer soaking times result in more plant matter dissolving in the ethanol while shorter soaking times result in an extract with less plant matter.

Advantages of ethanol extraction include a lower initial cost than CO2 extraction and the ability to quickly scale the volume of material processed.


Residual ethanol

While there is some concern about residual ethanol, when the process is performed correctly, there is very little if any residual ethanol. Putting the crude ethanol extract through a distillation process will further refine the extract and all but eliminate any residual ethanol. We spoke with a certified organic hemp processor in Maine recently who explained that ethanol extracts are indeed safe and that testing for residual solvents will ensure that