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 ethanol extracts meet state and federal guidelines. They mentioned that even CO2 extracts typically go through a winterization process which is performed by using ethanol, so in the end, CO2 extracts will also use ethanol at some point.


Per the FDA ethanol as a solvent is GRAS (generally recognized as safe) as long as the residual ethanol in the finished product is below 5000 parts per million. Some states in the USA have established lower legal limits for the permitted amount of residual ethanol.

For example, California allows a maximum of 1000ppm of ethanol in cannabis products for inhalation and a maximum of 5000ppm in other ingestible products. For ingestible products like tinctures and gummies, a trace amount of ethanol is considered safe. For products that are meant to be inhaled like concentrates and vape liquids, the potential dangers of inhaling ethanol in trace amounts is still relatively unknown.


Hydrocarbon Extraction

Use of Hydrocarbon extraction to make cannabis concentrates started when cannabis was broadly illegal and products like BHO (Butane Hash Oil) were popularized in the underground cannabis world. In part, this was because butane extraction could be performed at home using minimal equipment to produce high potency extracts, but in truth hydrocarbon extraction at home is dangerous. There have been many incidents of explosions and poisoning related to amateurs making and using hydrocarbon extracts over the years.

The process of hydrocarbon extraction is similar to CO2 extraction where the solvent passes through the plant matter, dissolving beneficial plant compounds and separating them from the plant fibers. Then the butane is separated leaving behind a concentrated oil, which can be further refined if desired. Butane extraction does pose the risk of chemical residue in the final product, with regulations in some areas allowing up to 5000ppm of residue.

These days, hydrocarbon extraction on a commercial/industrial scale appears to be on its way out, as more environmentally friendly and non-toxic options like CO2 extraction are preferred by consumers.


Crude/Raw Extracts

The first step of extraction as described above, regardless of method used, yields what is known as crude or raw extract. This crude extract is usually very thick, dark in color and contains waxes, lipids, chlorophyll in addition to terpenes and cannabinoids. Cannabinoid content at this stage can range from 30%-50% by weight.


Decarboxylation

While this might sound like a big word, decarboxylation or “Decarbing” is a relatively simple process. When the hemp flowers are harvested, most of the cannabinoids are in their acidic form. For example, CBD in a freshly harvested plant is actually in its acidic form known as CBDA or Cannbidiolic Acid. Over time through natural chemical processes of light and heat, the acidic form of cannabinoids (CBDA/CBGA/THCA) slowly turn into the active form (CBD/CBG/THC).


We can speed up this process by applying heat at a specific temperature for a set amount of time to hemp flowers or extracts. The same process applies to other cannabinoids like THC. When smoking cannabis, the raw buds contain mostly THCA which is converted to THC when heated and smoked or vaped. Decarboxylation can be performed before extraction with the raw flowers or after extraction with the crude extract.


Winterization

Once a raw extract is obtained, the processor can choose to use it in the raw form or to further refine the oil.

The next step in the refinement process of supercritical extracts is to winterize the raw extract. This is a process used to remove fats and waxes. Winterization is achieved by blending the extract with ethanol and then placing the mixture in the freezer for up to 24 hours. Once the plant waxes and fats are crystallized, the whole batch is run through a filter to separate the fats and waxes. Finally, the ethanol is evaporated out and reclaimed for reuse. The result is a purified oil that is free of plant matter resulting in improved appearance and taste.


Distillate

If the processor wishes to further refine the winterized extract, the next step is called short path distillation or fractional distillation. In this process, the winterized oil is distilled (heated and evaporated) – the processor can choose to keep all the cannabinoids together resulting in a full spectrum distillate or choose to separate individual cannabinoids and terpenes. Fractional distillation is achieved using specialized equipment that heats up the extract and allows for the controlled separation of individual terpenes and cannabinoids based on their boiling point. For example THC distills at 315F, CBD evaporates at 356F, CBN evaporates at 365F and so on. By controlling the temperature, a skilled operator can successfully separate individual cannabinoids and terpenes.


Isolate

CBD Isolate is almost 100% pure CBD in a powder form. CBD Isolate is used in a variety of different CBD products as it is inexpensive, contains no THC and it is easier to control potency. If a CBD isolate is desired, the CBD distillate is mixed with a solvent, heated and then cooled to produce a 99%+ pure powder form of CBD.

At Welliva we do not use or advocate the use of CBD Isolates for a number of reasons – to learn more about Isolates vs Full Spectrum CBD please check out our BLOG post on Full Spectrum vs Isolate.


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