The Whole Plant Extraction Blog

Botanical Extraction Methods and Post-Processing Techniques

Fritz Chess


Until cannabis was outlawed in 1937, anyone could walk into their local apothecary and buy various types of cannabis tinctures. Very little is known about these antique preparations except for the interesting fact that many of them were manufactured by pharmaceutical companies like Eli Lilly, Merck, and Squibb. The empty bottles that remain are now considered valuable collectors items.

There is no information available regarding the cannabinoid or terpene content of these heirloom strains, nor is there any records of how these preparations were made other than they were ethanol based and were presumably extracted with the same ethanol. Cannabinoid molecules were not even identified until the 1960's by an Israeli scientist named Raphael Mechoulam so modern analytical data was an impossibility. 

Most likely, the earliest cannabis concentrates were made by simply stirring cannabis in a warm solution of ethanol, then straining out the extracted plant material and bottling the liquid. Resins could be made by cooking the solution until all the ethanol had evaporated off. Old timers may remember the greenish black Jamaican hash oil from the 1970's and 80's which was made by this method.

In the early 1970's, author and inventor, D.J. Gold published "Cannabis Alchemy". This book was the forerunner to modern cannabis extraction and is still relevant today. He also manufactured and sold the first cannabis extractors which were sold in High Times and called the "Iso2". The Iso2 was short lived due to the fact the DEA forced him to pull the product because he was blatantly advertising it as a way to make an illegal product.

Fast forward to 1995. Eden Labs came out with the "Coldfinger" extractors which were designed to be an improvement on the soxhlet extractor, a tool used by organic chemists since the 1920's. The following year Eden Labs introduced its first supercritical co2 extractor to the market and around this time, "Psilocybe Fanaticus", an Olympia, WA-based company, introduced butane extraction. The modern cannabis extraction industry was born.

The first refinement technique used on heavy oleoresin extractions was carbon filtration. Ethanol extractions, and early methods of butane extraction, yielded oils that were greenish black due to the chlorophyll that extracted along with the oil. Eden Labs discovered that if the oil was dissolved in ethanol and run through an activated carbon filter, the chlorophyll could be removed which yielded a golden yellow oil that was more potent and tasted better.

Soon after, hash oil makers figured out that if the carbon filtered ethanol solutions were put in a freezer overnight, waxes would settle to the bottom of the vessel which could then be filtered out.  This method known as "winterization" gave cannabis the oil the proper viscosity, along with certain additives like cannabis derived terpenes, to work in vape pens- a very large segment of the modern botanical medicine industry.


This brings us to the present day.  There are now many levels and methods of plant extract refinement which will be briefly explained here. The categories are: steam distilling, cold ethanol extraction, supercritical CO2 fractionation, molecular distillation, and preparative chromatography.


Steam distilling is an ancient technique of extracting light terpenes or essential oils from plants.  The technique involves passing steam through plant material and then liquefying the steam on a condenser.  The essential oils are then floating on the surface of the recondensed water.  These light oils constitute the fragrance and taste portion of the plant and are responsible for the "entourage effect" that in combination with the cannabinoids, distinguishes one strain from another. Recent developments in the science of terpenes and the positive effects on health and wellbeing underscores the importance of essential oils.  The aromatherapy industry is obviously benefitting from these studies.


Extracting cannabis with cold ethanol, -20C or lower, has been discovered to pull cannabinoids and terpenes without extracting waxes and chlorophyll.  This effectively eliminates the older refinement techniques of using carbon and winterizing.  The only downside is yields tend to be lower so a warm ethanol extraction is often employed after the cold extraction to get remaining constituents. More about Cold Snap / Cold Ethanol 


Conventional CO2 fractionation uses 2-4 separators to capture the extract after the co2 is passed through the the vessel filled with plant material.  Pressure and temperature cascade downwards from the first to last separator resulting in different compounds of varying molecular weights dropping out in different vessels.  This generally means that waxes fall out in the first separator.  Heavy oils in the second separator, and lighter oils in any successive vessels.  This technique works well for many botanicals but is generally unreliable with cannabis although an alternative method using this design can often result in nearly pure THCA, (95%) dropping out in the first separator which is certainly of value.

Another alternative method of extracting terpenes with supercritical CO2 is quite dependable.  This method uses time instead of pressure and temperature to fractionate.  Terpenes are almost instantly soluble in CO2 whereas cannabinoids other constituents take some time to begin dissolving in solution.  This allows the machine operator to run the extractor for 15-45 minutes and collect the terpenes in relatively pure form before continuing the extraction to get the cannabinoids remaining constituents. More about Supercritical CO2 Extraction


This method is used to isolate terpenes and cannabinoids out of a first stage or raw, bulk extraction.  There are a couple different designs for doing this, but they all involve using a combination of stirring, high heat, and deep vacuum to get the cannabinoid containing heavy oils to vaporize and re-liquefy on a warm condenser for capture in a distillate receiver.  This method can yield oils with purity in the 95% range. 


This the final frontier of botanical oil refinement.This method separates all the different components of an extract into their molecular parts and is referred to as “purification”.  All the various terpenes and cannabinoids can be isolated and dropped into individual vessels.  This allows for the creation of standardized formulations that can be made from any starting materials as long as that material contains some percentage of the desired ingredients. 

The typical methodology here involves dissolving the extract in a combination of solvents and then pumping the solution through a column packed with an absorbent material.  The various compounds lodge themselves in different spots in the column allowing for later recovery.

Preparative chromatography is widely used in the pharmaceutical industry for making pure drug compounds so it should be assumed that future medical cannabis products will employ this method.  It's also highly likely that some future recreational products will use preparative chromatography so they can offer the exact same product at any time or place.


The importance of pure plant extracts cannot be overemphasized.  Entire industries have been created and/or legitimized by healthful extraction methodologies. However, while one industry recognizes its responsibility in providing safe consumer products and social impact, others focus on monetary gain at the expense of human prosperity and environmental sustainability. Creating a paradigm shift in botanical extraction has taken Eden 20 plus years of passionate R&D in the development of a myriad of plant based products, applying that to system engineering and messaging these ideals for the health of the world. We continue to work toward the spread of health focused extraction methods across industries. Help us help you. The future is all of ours to share. Lets get it right. Only together, can we make these shifts reality.

March 30, 2018