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The Practical Science of Cannabis Extraction

Practical Science of Extraction

Extraction Science from our In-House Experts

In this chapter of The Ultimate Guide to Cannabis Extraction, we’ll explore the practical science of cannabis and hemp extraction and cannabinoid manufacturing. We’ve asked our in-house experts for their top practical science factoids to help extractors and processors of all knowledge levels, from beginners, to intermediates and even experts will learn something new.

Chapter Contents:

  1. Biomass: Everything Starts with the Plant
    1. Three Different Types of Trichomes
    2. Major and Minor Cannabinoids
    3. Cannabinoid Development
  2. The Practical Science of the Extraction Process
    1. Ideal Milling Sizes
    2. Chilling Solvent Pre-Extraction
    3. Extraction Methods: Solvent vs. Solventless
    4. Temperatures: Cold or “Cryogenic” vs. Room Temperature
  3. Post-Extraction Refinement and Processing
    1. Types of Filtration
    2. Solvent Evaporation
    3. Decarboxylation
    4. Distillation (Short Path)
    5. Chromatography and Remediation
  4. Latest Developments in Extraction Science and Technology
    1. Sonication (Sound Waves) Extraction
    2. Membrane De-Solvation Filtration
    3. Microwave Assisted Extraction

Biomass: Everything Starts with the Plant

When it comes to producing a high quality cannabis derivatives from flower to hash all the way  through to 99% pure isolates, one truth remains eternal: it all starts with the wonderfully complex cannabis plant.

Three Different Types of Trichomes

Trichomes are the tiny, hair-like outgrowths that cover cannabis and hemp flower, making the flower look like it has been dusted in oily sugar or sand. Trichomes produce the valuable terpenes and cannabinoids like THC and CBD—and minor cannabinoids such as CBG and CBN—that drive cannabis and hemp markets.

Most of us have seen the oil-rich trichome of a cannabis or hemp plant but did you know that there are actually three different types of trichomes?

While this fact may not be hugely important to someone wanting to make high purity concentrates, to a grower or a hash maker this can be a crucial detail to look for because it may affect your extraction and refinement process and ultimately, your final end-product.

The three different types of trichomes are listed below (from smallest to largest, from least abundant to most abundant):

  1. Bulbous trichomes (10-30 micrometers)
  2. Capitate-Sessile trichomes (25-100 micrometers)
  3. Capitate-Stalked trichomes (50-500 micrometers *most abundant)

The Capitate-Stalked trichomes are those which are visible to the eye and are recognizable as the iconic oil-rich cannabis or hemp trichome. Bulbous trichomes and Capitate-Sessile trichomes are both invisible to the naked eye but do produce cannabinoids. These trichomes are frequently found on less-desirable parts of the plant such as leaves and stalks but are still a source of valuable cannabinoids.

The sought-after Capitate-Stalked trichomes increase in density during the flowering stages of the plant, and are by far the most abundant. They produce the highest quantity of desirable cannabinoids and terpenes, and which are ideal for the production of cannabinoid derivatives.

However, a smart extractor will try to use as much of their biomass as possible, and will therefore not overlook the Bulbous and Capitate-Sessile trichomes as a source of cannabinoids.

Major and Minor Cannabinoids

The Major Cannabinoids: THC and CBD

This wonderfully complex plant produces an incredible spectrum of chemistry in every flower, and THC and CBD are the most commonly produced of all the cannabinoids. They’re the ‘rockstars’ responsible for many of the therapeutic benefits enjoyed by cannabis and hemp consumers. Other cannabinoids, terpenes, and flavonoids can have a significant impact on their effects, but they’re the most sought after and well known. Consequently, THC and CBD are the best studied of the cannabinoids. All of this has led to their distinction as “major” cannabinoids.

Tetrahydrocannabinol (THC)

THC is the most well-known of all the phytocannabinoids. Specifically the neutral form, Δ9-THC. This is the compound that causes the classic feelings of euphoria or “stoned” feeling associated with consuming cannabis. It’s also where many of the therapeutic benefits—from pain-killing to cancer-fighting—come from. Most of those benefits appear to stem from its ability to activate both CB1 and CB2 receptors in the brain and other parts of the body. The concentration of THC in the flowering tops of the plant can reach 30% or higher.

Cannabidiol (CBD)

CBD is the most common phytocannabinoid produced by non-THC varieties of cannabis (aka industrial hemp), and is increasingly being bred to express high levels in plants that have had THC bred out of them.

CBD does not bind to the two receptors most commonly studied in relationship to cannabis, the CB1 and CB2 receptors. Instead it interacts or catalyzes with over 65 different targets in the body, from opioid receptors to the receptor that causes capsaicin to burn. Most studies to do with CBD are in their early days yet and we have a long way to go before we fully understand its impact on our bodies.

CBD is often described as being “non-psychoactive” but this is not exactly true. CBD is non-intoxicating—it doesn’t bind to the receptor that is associated with the feeling of being high. It does, however, bind to the serotonin receptor 5-HT1A. Its activation of that receptor is thought to be responsible for its anti-anxiety or calming qualities. Any compound that affects the mind, like quelling anxiety, is technically psychoactive.

The Minor Cannabinoids

The minor cannabinoids are every other cannabinoid that is found in cannabis and hemp besides THC and CBD. Well over 100 cannabinoids have been identified to date, and a handful of new ones are identified every year. Although we know next to nothing about most of them, there is enormous interest—from extractors and also from researchers—in discovering which one could be the “next CBD”.

The minor cannabinoids are every other cannabinoid that is found in cannabis besides THC and CBD. Well over 100+ cannabinoids have been identified to date, and a handful of new ones are identified every year. Although we know next to nothing about most of them, there is enormous interest in discovering which one could be the next big cannabinoid.

The minor cannabinoids have not been studied very extensively (yet) but some very early studies are showing that some minor cannabinoids are good for general wellbeing and others are limited to very specific medical applications.

Cannabimovone (CBM), for example, is a vanishingly rare cannabinoid that shows promise in sensitizing diabetes patients to insulin. And that’s just about all we know about it. If you do find a rare cannabinoid in one of your extracts, let people know! Researchers could just be your perfect market.

Cannabigerol (CBG) is the non-acidic form of cannabigerolic acid (CBGA), the foundational compound or precursor from which all other cannabinoids (THC, CBD, etc.) are developed. Extracting CBG efficiently begins while the plant is still growing. Because CBGA is the first cannabinoid to show up in young hemp or cannabis plants, there is a very slim window of opportunity to harvest the plants and ensure a financially viable yield.  If you’re thinking of extracting CBG, the most important factor to ensure quality CBG end-product is the strain of the plant you start out with. Ideally you should start with a high-CBG strain to ensure that your extraction process is viable from a business point of view.

If you’re interested in extracting minor cannabinoids from plant material, make sure that there’s a market demand for your end-product and be prepared to go through an enormous amount of biomass or source a strain that is high in that particular cannabinoid.

Cannabinoid Development

Phytocannabinoids go through several chemical stages as they develop and age. Those changes can result in compounds that have radically different effects in the body—and important consideration for any extractor interested in targeting a specific therapeutic benefit.

  1. Acidic cannabinoids (aka “raw” cannabinoids): Most cannabinoids found in the raw flower are in their acidic forms, although sunlight and time can change some of them into their neutral forms. All cannabinoids start out in their acidic forms—that’s why eating a raw flower won’t get you high, but smoking it will. The THC (tetrahydrocannabinol) you inhale once heated starts out as THCA (tetrahydrocannabinolic acid).
  2. Neutral cannabinoids (aka “active” cannabinoids): Arriving at this stage means that a tiny piece of the acidic cannabinoid has broken off due to heat, leaving the remaining compound chemically ‘neutral’. This is the stage most people aim for if they’re interested in the intoxicating effects of THC, or the therapeutic effects of CBD.
  3. Oxidized cannabinoids (aka “aged” cannabinoids): ‘Oxidized’, or aged, cannabinoids are degraded forms of cannabinoids that develop as the compound changes shape over time. You’ll find higher levels of these cannabinoids, like CBN, in older plant material.

The different stages of cannabinoids have different therapeutic values.

For example, THCA is thought to have some anti-inflammatory effects though it’s mechanism of action is unknown. The neutral form, Δ9-THC, is the most widely studied cannabinoid and has therapeutic potential across the board. Its slightly smaller size means it interacts with some targets in the body more easily.

The degraded form, CBN, is ⅙ the potency of THC and thought to share some, but not all, of the therapeutic properties of Δ9-THC.

The Practical Science of the Extraction Process

As we move on from the plant to the extraction process, the science—and art—of extracting cannabinoids becomes more complex and more reliant on the specific end-product derivative that you’re seeking to produce. However, there are several scientific processes are that universally utilized in the cannabis extraction and refinement process.

Ideal Biomass Milling Sizes

How finely you mill your biomass is going to play a large role in the speed and efficiency of your extraction process because the finer you mill your biomass, the more surface area is exposed to your solvent the quicker the ethanol or CO2 will dissolve and separate out your desired cannabinoids.

But there are also compounds within the biomass that we definitely do not want to extract and want to remain in the plant material. Many of these compounds are found within the cells of the plants, and may cause a lot of unnecessary and additional refining if we were to mill the biomass too small or at a similar size to fine powder for example, because it may mean that the cell wall is broken and the undesirable compounds are released into the solvent.

This is the main reason why there is an optimal window for mill size. While this size may differ for different end-products and plant strains, we recommend somewhere approximately around 1/4” particle size.

Chilling Solvent Pre-Extraction

Ethanol extraction can be performed under room or cold temperatures depending on your desired end-product. However, typically large scale ethanol extraction is performed most efficiently by pre-chilling the alcohol solution down to as low as -40°C to reduce post-extraction processes. The cooling of the ethanol is typically performed in an inline chiller such as the DC-40 Direct Inline Chiller.

This first step of the cold ethanol extraction process is performed to increase the efficiency of the solvent’s ability to separate cannabinoids and other desirable compounds from the biomass thereby reducing the number of post-extraction processes.

Of course, warm or room-temperature ethanol extraction can also be performed but it requires additional steps to ensure a high-quality end-product. It is for this reason that cold temperature ethanol extraction is more commonly used in large-scale ethanol extraction labs.

When the ethanol solution is chilled down to the desired temperature, it’s then ready for the next stage of the process: to be added into an extraction system such as the CUP Series (Centrifuge Utility Platform) system along with milled high quality cannabis or hemp biomass.

Extraction Methods: Solvent vs. Solventless

The widespread use of solvents to extract cannabinoids has been popular for many years in today’s cannabis and hemp industry. Solvents are popular for a good reason: they’re easy to scale, efficient at producing the desired end-product, and relatively safe—as long as you’re in compliance with local, state, and federal laws.

However, there is also a growing number of consumers who are now seeking cannabinoid derivatives that are produced via a “solvent-less” method. This is because this method is perceived as being safer or more ‘natural’ because they’re derived using a more ‘natural’ method. Whether that is true or not remains a contentious topic of endless discussion within the industry.

And if we’re going to be scientifically correct, solventless extraction is in fact, not technically “extraction” at all! But in fact, it’s actually “mechanical separation” because we’re not ‘extracting’ the cannabinoids, we’re simply separating them. The cannabinoid is not extracted from the plant material via a chemical process but separated from it through a physical force. A good analogy would be that separation is like knocking apples off a tree, whereas extraction would be like crushing those apples to make apple juice.

But an experienced extractor will never say that one solvent is better than the other because it all depends on your desired end-product. The better question is: what are you trying to produce? Always start with the end-product and work your way back from there. For example, if you’re seeking to make full spectrum crafted hash then water separation is ideal. However, if you’re seeking to make CBD isolates at scale, then CO2 is a better choice.

Solvents and solventless methods have their advantages and disadvantages, and the method right for you and your lab will be most accurately determined by what you’re trying to produce.

Temperatures: Cold or “Cryogenic” vs. Room Temperature

Knowing the true definition of technical and scientific terms is critical to ensure a successful result. When it comes to the chilled ethanol extraction process you may have heard the term “cryogenic extraction” used to describe what is simply—and technically—simply cold extraction.

When extracting cannabinoids using ethanol, one of the critical factors at play is temperature. Too warm and you run the risk of undesirable compounds being released. Too cold and your efficiency and profitability may be reduced significantly. For these reasons cold ethanol extraction is often the preferable method with an optimal temperature range ideally between -30˚C (-22˚F) and -40˚C (-40˚F).

Note, ethanol extraction may also be performed at ambient or room temperature but you’ll need to perform additional post-processing steps to ensure a similar result incurring extra time and cost. This is the main reason why cannabis and hemp extraction on a large scale prefers the use of chilled ethanol to extract cannabinoids.

While the term ‘cryogenic ethanol extraction’ has widespread colloquial use in the cannabis industry most people are, in fact, referring to simply cold extraction. The reasons for this misnomer are lost in the mists of ancient extractor lore but the term ‘cryogenic’ is a scientific one that refers to temperatures much lower than those we would use for cold or room temperature cannabis extraction.

In fact, the term cryogenic refers to temperatures between -153°C (-243.4°F) and absolute zero or -273°C (-523.4°F). These extremely low temperatures are much too cold for ethanol extraction because ethanol’s freezing point is much higher at -114.1°C (-173.5°F) therefore rendering it useless as an extraction solvent.

Post-Extraction Refinement and Processing

The post-extraction stage of cannabis processing involves further refining and increases cannabinoid concentration and potency, while also eliminating undesirable compounds—and most importantly—adds value to the final end-product.

Types of Filtration: Particulate/Adsorbent and Winterization

There are two main types of cannabis oil filtration:

  1. Particulate/Adsorbent Filtration: Particulate Filtration (a.k.a. “polishing“) removes suspended particulates/adsorbents, and also enables the most efficient use of your chosen solvent. The end result of filtration is a lighter-colored cannabinoid-saturated solution that is ready to go into the evaporator. Particulate filtration, wax removal, and color remediation is achieved via the use of a filtration skid. With regards to ethanol extraction, a four-stage filtration skid is used in the post-processing stage to clean up any unwanted plant particles, pigments (carotenoids, chlorophyll, etc.), and lipids from your tincture. An impregnated lenticular filter can be used with any filtration media you require, such as activated carbon, magnesium silicate, diatomaceous earth, or zeolite for color remediation.
  1. Winterization: Winterization removes the fats, waxes, lipids from crude oil. Achieved by mixing crude oil with ethanol and freezing the solution to allow undesirable compounds to solidify, the solution is then filtered to separate or winterize waxes, lipids, and fats. Note, winterization can be skipped for cold ethanol extraction because chilled ethanol prevents undesirable compounds from being extracted in the first place. The reason that other solvents such as hydrocarbons need winterization is that butane unlike ethanol, is non-polar and therefore dissolves excessive plant material, which is removed via winterization. Removing the ethanol from the solution is the final step.

Solvent Evaporation: Roto Evaporation vs. Falling Film Evaporation

Once you have saturated your ethanol solvent with cannabinoids, the next step is to separate the solvent out from the tincture via evaporation. There are two main ways to perform this step:

  1. Roto Evaporation is a popular tool for the removal of solvents because it is easy to scale for both startup and large scale extraction labs. It works by removing the solvent under a vacuum and via a rotating temperature-controlled vessel that is partially submerged in a water bath. The spherical distilling flask is filled to about half its volume with cannabinoid-rich tincture. The water is heated to about 30-40°C and the condenser temperature is set to -10°C to 0°C. The distillation flask is then rotated at 150-200 rpm producing a thin film on the inside surface of the glass cylinder to perform solvent evaporation.
  2. In comparison, a Falling Film Evaporation (FFE) machine works in a similar way but has increased efficiencies over roto evaporation. An FFE system maintains a higher evaporation rate significantly increasing the throughput of crude oil production, eliminating the need for multiple large rotary evaporator systems. This saves time and lab space in your extraction facility. Less contact with high heat alongside speed of processing makes the FFE-Series an essential part of the processing line. Short residence time is ideal for heat sensitive botanical compounds and decreases the risk of burning oil.

Decarboxylation

While we all know that the two most well-known plant cannabinoids are THC (tetrahydrocannabinol) and CBD (cannabidiol) they are hardly present in their desired form in the unprocessed raw plant where they are typically known as either THCa or CBDa. These cannabinoids are in their acidic or “raw” forms and they must be decarboxylated in order to obtain their neutral or “active” forms. To transform these into THC and CBD decarboxylation (or “decarbing”) is required.

Decarboxylation is a post-extraction process that involves using heat to transform the chemical structure of the acidic cannabinoids changes to a neutral (non-acid) form of THC or CBD.

Decarboxylation works via a chemical reaction achieved by heating cannabinoids to a temperature at which they release a carboxyl group (a carbon atom double-bonded to an oxygen atom), hence the term “de-carboxyl-ation” and resulting in quality cannabis end product—either THC or CBD or a mixture of both.

Distillation (Short Path)

Distillation is very common process in the extraction of the major cannabinoids CBD and THC. In its essence, distillation is used to separate and to “distil” desired cannabis compounds. The process works via differences in the conditions (heat, pressure) required to change the phase of components of the mixture.

Short path distillation works effectively to individually isolate and concentrate the major and minor cannabinoids such as CBD, THC, CBG, etc. and of course, terpenes. If we perform distillation correctly, the result will be distillates of around 99% pure. Short path distillation delivers clean and clear distillates by separating out and concentrating cannabis and hemp oil into three distinct categories:

  1. Cannabinoids – by controlling temperature and pressure points specific desired cannabinoids are extracted individually.
  2. Terpenoids and Flavonoids – each with their unique boiling points are collected or “pulled” individually. These may then be reintroduced or “recombined” to the final product, these are known as “recombined derivatives”.
  3. Contaminants and undesirables – removal of undesirable by-products like residual solvents, molds, and pesticides.

Terpenes are known for being quite fragile and may be destroyed during the distillation process if care is not taken. Terpenes boil at different temperatures than cannabinoids so terpenes extra care is needed to preserve them and ‘pull’ them at the right point in the process. Short path distillation does allow for the pulling of terpenes using vacuum pressure with the intention of saving them for later in the process or adding to other end-products.

Regarding the distillation of Cannabis oils in a lab setting, a workflow involving multiple cuts to remove several fractions of terpenes from decarboxylated crude oil ensures the absolute deepest vacuum possible during the cannabinoid pass. These terpenes must be removed as their highly volatile nature creates vapor pressure, which in turn increases the volume of gas that must be displaced by the pump to achieve a desirable distillation pressure for the desired oils.

After this step, preliminary fractions often referred to as the, “tails” will be distilled. This fraction is usually of lower quality and is separated from the main fraction known as the, “heart” fraction of the distillation which will yield the more pristinely colored and pure distillate.

The end portions of the distillation will also present with subpar quality oil that is separated and is also referred to as, “tails” fractions. The resulting lower-quality products are often used as the base for edible or topical products as opposed to the highest quality distillates that will be found in vape pens.

Chromatography and Remediation

Remediation is the process of removing certain undesirable compounds from cannabis or hemp distillate. This process is frequently used to remove THC from hemp-derived CBD products to ensure they contain ≤0.3% THC as per federal mandate so that they can be sold in all 50 states of the US. Other undesirable compounds that can be removed during this process are microbial contaminants and molds.

Remediation is typically performed via a High Pressure Liquid Chromatography (HPLC) device. How does it work? The analyte (a substance whose chemical constituents are to be identified and measured) is carried down a column at pressure while dissolved in a solution referred to as the mobile phase. The various different components each interact slightly differently as the pass across the solid components of the column known as the stationary phase and are sorted accordingly. The end of the column features a photo-diode reader that gathers spectral data that a chemist can interpret to determine how one sample compares to a bassline sample. Most analytical platforms operate in a similar way and vary in sensitivity and types of compounds they specialize in detecting.

How does HPLC help your cannabis extraction facility?

There are a few critical ways that HPLC can help your extraction lab be profitable.

  1. Plant Sourcing: Biomass Age and Quality: When you’re sourcing plant material to be processed through your lab, it’s crucial to be aware of the quality of the biomass because it directly correlates to the quality of the output or end product. The competitive advantage of HPLC testing before purchasing sourced biomass is obvious. Using the technology to perform a micro-extraction on questionable biomass or crude oil, and then analyzing the results against an ideal standard can provide a better picture of what cannabinoids are present in the sample—and in what quantity—before committing to purchase large quantities. Such knowledge could make all the difference in the decision to buy suspect crude oil or biomass from a source that could leave you with great buyer’s remorse. Checking the ratio of decarboxylated cannabinoid forms vs. their acidic variants can reveal the age of the biomass. The carboxyl groups present on the cannabinoids in their most fresh-off-the-plant form will degrade over time as they are exposed to any number of elements including heat, UV, and atmospheric oxygen.
  2. Remediation and Compound Removal: HPLC is also a vital tool in monitoring extraction efficiencies as lab averages. A pre- and post-extraction analysis of the biomass being processed can reveal the percentage of botanical compound removal—information that provides crucial data for the optimization of a manufacturing operation, helps a lab get the most out of their material, and ultimately affects bottom line results. The importance of this efficiency is paramount because it can raise your cannabis extraction and processing facility head and shoulders above the competition in a volatile industry that fluctuates regularly. While an HPLC is certainly the most widely applicable instrument one might find uses for in cannabis analytics, there are other platforms that have extraordinary applications that are certainly worth mentioning.

It is certain that all HPLC instrumentation will soon become commonplace at any manufacturing facility. It’s only a matter of time before the industry catches up to the pharmaceutical industry in its quality assurance practices. Science has always had a place in cannabis and embracing it will only enable those in the business to better their craft and grow alongside the industry.

Latest Developments in Extraction Science and Technology

So what’s next on the horizon for cannabis extraction science? As the industry is further decriminalized across the US and the world, cannabinoid extraction science and innovation is expanding at a rapid rate. By nature, cannabis extractors are inventors, tinkering quietly away in their labs seeking to refine and streamline extraction methods and techniques to produce the highest quality derivatives.

Sonication (Sound Waves) Extraction

One of the latest innovations to arise in the last few years is the use of sound waves otherwise known as “sonication” or “ultra-sonic extraction” to extract cannabinoids. The process works via a probe being that emits alternating high and low-pressure sound waves (up to 20,000 cycles per second!) to create fluctuations that break down cell walls and release desired compounds.

The benefits of sonication include:

  • Faster, easy to scale and replicate to ensure a consistent end-product.
  • More affordable to buy than other solvents—making it ideal for startups.
  • Safer because of its non-thermal nature; best results are achieved at a temperature between 0-60°C.
  • May also be used alongside with almost any other traditional solvent to increase efficiency, output, and profitability.
  • Solvents serve as a suitable environment rather than the actual extraction catalyst; resulting in a purer, toxin-free end product.

Ultimately, the advantage of sonication is that it’s very energy-efficient, clean, natural, and can be tweaked and replicated to produce cannabis and hemp extracts of desired potency and quality.

Membrane De-Solvation Filtration

Organic Solvent Nanofiltration (OSN) is a new method of extraction that uses multiple filtration steps to purify and concentrate cannabis derivatives. The core benefit of this extraction method is that simplifies the entire process by combining various steps into the one step. With OSN you can perform winterization, filtration, evaporation, and even decolorization (e.g. chlorophyll) and removal of other impurities while still producing CBD and THC concentrates of up to 90% potency.

Crude ethanol extract may be filtered via the use of a nanofiltration membrane with pores that prevent large molecules from passing through. The end result is decolorized, concentrated extract in fewer steps than typical ethanol extraction. The use of OSN has the potential to simplify and increase the profitability of the cannabis extraction process.

Microwave Assisted Extraction

Another new method of extraction involves the use of microwaves—just like you use in your own kitchen to extract cannabinoids via microwave assisted extraction (MAE). But how do microwaves work when applied to cannabis or hemp biomass?

The microwaves deliver instant heat but do so selectively. This means that certain compounds dissipate and absorb energy differently to others. MAE a pressure-driven process with instantaneous and focused heating of the cannabis biomass and can be applied on a larger scale while maintaining the full-spectrum profile of the plant. This makes MAE ideal for full-spectrum cannabis derivatives that retain their original plant strain profile and flavor. MAE has the ability to extract up to 95% of the active compounds from cannabis biomass at an industrial scale.

Other benefits included increased speed of processing at scale while still producing a high potency end product. Also, MAE can work at a continuous flow at atmospheric pressure allowing for large volumes of biomass to be processed in less time. MAE also eliminates additional steps required in most extraction methods, such as decarboxylation and winterization, which adds additional time to the extraction process.