Ethanol – the Versatile Cannabis Solvent
Ethanol has long been popular as the solvent of choice for cannabis and hemp extraction, and there are several very good reasons for this. Not only is ethanol easy to use but it’s also very versatile in that it can deliver an enormous diversity of desired end-products. This versatility makes it an ideal solvent for both small-scale cannabis ‘connoisseur’ processors (who may be targeting a wide array of full-spectrum cannabinoids and terpenes), and also for larger processors seeking to isolate specific cannabinoids such as THC and CBD at scale.
1. Ethanol Extraction Has Been Used for Thousands of Years
Ethanol (AKA alcohol) when used as a solvent, is one of the oldest forms of botanical extraction and has played this role for thousands of years. In fact, alcohol is one of the oldest recreational drugs used by humans and is relatively easy to manufacture. It has been a prevalent part of society for several millennia. The earliest evidence of alcohol consumption in the archeological record was pushed back 13,000 years when researchers found residue of ancient wheat-and-barley based beer in a cave in modern-day Israel.
The term ‘spirits’ is believed to come from the idea that when ancient peoples would soak high-proof alcohol solutions (wine or mead) with other plants and herbs, the alcohol would take on the properties, or the ’spirit’ of the plant or herb.
With the use of ethanol as a solvent on one hand being so primitive, and on the other hand having developed a multitude of technological breakthroughs over the past few thousand years, ethanol’s versatility places it in a uniquely good position for any type of botanical extract and none more so than cannabis and hemp extraction.
2. Ethanol is Safe and Easy to Use
When directly compared to the other two most popular solvents used to extract cannabis—CO2 and hydrocarbon—the ethanol extraction process is generally safer and easier:
- Ethanol is less explosive and toxic, and therefore largely considered safer to operate than hydrocarbon extraction systems.
- Not only must CO2 extraction systems operate under high pressure, creating another potential hazard, but the equipment cost is much higher and its throughput (how much biomass it can extract in a given period of time or batch) is much lower when compared to ethanol extraction.
- While all extraction processes have their respective intricacies, ethanol is largely considered to be one of the easiest forms of cannabis extraction to learn therefore making it easier and faster to train operators. This simplicity is primarily because an ethanol extraction process does not require the solvent to change phases, which in the case of CO2 and hydrocarbons, involves the manipulation of pressure in sealed systems requiring more in-depth training to ensure a successful result.
3. “Like Dissolves Like” (Solubility) Makes Ethanol Highly Efficient
Understanding solubility (the ability to, and the quantity of, a particular substance that will dissolve in another specific substance) and the mechanisms that underlie it, is perhaps the most crucial piece of information dictating the success or failure of designing an extraction SOP.
What does “Like Dissolves Like” mean?
This is perhaps the most useful and common piece of knowledge readily known about solubility, but what does it mean? When we look at solubility at a molecular level, there are generally two different categories of molecules: polar and non-polar.
- Polar having positively + and negatively – charged ends
- Non-polar having roughly no, or zero charge, or is balanced
It is best to view these categories as a spectrum. On one end we have a molecule that has absolutely zero charge. And on the other we have a molecule that looks like a straight line that is completely polarized with a positive charge on one end and a negative charge on the other. And in between these two extremes, with varying degrees of polarity, are all the molecules of the world.
- Polar compounds will mix, or dissolve, with other polar compounds
- Non-polar compounds will mix, or dissolve, with other non-polar compounds
So, this is what we mean when we say “Like Dissolves Like”.
The most common non-polar molecules we encounter are lipids and fats. Like cooking and motor oils. The most common polar molecule we encounter is water.
Hence you will also find these categories referred to as:
- Water-soluble (polar)
- Fat-soluble (non-polar)
So, what is ethanol, polar or non-polar?
4. Ethanol is both Polar and Non-Polar
Ethanol can be both polar and non-polar, and this is one of the reasons it is so useful and herein lies its versatility.
Ethane (C2H6), is an alkane or hydrocarbon molecule composed of 2 carbons and 6 hydrogens. It is very non-polar.
Ethanol on the other hand (C2H6O) is an alcohol and is classified as such because of its oxygen atom containing alcohol, or hydroxyl, (OH) group on the end, which causes a slightly negative charge. This is because oxygen atoms are more electronegative. They have a higher affinity for the electrons, which are negatively charged, and which tend to ‘hang around’ the oxygen atom more than the carbons and hydrogens. This results in a partial negative charge.
Hence, H2O is quite a polar molecule. The oxygen being slightly negative (-) and the hydrogens being slightly positive (+).
What this all boils down to is this; ethanol is in a uniquely good position to dissolve most slightly non-polar and slightly polar molecules, which turns out to be a lot of different molecules!
And primarily because it’s a non-viscous liquid at atmospheric pressure and ambient temperatures, it can do the job of dissolving (dissolution) quickly and easily.
5. Ethanol is Ideal for Cannabis and Hemp Oil Extraction
Now how does all of this coalesce to make ethanol a great solvent for extracting botanicals, most specifically for hemp and cannabis extraction? The target compounds (the molecules we are attempting to extract and separate from the rest) typically include cannabinoids like THC and CBD as well as terpene compounds. These are all fat soluble.
Which is ideal because ethanol will dissolve them quite well.
However, for those extractors and manufacturers whose goal is to isolate and extract these compounds exclusively, ethanol can present a challenge.
Because ethanol also picks up polar, or water-soluble compounds, it will draw out other compounds we don’t necessarily want like chlorophyll. Conversely, if you’re intending to make ingestible, full-spectrum, end-products this ability can be an advantage.
However, herein lies the flexibility of ethanol making it extremely suitable for extracting botanical compounds: the polarity of ethanol can be slightly modulated / adjusted simply by changing temperature.
The colder the ethanol, the higher its affinity for fat soluble compounds, and therefore a more efficient extraction of cannabinoids and terpenes.
And if extraction is performed with warm or room temperature ethanol however, the ethanol will not only grab the cannabinoids, but also a wider spectrum of terpenes as well as water soluble compounds.
A versatile solvent indeed!
Ethanol’s versatility places it in a uniquely good position for any type of botanical extract and none more so than cannabis and hemp extraction because it…
May dissolve most slightly non-polar and slightly polar compounds.
Has an affinity for polarity because it can be adjusted via temperature.
Is a non-viscous liquid at atmospheric pressure, so it extracts quickly.
Boils at relatively low temperatures which allows for the efficient recapture of the ethanol and the subsequent separation of the extracted compounds.
Is safe, easy to operate with, and is easily produced.