Ethanol: The Great Botanical Extraction Solvent
Long before modern botanical extraction labs, alcohol has been used for centuries as a solvent for botanical extraction. Alcohol has stood the test of time as an effective solvent that dissolves a wide range of plant compounds, is generally safe when properly handled, and can be easily recovered and reused. These same properties are what make alcohol one of the most practical and accessible solvents for botanical extraction today, bridging traditional herbal practices with modern extraction techniques.
Because of ethanol’s unique properties that make it ideal for extraction, it plays a key role in complementing aqueous extraction for dual extractions. Ethanol plays a cleanup role for aqueous extractions, and water used for aqueous extractions plays a cleanup role for ethanol extractions. Mushrooms, for example, have a wide range of compounds, some only able to be picked up by water and others only by ethanol. Dual extractions open the door to complete botanical extraction of complex botanicals.
Chamomile oil from ethanol extraction
Either a single ethanol extraction for perfuming, scenting, cocktail concoctions, and culinary magic or dual extractions for powerful medicinal products, for small-scale extraction, the combination of ethanol's accessibility, safety, and effectiveness is unmatched. Readers will finish this article with a clear understanding of why ethanol works, how its chemistry influences what it extracts from the plant, and how different process choices affect the final product.
What is a solvent?
In extraction, gathering the target compounds from a starting material while leaving behind unwanted compounds and plant material requires a tool. That tool is a solvent. A solvent dissolves a substance, called the “solute,” and then carries it in solution, allowing the remaining undesirable compounds and plant material to be strained and filtered out of the solution that carries the solute. The images below show what it looks like when a pure solvent is used to make a solution, often called the wash or tincture.
Weighing the pros and cons of which solvent to use is very important. Hydrocarbons like butane are highly efficient and excellent at targeting the desirable parts of the cannabis plant. Unfortunately, the dangers and health risks associated with their use make them a poor choice for home extraction. That leads us to the small-batch, home-friendly, age-old solvents of water and alcohol. Water, known as the universal solvent and used in the aqueous extractions mentioned earlier, is well understood and will be left aside as we focus on alcohol from now on.
What is alcohol?
Alcohol is a class of organic chemical compounds characterized by a hydroxyl group (-OH) bonded to a carbon atom. This simple structural feature gives alcohol a unique profile, making it useful as a solvent, disinfectant, fuel, and an intermediate in many processes. The larger family includes methanol, isopropanol, butanol, and many others, but our focus is on ethyl alcohol, or more commonly known as ethanol (C2H5OH or EtOH for short).
What is ethanol?
Ethanol is what most people recognize as common “alcohol” found in beer, wine, or spirits. Food-grade-use ethanol is produced by fermenting sugars and starches from sources such as sugarcane, sugar beets, corn, wheat, and other organic materials, then purified by distillation. Industrial-use ethanol is often produced from petrochemical feedstocks and synthetic methods. The molecular structure of both fermentation-derived and synthetically produced ethanol is exactly the same. However, there are significant differences regarding trace impurities. These differences stem from the biogenic versus petrochemical origins of the feedstocks.
Food-grade ethanol is produced through natural fermentation and is certified as “food-grade” or “USP”. Many terms like “anhydrous,” “absolute,” or “laboratory grade” are used, but unless it explicitly states “Food-Grade” or “USP,” it may not meet regulatory or safety standards for human consumption, or for what we require for cannabis extraction.
Ethanol grades
The two main alcohols used for home extraction are isopropanol (IPA) and ethanol. We explained the difference between the fermentation process that produces food-grade or USP-certified alcohol for human consumption and the synthetic process that does not. In the case of IPA, it is always comes from petrochemical sources and produced synthetically. Even at its highest purity, IPA still cannot be considered food-grade. For this reason, we always use food-grade or USP ethanol.
In addition to certification language, the terms “denatured” and “non-denatured” also come up when discussing alcohol purity. Food-grade and USP ethanol can contain only ethanol and water, making them non-denatured (unaltered). If an alcohol is denatured, it contains an additive that prevents people from drinking it. The most common denatured alcohol example is rubbing alcohol. It can be sold in stores to anyone, of any age, even though it’s 70% alcohol (IPA), because it contains a denaturing agent that makes it undrinkable. For extraction, “non-denatured” ethanol is essential, and if you are purchasing food-grade or USP-certified ethanol, you already know it’s “non-denatured.”
Ethanol concentrations
Ethanol comes in different concentrations measured by proof and percentage, just like beer and spirits. Clean extraction requires high-proof ethanol at 190 (95%) or 200 (100%) proof. Anything with a lower proof isn’t suitable for extraction due to its high water content.
High-proof ethanol enables precise targeting of desired compounds, allowing for tuning to avoid extracting unwanted ones, and facilitates easy distillation to separate ethanol from the solution, resulting in a high-quality end product. Conversely, lower-proof ethanol causes issues and produces the opposite effects. Distillation recovery rates slow significantly or almost halt, and much of the water remains in the final product, critically reducing its quality. If care is taken and the 190-proof level is maintained in the extraction and recovery process, the same alcohol can be used over and over. If care isn’t taken and moisture is allowed to get into the ethanol, it will lower the proof, behave like lower-proof ethanol, and be unsuitable for reuse.
The common proofs available, 151, 190, and 200, may seem arbitrary, but there are interesting reasons behind them. To start, there is no national regulation of alcohol content levels, so each state decides. In some states, the lower proof, which isn't suitable for extraction, might be the only option available. The most common historical maximum alcohol limit for consumable products in states that do not permit high-proof versions is 151. Even though ethanol above 70% ignites easily, 75% (151-proof) is the line in the sand for many states due to the dramatically higher flammability risk of higher proofs.
In states where high-proof alcohol is available, the most common version is 190-proof. The higher 200-proof isn’t usually found in liquor stores but can be purchased online or from lab supply stores. The difference between the two is explained by an interesting chemistry concept called an azeotrope. An azeotrope is a point where two compounds, in this case ethanol and water, bind so tightly that they can’t be separated through normal distillation, behaving like a single compound. This mixture is about 95.6% ethanol and 4.4% water, known as 190-proof. Achieving 200-proof by breaking the azeotrope requires additional processing and care, which increases costs. In theory, and somewhat in practice, the 200-proof is less polar and absorbs fewer water-based impurities from cannabis. However, this advantage is short-lived because ethanol is highly hygroscopic and quickly absorbs moisture from the air, plant material, or other surfaces until it reaches the 190-proof azeotrope, which happens quickly. You can get one run with the 200's heightened benefits, but thereafter it will revert to 190. Whether it’s worth the extra cost and effort to obtain depends on personal preference.
Ethanol’s advantageous characteristics
Sticking with the science behind ethanol, this part gets interesting. Ethanol is an amphiphilic solvent, meaning it acts as both hydrophilic (water-loving) and hydrophobic (oil-loving) at the same time. In extraction, we can benefit from this dual nature by adjusting the temperature to control the extent of its interaction with polar components. In other words, by using room temperature, freezing, or cryo temps, we can control which components from the botanical are extracted. At room temperature, ethanol aggressively pulls in a wide range of compounds, including polar and non-polar compounds such as chlorophyll, wax, fats, terpenes, and cannabinoids. Cold temperatures enhance hydrophobic properties, focusing on components like only terpenes and oils, resulting in a cleaner, clearer extraction.
The next advantage of working with ethanol is its low boiling point, especially under vacuum, with the right equipment. After the primary extraction, when making the solution/tincture/wash, the ethanol must be removed by distillation (ethanol recovery) to isolate the collected compounds as a concentrate. Ethanol boils at 173°F in open atmosphere at sea-level. Under vacuum, that can be lowered to as low as 80°F. Using the lower temperature during ethanol recovery is a significant benefit.
Aeration
One of the main benefits of ethanol is that if kept "dry," it can be used repeatedly. By "dry," we mean not picking up moisture and lowering the proof. If the proof drops due to moisture absorption, the ethanol won’t boil properly under vacuum. If the ethanol won’t boil, vapor can’t be created, and the process of ethanol recovery won’t work. There’s an interesting phenomenon that can occur when perfectly good ethanol mimics this undesirable behavior. Fresh ethanol boils evenly and smoothly, releasing vapor, enabling ethanol recovery. However, upon subsequent uses, even without picking up moisture, it can boil unevenly with only occasional, localized, large splashing bubbles we call “bumping,” caused by superheating.
It took me a long time and a lot of frustration to figure this out, but the cause and the fix turned out to be simple and are now common knowledge. Fresh ethanol naturally absorbs dissolved air during production. The compounds in dissolved air (N2, O2, CO2) boil readily and play a major role in jump-starting ethanol nucleation, ensuring it boils vigorously and evenly. Unfortunately, the dissolved air off-gases and is lost during ethanol recovery. The next time the ethanol is used, it behaves as if it’s dead. To revive this 'dead' ethanol, it just needs air. It should be placed in a large jar with plenty of headspace and given a good shake to reintroduce air into it. It’s that simple, and it now sounds like common sense, but I wish I had the time to tell the full story of how I discovered this about 10 years ago—something we’ll save for another time.
Safety
Food-grade ethanol is intended for human consumption, providing very strong health safety as a solvent. Minute amounts of ethanol are easily metabolized by the human body. Residual amounts of ethanol are not considered a significant health risk. I would argue it's even less of a risk because the botanical concentrate produced is usually substantially diluted into a larger recipe or formulation. Consider vanilla and almond extracts in the baking cupboard. Those are 35% alcohol, and no one has ever worried about those.
In addition to its health-safety profile, working with ethanol is safe if a few precautions are taken. High-proof ethanol is highly flammable and must be handled with care. Even so, it’s generally safe to work with it when proper safety measures are in place. Vapors quickly disperse in well-ventilated areas, and removing ignition sources nearby greatly reduces the risk of problems. If, in the rare event, an issue occurs, ethanol is fully miscible with water, making water an easily accessible and ideal extinguishing medium. It's easy to become comfortable working with ethanol and get sloppy with safety. First, always prepare the area for safety before bringing out the ethanol. Then, I highly encourage anyone working with ethanol to put in place safe handling procedures so an accident doesn't occur.
Happy Extracting!!!
I hope understanding how well ethanol works as a solvent with cannabis extraction leads to more fun and better extractions for you. If you have questions, want support, and would like to learn more about ethanol extraction reach out to support@torrkitchen.com any time or checkout more of the information and resources available on torrkitchen.com