The cannabis industry largely depends on solvent extraction to separate useful cannabinoids and terpenes from the hemp plant. The resulting extracts are used to manufacture products like cannabinoid tinctures, vapes, and more.
Many solvents are involved in the process, but all are not equal. Thus it’s important to look closely at the properties, advantages, and disadvantages to make the safest and best choice for your extraction business.
This article compares and contrasts the common organic solvents involved in the extraction, with a particular interest in denatured ethanol.
Let’s get started!
Types Of Organic Solvents For Hemp Extraction
Ethanol, propane, butane, and carbon dioxide are the most commonly used organic solvents in hemp extraction. Each has its unique properties that determine its potential benefits and downsides. Thus, the table below paints a clear picture of the properties of each;
|State At Room Temperature and atmospheric Pressure||Liquid||Liquid||Gas-liquid||Gas-liquid||Gas-liquid|
|Vapor pressure (mm/hg)||44||40||44151||1830||6398|
|Flammability Category||Category 2||Category 2||Category 0||Category 1||Category 1|
|Log-P (Octane- water)||-0.18||4.27||0.9-2.0||2.7||2.24|
From the comparison table, ethanol has a lower vapor pressure than other organic solvents. As a result, it does not vapourize like carbon dioxide, propane, and butane, leaving a highly concentrated mixture of cannabinoid oil and ethanol.
Thus, extraction may require specific equipment and facilities for solvent recovery, depending on the amount used during the extraction process.
In addition, the primary extract from ethanol extraction can be considered a category 2 B flammability hazard. Thus, it has to undergo solvent recovery to remove solvent residues from the final extract.
Butane and propane have a high vapor pressure (1830 and 6398 mm/hg) but passes slowly through the plant material. As a result, the primary extract may contain solvent residues. Thus, it has to undergo vacuum distillation for solvent recovery.
On the other hand, carbon dioxide has the highest vapor pressure ( 44151 mm/hg). Thus, the primary extract does not require to undergo solvent recovery to remove traces of residue.
In addition, it is reusable and non-flammable, making it the safest cannabis extraction method.
What Is Denatured Ethanol And Is It Safe For Hemp Extraction?
Denatured ethanol combines pure ethanol with other ingredients such as heptane, popularly known as denaturants. Manufacturers utilize denatured ethanol for extraction to avoid the high pure ethanol price.
Although various recipes are published by the alcohol and tobacco tax trade bureau (TTB), heptane is the most commonly used compound in cannabis extraction processes. In addition, others include methanol, isopropyl alcohol, and acetone.
The main reason heptane is preferred as a dilution agent is; there is a huge difference between the boiling points of ethanol and heptane. As a result, it’s easy to separate the two solvents.
The process may leave residues and chemical contaminants behind, but it will be less costly to the manufacturer if they distill denatured ethanol in a food-grade process. However, the process may be limited by the solvent reuse guidelines given by the FDA.
The use of denatured alcohol in solvent extraction may leave residues in the primary extract even after pre-distillation. However, the residues may be dilute and considered trace compounds.
There is no clinical data on the safety profile of heptane on humans after long-term exposure. However, the food and drug act accepts a maximum of 5000 ppm residue on class 3 chemicals because there is no sufficient clinical data to limit the presence of denatured ethanol in the final extract.
The limit was set in the 1990s by the FDA and USP due to a lack of data on safety. Thus, the duo agrees with the global pharmaceutical manufacturers association to the solvent limit for the three classes of solvents.
Many solvents are involved in cannabis extraction, and all are not equal.
Denatured ethanol is a safe alternative to pure ethanol and other organic solvents because it reduces extraction and manufacturing costs.
The extraction process may leave residues, but it remains safe provided they do not exceed 5000 ppm as recommended by the FDA and USP.