As the cannabis industry has mushroomed over the past few years, the share of the market attributed to cannabis extracts has burgeoned even faster. So far, two types of cannabis extracts, butane extracts and supercritical CO2 extracts, have accounted for the production of a vast majority of concentrates available on the market.
Yet a third solvent, ethanol, has been gaining on butane and supercritical CO2 as a solvent of choice for producers manufacturing high-quality cannabis extracts. Here’s why some believe that ethanol is the overall best solvent for cannabis extraction.
What is Ethanol?
Ethanol (C2H6O), also known as ethyl alcohol or grain alcohol, is a colorless and volatile flammable liquid. Ethanol is used to make gasoline, beauty products, solvents, paints, and food additives. If you’ve consumed beer, wine, or spirits, you’ve likely had ethanol in your system. Ethanol has also been used to distill chemical compounds from botanicals like cannabis.
Ethanol is fermented from a variety of sources and distilled. Corn is the most commonly used feedstock for ethanol production. Other sources include wheat, barley, potatoes, sugar cane, and grain sorghum. Because ethanol is derived from plant material, it’s considered a renewable energy source.
According to the Food and Drug Administration (FDA), ethanol is considered a Class 3 solvent with low toxic risks when used in pharmaceutical manufacturing where the residual is under 5,000 parts per million (ppm) or 0.5%. Lab testing can ensure the ethanol-based extracts don’t contain high amounts of residual solvent. Certain states will have lower cut-off points when it comes to ethanol cannabis extraction. Regardless, ethanol extraction is known for its ability to leave very little to no residual solvent behind.
Ethanol, Butane, or Supercritical CO2: Which is Best for Cannabis Extraction?
No solvent is perfect for cannabis extraction in every way. Butane, the most common hydrocarbon solvent currently used in extraction, is favored for its non-polarity, which allows the extractor to capture the desired cannabinoids and terpenes from cannabis without co-extracting undesirables including chlorophyll and plant metabolites. Butane’s low boiling point also makes it easy to purge from the concentrate at the end of the extraction process, leaving a relatively pure byproduct behind.
That said, butane is highly combustible, and incompetent home butane extractors have been responsible for the manifold stories of explosions resulting in serious injuries and giving cannabis extraction as a whole a bad rap. Furthermore, low-quality butane utilized by unscrupulous extractors can retain an array of toxins that are harmful to humans.
Supercritical CO2, for its part, has been praised for its relative safety in terms of toxicity as well as environmental impact. That said, the lengthy purification process required to remove co-extracted constituents, such as waxes and plant fats, from the extracted product can take away from the final cannabinoid and terpenoid profile of extracts yielded during supercritical CO2 extraction.
Capna Labs, a California-based extraction company founded in 2014, considered the benefits and drawbacks of several solvents, including butane and supercritical CO2, before choosing to work with ethanol as their solvent of choice. “Several factors drove our decision to move towards ethanolic extractions at Capna,” says principal engineer Gene Galyuk. “We knew that we needed a solvent as safe as CO2, but as efficient as butane.”
Ethanol turned out to be just that: effective, efficient, and safe to handle. The FDA classifies ethanol as “Generally Regarded as Safe,” or GRAS, meaning that it is safe for human consumption. As a result, it is commonly used as a food preservative and additive, found in everything from the cream filling in your donut to the glass of wine you enjoy after work.
Ethanol Extraction Process
Manufacturers can work under warm or cold temperatures, each method coming with its own pros and cons. Using the Soxhlet technique, ethanol is boiled, condensed, and cooled down. This warm ethanol soaks the flower material in a quick process that leaves very little residue. This technique is typically used to make smaller batches of cannabis oil. Additionally, this method can convert THCA into THC, which activates cannabis’ chemical compounds. This may require more post-processing to remove unwanted matter.
Most ethanol extractors will use room temperature or cool conditions to extract specific cannabinoid acids like THCA and CBDA to make shatter crystals or other infused products. Using room and cool temperatures significantly reduce the levels of plant pigments and waxes in the final product, but also total cannabinoid recovery. Cooler temperatures, however, can be efficient at extracting THCA and CBDA because the temperatures preserve cannabinoids in their precursor acid forms.
During the extraction process, solvents (ethanol, butane, CO2) are mixed with the cannabis material to remove the cannabinoids and terpenes. Ethanol is considered a polar solvent that can dissolve cannabinoids, but also dissolves water-soluble molecules like chlorophyll. Leaving the chlorophyll in the final product can result in dark-colored and grassy-flavored extracts.
Ethanol and cannabis are mixed into a column (in a lab setting) at room or colder temperatures. Once the cannabinoids have been removed, processors remove the solvent through evaporation leaving behind pure cannabis oil. Post-processing is required to refine the extract from the organic plant material. Removing the chlorophyll removes the harsh, earthy flavor.
Benefits of Ethanol Extraction
Many manufacturers believe that ethanol has advantages over butane and carbon dioxide cannabis extraction methods. Ethanol extraction has its limitations, like any other solvent, but this extraction process all-but-removes the presence of residual solvents in the final product. Additionally, ethanol extraction gives producers the ability to remove cannabinoids and terpenes effectively to make products like THCA crystals.
In terms of cost, ethanol extraction can be a cost-effective option for many manufacturers who still want a big yield. Plus, ethanol extraction, when performed under the right conditions, is safe to work with. State-of-the-art ethanol extraction equipment can be automated and controlled through a digital interface with minimal intervention. Plus, closed-loop systems prevent any solvent leaks or fire hazards.
Compared to other extraction methods, ethanol extraction can have a lower startup cost in terms of equipment, labor, and throughput. More importantly, however, ethanol-based products retain a high purity (90%+). When warm extraction methods are used, decarboxylation can create ready-to-consume products.