In the race for extraction supremacy and efficiency, ethanol and CO2 extraction are high on the list of the most efficient ways to create cannabis oil. Solvent-based extractions have taken the market by storm and enabled the production of countless derivative products such as edibles, topicals, concentrates, tinctures, and more.
Whether processors are looking to create THC-rich products with cannabis or CBD-rich products with its hemp variety, it is important to understand how each extraction method works and the pros and cons of each technique to make an informed decision. In most cases, it all comes down to the type of products and the amount an operator intends to produce.
What Is Solvent-Based Extraction?
Cannabinoids such as cannabidiol (CBD) and tetrahydrocannabinol (THC) can be extracted using a variety of methods. Solvent-based extractions use a chemical solvent to remove the cannabis oils from the plant material. After the primary solvent wash, any residual solvent is removed from the solution to produce a pure and potent cannabis oil. Cannabis oil can be used to create a range of derivative products including edibles and topicals.
Cannabis companies can choose from a handful of polar and non-polar solvents to remove the plant's soluble components. Extractors can employ a variety of solvents, primarily hydrocarbons, ethanol, and CO2, at a certain temperature and pressure. In this piece, we will focus on the last two popular solvents in the cannabis industry.
A Brief History of Ethanol and CO2 Extraction Methods
Before we get into the cannabis extraction systems of today, it is important to understand the rise of these extraction methods, how far they have come, and where the technology is going to determine the best method for extracting cannabis.
Ethanol extraction of cannabis was popularized in the early 1900s. Alcohol-derived tinctures were widely available at apothecaries up until cannabis prohibition in 1937. In the 1970s, there was a resurgence of interest in ethanol extraction with books and magazines covering this exciting technique. In the mid-1990s, ethanol extraction equipment went from table top systems to commercial-grade extractors for the developing medical markets.
Today, ethanol extraction equipment at a commercial scale is able to extract thousands of pounds per day to keep up with demand from the medical and recreational cannabis markets.
CO2 extraction is a more recent innovation. CO2 was first liquefied in 1835 by Humphry Davy and Michael Faraday. CO2 is widely used in the beer industry to extract hops. Today, this extraction method is prized for its relatively lower daily operating costs and facility requirements, as well as high efficiency in extracting cannabinoids and terpenes.
What Is Supercritical CO2 Extraction?
Supercritical CO2 extractions use carbon dioxide gas in its supercritical state, which has properties of a liquid and a gas. In this state, the solvent can easily work its way through the biomass and pull out a considerable number of cannabinoids and terpenes. The result is a full spectrum product that requires minimal post-processing.
The Extraction Process
During the supercritical carbon dioxide extraction process, CO2 systems cool and pressurize by carbon dioxide gas until it reaches its supercritical state. Then, it is passed through the biomass plant material to separate the cannabinoids and terpenes. At the end of the process, the CO2 can be recaptured and recycled for future use.
What Is Ethanol Extraction?
Ethanol extraction is an extremely efficient method of extracting cannabinoids from the plant, particularly hemp. The alcohol solvent is polar in nature making it a good solvent to bond with water soluble and fat soluble compounds. Essentially, the solvent can pull out a high amount of the plant's active ingredients at a fast rate.
The Extraction Process
During the ethanol extraction process, processors use food-grade ethanol to separate the cannabinoids and terpenes from cannabis material. The solvent is passed over the biomass at very low temperatures. The solvent is removed from the solution and recirculated through the biomass several times for higher extraction efficiency.
Ethanol Extraction vs CO2 Extraction: Which One Is Better?
Which extraction method is better for consumers and producers? There is not an easy answer. In fact, there is no best method overall. Ultimately, it depends on what the producer needs to create. Here, we cover the most important factors to consider when making the choice between ethanol vs. CO2 extraction.
Out of all the methods available to producers, carbon dioxide is by far the most expensive method in terms of upfront costs. Processors must pay a steep price for a CO2 extraction system compared to lower-priced, entry-level ethanol and hydrocarbon units. Hydrocarbon systems that use butane and propane can be the most affordable.
An entry-level CO2 extraction system can start at about $100,000. In addition to the cost of the equipment, processors may need to invest more in employee training to handle the specialized machinery. Ethanol requires a lower upfront investment and will not require as much intensive training for operators.
In terms of operating costs, there are a few variables to consider for each method. Ethanol extractions can include high variable costs and overhead due to the solvent price, ethanol losses, insurance premiums, hazardous waste disposal, and lower recovery. CO2 has low variable costs. Business insurance is not hard to get with CO2.
Food grade ethanol is relatively safe and can reduce the likelihood of chemical contamination but it comes at a higher price. Denatured ethanol solvents are more affordable but include a wide range of non-food grade solvents. In comparison, CO2 has a low price per kilogram.
Ethanol as a solvent requires additional infrastructure investment due to the limits on ethanol storage, requirements for alarm lights, deflagration alarms, detectors, and a complete alarm system for gas detection. CO2 does not require any of these additional expenditures since there is no limit on the amount of CO2 that a facility can store on site.
Overall, CO2 extractions may cost more initially but can have lower operating costs that may pay for themselves in the long run. In the battle between ethanol extraction vs. CO2 extraction, it is hard to choose the best method in terms of cost.
For operators looking to make high-potency distillate, ethanol extraction is the way to go. Ethanol can extract a high amount of active compounds quickly to create a high quality extract. For processors that want to create full spectrum extracts featuring high concentrations of terpenes and cannabinoids as well as flavonoids and carotenoids, CO2 extraction may work for them. This method can help them produce a product that more closely resembles the plant material.
For many producers and consumers, CO2 extractions may reduce the risk of the carbon dioxide ending up in the final product compared to other methods that may leave behind residual solvents. When processors want to create pharmaceutical-grade products, CO2 may be a viable option.
Ethanol extraction is flammable, but not nearly as much as light hydrocarbons such as butane and propane.
However, for those that want peace of mind, CO2 can offer more safety than other extraction methods since carbon dioxide is not flammable and less toxic than ethanol. In addition, there is a lower risk of ending up with residual solvents in the end product.
Ethanol extraction can run the risk of leaving behind chemical contaminants that can increase the health risk for consumers (medical and recreational), especially when using denatured ethanol that include non-food-grade chemicals.
While the process occurs at high pressures, peer-reviewed systems are designed to handle any risks associated with the high pressure process.
However, CO2 is not entirely risk-free. If there is a leak in the room, it could replace the oxygen and suffocate operators. An adequate alarm system and sensors to detect leaks can offset these dangers.
In terms of solvent recovery, ethanol extraction requires more investments in the recovery process. Generally, CO2 extractions do not need to recover the solvent. However, they may want to recycle the carbon dioxide within a run or batch due to the affordability of CO2.
In terms of its effect on the environment, ethanol has a higher carbon footprint. The higher footprint comes from the production of the ethanol solvents, the high amount of energy needed to cool the system down to cool temperatures, and the environmental costs of disposing of the hazardous biomass waste.
CO2 extraction uses CO2, a byproduct of many industrial operations that is currently in the atmosphere. CO2 is non-toxic, renewable, and able to be recycled for use. CO2 is also considered a green solvent by the American Chemical Society.
Efficiency and Throughput
Ethanol extraction is extremely efficient at isolating cannabinoids for a distillate at high volumes.
In addition, this method does not require too many steps in between, or post-processing, if done right. Ethanol extraction can process thousands of pounds of biomass per day with a single unit. Essentially, a processor's efficiency and scale depends on the size of the unit.
Compared to ethanol, CO2 extraction is a lot slower. CO2 can perform considerably fewer runs per day compared to other extraction methods.
On the other hand, ethanol’s polarity as a polar solvent is also capable of dissolving water soluble components in the material such as chlorophyll, which may require additional clarification steps to remove.
In terms of winterization, both processes can require this step. In ethanol extraction, the winterization step can be sidestepped if extractions are at very cool temperatures, although this can increase energy costs. Warm ethanol extraction requires winterization.
CO2 does require winterization after extraction. However, new technologies are coming out and allow winterization to happen during extraction without a chemical solvent.
Overall, ethanol extraction can produce a product with between 50 to 80% cannabinoid recovery, although carbon scrubbing may be required to remove the chlorophyll, which may also reduce cannabinoid concentration since the carbon can pull in cannabinoids.
In comparison, supercritical CO2 extraction has a cannabinoid recovery rate of between 85 and 95% without the need for carbon scrubbing.
After the biomass has been processed, both methods have different waste and storage requirements.
Biomass that has been processed with ethanol is considered a hazardous waste until most of the ethanol has been removed to negligible amounts. Its transportation may be subject to regulations.
Biomass that has been processed by CO2 is cleaner and a good source of food-grade essential amino acids. Unlike ethanol, its transportation is not regulated.
Choosing a System
Ultimately, the type of system a processor chooses will depend on their budget and specific production needs. If companies have the budget and want to create full-spectrum products with slightly lower yields, then CO2 is a good option. Companies that want to get their operations off the ground quicker and for a lower upfront investment while still producing quality CBD from hemp, ethanol extraction may be the best option.