One of the most common questions being asked these days by aspiring cannabis processors is “Which method of extraction should I use? CO2 or ethanol?”
The answer to this question is another question. What products are you going to produce and in what volume?
There are advantages and disadvantages to both methods and efficiencies created when utilized together, which when taken into consideration, will help you decide what’s best for you given your unique business model short and long term.
Before addressing the pros and cons of the two methods, it is helpful to take a brief look at the histories of these techniques and how we ended up where we are today.
A Brief History of CO2 and Ethanol
Ethanol extraction of cannabis has been around for a very long time. Although it would be hard to say exactly when and where this started in human history, there are detailed records of ethanol-based cannabis tinctures being sold in apothecaries throughout the United States up until 1937 when cannabis was outlawed.
An Eden Labs' Coldfinger Commercial ethanol extractor
Ethanol extracted cannabis oils enjoyed a brief renaissance in the mid 1970’s when D.J. Gold, author of “Cannabis Alchemy”, launched the Iso 2 extractor in High Times magazine. The DEA forced this product off the market in short order. In the early 1990’s Eden advertised small tabletop systems in High Times and then in 1995 Eden launched the first commercial sized “Coldfinger” ethanol extractors for the new medical markets. This was the beginning of the cannabis industry that we have today.
Ethanol extraction has come a long way since 1995 with large scale commercial and industrial systems extracting thousands of pounds per day to serve the expanding medical and recreational markets. There are quite a few companies marketing ethanol extraction machines with a wide range of variance in the way they perform an extraction but the biggest variable is whether to perform the extraction with warm or cold ethanol and if the system can produce a pure terpene fraction. Warm or cold will be addressed in a later blog. Eden has designed a series of tests that should settle once and for all which temperature parameters are the most efficient.
CO2 extraction has a much briefer history. This method was invented by the Nazis and was originally intended for extracting oil from shale for the war. When the war ended, these large scale CO2 extractors were repurposed to extract hops for the beer industry.
An Eden Labs CO2 separator vessel at Heylo Cannabis in Seattle, WA
Supercritical CO2 extraction is still the primary method for extracting hops. Large commercial breweries use a highly refined alpha acid hops oil for the top selling pilsners that dominate the market. More recently, microbreweries have started using smaller and more specialized CO2 extractors for creating unique flavor profiles of boutique hop strains that have opened whole new areas in the taste and terpene profiles of beers. The next time you enjoy a micro-brew, you may notice it smells a bit like cannabis. This is because hops are the closest relative to cannabis and the CO2 extraction nicely preserves the native terpenes.
The current state of the hops industry is a good indicator of where cannabis is headed. Large scale hops production is done with CO2 because it makes a high-quality product and the daily operating costs and facility build outs for solvent storage of CO2 are far less than other methods. No one in the hops industry extracts with butane or ethanol.
An Eden Labs' Hi-Flo FX2 CO2 Extraction system in a hemp field in Washington State.
Thinking About Scale in Cannabis Extraction
Why then are these other methods so popular and highly regarded? It really comes down to cost. All the methods can make quality product with the right operators and SOP’s. The cost of entry for butane and ethanol is much less than CO2, and ethanol is the lowest price method in terms of entry costs.
As large-scale production ramps up, the cost of equipment becomes a bigger factor in a business plan. A startup that needs to extract hundreds or thousands of pounds per day can get started in ethanol for a cost in the hundreds of thousands.
So why invest so much more in CO2? The lowest daily operating costs, which was previously mentioned, is the primary rational. The other methods require the constant purchase, storage, use and disposal of large amounts of flammable liquids. This can be a heavy burden from a workflow, regulatory, and monthly expense perspective. CO2 is highly tunable. With CO2 you can vary factors such as time, temperature, and pressure to create different products. Ethanol products need to go into more stages of refinement to be turned into various products such as distillate.
Processors who choose CO2 as their primary extraction method are often considering long-term viability and survivability.
The final reason for selecting a CO2 extractor for your processing is marketing cachet. Supercritical CO2 has gained a reputation for being the cleanest, safest, and most cutting-edge method of extracting natural products. Health food stores often have special displays of their CO2 extracts which garner a higher price than other herbal remedies. Processors who choose CO2 as their primary extraction method are often considering long-term viability and survivability. They may emphasize the chemistry of their extractions, such as high-levels of THC, CBD and terpenes. As competition increases and the industry consolidates, daily operating costs may become a "make or break" factor. In addition, as large corporations begin to dominate sectors of the industry, many of them may choose to contract processing to the best existing facilities rather than build their own plants