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Busting the Myth: Examining CO2 versus Butane Extraction

By John A. Mackay, Ph. D.
23 Comments
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Butane can provide for a fast extraction, but little control while you can tune CO2 extractions to collect the same material.

The basis of anecdotal controversy continues about the use of hydrocarbons versus carbon dioxide. It is important to note that hydrocarbons span a range of phases on the planet earth.

It is important to eliminate the cost of the instruments and the cost of the facilities from this comparison to keep the discussion on specifically the extraction principles.

Source: (https://en.wikipedia.org/wiki/Butane#Isomers)
Source: (https://en.wikipedia.org/wiki/Butane#Isomers)

Butane is a gaseous hydrocarbon. As you add more carbons to hydrocarbons, they move from gaseous to liquid.

It is also important to note that the same is true of carbon dioxide in its natural form on the earth’s atmosphere, it is a gas. It is nonflammable and used in fire extinguishers.

At typical conditions, carbon dioxide in the supercritical range is similar to hexane (C6H14) and ethyl acetate in its solubility characteristics. Propane (C3H8) and butane (C4H10) are gases at normal atmospheric conditions. Both must be manipulated for the extraction of CBDA and CBD. For example, both CO2 and C4H10 must be placed under pressure and then passed through the material to extract the lipophilic terpenes and cannabinoids.

For this short discussion, let’s remove the concern about the different volatilities of the compounds. Hydrocarbons with a spark will be significantly more powerful of an explosion than carbon dioxide (note it could be used to put out the butane fire). The hydrocarbons can be in more configurations and therefore the getting the correct form initially is critical. For example, butane can have all the carbons in a row like a train, or branched like a tree. Those are very different and have different characteristics too. Getting pharmaceutical grade butane is essential to ensure safety. The concern that people have expressed with butane is what is in the other 0.1% for 99.9%. Checking for residual butane is less of a concern than the polyaromatic hydrocarbons in the untested cylinder. Furthermore, in the wrong hands it can be more volatile.

Source: (https://en.wikipedia.org/wiki/Carbon_dioxide)
Source: (https://en.wikipedia.org/wiki/Carbon_dioxide)

The critical premise that needs to be considered is the final formulation. Is one solvent significantly more applicable than the other? No. They have different characteristics.

Propane is a common solvent in the spices, flavors and fragrances industry. For example, the extraction of lipids and oils from vegetables and the fatty oils from seeds, it would be an advantage to have a solvent that is totally miscible, i.e. will be totally soluble in a fluid. This is similar to the idea of sugar in hot water versus in water in ice. If an example of cardamom were used comparing CO2 and propane (which is similar to butane), the pressure needed for CO2 would be 100 bar, while propane would be only 20 bar. However the increasing the pressure of the propane from 20 to 50 bar at a constant 25 C, also increases the chlorophyll from 3.4 g/g oil to 10.8 g/g oil. Meanwhile with the more finely tunable CO2 from 80 to 100 to 200 the amount of chlorophyll is negligible (0.36 g/g oil) but at 300 bar it dramatically increases to 4.53 g/g oil.

Additionally the CO2 is a better extraction for the terpenes in the cardamom. The beta-pinine, Cineole, linalool, alpha-terpinol and bornelole. The increase in the propane pressure will allow us to increase the yield of the CO2 (Illes, V, et. al. Proceedings of the Fifth Meeting of Supercritical Fluids, Nice, France, Tome 2, 555-560).

This example is the same with the butane and cannabis. Butane is a stronger solvent and if left too long will continue to pull out more and more polar compounds like chlorophyll. With the fine-tuning of CO2, you can eliminate or you can pull out the chlorophyll if you choose the wrong conditions.

So fast extractions are possible with butane but little control of all the material, while CO2 can be tunable and therefore is able to collect all of the same material, just through a segmented process.

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Comments

  1. Jeremiah MacKinnon

    I am very impressed. This is a very scientific article. I hope our Massachusetts Department of Public Health takes this scientific guidance and does not bar hydrocarbon based extractions by imposing a 1ppm residual solvent limit for butane, propane, and iso-butane. Medical marijuana patients have not noticed negative side effects from hydrocarbon extracts. As Dr. Mackay answered, “Is one solvent significantly more applicable than the other? No.” They are both applicable, efficacious, and necessary. This is science people.

  2. Anonymous

    I like your chemistry approach to this issue. Problem is, the danger for consumption between CO2 and Butane used in cannabis extract has nothing to do with the chemical properties or residual limits of those actual solvents. THE MAIN ISSUE is the “mystery oil” aka machinery lubricant oil that is impossible to completely remove from the tank and machinery used to make this gas. THAT IS THE ISSUE. CO2 extracts are in genereal, tasteless and less potent. Butane tastes better, but smells like a Tire Fire.

    1. Zack I.

      Very true on all points. Purchase of pharm. grade alkanes, or high-quality refrigerant grade alkanes, followed by several distillations in-house, are required for the best GMP. This is the key reason that open-blow is dying as a common practice, as there is no opportunity to purify the gas after purchase.

  3. Mai Tai

    CO2 extractions remove all of the pesticides in the plant and deposit them right into the extraction ….. hence a potentially quite harmful and poisonous product. Butane does no such thing.

    1. Jon

      Mai Tai, can you site ONE lab sample of a Co2 oil that has pesticides in it. Both Co2 and hydrocarbons can remove pesticides. Hydrocarbons are less selective thus Hydrocarbons will remove more pesticides than Co2.

      Also Co2 extraction can be more potent than BHO (+80% active) with greater clarity. From the same material Co2 can produce better results than any Hydrocarbon extraction.

      1. Vinod

        Adding, CO2 extraction usually removes Organo chlorine pestisides almost from material so that you wont get any traces in extracted oil. Pyrethroids and organo phosphorous I am not sure. I have done this on cardamom with all three kinds.

    2. Zack I.

      Butane WILL dissolve pesticides just like CO2, but it will dissolve a slightly narrower range of pesticides at sightly less efficiency than CO2. The difference in pesticide residue retention is negligible, however, because ANY pesticide retention is bad. The key is starting with clean source material.

  4. Leah

    I am curious about butane residues. We had CBD butane oil extraction come back with high numbers in residues. How can I get rid of them? A friend wanted some for his father that has cancer but he wants all the residues out…… help.

    1. Courtney Bostdorff

      Leah, you have to distill the butane. We use the same process when distilling propane. You will need a closed loop system to do it. You basically run the solvent through your material chamber which then pools as a liquid into your collection pot. You’ll want to keep the collection pot chilled in an ice bath while you do this. The bath should be right around 33 or 34 degrees Fahrenheit. Butanes boiling point is 30.2 degrees. You are basically separating the butane from the mystery oil by only allowing the butane to vaporize back into a gas while leaving the residual gook in the collection pot. The gas then goes from the collection pot into a recovery pump where it’s forced to recondense back into a liquid in the recovery tank. Try to make sure your collection pot never reaches a negative pressure otherwise you will end up lowering the boiling of whatever is in the mystery oil and run the risk of sucking it right back into the recovery tank. When your collection pot reaches just above negative pressure then you can stop recovering. When you open the collection pot for cleaning you will be greeted with the lovely aroma of the mystery oil……smells a lot like used car oil. Clean out your collection pot with ISO and be sure to heat gun the pot afterwards to burn off any ISO residuals. Now do the exact same procedure one more time. A 20lb butane tank will take 6 to 10 hours to distill 2 times because you are keeping the collection pot so cold. Recovery time also depends on your equipment. Hope that helps.

  5. Joey

    I have yet to find a CO2 product that is as good or better than BHO. Never matches BHO in terms of terpene content, never.
    CO2 can be good for edibles and pens (with added, artificial terpenes) but for dabbing, BHO all day.

  6. TS

    A quality extractor like what is manufactured by SUBZERO SCIENTIFIC distills the butane or propane first before using it to extract the product. This eliminates mystery oils altogether and is a far better extractor. CO2 tends to ‘wash’ the flavor out of the product being extracted.

  7. Emil Bucher

    My Story .
    As a natural born skeptic, I spent countless time and energy researching all the available treatment options aside from what my oncologist recommended. I was DETERMINED to cure my cancer, and knew there was something out there after witnessing a number of people who not only survived, but thrived and went on to live fulfilling lives cancer-free. In addition to reading about Rick Simpson Oil, and watching the Run From the Cure video, I also spoke with people who had actually used the oil, and it was shocking to hear one after another how effective this medicine really was. I just couldn’t believe there was a cure out there and how wrong it was that this information is not being shared with the public!
    Treatment Regine:
    I have a pretty big tolerance for marijuana, so I started off with a full grain of rice sized amount of oil instead of a half grain. I gradually increased the dosage every night until I reached a full gram each night. The standard protocol for Rick Simpson Oil is ingesting a total of 60 grams over the course of 90days which is 3 months, but I had 80 grams in total for safe measure. I used the excess as a topical skin care treatment, attacking the visible brown spots on my face and neck.
    3 months later, my cancer was in full remission. Within 4 months, I am cancer-free and officially received a clean bill of health from my doctors. What they don’t know is that the majority of my treatment was using the Rick Simpson Oil. I did use some of the medication they prescribed, but it was in combination with the oil.
    I am elated I want to continue sharing with people who are experiencing what I went through that there is absolutely hope and a cure out there. They just need to be proactive and aggressive with treatment, not wait until it is too late. Get your medication at Rick Simpson medication centre via Email: ricksimpsonoil02@gmail.com
    In addition to being an effective cancer fighter, there are some nice side effects that come from using the Rick Simpson oil, for instance, I no longer need to take any pain killers. Just one or two drops of the oil will ease the pain and help you sleep like a baby. Best of all, its natural . . . Thanks to all the staff at Amsterdam’s Garden who guided me throughout this journey. You guys are awesome!.

    1. eeenok

      oh look YET ANOTHER testamonial for the curative powers of cannabis when it just happened to be combined with chemotherapy but purely as a courtesy to those sadly deluded doctors who wouldn’t be able to understand why i attribute one hundred percent of the cure to Snake Simpson Oil tm. although i’m starting to suspect poor spelling might literally cure cancer. has anybody run a double blind test on that yet?

  8. LRAS

    “fast extractions are possible with butane but little control of all the material”

    Please be a bit more elaborate and define exactly what you mean by ‘little control of all the material’ ???

  9. Kathleen

    Beware – ricksimpsonoil02@gmail.com is a FRAUD – reported to Western Union: Fraud Case #1670289

    Deborah Gali Stallings – picked up in February 2017 – 2 payments at the Food Lion in Rocky Mount, VA 24151 – kept demanding more money to be sent… and refused to send the oil…

    Authorities have been alerted…

  10. Dr.Terpp

    There are systems (with 12 yr safety rating 0 accidents) for using light hydrocarbons that are able to extract under negative pressure, and sub-0C temperatures. One patented system used by large perfume companies does not use a column extraction vessel. Instead, uses a cone shaped vessel, limiting the need to pack a column consistently. Systems like this have benefits over CO2 in that they are better suited for extracting from the surface of the leaf, (like trichomes) with minimal solvent leaching into the leaf yielding more chlorophyll etc. They can be much cheaper to build and operate, capturing waste heat from the phase change of gas during extraction and recovery, not needing high pressure vessels.

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