When discussing extraction techniques with cannabis processors, I am often asked why I typically recommend using CO2 as the extraction solvent vs. ethanol, enabling a much faster extraction process. I typically reply with this analogy:
I like to make a cake from scratch in my spare time and angel cake in particular. If you have ever made angel cake, you know that its fluffy texture is due to egg whites vs. yolks preparing the cake batter. Because my spare time is limited, I like to be as efficient as possible when making the cake and reduce the preparation time before it goes into the oven to bake. To that end, I have adopted a methodical process whereby I process one egg at a time: I crack the egg, separate the egg white from the yolk by swishing it around in its shell. I capture the egg white in one bowl and the egg yolk in another and discard the shell. I then check the egg white bowl and remove any eggshells that may have fallen into the egg whites. Once completed, I place the homogenous egg whites into a mixing bowl. The recipe calls for 12 eggs, and I complete the same process for each egg. In the end, I have the pure egg whites that I need, add the other ingredients to the mixing bowl, and ready to bake. There are no further steps I need to take. Furthermore, I also have a bowl of pure egg yolks that I can use for other purposes, like browning the outside of my pizza bread.
My next-door neighbor also likes to make angel cake from scratch, and one day I watched his preparation technique. Instead of processing each egg individually like my method, he thought it was faster and more efficient to quickly crack each egg and put both whites and yolks into the mixing bowl (plus any cracked shell bits that may have inadvertently fallen into the bowl as well). Of course, since the recipe called for egg whites only, he had to remove the mixture’s egg yolks. I noticed that he had bought a special spatula to help him remove the yolks from the mixture, and it seemed to be quite a time-consuming and messy process, as many of the yolks broke apart and yolk residue mixed in with the whites. I then observed that he tried other techniques (fingers, spoon, and fork) to remove the tiny bits of eggshell that were inadvertently added to the mixture. When those steps were completed, the batter was mixed and finally ready for baking.
I spent more time than I intended to watch his process and invited him over to my house next time to see how to save himself some time and aggravation in the future.
Now, what does this have to do with using ethanol vs. CO2 for cannabis extractions?
I look at my neighbors’ preparation process as similar to an ethanol extraction method. All of the cannabis material components (egg whites, yolks, and shells) are extracted together, and then post-processing methods and equipment are required to separate the desired components from the unwanted components (collection of egg whites and removal of yolks and shells). In the extraction world, post-extraction processing can be time-consuming and expensive.
CO2, on the other hand, enables a very selective extraction process, and by adjusting temperature, pressure, and flow rate, you can extract the desired components without requiring post-extraction processing.
In the end, CO2- based extractions are typically faster, more efficient, produce higher yields, and are less expensive without requiring post-extraction processing equipment and time-consuming purification steps.
Ethanol proponents would say that their primary extract could be crystallized by further purification or downstream processing, and they would be right. The purification process to make crystalline is labor-intensive, costly, and hard to scale. The process normally involves multiple stages of filtration, separation, chromatography, and solvents such as dimethyl ether, chloroform, and dichloromethane in some instances.
