Cold Ethanol Extraction

Our lab is going to be utilizing a cold ethanol extraction system, and I have seen a lot of posts recommending getting the ethanol temp down to -80c. I understand the reasoning behind this (to pull as few unwanted compounds out of the plant material as possible - plant fats, waxes, lipids, chlorophyll, etc.).

We are planning on winterizing, filtering, carbon scrubbing, and de-gumming (via silica bed) the crude after the extraction process is complete. That being the case, is it still absolutely necessary to get the temp down that low during the extraction process?

The reason I’m asking, and a point that I’m sure anyone utilizing cold ethanol extraction can appreciate, is that to get temps that low during extraction requires considerably more of an investment than say extracting at temps of around -20c to -40c.

Also, does carbon scrubbing remove chlorophyll? If not, I can understand the reason for the colder extraction temps.

Thanks!

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You don’t need to go that low to avoid removing lipids or chlorophyll, and cooling bulk quantities of solvent to -80 C is going to get very expensive very fast. I don’t see the purpose in winterizing if you’re doing a proper cold solvent extraction - the major benefit to cold polar solvent is that its intended to eliminate the need for winterization by leaving behind the lipids altogether. I have no idea about carbon removing chlorophyll, but if you dont extract it to begin with then you wont have to worry about removing it downstream, right?

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That is correct, but I won’t be able to go to -80c for the extraction. -30c is my limit (due to equipment and freezer limitations)…hence the need to winterize and filter. My main concern was in regards to the chlorophyll. I just want to make sure that it can be removed post-extraction through carbon scrubbing and/or wiped film distillation.

Non of the above are ideal
Beaker has a methanol / iso sop for clorohpyl extraction
The saline wash with non polar solvent also works

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Shorten your soak times
I guess rinsing your biomass picks up even less
Try to keep your etho at -30 during your extraction process iT heats up pretty fast
So You start at -30 but You end at -20 due to heatloss of containers filters strainers spatulas etc. Etc

I disagree. For high end concentrates extracted with Ethanol you should get as close to -80ish as possible to avoid all the garbage and minimize post processing needs. At these temps all you need is a single pass through a 1micron and your done, on the evaporation. -70 will work so will -40 but you will still get fats and waxes depending on soak times and method. I’ve done it first hand. In my experience any nasties you pick up can be remediated with good filtering and carbon scrubbing if needed. Just be mindful that carbon will pull CANNs too. For distillate -30 is fine with a solid winterizing, filtering, carbon/cbleach, sailing washing procedure you can get water clear.

I see, so you are working under the impression that -80C is the minimum temperature required to leave behind lipids and chlorophyll. I would do a few experiments to ensure that that is correct, or to determine what conditions might allow you to avoid going that cold while still leaving behind unwanted components. The cost of adding additional unit operations to a process, such as filtering and scrubbing and this that and the other, should never be taken lightly - those are bottlenecks and will effect your bottom line. As a general rule of thumb, chemical engineers do considerable due diligence before adding even a single unit operation, let alone multiple (in industry, adding multiple unit operations requires meticulous cost/benefit justification and even then the approach may be scrapped all together if it requires such tribulation). It would be a bummer to go through all of that trouble, at the cost of throughput and labor and materials, if either A) it has little/no effect on the quality of the distillate or B) youre performing those filtration steps to remove something that can be avoided extracting to begin with.

That’s fine to disagree, I have confidence in what I’ve performed in lab and process design/economic evaluation. Sure, we all know the solubility axiom “colder solvent extracts less.” I cant disagree with that since that’s just the nature of solubility. Maybe the scenario youre envisioning is different from those I’ve seen or even OPs, or maybe I didnt explain my justifications clearly enough.

The scenario as stated is this: OP is intending to perform cold solvent extraction and use wiped film distillation, which is a rather robust distillation process that doesnt usually yield a product much above 90-95% regardless (on a good day for most). I mention the robustness of these pieces of equipment with the intention of illustrating that a properly optimized WFE system can tolerate small amounts of some of those unwanted components. One’s goal should not be perfection in removing those components to 0.000000 wt%, but rather to reduce the concentrations of those components to the threshold at which downstream processes are robust enough to tolerate, all the while as quickly/inexpensively with as high of a throughput as possible.

So, OPs questions are “can I get away with a temperature above -80 C” and “do I need to perform these additional purification steps/will they work?” To the first I say, you probably can find extraction/distillation process parameters to avoid going that cold and still produce distilled product within your quality parameters. You should analyze your WFE systems to determine their tolerance for lipids/chlorophyll AND determine what is the maximum temperature extraction that will produce crude that your WFE can remediate. Perform experiments to determine what temperatures extract what undesirables and to what degree. To the second I say, before adding even a single unit operation perform a true cost/benefit analysis. In doing so I would consider the following: The cost difference in equipment/electricity/time to cool large quantities of solvent to -20 C, -40 C, and -80 C. Next, consider the time/labor/raw material/equipment/energy costs/opportunity cost of performing those additional scrubs and filtrations (thus producing bottlenecks and reducing throughput). Consider if the raw materials necessary to meet your demand AND perform those extra steps will put you over your facility’s solvent/general storage thresholds. All of those costs must be offset by how must “better” your final distillate may be, which you also should determine.

Long story short, I’m very doubtful of the process as described (-80C extraction + further downstream scrubs/filtrations). A few weeks’ experimentation and time spend doing a true economic evaluation as well as a cost/benefit analysis are the least that OP should do before saying “yeah I’ll spring for the equipment to reach -80 C, as well as reduce my bottom line further by performing additional potentially unnecessary unit operations.” I’m sure OP and his investors would not be amused to learn after significant investment that they’re going to generate 10% less profits per quarter to raise their potency 0.5%.

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optimal solvent residence time varies with temp.
-80 means forever.
-40 means quickly.
-20 quicker still.
0C or even rm temp can and do work too.
depending on where you’re going with it, and what you’re willing to do to get there.

I would agree with @eyeworm that experimentally confirming where the sweet spot is for YOUR specific equipment/biomass/endpoint combination is the correct approach. you can approximate a CUP with a panda. you can test multiple solvent temps and residence times, and see where your clean up steps get you. or which once you can skip.

I’ve got a house guest right now who insists that ethanol extraction should go from moon to moon. at rm temp. 90sec will get that shit done…

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I agree. I did not and would not recommend -80, -70 or even -40 for distillate i was talking about high end concentrations. I just miss understood what he was asking.

We are definitely on the same page. Gotta maximize those margins. -30 (-20 or even room temp) with post processing will most likely do the trick while balancing overhead. The good thing is that because filtration processes can remediate so many otherwise problematic situations we can have some fun dialing it all in without to much worry about going to warm. I’ve used %5 carbon, heat, and a large paddle for stirring to go from super green rich in chlorophyll warm ethanol extracted crude to a decent level of clarity and green free crude ready for 1st pass on a SPD. But the energy and time required to heat the solute to temp, agitate for 30+ min and sit for a long carbon scrub then rapidly chill it for filtration wasn’t worth it. So yes you are very much right ya gotta tinker with it to figure out the sweet spots and maximize return on investment. Luckily there are so many ways to approach it and they all full requirebreally fun R&D!!

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Wow, that is a lot of great information and definitely some factors to consider. Thank you @eyeworm, @cyclopath, @Jay-TL, @Roguelab, @Nlisa for taking the time to respond, and provide some much needed info.

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chlorophyll is very easily removed by carbon scrubbing… in fact, its what carbon seems to do best, and it doesnt take very much. Ive done many room temp, or even warm ethanol soaks that produced a dark green tincture. One fine carbon scrub removes all of it and the tincture left is golden yellow.

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But using a carbin scrub also absorbs precious thc.

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It is far more important to remove the chlorophyll than keep the 1-5% maybe 10% THC you may loose. Plus as you remove the chlorophyl you increase potency so its not an issue. For every little bit of Cann’s you may loose you recover that in revenue by increasing the value of the concentrate. You can manipulate issues like Cann’s adsorption by closely monitoring temperature and resonance time.

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Does Carbon scrubbing remove just thc, or does it remove CBD also? Is carbon scrubbing an effective way of sequestering THC from hemp oil?

As far as I know it dose not show an infinity for one over the other but I have not verified this via testing. No it is not. To separate THC and CBD you will need a chromatography column.