Ethanol evaporation/recovery to a specific solvent % in crude?

Doing ethanol extraction on hemp for the CBD, with the eventual goal of taking it to crystallate.

It seems pretty pointless to me to evaporate off all of the ethanol that the chemicals we’ve extracted from the plant were dissolved in, just to re-dissolve that crude in ethanol at a known ratio and homogenize, winterize and have to evaporate that ethanol off again a second time.

Is anyone running a setup where they evaporate a certain amount of their input ethanol so as to not have to re-dissolve their crude in order to winterize? And if so, how are you determining that your dissolved crude is at the correct ratio with the ethanol it’s dissolved in before it goes in the cryo freezer? Keep in mind I’m talking about potentially hundreds of gallons here so a small lab setup where I could watch the amount of mL reduce as it evaporates some portion of the ethanol is not a viable solution. Could a person determine this via specific gravity if they were processing a variety of different plant inputs from different farmers?

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If you extract with etoh around -40 you will not need to winterize, you can proceed with filtration/evaporation.


If you extract with etoh around -40 you will not need to winterize, you can proceed with filtration/evaporation.

On the scale I’m moving towards I don’t think keeping all my ethanol, as well as maceration tanks at -40 is going to be practical. As well I’m concerned with what (if any) yield I may lose by doing that cold of a plant material soak

Big operations are using liquid nitrogen in counterflow heat exchangers against the etoh. You can chill the feed stream.the cryo freezer you mentioned will be more costly in maintenence and electricity.


I second the idea that you should extract with -40c etoh to limit the amount of lipids extracted. Not only does this significantly reduce the filtration needed, but also allows the etoh to absorb significantly more Cannabinoids. Yes you need to slightly increase the residence time, in a vat style system I usually soak for 10 minutes. But if you don’t plan on saving the fats, extracting them is an expensive waste of time.


-40c etoh to limit the amount of lipids extracted. Not only does this significantly reduce the filtration needed, but also allows the etoh to absorb significantly more Cannabinoids.

Is this a solubility limit thing, that if the ethanol doesn’t absorb lipids it has more room for the CBD i’m after?

I know I have a limited understanding of chemistry but curious if real world results have actually shown an increase in CBD extracted when done under -40C conditions? That goes against a lot of my understanding of solubility vs temperature but like I said, I’m not well versed enough in the chemistry of this application to know better, and there doesn’t seem to be much info available publicly to verify.

Does it allow for more effective extraction of cannabinoids because the lack of lipids in the solvent means a slower approach to saturation?


I think the main reason it can hold more is because it dissolve/absorbs less liquid water into the solvent solution. There r other effects too but i think thats the biggest cause even a couple percent h20 in solution means a much lower saturation point for cannabinoids

Extract at -40 or more scientifically, very fuckin cold. Test your ratios of ethanol to raw material to see if your cbd % changes with different ratios. Should not need to winterize if you extract at these temps. If you want to throw it in a cryo freezer for a while just do it as diluted crude in buckets. Then remove and recover ethanol for some delicious RSO.


I have seen many test results with the crude extractors that I am working with that continually show higher CBD and cannabinoid %s higher for cold ethanol extracted compared to CO2 extracted. And that is only a 3 minute soak in -18C ethanol. Almost nothing needs to be filtered or winterized. The 1um filter paper catches the ever so slightest amount of fat, never covering the entire surface.

Hey all, I know this is an unorthodox way to post. But i have a question and cannot figure out how to create a topic at all lol. so heres my deal:

My company has the Ethos 6 by capna (yes i know most of you here are not fans of it) but it is what i have to work with. Unfortunately we do not have a rotovap or centrifuge yet. We have been taking the washed flower and placing them in the 55 gallon barrels until waste disposal has picked it up. At the bottom of the barrels there is always ethanol that is the darkest green you could imagine, basically black. I am not 100% sure what all i can do with it. Possibly evaporate the ethanol off using a hot plate? I do not want to send this solution through the Ares by Capna because it will stain the system very bad. If anyone has any suggestions I would REALLY appreciate the help and I may have some more questions for you!

Thank you!!

If you put it into a large flat dish and pointed a fan at it the dish, eventually all of the solvent would wander off.

Or you could toss a bit more ethanol at it and practice chlorophyll remediation and winterization.


I would highly recommend getting yourself a centrifuge or a screw press, that you have any amount of ethanol dripping off your biomass after extraction tells me you’re flushing $$$ down the drain in ethanol losses, even with a centrifuge you’ll likely see 5%+ losses depending on basket size and rotation speed.

Unfortunately that stuff has had a long exposure time to the plant material at room temperature which means its chock full of chlorophyll, plant fats/waxes and likely a bunch of water and water soluble compounds too. “staining” your Capna is the least of your concerns, this will almost certainly deproof your recovered ethanol and contaminate your crude oil as well with undesirable compounds that are difficult to remove. Even with a rotovap you’ll have plant sugars and other nasties making buildup on the inside of your evaporation flask and it’s a real PITA to remove (ask me how I know). Putting that kind of crude thru a short path or wiped film without winterizing and remediating will produce streaky and nasty distillate.

If you don’t have a rotovap how are you getting your last bit of ethanol out of your crude oil and decarbing before further refinement?

Don’t know where you’re located but I’m going to have a 20L and 50L rotovap systems for sale soon in the Denver area.

Edit: for anyone else reading this I did eventually get a system scaled to extract cold and do 1200+ lbs/day, just cost a lot of money to get there. Winterizing as a separate process from extraction ended up being a time-, equipment- and labor-intensive headache.


I have been purging the last bit of ethanol with a vacuum oven. We have 4" wiped film still by Pope that should remove the remaining ethanol if there is any, or so im told. We are located in Oklahoma. The Ethos & Ares system removes the winterization process. I have thought about taking the ethanol solution in question freezing it, run in through a Buchner, and then send it through the Ares, although we dont have one of those either. I have definitely have expressed that we are flushing money down the toilet to the higher ups, although no moves have been made to purchase more equipment yet. Roughly, for every 7 gallons of ethanol i run through the Ethos, I end up losing 2 gallons of ethanol per run due to what remains in the biomass, which is very frustrating. Just trying to figure out if there is absolutely any use i can make out of it at this point.

Tiny panda army :panda_face::panda_face::panda_face:

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so quantify it for them…

send your spent biomass out for testing, if you left that much tincture, you left cannabinoids too.

send the black goo at the bottom out for testing. figure out how many kg of THC are going out the door in each barrel.

assuming you’ve actually sold crude, put a dollar amount on what they are PAYING to throw away.

look like a genius…

yeh, you could use it to recover ALL of your alcohol if you insisted, but it’s not the most efficient use of your equipment unless you’ve got a surplus of the things.

at your scale a rotovap you can turn up to decarb temps is the correct response imo.