Low % Hemp Process Modifications

What sort of modifications would you make to the classic ethanol extraction process to produce crude oil when dealing with 1) Hemp in general and 2) Flowers with low CBDA concentrations (~3-5%)? (or low THCA for that matter).

Dealing with many inexperienced growers who aren’t necessarily pumping out high-end material. I know this is kind of the concentration threshold but why not push the barriers eh?

Currently extracting unground flower at -20C for 45 min, straining, and rotovaping at ~35C finishing in vac oven at ~40C high vac. Seeing atrocious yields (~1-2% overall) even without filtering and low temps.

Some things we’re thinking of testing:

  • adding dry ice to drop extraction temp to <-40C
  • increasing temp of extraction and proceeding with dewaxing/winterization
  • decarbing material before extraction
  • trying 90/10 etoh/n-heptane solvent blend
  • grinding flower to increase surface area of extraction
  • adding agitation to extraction

Have an in-house HPLC machine to quantify experiments, just need ideas! Will report results.

Any help is greatly appreciated!

Grinding and agitation should help, and I seem to remember reading somewhere that decarbing may as well, though I can’t be certain on that one.

Adding in a centrifugal or other solvent recovery step should help as well, if you’re just straining you’re probably leaving a lot of ethanol in the plant, which will be holding cannabinoids.


If you’ve got in house analytics, you should be able to figure out where your cannabinoids are going.

I agree with @Lincoln20XX that they are currently most likely still in your biomas.

I recommend you stop looking at “total extracted mass” as a measure of yield.

Quantify how many gram (mg, kg, lb, whatever) of cannabinoids are going in to you process, and how many are coming out.

Dry your spent biomass and test it.
THEN, calculate your yields. As a percentage of the input cannabinoids.

Running colder will not increase yield. It should decrease total extracted mass, because it will be more selective. You should see higher purity, and slightly less total cannabinoids.

Extracting warmer will increase total extracted mass, and probably even total cannabinoids extracted, but you will need to balance that gain against the extra purification steps you’ll need to add. Which may (or may not) decrease your FINAL total cannabinoid yield.

…but you’ve got an hplc, so you can figure that out.

Grinding allows you to get more biomass into the vat (tube, reactor, …) but it also tends to break cells and release unwanted. Everything you are actually after is in the trichomes, no need to release cellular contents. When using higher cannabinoid input, minimal grinding gives acceptable yields and brings along less ballast (that which you don’t want/need). With lower yielding input, it might make a significant difference in your yield.

If you’re loosing 10% of your solvent to your spent biomass, you will find you’re also loosing at least 10% of your theoretical yield. Using a centrifuge or press (more green ballast with a press) to get to 95% solvent recovery (or 98% if you can spin fast enough) is likely to be your biggest achievable yield gain.

You’ve presumably read that you can reuse the same solvent on multiple batches of biomass. While true, there are yield losses associated with that strategy.

Old skool would have you extract the same biomass 3x to get all the good stuff…