Reclaiming Solvent From Biomass

When I look at my production log sheet, I have the dry weight of the biomass and the wet weight (to see how much ethanol I lost). Currently, I’m losing about 0.15kg EtOH/kg biomass (around $3/kg since its organic ethanol) which is pretty good. But thinking about that number, that’s still pretty high. Looking at the spent biomass, 13% of it is ethanol. What I want to do is design something the majority of that out. Currently, I have a panda dryer so spinning it out won’t work.

I’m picturing something where I place my bagged material in a chamber where it sits on top of a mesh screen and is heated. Beneath the mesh, it reduces down to an p-trap to catch particulate (look at your sink drain) which then goes to a plate heat exchanger that condenses the vapors into a tank or keg. I figure using a mesh bottom to allow vapors to flow down will help performance and the p-trap will stop particulate from contaminating the vessel.

Does anyone have anything like this currently?

(Note, I will post context and why I think this is worth pursuing)

Context and why I’m asking
Since ethanol suppliers charge around $700 per barrel of denatured ethanol, it likely costs between $400 and $600 per barrel in energy for large processors to make it. I’m using food grade ethanol, so I’m paying $1,700 in excise tax to the government, so I can put up to $1,700 of time and energy per whatever pound of biomass processed to be worth it, which is a lot.

I know many people use non-denatured ethanol, so they don’t really care, maybe this would save ~$400 per couple thousand pounds or so and would limit environmentally harmful denaturants from getting into the environment. For those of us who use organic ethanol, the tax is basically waste, so anything we can do to prevent buying another barrel and wasting money on taxes would be a smart play.

you can absolutely get it back using a still if you insist. it is unlikely to be worth your effort, but I have run into one group who have implemented. talk to Paul at affordable distillery equipment.


I’ve been playing with ethyl acetate with great results. My only issue is recovering all of the solvent from the biomass. Wish I could use a Panda but I have reservations about trying it due the aggressive nature the ester solvent. A fuge is definitely the route I’d love to try but it’s hard to justify on the personal scale I am on.

I know the ethanol evaporates pretty readily. Even after coming out of the panda, I can smell a bit of ethanol, but after a few minutes I can’t. I’m assuming there’s some more stubborn molecules that adsorb onto plant structures, or have penetrated too deep to be removed in a timely manor, but still, I have basically $1,700+ of electricity per 560 lbs of biomass ($3/lb). It makes me think I’m leaving money on the table.

And thank you for the tip!

Every company I know that’s implemented something to recover the solvent from spent biomass has found it to be not worth the investment, time and effort.


Id spend that 1700 on a 330gal IBC tote, some (organic) sugar, yeast and a still.


maybe upgrade your panda to a real centrifuge first


You can recover the ethanol from biomass in a milk bottle still with a jacket.

With the still filled with oil you can apply heat to the biomass without air exposure. The vapors are condensed and your tax dollars are saved.

The rest of the still works as normal and your oil gets infused by the leftovers from the extraction.

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a chamber for your mesh bag with a jacketed round coil. The mesh bag sits on top of the coil and when you heat the coil the ethanol turns to vapor and the vapor goes through a molecur sieve then into a recovery unit by means of shot gun condenser. that’s kept at -20.

Maybe get a chamber with a coil made for the size of your bag to sit in and work from there.

You could have a splatter platter made with a visual round coil for your mesh bag and have a visual inner coil that hugs the bag and then another top coil but that’s over kill.

… You could just take the loses.

Edit: now that I think of it, you’d be spending a lot to save a little and it would basically in the end just be a fancy alcohol still.

I know it would be a bit of an investment (I’m not a big lab, so it will cost somewhere on the order of ~$600-$1,500).
I would like to upgrade to a centrifuge, but I think the issue might get worse when I do that. Currently I’m using 100 micron bag filters with a ~6" diameter and the panda dryer gets up to 3200 RPM. The centrifuge I’m looking at only gets up to 1600 RPM and the bags have an 11" diameter. I may be overlooking something with the design of the centrifuge (maybe vapors are trapped).

This may not be an issue with enough run time, ratio of radius to rotation speed is 4x worse on performance, this certainly doesn’t mean 4x more ethanol loss, but I’m not sure it will be better than the panda.

Is it legal for me to do that?

panda is rumored to be ~9.5in in diameter.
which at 3200rpm gives an RCF of ~1330g

an 11.5in rotor spinning at 1600rpm is about 400g

if you could get it up to 2500 rpm you’d be in the right range (1000g)

you’d imagine a longer spin would get the job done, and it helps a little, but below about 800g it really doesn’t seem to…


@cyclopath Much better calculation, I was referring to my material socks’ diameter. I currently place 4 socks with 0.5kg of biomass per and there is a small gap in the center. However, they do compress and flatten out, so the mass distribution is centered around maybe 8.5" inches for each bag. I’m guessing as the ethanol travels out towards the edge, it travels faster and escapes quicker, so really its only the inner most diameter that counts (along with the capacity of biomass to adsorb ethanol)

Another specification that I think is important is about my production logs. Once we spin them down, we immediately weigh them, and it’s abut 0.15kg of ethanol left. However, this doesn’t account for the mass loss that was extracted from the biomass. I extract mostly flower, so this could be 5-10% weight of the biomass (accounting for test results being by dry weight) increasing the loss.

Also, I made a mistake, 11" is the depth, 17.7" is the diameter. That actually helps a lot making the RCF 1134 for the centrifuge. I’m guessing the remaining losses that the centrifuge would cover is the vapors that escape from the panda along with transfer loss.

I’m getting ready for MJbizzcon so I don’t have time to do this stuff, but I’d like to do a proof of concept run with maybe a heat gun and some clever bucket work.

I don’t recommend playing with flammable solvents and heat guns at the same space/time co-ordinates…

Ethanol has a flash point of only 16C, so it’s pretty easy to ruin your day/lab with an ignition source.

This one wasn’t too bad; How do you make a centrifuge go WOOF?


Fair enough, even more buckets then!

oldie but goodie, showing what can happen when you use a heat gun on a freshly poured out puddle of concnetrate that’s still nice and flammable near an operating extractor

edited my comment to be politically correct

I mean more of heat gun to heat a closed vessel, not pointing in the chamber

Also, jesus that’s a fucking awful video