Ethanol, CO2 and hydrocarbon extraction all pull the same target compounds out of biomass — what separates them is the solvent, and the downstream hardware each solvent forces you to buy. Ethanol extraction lives or dies on solvent recovery, CO2 extraction skips the evaporator but not the refinement, and hydrocarbon sits in between.
How does each solvent actually behave in the extraction vessel?
All three methods are the same unit operation: a solvent washes the feedstock, dissolves the target compounds, and then has to be separated back out. What changes from method to method is the solvent’s personality — and that personality dictates your equipment list more than any brochure claim does.
Ethanol is a polar solvent. It grabs the target compounds efficiently, and it also grabs a share of things you did not ask for: waxes, fats, pigments. Colder washes pull less of that load, warmer washes pull more. Either way, everything the ethanol dissolves travels with it into the next stage — and the ethanol itself, the bulk of your wash volume, has to be evaporated and recovered before the line produces anything.
CO2 works differently. Compressed into a supercritical state, it becomes a tunable solvent whose dissolving power shifts with pressure and temperature. When the extraction is done, you drop the pressure and the CO2 returns to gas, leaving the extract behind with no residual solvent. That is the genuine strength of CO2 extraction, and the reason buyers tolerate the cost and complexity of a high-pressure skid.
Hydrocarbon solvents — the butane and propane class — are non-polar and run cold. They leave most of the waxes and pigments in the biomass and are kind to the volatile aroma compounds that hotter handling strips away. The trade is that the solvent is flammable, so the extraction skid itself is specialized closed-loop equipment sitting in rated surroundings.
The co-extractive load deserves one more sentence, because it drives your cleanup stages. A solvent that pulls waxes and pigments along with the target hands you extra separation work after the wash; a solvent that leaves them in the biomass hands you less. That difference shows up again in the equipment table below.
One disclosure before we go further: we do not build extraction skids for any of the three methods. We build the downstream equipment — evaporation, separation, distillation — that every one of them feeds into. That is exactly why we can compare the three without grading on our own axis: we have no method to sell you, only the hardware each method makes you buy.
What downstream equipment does each method force on you?
Most comparisons of these three methods are written by a vendor of one of them, and graded on that vendor’s axis. The axis all three share — and the one that hits your budget after the skid arrives — is the downstream train. Here is how the methods compare on it:
| Downstream stage | Ethanol extraction | Supercritical CO2 extraction | Hydrocarbon extraction |
|---|---|---|---|
| Bulk solvent removal | Heavy — most of the wash volume is ethanol that must be evaporated and condensed for reuse | Minimal — the CO2 separates from the extract when pressure is released | Mostly handled inside the closed-loop skid; residual solvent still needs a vacuum purge |
| Phase separation and settling | Yes — after cold cleanup steps, mixtures settle into layers that must be drawn apart | Rarely | Sometimes, when cleanup washes are added |
| Final refinement of the extract | Yes, when the target is heat-sensitive or high-boiling | Yes — depressurization separates solvent from extract, it does not purify | Yes, same as ethanol |
Read the table and the pattern is clear. CO2 extraction moves the burden upstream into the skid — pressure vessels and control systems instead of evaporators. Ethanol extraction moves it downstream into solvent recovery, and the size of that recovery stage decides the real throughput of the whole line. Hydrocarbon splits the difference. No method escapes refinement, and no method escapes the question of where its solvent goes.
Why does ethanol extraction stand or fall on solvent recovery?
Because the ethanol is the bulk of what you process. A wash produces far more solvent than extract, and until that solvent is evaporated off and condensed back for reuse, the line is not producing — it is storing liquid. This is why we tell every ethanol-line buyer to size the rotary evaporator first and work backwards to the wash vessel.
The recovery loop is a closed system. Vacuum holds the boiling point down, rotation spreads the mixture into a thin film, the heated bath replaces the heat of vaporization as fast as evaporation pulls it out, and the condenser turns solvent vapor back into liquid. The loop’s speed is whichever stage is slowest — bath heat input, condenser capacity, or the pump holding vacuum against cold solvent vapor. How much of each you need depends on your solvent’s behavior and your batch volume, not on a number printed on the evaporator itself.
Here is the unit we put into most pilot-scale ethanol lines, the RE-501:
| Model | RE-501 |
|---|---|
| Evaporating flask capacity | 5L |
| Glass material | GG3.3 borosilicate glass |
| Vacuum | up to -0.095MPA |
| Motor power | 40W |
| Rotation speed | 0-120 |
| Bath size (mm) | 280*160 |
| Bath lift | Manual |
| Heating power | 1500W |
| Temperature range | Room temp~200℃ |
| Temperature accuracy | ±1℃ |
| Power supply | AC220V; /50Hz |
Three judgments from that spec sheet. First, 1500 W of bath heating behind a 5 L flask is a real recovery engine — but only if the condenser and cooling source re-liquefy vapor at the same pace, so we confirm condenser type, cooling source, vacuum pump, bath temperature, lift mode and solvent characteristics together before we stand behind a configuration. Second, the bath runs from room temperature to 200℃ with ±1℃ accuracy, which covers ethanol recovery with headroom to spare. Third, check the joints before you assume you need this size: on the benchtop line the 1 L RE-101 and RE-201D carry a 24# ground joint while the 3 L RE-301 steps up to a 50# flange port — if your batch sits at 3 L or below, stay benchtop and skip the 5 L.
The 5 L rotary evaporator (RE-501) keeps the same 40 W motor and 0-120 rpm rotation as the benchtop units but pairs them with a larger 280*160 mm bath. That pairing is deliberate: a bigger flask needs a bigger heated surface, not just a hotter one. If your batches outgrow 5 L, the answer is a larger evaporator rather than a second shift of waiting — our rotary evaporator category covers the range upward from here.
Where do phase separation and settling fit in the line?
Ethanol lines run cold cleanup steps to drop waxes and fats out of solution, and after those steps — or after any wash where two liquid phases form — the mixture has to settle and the layers have to be drawn apart cleanly. Hydrocarbon lines hit the same need when cleanup washes are added. CO2 lines mostly skip it. The vessel for this job is a glass liquid separator, and the glass is not decoration: seeing the interface between layers is the whole point.
Our spherical vacuum separator line runs from 10 L to 50 L:
| Model | FY-10L | FY-20L | FY-30L | FY-50L |
|---|---|---|---|---|
| Vessel volume | 10L | 20L | 30L | 50L |
| Vessel shape | Spherical | Spherical | Spherical | Spherical |
| Glass material | Thickened borosilicate 3.3 | Thickened borosilicate 3.3 | Thickened borosilicate 3.3 | Thickened borosilicate 3.3 |
| Pressure range | Normal or negative pressure | Normal or negative pressure | Normal or negative pressure | Normal or negative pressure |
| Vacuum | -0.095Mpa | -0.095Mpa | -0.095Mpa | -0.095Mpa |
| Frame material | Stainless steel | Stainless steel | Stainless steel | Stainless steel |
| Motor power | 90W | 120W | 120W | 120W |
| Stirring speed | 60-600rpm | 60-600rpm | 60-600rpm | 60-600rpm |
| Power supply | 220V/50Hz | 220V/50Hz | 220V/50Hz | 220V/50Hz |
Every model in the line is thickened borosilicate 3.3 glass on a stainless steel frame with PTFE sealing, rated for normal or negative pressure down to -0.095 MPa. Stirring runs 60-600 rpm across the range — 90 W on the FY-10L, 120 W from the FY-20L up — because mixing and settling are both part of the job: agitate to wash, then stop and let the layers form before you draw one off. All four run on 220V/50Hz.
Size the vessel to the batch, not to the ambition. If your separation step handles 20 L per run, the FY-50L buys you nothing but a taller frame and a slower drain. When you configure a spherical vacuum glass separator in the 10 L to 50 L range, the checks that matter are vessel volume, vacuum requirement, stirring speed, discharge valve, frame material and pump matching — the same list we run through ourselves. For the wider picture of where glass separators sit against other separation hardware, our comparison of liquid-liquid separation equipment lays the options side by side.
When does the crude extract need molecular distillation?
Whichever solvent you ran, you now hold a crude extract. If the valuable fraction in it is heat-sensitive or high-boiling, the final polish is short-path molecular distillation: separation under high vacuum, where vapor travels a short distance from evaporator to condenser, so the material sees gentle conditions instead of a hard boil.
This is the stage CO2 extraction buyers most often forget. Depressurization separates the solvent from the extract — it does not purify the extract. If the product specification demands purification or concentration of a heat-sensitive compound, a supercritical CO2 extraction line ends in the same place an ethanol line does: in front of a still. Our short-path molecular distillation equipment is built around exactly that job, with the evaporator, condenser, receiving system and vacuum support selected by process rather than copied from a fixed template.
There are no universal numbers for this stage, and anyone who hands you one without seeing your material is guessing. The variables that decide a configuration are the feed material, vacuum stability, heating temperature, feed rate, condenser support and the receiving setup. Our molecular distillation equipment selection guide walks through how we weigh each one with a real feedstock in front of us.
Which extraction method should you choose?
Start from the product and work backwards:
- Choose ethanol when throughput and process simplicity matter more than selectivity, and when you can justify a real solvent recovery stage. The solvent is familiar, the chemistry is forgiving, and the downstream train — evaporator, separator, still — is standard hardware we build every day. Our guide to ethanol extraction process and equipment maps that line stage by stage.
- Choose CO2 when the product cannot tolerate residual solvent and the batch economics support a high-pressure skid. You trade downstream hardware for upstream complexity, and you still budget for refinement at the end.
- Choose hydrocarbon when the aroma profile is the product and you can site a rated closed-loop installation. Plan the vacuum purge and the refinement stage alongside the skid, not after it arrives.
The mistake we see most often is a buyer sizing the extraction skid with care and treating the downstream train as an afterthought. Do it the other way around. The skid decides what the extract looks like; the downstream decides how much finished product actually ships per day.
FAQ
Is CO2 extraction really solvent-free?
No — CO2 is the solvent. “Solvent-free” describes the residue in the finished extract: when pressure drops, CO2 returns to gas and leaves nothing behind. During the extraction itself it is very much a solvent, chosen precisely because it disappears afterwards.
Does a CO2 extraction line still need downstream equipment?
Yes, for refinement. Depressurization separates the CO2 from the extract, but it does not purify or concentrate the extract. If your target compound is heat-sensitive or high-boiling, the crude still goes through short-path molecular distillation, exactly as an ethanol or hydrocarbon crude would.
Why does ethanol extraction need a rotary evaporator when CO2 extraction does not?
Ethanol stays liquid at room conditions and mixes through your whole wash, so the only way to separate it from the extract is to evaporate it under vacuum and condense it back — that is the rotary evaporator’s loop. CO2 separates by itself when you release the pressure, so no evaporator is needed for bulk solvent removal.
Can one downstream line serve both ethanol and hydrocarbon extraction?
Partly. The bulk solvent removal stage differs — ethanol needs an evaporator, hydrocarbon residuals need a vacuum purge — but the separation and refinement stages overlap. A glass liquid separator and a molecular distillation unit can serve both methods, which is why multi-method facilities usually share that part of the train.
The bottom line
Pick the solvent for the product, then size the downstream before you sign anything. If ethanol is your method, your line lives on its recovery stage — start with the evaporator in our rotary evaporator category and add separation and distillation to match. If CO2 or hydrocarbon is your method, skip the evaporator debate and go straight to refinement. Either way, send us your feedstock, batch volume and target product and we will confirm a configuration; the answers on our FAQ page cover the questions buyers ask most before that conversation starts.