Temperature is the selectivity control
Ethanol is a strong, cheap and widely available solvent, and that is exactly the problem with using it at room temperature: it dissolves almost everything in the plant, including chlorophyll, waxes and lipids. Chilling it changes the balance. At around -75°C ethanol still dissolves the target actives readily, but it is a poor solvent for waxes and chlorophyll, so most of that unwanted load never leaves the biomass.
What a cleaner crude is worth
Every kilogram of wax and chlorophyll that stays in the biomass is a kilogram that does not have to be removed later. In practice that shows up in four places:
- A shorter winterization hold, because there is less wax to precipitate.
- Less filter media consumed per batch.
- A lighter colour going into distillation, so fewer remediation steps.
- Less loss of product bound up in the material that gets filtered out.
Throughput is the trade-off
Cold ethanol lines are chosen where daily biomass volume matters. Chilling a large ethanol inventory takes refrigeration capacity, and that capacity has to be sized against the throughput target rather than added afterwards. This is why the useful question at quotation stage is not which machine but how much biomass per day.
Where it sits against CO2
Supercritical CO2 gives a crude with no residual solvent at all, which suits food, flavour and cosmetic ingredients where a solvent declaration would be a problem. Cold ethanol handles higher volumes per day and produces a lighter crude that needs less refining, at the cost of a solvent recovery and purge step. Neither is universally correct; the material, the finished product and the daily volume decide.
Building the chain
Cold ethanol extraction, winterization and short path distillation can be quoted and engineered as one production chain, so the output of each stage matches the feed the next stage expects.