Ethanol extraction dissolves cannabinoids and terpenes out of dried cannabis or hemp by soaking or washing the plant material in food-grade ethanol, filtering off the spent material, and then evaporating the ethanol to leave a crude oil. Its main strength is that ethanol dissolves cannabinoids very efficiently and is a comparatively low-toxicity solvent. Its main weakness is that it is not very selective: at room temperature it also pulls chlorophyll, plant waxes and other unwanted material, which is why the solvent temperature, the recovery step and residual solvent testing define the quality of the result.
Why ethanol is used
Ethanol is a polar solvent that still dissolves cannabinoids well. A narrative review of medicinal cannabis processing in the Journal of Cannabis Research reports that when acidic cannabinoids were measured, ethanol gave the highest yield among the organic solvents compared, and it describes ethanol as a preferred solvent for cannabinoid extraction. The review’s solvent table lists ethanol’s boiling point as 78.4 °C, far above butane at about −1 °C, which is one reason ethanol is handled as a liquid at normal pressure rather than as a liquefied gas.
A 2022 cold ethanol study in the journal Molecules adds that food-grade ethanol is commonly treated as a “green” and GRAS (generally recognised as safe) solvent. That is a statement about the solvent itself, not about the finished extract, which still has to be tested.
Cold vs warm ethanol
The biggest single variable is temperature.
Warm or room-temperature ethanol extracts quickly and broadly. Along with cannabinoids it pulls chlorophyll, waxes and water-soluble material, giving a dark, grassy crude that needs further refining.
Cold ethanol, chilled well below freezing, is more selective. The same Molecules study states that cold ethanol extraction limits the extraction of chlorophylls and waxes compared with supercritical CO2 and other traditional systems, and that oil extracted at room temperature “must be winterized” to remove residual waxes.
The study’s numbers are worth reading carefully rather than summarising as “colder is always better”:
| Extraction temperature | Yield (g per 100 g dry matter) | THCA extraction efficiency | Terpene content vs −40 °C |
|---|---|---|---|
| −20 °C | 18.2 | 83.6% | 54.1% lower |
| −40 °C | 19.7 | 97.7% | reference |
| Room temperature | 18.5 | 102.1% | 32.2% lower |
Conditions were a 1:15 cannabis-to-ethanol ratio and 10 minutes of extraction. Room temperature recovered the most THCA, −40 °C kept the most terpenes, and the −20 °C run did worse on terpenes than room temperature. The authors reported no significant difference in yield between the three temperatures. In other words, cold ethanol mainly changes what comes along with the cannabinoids, not how much total material you get.
Selectivity: chlorophyll and waxes
Chlorophyll and waxes do not add therapeutic value and affect taste, colour and stability. A 2025 paper describing a GMP-grade full extract cannabis oil lists lipids, carbohydrates, chlorophyll and polyphenols among the undesirables its purification set out to remove, and reports reducing chlorophyll to residual values after purification. There are two ways to deal with them:
- Avoid pulling them, by extracting cold and keeping contact time short.
- Remove them afterwards, by winterization: the crude, dissolved in ethanol, is chilled so waxes precipitate and then filtered cold. A published hemp protocol held its ethanol solution at −20 °C for 24 to 48 hours before filtering.
Warm extraction plus winterization and cold extraction alone can reach similar end points; the choice is usually about equipment, throughput and energy cost.
Solvent recovery
Once the plant material is filtered off, the ethanol is evaporated under reduced pressure and condensed for reuse. In the Molecules study, the lab setup used a vacuum rotary evaporator at 50 °C to remove the ethanol and determine crude yield. Lowering the pressure lets the ethanol boil well below its normal 78 °C, which protects heat-sensitive compounds and speeds up recovery. Recovering and reusing ethanol is also a large part of the economics, since the solvent-to-plant ratios used are high; the Molecules authors specifically flag the cost of ethanol at scale.
Residual solvent
Whatever evaporation method is used, some ethanol can remain in the crude. The reference framework in pharmaceuticals is the ICH Q3C guideline on residual solvents. It places ethanol in Class 3, solvents with low toxic potential, and states that residues of 50 mg per day or less, corresponding to 5000 ppm or 0.5% under its Option 1, are acceptable without justification. Cannabis product rules vary by country and some set their own limits, but a certificate of analysis for an ethanol extract should report residual solvents, and “ethanol-extracted” on a label is not a substitute for that number.
One related point often gets missed: denatured alcohol contains added substances that are not ethanol, and those end up in the extract if the solvent is not food or pharmaceutical grade.
Fire safety
Ethanol vapour ignites easily. The US occupational safety agency OSHA lists ethanol’s flash point at 55 °F (about 13 °C), meaning it gives off enough vapour to ignite at ordinary room temperature, a lower explosive limit of 3.3% in air, and a vapour density of 1.59, so the vapour is heavier than air and can collect low down. Commercial ethanol extraction is therefore run in rated rooms with ventilation, gas detection and equipment designed for flammable atmospheres. Heating ethanol on a stove or hot plate in a kitchen combines a flammable vapour with an ignition source, and this post deliberately does not give home procedures.
Common mistakes
- Assuming colder always means better. The data above show different trade-offs at each temperature.
- Skipping winterization after a room-temperature run. The crude will carry waxes and chlorophyll.
- Using denatured or unknown-grade alcohol.
- Treating “evaporated” as “solvent-free”. Only a residual solvent test shows what is left.
Thailand context
Making an extract with more than 0.2% THC by weight in Thailand falls under the Ministerial Regulation on Cannabis or Hemp Extracts B.E. 2569, in force since 26 April 2026, which limits production licences to Thai juristic persons that are not “foreign” under the Foreign Business Act B.E. 2542 (1999), government agencies and the Thai Red Cross Society. Check the current rules before acting on anything in this post.