Cannabis extraction is the process of pulling the resin fraction of the plant, the cannabinoids and terpenes held mostly in the glandular trichomes of the flower, away from leaf, stem and other plant material so it can be concentrated, measured and formulated. Every method belongs to one of two families. Solvent-based extraction uses a liquid or pressurised gas, most often CO2, ethanol or a light hydrocarbon such as butane or propane, to dissolve the target compounds, and the solvent is then removed. Solventless extraction separates the trichomes physically, using cold water, sieves, or heat and pressure. The family you choose decides what ends up in the concentrate, what has to be cleaned out afterwards, and which hazards have to be controlled.
What extraction is actually separating
Cannabinoids are not spread evenly through the plant. The Austrian food safety agency AGES describes them as stored in special glandular hairs in the flowering area, with smaller amounts in leaves and stems. Extraction is therefore a concentration step: the goal is to move as much of that resin as possible into a small mass while leaving behind fibre and, depending on the product, chlorophyll, plant waxes and water-soluble material.
No single method does this perfectly. A narrative review of medicinal cannabis processing in the Journal of Cannabis Research summarised the differences this way: dry sieving and water extraction collect whole trichomes, hydrocarbon methods avoid water and pigments such as chlorophyll, ethanol also pulls flavonoids, and CO2 can be tuned to extract different compounds depending on the conditions. The same review lists ethanol, butane, propane, hexane, CO2 and even olive oil among the solvents used.
Solvent-based methods
CO2
Carbon dioxide becomes a supercritical fluid above roughly 31 °C and 74 bar. In that state it acts as a non-polar solvent, and changing pressure and temperature shifts which compounds dissolve. The review notes that CO2 is non-flammable and easy to remove, which is why CO2 extracts do not carry the residual solvent question in the way liquid solvents do. The cost is in the equipment: everything runs inside rated high-pressure vessels.
Ethanol
Ethanol is polar enough to dissolve cannabinoids but also pulls chlorophyll and waxes, especially at room temperature. Chilling the solvent reduces that. The solvent has to be evaporated and recovered afterwards, and ethanol vapour is flammable, so ventilation and ignition control are part of the method, not an extra.
Hydrocarbons
Butane and propane are liquefied under pressure or cold, passed through plant material and then evaporated. Butane boils at about −1 °C, which makes it easy to drive off, and that same volatility is the hazard. A review of butane hash oil production put it plainly: amateur “blasting” can leave flammable vapour pooling in enclosed spaces, where a spark or static discharge ignites it.
Solventless methods
Solventless concentrates are made without any added solvent. Dry sifting shakes trichome heads through fine screens; the review above cites kief from dry sieving at roughly 35–50% THC. Ice water separation knocks trichomes off with cold water and agitation, and rosin uses heat and pressure to squeeze resin out of flower or hash. Ice water hash and rosin deserve their own detailed treatment, so they are only summarised here. The review also notes that these long-established methods are thinly covered in the scientific literature and are hard to scale.
How the methods compare
| Method | Family | What it tends to carry over | Main hazard to control | Typical clean-up |
|---|---|---|---|---|
| CO2 | Solvent | Adjustable with pressure and temperature | High-pressure equipment | Often winterized in ethanol afterwards |
| Ethanol | Solvent | Broad; chlorophyll and waxes unless chilled | Flammable vapour | Evaporation, residual solvent testing |
| Butane / propane | Solvent | Non-polar resin, little water or chlorophyll | Explosive vapour | Purging, residual solvent testing |
| Ice water | Solventless | Whole trichome heads | Low; wet material must be handled cleanly | Drying |
| Dry sift | Solventless | Trichome heads plus some fine plant matter | Low | Repeat sieving |
| Rosin | Solventless | Resin melted from flower or hash | Hot plates | Filtering |
The table is a map, not a ranking. A medical manufacturer, a lab running potency tests and a hash maker will pick differently because they need different end products.
Safety: fire and residual solvent
Two hazards dominate solvent work. The first is fire. Butane vapour pools and ignites, as described above. Ethanol is less dramatic but still a real fire risk: the US occupational safety agency OSHA lists a flash point of 55 °F (about 13 °C) and a lower explosive limit of 3.3% in air. Neither solvent belongs near an open flame, a hot plate, or an unrated electrical fitting. This is why solvent extraction at commercial scale is done in rated rooms with gas detection and extraction ventilation, and why this post does not describe home procedures.
The second hazard is what stays in the product. The pharmaceutical reference for this is the ICH Q3C guideline on residual solvents. It puts ethanol in Class 3, solvents with low toxic potential, where up to 5000 ppm (0.5%) is accepted without further justification. Hexane sits in Class 2 with a much tighter limit of 290 ppm. Cannabis-specific rules differ by country, but the principle is the same everywhere: a solvent extract is only as safe as the evidence that the solvent has been removed.
Common mistakes
- Treating “solventless” as “tested”. No added solvent is not the same as verified potency or verified absence of contaminants. A solventless concentrate still needs a lab result.
- Assuming CO2 needs no further processing. CO2 crude is often redissolved in ethanol and winterized to drop waxes; one published hemp protocol held the ethanol solution at −20 °C for 24 to 48 hours before filtering.
- Comparing extract and flower percentages directly. Kief at 35–50% THC and solvent concentrates at higher figures are a different category from flower, and should be handled that way.
- Reading a solvent’s boiling point as a safety margin. A low boiling point makes a solvent easy to remove and also easy to ignite.
Thailand context
In Thailand the cannabis plant was removed from the narcotics list in 2022, but extracts containing more than 0.2% THC by weight remain Category 5 narcotics. The Ministerial Regulation on Cannabis or Hemp Extracts B.E. 2569 took effect on 26 April 2026. It allows production, import, export, sale or possession of such extracts only for four purposes: official narcotics control, medical use, analysis, education or research, and industrial use. Producers must be Thai juristic persons that are not “foreign” under the Foreign Business Act B.E. 2542 (1999), government agencies or the Thai Red Cross Society, and licensed producers must test THC content every time they produce. Anyone considering extraction work in Thailand should check the current text of that regulation and the licensing requirements before acting.