THC extraction is the industrial process of separating and concentrating desirable compounds, primarily cannabinoids and terpenes, from raw plant material. The goal is to isolate the resinous trichomes, which contain the majority of these compounds, from the inert plant fiber. This separation creates potent, refined products like oils, waxes, and distillates, used in vape cartridges, edibles, and tinctures. The initial crude extract is then purified through subsequent steps.
Preparing the Plant Material
Before extraction begins, the plant material undergoes specific preparation steps to maximize yield and quality. Proper drying and curing of the harvested biomass reduces moisture content, improving extraction efficiency. Curing also ensures a stable starting material for processing.
The most important chemical preparation step is decarboxylation, often performed on the dried material or the crude oil extract. Raw cannabis contains tetrahydrocannabinolic acid (THCA), a non-intoxicating precursor to active THC. Decarboxylation involves applying heat to convert THCA into psychoactive delta-9-THC by removing a carboxyl group. This conversion is typically achieved by heating the material for 30 to 45 minutes at temperatures around 220°F (104°C). This temperature activates the compound without destroying valuable terpenes.
Supercritical CO2 Extraction
Supercritical CO2 extraction is a precise method using carbon dioxide under extreme pressure and temperature to isolate compounds. A substance becomes “supercritical” when heated and pressurized past its critical point, exhibiting properties of both a liquid and a gas. In this state, CO2 acts as a tunable solvent that penetrates the plant material like a gas but dissolves target compounds like a liquid.
The process involves pumping pressurized CO2 into a chamber containing the ground plant material, dissolving the cannabinoids and terpenes. Operators manipulate temperature and pressure to isolate different fractions, such as extracting volatile terpenes first, then increasing pressure to extract heavier cannabinoids. This method is favored because CO2 is non-toxic and evaporates completely when pressure is released, leaving no residual solvent. The resulting crude oil is generally cleaner, though further refinement is often performed to increase purity.
Chemical Solvent Methods
Chemical solvent methods use a liquid chemical to dissolve desirable plant compounds, separating them from the bulk plant matter. These techniques fall into two main categories: hydrocarbon and polar solvents.
Hydrocarbon solvents, such as butane and propane, are highly non-polar and effectively strip only cannabinoids and terpenes, resulting in waxy or glassy concentrates like shatter. Because these solvents have low boiling points, they are easily removed from the final product through purging, which involves applying a vacuum and gentle heat.
Polar solvents, like ethanol, are widely used for large-scale extraction because they are cost-effective. Ethanol is versatile, pulling out both non-polar cannabinoids and polar compounds like chlorophyll, which can give the crude oil a dark tint. Using chilled ethanol minimizes the co-extraction of undesirable compounds like waxes and chlorophyll, leading to a cleaner initial extract. Complete removal of any residual solvent is always the final step to ensure product safety.
Refining the Crude Extract
After initial extraction yields crude oil, several purification steps remove undesirable compounds and achieve a highly concentrated product. One common process is winterization, designed to remove co-extracted fats, waxes, and lipids. The crude oil is dissolved in ethanol and placed in an extremely cold environment, sometimes as low as -40°C, causing waxes and fats to solidify. The mixture is then filtered through a fine medium, leaving behind a cleaner, dewaxed oil that will not cloud at room temperature.
The final stage for high-purity products is distillation, which separates compounds based on their boiling points under a deep vacuum. The oil is heated precisely in a distillation apparatus. Terpenes are vaporized first and collected separately, followed by cannabinoids like THC at higher temperatures. This fractional distillation allows for the collection of a pure, colorless, and odorless oil, often reaching potencies above 90% THC, known as distillate.