• CO₂ extraction:
• To understand CO₂ extraction, its important to first understand some thermodynamic concepts:
• Matter can exist in three different phases (solid, liquid and vapor).
• The boundaries that separate phase are specified by pressure (P) and temperature (T) conditions.
• The "critical point" is defined as the P and T combination (P_c and T_c) where two phases coexist.
• The "critical point" of CO₂ is reached when T_c = 87.98℉ and P_c = 1,071 psi
• When CO₂ reaches or exceeds its "critical point" its said to be supercritical.
• behaves as a supercritical fluid (SCF), adapting properties of both a gas and liquid.
• expands to fill its container (like a gas)
• has high density (like a liquid)
• Pros
• CO₂ is a unique, highly selective "tunable solvent".
• can be "tuned" to selectivity extract different compound groups
• i.e. can separate (fractionate) terpenes from cannabinoids
• CO₂ solvency properties can be "tuned" by adjusting its T and P.
• can function as a supercritical solvent (a SCF)
• can function as a subcritical solvent (a liquid)
• Supercritical fluid extraction (SFE):
• high pressure/high temperature (P= 1083 psi and T = 88℉)
• a strong solvent, which results in high yields
• can extract:
• all of the lighter molecular weights (volatile oils, light waxes)
• all of the heavier molecular weights (heavy waxes, lipids, fats, paraffin)
• good for separating out cannabinoids (as a group)
• Subcritical fluid extraction (SbFE):
• low pressure low temperature (P= 75 psi and T= 33 ℉)
• When supercritical CO₂ T is dropped below 88℉, it changes phase (from a SCF to a liquid).
• a weaker solvent, which results in lower yields and longer extraction time
• extracts just the lower molecular weight compounds
• lower temperature prevents degradation of heat sensitive compounds
• good for separating out terpenes (as a group)
• Clean and safe solvent
• Non toxic
• Not flammable or explosive
• Environmentally friendly
• No need to purify
• No residual solvents remain in bulk extract
• kills microbial bacteria, mold, mildew and insect mites
• the only method that completely removes heavy metals and toxins
• runs without air, which prevents oxidation
• preserves more THCA and terpenes than other extraction methods
• Can be automated because CO₂ is not explosive
• Low facility and operation cost
• Good for vape pens, terpenes and oils
• Cons
• High equipment cost due to high operating pressures
• Slow extraction times
• NOT good for live resin
• Hydrocarbon extraction: (butane, propane, hexane, naptha)
• Pros
• Low equipment cost due to low operating pressure
• High yields
• Medium extraction times
• Good for vape pens, distillates and dabbing products (shatter and live resin)
• Cons
• High facility and automation costs due to explosivity
• Residual toxic solvent remains in bulk extract
• NOT good for oils and infused products
• Ethanol extraction:
• Pros
• Low equipment cost due to atmospheric pressure
• High yields
• Fastest extraction times
• Good for vape pens, distillates and infused products
• Cons
• Moderate facility cost due to flammability (even though not explosive)
• High operation costs
• Ethanol is taxed
• Significant post processing energy to recover ethanol
• Residual solvents remain in bulk extract
• NOT good for dabbing and terpenes

Some secondary processing is required for each extraction method:

• Decarboxylation:
• converts the cannabinoid acids into cannabinoids
• a secondary process for most extraction methods
• a pre-extraction process when using CO₂ method
• ground buds are placed in a forced air oven (not a vacuum oven)
• preheated to 240-250℉ (115.56-121.11℃)
• baked for 1-2 hours
• decreases extraction run time
• increases extraction yields
• Winterization:
• chemically separates the fats and waxes from the essential oils
• the bulk extract is mixed with 200 proof ethanol
• 10 : 1 ratio of ethanol : extract
• i.e. 800 mL ethanol : 80 grams extract
• mixture is placed in a sub-zero freezer (-84.6℉) (-64.78℃) for 24-48 hours
• Filtration:
• Winterized extract is poured through a vacuum filter
• physically separates the fats and waxes from the essential oils.
• Ethanol recovery:
• The filtered oil/ethanol suspension is put into a roto-vac
• flask is rotated in warm water (66.6℉) (19.22℃) to vaporize the ethanol
• vapors are sucked onto cold condensation coils, which distil (recover) the ethanol
• amber suspension is converted into a dark oil
• Vacuum oven - for dabs and shatters
• Distillation - for further concentration:
• actually a tertiary processing
• can result in pre distilled extracts with 80% THC, being further concentrated to as high as 90-95% THC
• not good for vape pens because all flavor is removed