Table of Contents
Not long ago cannabis extraction conducted via highly flammable hydrocarbons used to be a risky, small-scale affair—the kind of thing amateur chemists performed in their garages and backyards, with notoriously explosive consequences. And while people still do dangerous extractions, legalization has spawned safer production methods, including CO2 extraction.
In the modern era of cannabis consumption, extracts have become more popular than ever. However, it’s not just popularity that’s changing the game for cannabis. Patients and recreational users are increasingly concerned with purchasing reliable, consistent, and safe methods of cannabis extracts.
Whether vaporizer pens, salves, edibles, or elixirs, chances are if it’s a quality cannabis product, it’s been produced using some form of carbon dioxide (CO2) extraction technology—a non-toxic, environmentally-friendly way to create potent concentrates saturated with cannabinoids and terpenes geared towards the modern consumer. Yet, CO2 extraction is a broad term that houses a couple of different methods under its umbrella. Below, we look at two different CO2 extraction processes, supercritical and subcritical extraction, and how they are changing the game for cannabis extracts.
How Does CO2 Extraction Work?
CO2 extraction uses pressurized carbon dioxide to pull specific compounds from a plant. It’s the most expensive, effective, and safest extraction method because it removes the many dangers that come with solvents.
Although relatively new in cannabis concentrate processing, this technology is anything but green to the botanical extraction and food industries. In fact, carbon dioxide has been used as a standard extraction method for years from producing carbonated soft drinks and removing caffeine from coffee beans to crafting essential oils.
Today the use of CO2 for cannabis extraction is quickly positioning itself to be one of the leading technologies in the industry. Retailers (more now than ever) are labeling their concentrates by extraction method, detailing whether solvents were used and to what extent— igniting an effort to eliminate the use of petroleum-based solvents such as butane or propane and moving towards more modern supercritical and subcritical CO2 processes.
But what exactly is the difference between subcritical and supercritical extraction?
Supercritical CO2 Extraction
At standard temperatures and pressure, CO2 is a gas. However, when heated above 31.10C (critical temperature) and 1,071 psi (critical pressure), it exudes both the properties of a gas and a liquid, becoming what is called a supercritical fluid, and the start of the supercritical CO2 extraction process.
This supercritical liquid acts as a solvent and can slide into porous materials in addition to dissolving them. So, in the application of cannabis, the supercritical fluid passes through a chamber containing raw cannabis material, gently dissolving the membrane of the trichomes to capture their active compounds. Next, the compound-enriched solvent passes into another pressurized separation vessel. As pressures and temperatures fluctuate, compounds such as cannabinoids and terpenes are fractionated away. Finally, the remaining CO2 is transferred to a condenser vessel where the temperature and pressure allow the fluid to stabilize back into a gas.
While supercritical extractions produce a greater yield and take less time than subcritical extractions, they are too harsh for some terpenes—resulting in a loss or a transformation of these compounds.
Subcritical CO2 Extraction
Subcritical CO2 extraction is the same kind of process; only it requires less pressure and lower temperature (non-supercritical liquid) than supercritical CO2 extraction. This process is longer, less efficient and produces smaller yields, but it retains and protects fragile constituents like essential oils, terpenes and other sensitive chemicals within the plant, which is highly desirable when producing full-spectrum cannabis products.
These temperature and pressure differences result in very different cannabis products. Supercritical systems produce a substance with the consistency of peanut butter. Higher temperatures and pressures used in supercritical systems can extract much larger molecules such as omega 3 and 6 lipids, chlorophyll and waxes which can then be removed through a process called winterization—leaving behind just cannabinoid oil. Subcritical CO2 extraction produces a substance with a consistency closer to molasses, which, as mentioned above, preserves additional cannabinoids besides CBD.
Which is Best: Supercritical or Subcritical?
Up until recently, supercritical CO2 extraction was the most commonly acknowledged method of CO2 extraction, but as more emphasis is placed on full-spectrum plant products and the role of terpenes in cannabis products, subcritical CO2 extractions have challenged common thought and practice.
The argument being that the medicinal impact of the whole plant is greater than the sum of its parts—or what scientists refer to as the “entourage effect,” a hotly debated topic of the cannabis industry.
Frequently Asked Questions: Supercritical vs. Subcritical CO2 Extraction
What is the difference between supercritical and subcritical CO2 extraction?
Supercritical CO2 extraction operates above 31.10°C and 1,071 psi, where CO2 behaves as a fluid with both gas and liquid properties — producing higher yields, faster cycle times, and a peanut butter consistency. Subcritical CO2 extraction uses lower temperatures and pressures, producing smaller yields more slowly but preserving fragile terpenes and creating a molasses consistency.
How does CO2 cannabis extraction work?
Pressurized CO2 passes through a chamber containing raw cannabis material, dissolving the trichome membranes and capturing cannabinoids and terpenes. The CO2-compound mixture moves to a separation vessel where pressure and temperature changes fractionate the compounds. The CO2 then condenses back to gas and is recycled, leaving behind the purified concentrate.
Why is CO2 extraction considered safer than other methods?
CO2 is non-toxic, non-flammable, and food-grade — eliminating the explosion risk of hydrocarbon solvents like butane and propane. It leaves no residual solvent in the final product when properly purged. CO2 extraction is the same method used to decaffeinate coffee and produce essential oils, with a long safety record in regulated food and botanical applications.
Which method preserves more terpenes, supercritical or subcritical CO2?
Subcritical extraction preserves more terpenes because the lower temperature and pressure protect heat-sensitive volatile compounds. Supercritical extraction can be too harsh on delicate terpenes, causing some loss or transformation. For full-spectrum products that depend on the entourage effect, subcritical is preferred despite its lower yield and longer extraction time.
What is the entourage effect and why does it matter for CO2 extraction?
The entourage effect describes how cannabinoids and terpenes work synergistically — the whole plant produces effects greater than isolated compounds alone. Subcritical CO2 extraction supports the entourage effect by preserving the full chemical profile, including fragile cannabinoids beyond just CBD or THC. This is why full-spectrum products typically use subcritical or hybrid CO2 methods.
What does winterization do to CO2 extracts?
Winterization is a post-extraction step that removes lipids, omega-3/6 fatty acids, chlorophyll, and waxes from supercritical CO2 extracts. The crude oil is dissolved in cold ethanol, frozen for hours, then filtered to drop out fats and other large molecules. The result is a clean cannabinoid-rich oil suitable for vape cartridges, edibles, or further refinement.
