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Ethanol Extraction and CO2 Extraction: Extraction Steps, and seven differences

300L CO2 Essential Oil Extraction Equipment

Solvent Extraction

Plants produce essential oil, extraction is the process of removing valuable oil from the plant, but oil cannot be removed from the plant through purely mechanical processes. A solvent is needed to separate the essential oil from plant matter and further processing is to filter the oil from any remaining plant matter.

Professional extractors use many different solvents to concentrate the essential oil of plant matter, such as ethanol, CO2, and hydrocarbons to dissolve the plant’s cannabinoids, terpenes, and other therapeutic essential oils. All solvent types used in the cannabis industry are “generally recognized as safe” (GRAS) by the Food and Drug Administration (FDA).

Yet, not all solvents and extraction methods are created equal. Some, like ethanol and CO2, are safer for consumers and processors alike. However, even these two processes can produce dramatically different products.

What is Ethanol Extraction?

Ethanol extraction has been used since before the prohibition of hemp in the early 20th century, it is a liquid solvent with high solvating power, and is the most versatile of extraction solvents because it is safe for infused edibles and compatible with any type of container. Ethanol also provides consistent results while being easily recoverable.

Ethanol is a polar solvent but can have both polar and nonpolar properties. It attracts polar and ionic molecules, through its hydroxyl group, and can attract nonpolar molecules because of the nonpolar nature of the ethyl group. This polarity is perfectly suited for capturing cannabinoids and terpenes while leaving plant fats and waxes behind. By reducing the ethanol temperature during extraction, the solvent removes the oils while freezing the water and fat-soluble plant compounds in place, so no winterization is necessary post-extraction.

Six steps of ethanol extraction

Technologically-advanced ethanol extraction technology passes ethanol through plant material and then recollects the ethanol at the end of the process. The ethanol can be recirculated around the plant material multiple times, allowing for the optimal extraction of essential oils.

  1. Drying and grinding of raw biomass
  2. Ethanol extraction: first run
  3. Ethanol evaporation
  4. Winterization/clarification with recovered ethanol: second run
  5. Crude oil distillation
  6. Distillate can then be rendered into crystalline isolate

Top Three Pros of ethanol extraction

  • Smaller Initial Cost: Compared to other solvent-based extraction methods such as those that use CO2 extraction, butane, and propane, ethanol extraction systems are the most cost-effective systems available. They also require far less specialized training, making it easier to get operators ready for production.
  • Larger Production Rates: The process is fast, making it a good choice for high-volume harvests. Batches can be produced one after another without as much need to prepare the systems again.
  • More Environmentally Friendly: Than alternative extraction methods, as ethanol can be recovered and reused.

What is supercritical CO2 extraction?

Supercritical carbon dioxide (CO2) fluid

CO2 (carbon dioxide) is a common gas that naturally exists in the Earth’s atmosphere. The CO2 gas is under immense pressure and heat(Pc=72.8 atm, Tc=31.1 ℃), when the CO2 is neither liquid nor gas, we called supercritical carbon dioxide (CO2) fluid, it is an odorless, non-toxic, and colorless fluid, and it makes for an effective extraction solvent, that is safe to use to create high-quality extracts.

Supercritical CO2 extraction

Supercritical CO2 extractions use carbon dioxide gas in their supercritical state, which has the properties of a liquid and a gas. With its gas-like characteristics, it can diffuse through the entire biomass tank full of biomass such as hemp or cannabis. Its liquid properties under compression dissolve non-polar compounds.

Fully supercritical CO2 extraction process

CO2 extraction is often marketed as ‘solvent-free,’ suggesting it is a cleaner alternative to other extraction methods.

After the supercritical CO2 fluid passes over the biomass at the CO2 extraction vessel, it goes through a CO2 separation vessel, where changes in temperature and pressure allow the CO2 to evaporate and leave behind cannabinoids, terpenes, and wax. The CO2 vapor then passes through a condenser to be returned to its liquid state and saved for future use. Like ethanol, the ability to recapture and reuse CO2 makes this type of extraction fairly clean and efficient.

Supercritical CO2 extraction technology provides an efficient extraction method that provides good extraction efficiency, low operating cost, and a product that can be marketed as both “green” and organic. Local regulators are almost always very amenable to the implementation of a CO2 extraction facility because they perceive the process as being safer than processes that require flammable materials.

Five steps of CO2 extraction

  1. Drying and grinding of raw biomass
  2. CO2 extraction
  3. Ethanol winterization/clarification
  4. Crude oil distillation
  5. Distillate can then be rendered into crystalline isolate

Four Pros of CO2 extraction

Supercritical CO2 Extraction Machine
  • Safety: Supercritical CO2 extraction is the fact that, as a solvent, it’s inert, meaning it is non-flammable, which reduces the risk of explosions.
  • Low risk of toxicity: CO2 is also less toxic than ethanol and leaves behind less residue in the oil.
  • High purity: The CO2 also acts as a cleaning agent, killing off mildew and bacteria, making for purer CBD products.
  • Environmental friendliness: After the CO2 passes through the trim, operators can cycle it back into the original tank to be reused in the process.

CO2 extraction vs ethanol extraction: seven differences

difference 1#: Safety

Ethanol extraction is flammable, but not nearly as much as light hydrocarbons such as butane and propane. CO2 can offer more safety than other extraction methods since carbon dioxide is not flammable and less toxic than ethanol. In addition, there is a lower risk of ending up with residual solvents in the end product.

difference 2#: Solvent recovery

In terms of solvent recovery, ethanol extraction requires more investments in the recovery process. Generally, CO2 extractions do not need to recover the solvent. CO2 is non-toxic, renewable, and able to be recycled for use. CO2 is also considered a green solvent by the American Chemical Society.

difference 3#: Quality

Ethanol can extract a high amount of active compounds quickly to create a high quality extract. For processors that want to create full spectrum extracts featuring high concentrations of terpenes and cannabinoids as well as flavonoids and carotenoids, CO2 extraction may work for them. When processors want to create pharmaceutical-grade products, CO2 may be a viable option.

difference 4#: Cost

Overall, CO2 extractions may cost more initially but can have lower operating costs that may pay for themselves in the long run. In the battle between ethanol extraction vs. CO2 extraction, it is hard to choose the best method in terms of cost.

difference 5#: Cannabinoid recovery rate

Ethanol extraction can produce a product with between 50 to 80% cannabinoid recovery, although carbon scrubbing may be required to remove the chlorophyll, which may also reduce cannabinoid concentration since the carbon can pull in cannabinoids.
Supercritical CO2 extraction has a cannabinoid recovery rate of between 85 and 95% without the need for carbon scrubbing.

difference 6#: Extraction speed

Compared to ethanol, CO2 extraction is a lot slower. CO2 can perform considerably fewer runs per day compared to other extraction methods.

difference 7#: Winterization

In terms of winterization, both ethanol and CO2 extraction processes can require this step. In ethanol extraction, the winterization step can be sidestepped if extractions are at very cool temperatures, although this can increase energy costs. Warm ethanol extraction requires winterization.
CO2 does require winterization after extraction. However, new technologies are coming out and allow winterization to happen during extraction without a chemical solvent.

Works Cited: Ethanol vs CO2 Extraction: Which Is Best for the Cannabis Industry?