There are different extraction methods on the market to process herbal oil, but generally, it can be concluded into three most common ways: ethanol extraction, supercritical/subcritical co2 extraction. No matter which extraction method you want to use, they are all processed with solvent. Before making a choice, you might be wondering what are the key differences among them. Please check the below content, which may help you with making the right and suitable decisions for your business, to obtain highest possible quality of products.

Cryogenic Ethanol Extraction

Ethanol extraction is very commonly used when dealing with herbal oil production. The reason why it is called cryogenic ethanol extraction is that it uses ethanol as the solvent to soak and extract plant leaves under a very low temperature for ethanol's low boiling point and easy volatility.

With that being said, the machine to proceed with ethanol extraction is often called centrifuge extractor, and it is usually used by connecting with chillers to keep the temperature inside the machine down so as to fully soak and extract in a stable state. The centrifuge extractor only washes, agitates, soaks, and then spin-drys to get the most initial crude oil which contains a bit of solvent and needs further steps for refining treatment.

Ethanol extraction can not remove all of the ethanol out of the initial crude oil, so it needs further steps for refining treatments. It will then be proceeded with ethanol recovery by evaporation machines, such as the rotary evaporator, wiped film evaporator, and falling film evaporator. Also, ethanol extraction is mainly used in the industry.

Supercritical CO2 Extraction

Supercritical CO2 extraction uses carbon dioxide (CO2) as the solvent. In a normal situation, carbon dioxide stays in a gaseous state. However, under the specific condition, the carbon dioxide will change into a both-gas-and-fluid state. More precisely, when the temperature is higher than 31-celsius degrees and the pressure is higher than 1071 PSI, CO2 steps into the supercritical phase, meaning it becomes fluid featuring the gaseous property.

CO2 is powerful and cheap as the solvent, and its price is so much lower than ethanol, leading to a drastically decreased maintenance cost. When stepping into the supercritical phase, it is time for the CO2 to sparkle its advantages. Since it features both gas and fluid properties, the supercritical CO2 can easily flow through the solids and space due to the gaseous quality and dissolve the materials by the benefit of its fluid attribution. CO2 gains the qualities of low viscosity and no interfacial tension, so the solubility capacity and extraction efficiency are thus improved. Moreover, it will not damage the flavonoids and essences of the material for extraction, which enables it to be largely applied in many industries like coffee, pharmaceuticals, cosmetics, essential oil, and perfume.

Unlike ethanol extraction, supercritical extraction does not require the further solvent recovery step because in the final step the chilling effect will make the temperature drop, and the fluid CO2 will instantly change back to gas, thus separating the crude oil and solvent without effort. What's more important is that the supercritical extraction can focus on extracting the specific particle you favor and you have more controlling abilities about the selective compounds you target by changing the pressure and temperature, which the ethanol extraction and BHO extraction are not able to do.