Extracting botanical oils

The plant oil market sells over 14 billion dollars per year in the United States. Various plants contain many useful oils important for medicinal, aromatherapy, skin care, and food applications. Some examples of these uses include: 

  • Aloe vera extracts for skin treatments 
  • Peppermint oils as miticides 
  • Lemongrass oils as antimicrobials 
  • Orange blossom oil for fragrance 
  • Neem oils as pesticides 
  • Cannabis oil extracts for medicinal and recreational uses 

Based on which plant oils and chemicals are being extracted, different techniques are preferable. Some of the main methods of extracting botanical oils include:   

  • Solvent extraction 
  • Steam distillation 
  • CO2 extraction 
  • Enfleurage 
  • Water distillation 
  • Cold-press extraction 
  • Water and steam distillation 
  • Maceration 

Alicat mass flow and pressure controllers provide precise, accurate, repeatable control for various types of botanical extraction systems, offering extensive automation options, batching and totalizer settings, and continuous metering.   

Solvent extraction 

In this method, food grade solvents such as ethanol or hexane are used to separate essential plant oils from remaining biomass. Relative to other techniques, this method is best for plant oils that are normally difficult to extract due to being highly resinous or naturally low in concentration. 


  1. A liquid mass flow controller adds the solvent, such as ethanol, to a reservoir containing the plant material.
  2. Once dissolved with the solvent, the plant oil and solvent mixture is sent through vacuum distillation and a condenser to remove the solvent, leaving behind the plant oil extract. 


Mass flow and pressure control solutions

Alicat’s LC-Series or CODA KC-Series of liquid mass flow controllers can optimize vacuum distillation in solvent extraction systems by automating the flow of solvents on a temperature control loop using a PLC. Additional features and specifications include:  

  • LC-Series NIST-traceable accuracy up to ±2% of full scale  
  • CODA KC-Series Coriolis controllers NIST-traceable liquid accuracy up to ±0.2% of reading or ±0.05% of full scale  
  • Multivariate flow control using either liquid volumetric flow rate or pressure with simultaneous measurements of temperature using LC-Series 
  • Totalizer and batching settings
  • Analog, serial, and industrial protocol communication options 

Additionally, Alicat’s PCS-Series pressure controller can moderate downstream vacuum distillation chamber pressure in combination with a vacuum pump, allowing for seamless vacuum separation of solvents and extracts. For this application, Alicat’s PCS-Series offers:  

  • NIST-traceable accuracy up ±0.125% of full scale  
  • Control range to 0.01% – 100% of full scale  
  • Repeatability up to 0.08% of full scale  
  • Compatibility with many pure corrosive gases in addition to all non-corrosive gases and a variety of liquids  
  • Analog, serial, and industrial protocol communication options 

CO2 extraction 

In CO2 extraction, a supercritical CO2 fluid is used as the solvent to extract the botanical oils. Compared to other techniques, CO2 extraction offers the advantage of producing higher quality oils since none of its steps involve heat treatment, unlike steam distillation. Therefore, extremely sensitive plant oils are not significantly altered in the process. Compared to other plant oil extracts, CO2 oil extracts are normally thicker and more aromatic, containing more plant constituents than other techniques.  


  1. Pump pressurized CO2 using a liquid mass flow controller into a pressurized chamber with plant material. Use a pressure controller to maintain operating pressure in the chamber. The operating temperature should be between 95 and 100 F.
  2. Once the plant oils have dissolved into the CO2 solvent, the mixture is pumped into a separator where the CO2 is depressurized and allowed to expand back into a gas, separating all the oils from the CO2. After the CO2 is completely removed, the remaining extract is extremely pure and nontoxic.

Mass flow control solutions

Just as in previous applications, Alicat’s liquid mass flow controllers can be used for CO2 extraction. Due to the high operating pressure requirements to create supercritical CO2 at operating temperatures, Alicat’s CODA KC-Series can be used to flow the liquid CO2 into the reaction chamber and to the separation tank. For supercritical CO2 extraction, Alicat’s CODA KC-Series include: 

  • NIST-traceable liquid accuracy up to ±0.2% of reading or ±0.05% of full scale  
  • Repeatability up to ±0.05% of reading or ±0.025% of full scale, whichever is greater 
  • Operating range from -35°C to 70°C for liquids 
  • Proof pressure up to 4000 PSIA in larger flow systems 

Cold-press extraction 

Another method of plant oil extraction is cold-press extraction, which uses water and pressure to separate plant oils and plant matter.  


  1. The process begins by pressing and squeezing plant material, rupturing essential oil sacs.
  2. The plant oils and juices are then separated from the remaining plant matter using a centrifuge that filters out the solids from the liquids.
  3. The emulsion is then spray washed and sent into a separation tank where the lighter oils diffuse from the heavier water.  

Mass flow control solutions

In this system, Alicat’s liquid mass flow controllers can be used to control the spray wash or movement of the plant material or a CODA and pump system can be used to generate the positive pressure to move liquid through the system.

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