The Whole Plant Extraction Blog

The Most Common Questions on CO2 Extraction Yield

Fritz Chess

What is the Yield on Your CO2 Extraction Machines?

One of the most common questions that Eden Labs has heard over the last 21 years is "what is the yield?"  

This question can be particularly exasperating when the inquirer is under the impression that the yield is dependant on the extraction system. This is a nuanced answer that encompasses multiple components - the system, the solvent, the plant material and the process developed to create a particular product. All have a significant impact on yield.

The simple answer is that whatever percentage of oil is in the plant material will be the final yield if the extractor is optimized for that material and is run according to the process developed for material and desired product. An example would be a terpene rich product. Running the system at subcritical (over 1100 PSI and under 87F) will extend the run time and decrease total yield as the process is not pulling the components that come out in the Supercritical phase.

A better answer, however, is more complicated. Given how important this question is to most buyers there is a tendency among manufacturers of herbal extraction equipment to boast that their system gets higher yields. We've broken down what to look for in the following question:

Which Type of CO2 Extraction System is Best?

When it comes to supercritical CO2 extractors there is a clear difference in the expected yields between two types of extractors on the market. CO2 extractors can be broken down into two basic categories: liquid pumping systems and gas booster systems. This means that the CO2 is moving through the material as well as the pump in a liquid phase.

Liquid pumping systems have several strengths processors should consider.

Advantages of liquid pumping CO2 extraction systems:

  • Energy savings. With a liquid pumping system the same amount of energy input is utilized to move more CO2 in its liquid phase than its gas phase.
  • Dramatically shortened run times.
  • Liquid systems are far more tuneable when it comes to fractionating various compounds like terpenes and oleoresins. Compounds can be collected separate and a wider selection of products can be obtained.
  • Yields are always better with full liquid systems.  

Note: Eden Labs made the switch to liquid pumping design and manufacturing in 2012.  

Why Are Yields Better with Liquid Pumping Systems?

Gas booster pumping systems pump vapor. When a system is pumping CO2 vapor (gaseous state), the CO2 does not go into a liquid or supercritical phase until it actually passes through and exits from the outlet of the pump and begins to enter the extraction vessel. This is a crucial stage in efficiencies as the pressure gauge may not accurately reflect that liquid is indeed filling the extraction vessel. If liquid is not filling the vessel then proper saturation does not occur for a full extraction.

Liquid pumping systems turn the vapor to liquid long before reaching the extraction vessel by condensing the vapor in the condensing tower and accumulator before it reaches the pump inlet. With this process, the gas is already in a state where it can get a head start on solubilizing plant compounds before it reaches the pump. Therefore, liquid systems are simply more reliable at getting consistently high yields, as well as drastically extending the life of the pumping system.

‍A liquid pumping CO2 extraction system, a Hi-Flo™ FX2 machine by Eden Labs.

How Long is the Ideal CO2 Extraction Run?

There is a general rule when doing supercritical CO2 extractions that 70-80% of the plant oils will come out in a given time frame which depends on the equipment used, the plant material being extracted, and the temperature and pressure of the extraction. To get the remaining 20-30%, you will have to run the extractor twice as long. So the operator needs to ask themselves whether time is more important or full yield is more important.  

Two things affect this decision and can be intertwined: 

  1. Are you producing for a client who needs a full extraction or are you producing product for yourself?
  2. If you have a limited quantity of a very expensive herb, full yield is more important. If you have an abundant supply of inexpensive herb, 70-80% is probably a good stopping point based on the rule of diminishing returns vs overhead.

When shopping for a CO2 system, the more relevant question is, how many grams per hour does it put out? Most of the manufacturers in this market have systems that generate 15-30 grams per hour. The gas booster systems are closer to 15 gm/hour while there are several liquid systems that are closer to 30. Eden Labs standard Hi-Flo™ CO2 extractors are in the 30-40 gm per hour range. Our Hi-Flo FX2 series is 100-180 gm per hour. Our most advanced systems like the 2x20 and 3x20 can be as high as 400 gm per hour.

And So, Really, What Can I Expect for Yield?

Getting back to the original question, if someone wants to start an herbal extraction business and they are looking at extracting a wide range of medicinal herbs, 10% yield is the number they should plug into the spreadsheet of their business plan. Much higher yields can be achieved, but for planning, 10% is a good baseline to accommodate the multiple factors listed above. Yield can vary widely between different herbs, horticultural factors, systems and process development. However, it is surprising how often 10% is the real number when generally analyzing the various extractions used in herbal medicine.

October 26, 2016