This question can be particularly irritating when the inquirer believes that the yield depends on the extraction system. It's a nuanced answer surrounded by multiple components - the system, the solvent, the plant material and the process developed to create a specific product. All of these can have a significant impact on yield.
The simple answer is that if the extractor is optimized for that material and runs according to a process developed for the material and the desired product, then whatever percentage of oil is contained in the plant material is the final yield. An example is a terpene rich product. Running the system at subcritical (above 1100 PSI and below 87F) will extend the run time and reduce the total yield because the process will not pull the components that occur in the supercritical stage.
However, the better answer is more complex. Considering how important this issue is to most purchasers, there is a tendency among herbal extraction equipment manufacturers to brag about getting higher yields from their systems. We have broken down what to look for in the following questions.
Which type of CO2 extraction system is best?
When it comes to supercritical CO2 extractors, there are significant differences in expected yields between the two types of extractors on the market. Supercritical CO2 Extraction Machine can be divided into two main categories: liquid pumping systems and gas boosting systems. This means that the CO2 passes through the material in the liquid phase as well as the pump.
Liquid pumping systems have several advantages that processors should consider.
Advantages of liquid pumping CO2 extraction systems.
Energy saving. In a liquid pumping system, the same amount of energy input is used to deliver more CO2 in the liquid phase than in the gas phase.
Significantly shorter run times.
Much better tunability of the liquid system when fractionating various compounds, such as terpenes and oleoresins. Compounds can be collected separately, allowing for more product options.
Yields are always better when using an all-liquid system.
Note: In 2012, Eden Labs moved to liquid pump design and manufacturing.
Why are liquid pump systems more productive?
Gas booster pump systems pump vapors. When the system pumps CO2 vapor (in the gaseous state), the CO2 does not enter the liquid phase or supercritical state until it actually passes through and exits the pump outlet and begins to enter the extraction vessel. This is a critical phase for efficiency, as the pressure gauge may not accurately reflect that the liquid is actually filling the extraction vessel. If the liquid does not fill the vessel, proper saturation for complete immersion will not occur.
Liquid pumping system The vapor is converted to liquid long before it reaches the extraction vessel by condensing the vapor in the condensing tower and accumulator before it reaches the pump inlet. Through this process, the gas is already in a state where it can first dissolve the plant compound before reaching the pump. As a result, the liquid system is more reliable in terms of achieving consistently high throughputs as well as greatly extending the life of the pump system.
Hi-flo-fx2-co2-extraction.jpg
Eden Labs' liquid pumping CO2 extraction system, the Hi-Flo™ FX2 machine.
How long does an ideal CO2 extraction need to run?
When performing a supercritical CO2 extraction, there is usually a rule that 70-80% of the vegetable oil will be produced in a given time frame, depending on the equipment used, the plant material being extracted, and the temperature and pressure of the extraction. To obtain the remaining 20% to 30%, you will have to run the extractor twice as long. Therefore, operators need to ask themselves if time is more important or full yield is more important.
Two factors influence this decision and can be interrelated.
Are you producing product for a customer who needs full extraction or are you producing product for yourself?
If a limited number of very expensive herbs are available, then full yield is especially important. If you have a large quantity of inexpensive herbs, then a 70-80% price is a good stopping point, depending on the law of diminishing returns versus overhead.
A more relevant question when buying a CO2 system is how many grams per hour are emitted? Most manufacturers in this market have systems that produce 15-30 grams per hour. Gas booster systems are closer to 15 grams per hour, while some liquid systems are closer to 30 grams per hour. the standard Hi-Flo™ CO2 extractor from Eden Labs has a rate of 30-40 grams per hour. Our Hi-Flo FX2 series has speeds of 100-180 grams per hour. Our most advanced systems (such as the 2x20 and 3x20) can go up to 400 grams per hour.
So, really, what can I expect in terms of production?
Going back to the original question, if someone wants to start an herbal extraction business and they are considering extracting a wide variety of herbs, then they should insert a 10% yield into the business plan spreadsheet. Higher yields can be achieved, but for planning purposes, 10% is a good benchmark that can accommodate multiple factors mentioned above. Yields vary greatly between herbs, horticultural factors, systems and process development. However, it is surprising that the true figure has a 10% frequency when typically analyzing the various extracts used in herbal medicine.