Well Begun is Half Done!

Pre-processing hemp i.e. drying and grinding before subjecting it to Carbon dioxide (CO2) Supercritical Fluid Extraction (SCFE) is essential for obtaining prime hemp extracts.

At the heart of these procedures is the necessity to retain the terpene and cannabidiol (CBD) content of the freshly harvested hemp while maximizing the efficiency and yield of the downstream SCFE process.

Terpenes lend the characteristic flavor and aroma to hemp [1]. CBD is effective against a host of medical conditions that include pain, anxiety, depression, inflammable bowel disease, nausea, migraines, psychosis, seizures, and inflammation [2].

Hemp flowers or buds contain maximum cannabinoid concentration and deliver topmost quality extracts. Trim is the green material removed to access the bud and gives the second best quality extracts. Stem and root extracts are poor [1].


Drying Hemp

Methods applied to dry hemp have the single largest influence on the final product quality [3]. Proper drying provides excellent grade products by preserving the terpene and cannabidiol (CBD) content, the precious ingredients in hemp [3].

Conventionally, either whole hemp plants or their individual branches were hung upside down in large, well-ventilated spaces at 60% humidity and 600F to 700F temperature [4]. These facilities were roofed, keeping direct sunlight away from the drying hemp [4].

Belt Hemp Dryers speed up the drying process by using conveyors to continuously move the hemp harvest while, at the same time, applying heat and air flow. With the capacity to dry hundreds or even thousands of pounds of hemp per hour, this equipment dries hemp in a matter of hours [5].

Heat recapture systems in many dryers bring down operational costs. Some of these have mechanisms to recover material that flies away from the heating chamber – raw hemp is costly [5].

Box Dryers use a combination of automated control over airflow, temperature, and humidity inside an insulated chamber. The result is high operational efficiency delivering dry hemp with maximum terpene retention. With lower drying capacity, box dryers take somewhat more time than that of belt dryers [6].



Grinding Hemp

Grinding substantially increases the surface area of the hemp plant. As a result, supercritical carbon dioxide gets more surface area to act on. Such action delivers higher extraction yields [7].

Plant materials have low packing density. This limits the quantity of material personnel can load into the extractor of the SCFE system. Grinding and milling improve the packing density, thereby hiking the extraction efficiency [8].

Grinders must not heat up the hemp plant for the warming action releases terpenes and degrades the ultimate extract quality. On the contrary, a grinding machine should [1]:

  • Prevent piling up of the hemp feedstock to avoid heating the hemp.
  • Cut the hemp plant, but not compress it – compression causes plant material to stick and warm up.

Personnel pack the hemp plant loosely in the grinder, allowing the cutter to efficiently shred it. Tight packing binds the material and heats it up. To prevent the inhalation of cannabis dust created during grinding, personnel wear masks or hoods [1].Flour hemp in clay bowl with leaf on board

Cryogenically cooling hemp samples before and during grinding has emerged as an efficient way to prevent their thermal degradation during grinding. Lower temperatures [9]:

  • Induces microscopic fractures in hemp before grinding, reducing the energy required to grind it.
  • Make the hemp brittle, which is easier to grind.
  • Lower the heat capacity i.e. decrease the amount of energy needed to cool down hemp, thereby boosting the efficiency of grinding.
  • Minimize contamination of the sample by worn down metal from the grinder cutters.


Opportunities in Hemp Legalization

Executing correct hemp pre-processing techniques becomes increasingly essential at a time when more and more countries are legalizing hemp. The legitimization will unleash the health benefits of hemp for a larger population and open up fresh avenues for related advances in farming and industry.

Industrial HempIndustrial Hemp

Buffalo Extraction Systems has expertise in the Carbon dioxide (CO2) Supercritical Fluid Extraction (SCFE) business.

To know more about our SCFE systems, write to us at info@buffaloextracts.com




  1. Cannabis Extraction by Supercritical Carbon Dioxide – Selection and Preparation of Feed Stock. Supercritical Fluids.  
  2. A Comparison of CBD and THC. Jenna Fletcher. Medical News Today.  
  3. Hemp Processing: Post Harvest Processing. Rhizo Sciences.  
  4. How to Harvest and Dry Hemp for CBD Production. George Place.  NC Cooperative Extension.  
  5. Belt Trimmer. Triminator.  
  6. Box Dryer. Triminator.  
  7. CannabisSFE Supercritical CO2 Extraction Systems. Supercritical Fluid Technologies, Inc.  
  8. Cannabis Milling: Improving Output and Product Quality. Hanningfield.  
  9. Sample Processing and Preparation Considerations for Solid Cannabis Products. Patricia Atkins. Journal of AOAC International.