Safety & Compliance

Hydrocarbon Solvent Removal using Vacuum Ovens

Written by Asia Mayfield

Forget about flower. Many cannabis connoisseurs are turning to concentrates. In the first three months of 2018, dispensaries using the online database Leafly to track their inventories added more than 300,000 new extracts to their menus. The number represented a whopping 600% increase over the previous year, in three months alone!

Cannabis manufacturers continue to refine the extraction process as consumer interest surges. As with any manufacturing process, both efficiency and safety are keys to success. In hydrocarbon extraction systems, cannabinoids and terpenes are pulled from the plant material with the assistance of a hydrocarbon solvent, often butane or a butane/propane mix. [1] This is sometimes referred to as the “carrier solvent”, since it mobilizes (“carries”) the desired compounds away from the plant, and is then removed before the final composition, to yield a solvent-free extract.

In hydrocarbon systems, the vast majority of the carrier solvent is recovered inside the closed loop. This initial separation of solvent from extracted compounds yields a viscous, but not solvent-free, mixture. To eliminate any traces of residual solvent, an important step in assuring the safety of the consumer and the quality of the extract, is to further refine this “crude” extract inside a vacuum oven. This is a specialized apparatus designed to remove residual solvent molecules at low pressures to minimize the degradation of cannabinoids and terpenes.

The process isn’t perfect. Physical parameters such as temperature and pressure settings can lead to the loss of the more volatile terpene components in full spectrum extracts. However, an additional step that ensures the removal of residual solvents from the extract provides a further layer of protection to the consumer. It also increases the manufacturer’s efficiency.

“This [vacuum oven technique] leaves behind a purified oil extract and greatly reduces the risk of fire when using solvents like butane,” writes Tim Youngblood of Cannabis Tech. “This allows for extracts to be processed faster, and more importantly, safer. Producing cannabis oil extracts the old-fashioned way with the massive fire hazard is hard to sustain and even harder to scale.”

Image source: Impact Lab


[1] Mahon, D. “Hydrocarbon Extraction: Look Past the Open Blast!”, Extraction Magazine, May-June 2019.

About the author

Asia Mayfield

Asia Mayfield is a freelance writer who focuses on the cannabis industry. She can be reached at [email protected]