In their pursuit of purified extractions of THC, manufacturers of cannabis concentrates use solvents like butane, propane, ethanol, and supercritical CO2 to strip cannabis plants of their desired resins and oils. The solvents are then purged from the extract, but what happens to them afterwards? In an industry with high startup costs, solvent recycling and recovery is an important way to increase your extraction efficiency.
Professional cannabis extractions and solvent recycling take place in a closed-loop system. The process begins with the solvent flowing from a solvent tank into a material column where the solvent strips cannabinoids and terpenes from cannabis biomass. This mixture of liquid solvent and cannabis oils is then transferred into a collection vessel, where warm water heats the vessel to the relatively low temperature of the solvent’s boiling point while preserving the cannabinoids and terpenes. The vaporized solvent travels through a molecular sieve, removing any moisture. A pump then pushes the gaseous solvent into a condensing coil, returning it to its liquid form before being returned to the solvent tank where the process began.
This process is fairly efficient. However, you won’t be able to recover 100% of the solvent used in your extraction. A small amount of solvent can linger in the extract, decompose, or be lost to vapor traps. A source familiar with industry practices told us that, in a column containing 3 lbs of plant material, you can expect to lose 1 ± 0.4 lbs of solvent. Higher recovery is possible given more time and energy expended. Some highly efficient cannabis operations that recycle their solvents using specialized equipment have been able to reduce new solvent purchases by 95% because you can recycle solvents many times over. Every time you recycle a solvent, all of the bacterial and solid contaminants are removed and the clean solvent will be returned back to near-original purity. However, over time, other gases with similar boiling points to your solvent – like water or alcohol – may get mixed in.
Cannabis cultivators and infusion operations have high start-up costs. Extraction machinery and rotary evaporators can cost well over $500,000 combined, and that’s not to mention the costs of buildings, licenses, and salaries for lab technicians. Making the decision to recycle and reuse the solvents used in your extraction process is an ecologically friendly way to minimize one of your recurring operational expenses.
