Hydrocarbon Extraction: Look Past the Open Blast

Hydrocarbon (butane and propane) extraction and BHO (butane hash oil) have always gotten a bad rap. The ease of production, the availability of canned butane, and its low vapor point and flammability have made for some explosive results. The news stories that keep surfacing gave the technique its bad name, and they were almost always caused by someone who was uneducated and "open blasting."

Why open blasting is so dangerous

Open blasting packs plant material into a vessel with a small opening at the top and a large filtered opening at the bottom. A can of liquid butane is deployed through the top and captured in a collection vessel, which is then heated so the hydrocarbons boil off into the atmosphere, leaving raw hash oil. Butane and propane are heavier than air, so they sink to the ground. That is where people get into trouble.

Because most of these extractions happen illegally, the person doing it tends to hide the act, typically (especially in Colorado) in a basement. Once the atmosphere reaches 1.8% saturation of butane, it becomes explosive. This is the Lower Explosive Limit (LEL). The only thing missing is an ignition source: a water-heater pilot light, a refrigerator fan, anything that generates a spark, even static electricity.

Hazardous solvent extractions should only be performed by trained professionals, with professional, peer-reviewed equipment, in a professional, peer-reviewed facility.

The closed-loop system

The professional answer is the closed-loop system. The same concept as open blasting applies, in that a vessel is filled with plant material and saturated with liquid hydrocarbons, but in a closed loop all of the solvent is maintained in a sealed vessel and never sees the light of day.

The vessel and the collection chamber are both vacuumed free of atmosphere. This is crucial, because neither butane nor propane exist as a liquid in our atmosphere; under vacuum they remain liquid. Once the solvent runs over the plant material, through the filter, and into the collection vessel, that vessel holds a solution of hash oil and liquid hydrocarbons. Adding heat converts the hydrocarbons back to a gas, which is distilled off, re-condensed, and returned to the starting tank, completing the loop. The hydrocarbons are then reused.

C1D1 and the engineering that makes it safe

This process must be performed inside a room specifically engineered for it. The requirement of Class I, Division 1 extraction rooms with hazardous exhaust systems has stepped up the level of safety dramatically. C1D1 is an electrical classification for electronics designed to be intrinsically safe and "explosion proof" under the International Electrical Code. Paired with a hazardous exhaust system meeting the International Mechanical Code, it creates a nearly impossible environment for an explosion. Flammable-gas detection units are mounted at 12 inches or lower to catch heavier-than-air vapor, and visual strobes and audio horns trigger well before vapors approach the LEL.

Why blend butane and propane

Both are non-polar (non-water-soluble) solvents, which suits the oils we want from the plant. But they behave differently. Propane sits at the far non-polar end with virtually no affinity for water, runs at roughly 150 psi, and moves fast enough to miss some compounds. Butane falls closer to the middle, runs at about 40 psi, moves slowly, and can pick up more impurities and darker color, but its slightly polar character captures terpenes propane would miss. A good mix of the two tends to be the magic ticket for flavor, color, and yield.