A closed-loop extraction system can seem daunting at first when you look at all of the components. Bear in mind that it’s a professional setup and requires a basic understanding of things like maintaining pressure and operating control valves. In general, a closed-loop system is made up of a large tank and attached tube, which is where the confined “blasting” occurs; a recovery tank; a recovery pump; a refrigerant pump; and a refrigerant scale to measure the weight of the recovery tank.
Finally, when making BHO, you will also need an oven and a pump, which are used in combination with each other, creating a vacuum oven. This “cleansing” system ensures that your product is purged of any residual solvents. However, for our purposes here, we will discuss only the extraction and not the purging process.
Here’s a quick thumbnail sketch of how the system works: Ground-up cannabis material is packed into the extraction tube—but not too tightly, since that will decrease potential yields. (It is also recommended that you use fresh-frozen buds or just-harvested plants, as they contain the most terpenes.) A tank of pressurized solvent is then attached to the tube, using a series of lock-down clamps and valves to ensure that the solvent stays under pressure throughout the process.
As the liquid solvent passes over the compacted cannabis material, the trichomes—or resin glands, which cover the buds and contain most of the plant’s cannabinoids—are stripped away and deposited in the basin of the extractor. The residual solvents are collected separately in the recovery tank and can be stored for later use.
Even though the closed-loop technique is safer, it’s still important to have tremendous respect for the system and the process, since any small faults (such as a blown gasket) can mean big trouble. For this reason, frequent and regular safety checks on your equipment are a must. It is also important to set up your blasting facility like a true lab, meaning proper ventilation and fire-safety controls.