A closed-loop extraction system resembles an open-butane run, but unlike butane extraction, the solvent is sealed off and contained from the air. Using a closed loop system for extracting essential oils has been used for decades in perfume production or the creation of food additives. By using a closed loop system, the resulting substance is cleaner and purer in addition to being a safer process than an open blast system.
A closed-loop system is comprised of a large tank with an attached tube, a recovery tank, a refrigerant scale, a refrigerant pump, and a recovery pump. Users can require an additional pump and recovery tank to create a vacuum oven.
A closed-loop system operates by packing the tube with fresh plant material. A pressurised solvent is then connected to the plant-filled tube. Various valves and clamps help to ensure that the solvent remains pressurised throughout the process.
The solvent permeates the plant matter so that the essential oils are pulled from the plant material which is collected in a recovery tank.