Using butane as the extraction solvent creates what is known as butane hash oil. To do this, the process starts with cannabis and liquid butane in a pressurized and heated system. By using evaporation under a vacuum, it is then possible to remove the butane solvent. The vacuum turns the butane from liquid to a vapor, making it easier to remove.
This kind of extract is also known as shatter, which is a clear material that typically includes THC, CBD and other chemical components, including terpenes. This extraction method includes some potential hazards. Butane burns easily in its gas phase and requires careful temperature management to avoid the risk of the gas exploding. It is also important to remove any residual butane in the extract as it is toxic to humans. However, butane extraction has remained popular due to the relatively low equipment and operations cost. It also produces flavorful extracts with higher terpene content than can be achieved by CO2 extraction, for example.
In other methods, liquid propane can be used in place of butane. High pressure keeps the propane liquefied and extraction occurs at a lower temperature as propane has less of a boiling point than butane.
The extraction temperature impacts the components removed from cannabis. So, these two similar methods—butane and propane extraction—produce dissimilar extracts. In some cases, butane and propane extraction can be used in combination to create a product with a broader chemical profile. Like the butane process, though, special care must be taken with propane extraction to remove as much of the chemical as possible and prove it.
Butane/Propane Extraction References