CO2 extraction
From Wiki Weed
When high pressure is applied to CO2, it becomes a liquid that is capable of working as a solvent, stripping away cannabinoids and essential oils from plant material. This process is called supercritical extraction and is the most common method of making hash oil using CO2 instead of a hydrocarbon solvent such as butane. CO2 extractions can take many of the same textures as BHO, but generally they tend to be more oily and less viscous.
