There are many beneficial components in plant material that can be extracted for medicinal benefit. Many of the compounds desired by herbalists are non polar fat soluble molecules due to their high bio-availability and ability to be boiled and taken into the lungs. Most cannabiniods, terpenes and flaviniods are non polar substances. There are also beneficial compounds in the polar water soluble fraction of cannabis including some flaviniods and terpenes. Extraction is a method to separate desired components from the rest of the material.
Co2 is a great non polar solvent in that it is completely non toxic and evaporates from the sample leaving hardly any residue. The process is low temperature and co2 non reactive allowing the extraction to maintain the large majority of its original native properties. Co2 is also non flammable and not subjected to high temperatures to risk accidental burning. The co2 extraction process is also much faster than organic solvent based methods, 10-20x faster.
Co2 extractions are not good at extracting polar hydrophilic molecules due to it’s physio-chemical properties at supercritical phase. Also the equipment and technical ability to keep co2 at such a high pressure needed for the reaction is hard for most people to obtain.
Price of co2 extractors are high and can range anywhere from 80,000 to 700,000 depending on the size of the extractor and it’s capabilities.
Propane and butane extraction behave very similar due to their high similarity shape, size and chemistry. Propane is just one more carbon chain longer and thus dissolves larger plant molecules slightly better than butane, and butane dissolves relatively smaller plant molecules slightly better than propane.
These gases extract the desired compounds at much lower pressures than co2. They are just as efficient if not more that co2 extractions at obtaining non polar compounds. They do not react with cannabiniods and maintain their structure. They are cheap to buy, readily available and the extraction equipment is cheap. Butane and propane purge themselves efficiently from extracts due to their boiling points being below normal atmospheric conditions.
These gases are highly flammable. There is still residue in the extract which has to be removed before use, whereas co2 can be consumed no problem. The temperature and pressure of these gases can’t be as easily manipulated as co2 or carry on all of co2’s properties as a supercritical fluid.
You can diy a BHO or PHO system for less than $50, or you can spend up to $10,000 for a deluxe high capacity extractor.
Alcohols don’t need to be subjected to high pressures or temperatures for extraction. Alcohol is readily available and cheap. Alcohols require no pressure manipulation at all compared to butane and propane. Ethanol is relatively non toxic. Alcohols can dissolve in polar or water based media very easily compared to co2, butane, propane. Alcohols can dissolve miscible and non polar components like some terpenes and flaviniods not soluble in butane, propane, or co2.
Alcohols are flammable. If other alcohols besides food grade ethanol are used then extra purging procedures need to be done, more time. In addition to the desired therapeutic compounds, other compounds are seen in the extraction that might not be desired (ie chlorophylls, waxes), this also affects concentration of cannabiniods.
No heat or pressure are utilized in hash production, although some can help the process. Solvents are not used at all so impurities, toxins and purging are not issues. The whole trichome of the plant is extracted together so all terpenes and cannabiniods, as well as other bio-active compounds are extracted, except some flaviniods in the leaf tissue. Few materials needed to make hash.
Takes longer and is more physical than most extractions. Not efficient at getting material out of the stem or leaves, leaves a lot of material behind.
Hash can be made with a simple cooking sifter all the way up to more complex ice-water separations as well as heat and pressure manipulated systems.