Which solvent is best ? Research and you decide.
BHO and Ethanol Solvent
Hydrocarbons (such as Butane or BHO) and Ethanol are cheap solvents, that can degrade terpenes, nutraceuticals, and extract non-desirable components that require a great deal more post-processing. Both are highly flammable and explosive. So much, that specially designed blast rooms are required for code, and are outlawed in some areas. BHO specifically, can leave residues, which if are not properly removed during distillation, can result in nose-burn or heart aches (Google – butane in the bloodstream or dangers of butaneingestion for more info). If not properly processed, BHO only has a shelf-life of a few weeks. Reference: Human Toxicity of Butane
CO2 is one of the preferred solvents for botanical extraction, which can better target oil (minimize wax and other undesirable extractions which need to be post-processed removed). It has a relatively unlimited shelf life if properly prepared. With proper extraction technique, CO2 can preserve both terpenes and nutraceuticals.
Organic Extraction Using Water
Using water as the botanical oil extraction method is the holy-grail of methods, since it does not require high-pressure gas containment, and uses one of the most abundant elements available, water.
An additional benefit is that it is a organic process, can be continuous feed, and smaller footprint with less overall equipment costs in large processing operations.
Currently there is only one manufacturer that builds the SDR (Spinning Disc Reactor) for this method of botanical oil extraction, Infinity Supercritical.