Why is CO2 Extraction Better than Butane / Solvent Extraction?
Butane hash oil, also known as BHO, is a cannabis-derived oil made using butane as the solvent. In a basic BHO extraction the first step, known as a ‘wash,’ involves passing butane through a column containing the plant material. The butane strips the cannabinoids, terpenes, waxes, lipids, and other chemical compounds from the plant material. The butane must then be separated, or ‘purged’ from the extracted plant oil. This can be done through heating, by vacuum, or through some combination of the two.
BHO extraction time can vary depending on the size and model of the extraction equipment, though typical run times average from 5-10 lbs of plant material processed per hour. Excluding the price of Butane, you must factor in the cost of ventilation, or a protected explosion proof environment. Although the install can pose hazards, closed loop systems significantly decrease operating risks for owners.
Butane is a highly flammable colorless gas. The flash point, or the lowest temperature at which vapors will ignite when given an ignition source, is -60 °C (−76 °F). Thus, a spark from a light switch, an electric hand tool, or even a static charge can trigger an explosion. Furthermore, the autoignition temperature, or the lowest temperature at which a substance will spontaneously ignite in normal atmospheric pressure without an ignition source, is 288 °C (550 °F), which is a temperature easily reached by a stovetop or oven element.
The National Fire Protection Association has assigned a flammability rating of 4 (on a scale of 0 to 4), classifying n-butane as extremely hazardous. For these reasons, most states that allow for BHO extraction systems require a properly ventilated Class 1/Division 1 explosion-proof room. Both the room and BHO extraction system must be inspected by a certified industrial hygienist or engineer to be sure they conform to regional and municipal codes and nationally recognized accreditations. Workers must be adequately trained and understand the hazards associated with working with closed loop BHO extraction systems.
Even with proper training, equipment, and environment, BHO extraction systems can be dangerous. In 2014 in the US, there were 3 BHO extraction explosions, 30 injuries, and 32 explosion related deaths. This is in comparison to 12 explosions and 18 injuries in 2013.
Supercritical CO2 Extraction (SCE):
Supercritical CO2 Extraction is quickly becoming the preferred solvent in the Cannabis and Hemp industry. Despite having a costlier initial setup, CO2 is cheaper than butane, making the system more cost-effective to run. As CO2 is produced by natural means, if it is released back to the environment it does not have a negative impact on the atmosphere, making it a much safer and environmentally responsible choice than BHO. SCE does not require the same explosion-proof facility setup that BHO does, or safety equipment and training for operators to work with.
CO2 is also non-toxic- it is a natural waste product from human bodies and fermentation. Due to this and its gaseous state at atmospheric pressure, all extracts made from SCE are pure and completely clean of any potential toxic or heavy metal residues that can be left behind in BHO.
The conditions of a SCE system can be manipulated to fractionate desired compounds like terpenes, cannabinoids, waxes and esters out of the oil mixture in differing concentrations. This also provides the opportunity to refuse undesired compounds like chlorophyll from the extract. Manipulation in this manner makes SCE the perfect option for drug manufacturers looking to obtain higher concentrations of different biologically active components.
CO2 has solvency power at a much lower set of extraction parameters in comparison to other solvents, and therefore can extract compounds that usually are degraded at higher temperatures or pressures such as terpenes. Carbon dioxide extracts are accordingly stronger in aroma and flavour and bear a profile that most closely resembles the original plant. These extracts are preferred in market as their scent and flavouring are highly valued by purveyors.
Although BHO products may appear to be easy to make, the underlying risk involved with the extraction process and requirements for a Class 1/Division 1 explosion-proof room are additional factors that must be taken into consideration. On the other hand, CO2 extraction provides a cleaner and safer option for operators to process cannabis, with the bonus of being able to produce a full spectrum cannabinoid-rich product with an enriched perceived value.