A hydrocarbon is an organic chemical compound composed only of the elements – carbon and hydrogen.

Each method of extraction has its place and purpose.  Hydrocarbon extraction is what would be considered as a “gentle” method of extraction.  Hydrocarbons have a short runtime vs. other solvent methods and does not degrade botanicals in the same way.  Resulting in a higher retention of chemical compounds of plants. Hydrocarbon is also a cost-effective method of extraction with a large product diversity capability.  Ethanol extraction is great for large scale field processing of botanicals like hemp. Ethanol can also be cost efficient but is limited for product diversity but great for crude oil production at scale.  CO2 is the most aggressive method of extraction. CO2 can serve a purpose of fractional terpene separation and limited product lines. However due to its long runtimes, extreme pressure and temperatures – CO2 (when done incorrectly) can degrade botanicals and also leave excessive amounts of moisture – resulting in products developing mould or going rancid.

A closed loop system is – A system that uses the concept of an open loop system (open blasting), as its forward path of direction. It has one or more return paths between its output and input.

Naturally, there is concern that the operator will be over exposed to solvent causing health complications or the end-consumer may ingest product containing residual solvent that may harm them. As an extraction environment requirement, it is necessary to constantly replace the air in the C1D1 room, spontaneous replace all the air in the event the detector reads 25% of the LFL, and use peer-reviewed equipment by a trained operator. “The 10-min Acute Exposure Guideline Limit (AEGL-1, non-disabling) value is 10,000 ppm (24,000 mg/m3) which is greater than 50% of the lower explosive limit for butane in air of 19,000 ppm. Therefore, extreme safety considerations against the hazard of explosion must be taken into account.”[3] Likewise a similar response is given for propane; “The AEGL-1 (non-disabling) value is greater than 10% of the lower explosive limit for propane in air of 23,000 ppm. Therefore, safety considerations against the hazard of explosion must be taken into account.” [4] The AEGL value is the value at which a human can start to feel the effects of exposure to solvent, at AEGL-1 (19,000 ppm over 10 minutes) this effect is drowsiness, at AEGL-2 (24,000 ppm over 10 minutes) this effect is disabling, at AEGL-3 (77,000 ppm over 10 minutes) this effect is lethal. Due to the fire and explosion protections in place the operator is extremely unlikely to feel the effect of exposure to solvent even in the worst-case scenario because he will never be exposed to even half this amount in any given instance over any period of time.

This same concept explained above extends to the end-user’s safety. The safety of the solvents used for cannabis extraction need to be re-evaluated from a scientific and health perspective in order to determine if residual solvents in products are detrimental to our health. The best-case study for this is from the oldest regulated cannabis market in the US. Colorado changed their residual solvent content in cannabis extracts to be consistent with the pharma industry. “The proposed limits are consistent with those adopted by international organization [5] for residual solvents in pharmaceuticals and by the Association of Public Health Laboratories [6] for residual solvents in cannabis extracts. These proposed health-based limits (except benzene) are based on the toxicity of individual solvents and the magnitude of exposure expected to occur from consuming 10 grams.” [7] In short, the regulation adjusted the maximum residual solvent content in cannabis extracts to be consistent with other industries which raised the limit from <800 ppm of butane to <5000 ppm of butane and from <500 ppm of propane to <5000 ppm of propane. This massive increase was a conclusion “to reflect conservative health-based criteria” [7] drawn from scientific data collected and/or analyzed by the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use and The Association of Public Health Laboratories. This conclusion makes sense given that a person must be exposed to 10,000 ppm over the duration of 10 minutes to reach AEGL-1 and the act of smoking or using a product derived from concentrate cannot come remotely close to ingesting the amount of solvent needed to cause drowsiness or any other adverse effect. On the manufacturers’ side, in practice, the actual likelihood of producing a product with a residual solvent level of 5000 ppm is very unlikely due to the boiling point of butane being -1⁰C and propane being -42⁰C and the post-processing steps require the use of low heat under vacuum which lowers these boiling points much further