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.

Organic solvent-based extraction is very common throughout the chemical, food, personal care, pharmaceutical and perfumery industries, as well as many others. The modern cannabis industry repurposed current methodologies from these previous industries. Cannabis extraction using organic solvents is easily comparable to the making of absolutes for the personal care and perfumery industries. An absolute is a concentrated, highly aromatic oil extracted from plants. “First, an organic solvent, such as hexane, is added to the plant material to help extract the non-polar compounds. This solution is filtered and concentrated by distillation to produce a waxy mass called concrete. The more polar, fragrant compounds are extracted from the concrete into ethanol. When the ethanol evaporates, an oil—the absolute—is left behind.” [1] The process explained above involves the use of two consecutive extractions using two different organic solvents. This process or a similar process is used to make vanilla concentrate, rose oil, jasmine concentrate, mimosa concentrate, beeswax, and several other natural derivatives we enjoy in our daily lives. This same process is currently being used to manufacture cannabis concentrates.

Currently, the most popular solvents for cannabis extractions are butane and propane. These solvents are chosen over other organic solvents because they are superior for the purpose of economically producing high quality extracts at an accelerated rate, safely. These are being produced using quality organic solvents that test to instrument grade specifications. Less processing time at a lower cost creates a higher supply of a quality product. This, in turn, drives down the price per unit once the demand is met and results in increased “reasonable access” for patients. It’s important to note that the same quality, price point, or purity of extracts produced from organic solvent extraction cannot be re-produced using CO2 extraction or any other non-organic solvent based extraction method. Consequently, there is a possibility that not allowing these types of products in a legal market will cause a demand for these same products in the black market, at a higher price. Black market hydrocarbon extraction is usually done using a technique called “open-blasting” which is an extreme hazard to the environment due to its high volume of waste from not using a closed-loop system and is an extreme safety hazard likely to cause fires and explosions. Allowing patients to buy these end-products in a store at a low price would deter them from making them at home and potentially endangering themselves, the environment, and their neighbours.

The use of organic solvents for cannabis extraction is being debated due to the safety of the manufacturing process, the end-consumer, and the environment. Organic solvents as defined by the law are “any organic compound that is explosive or highly or extremely flammable, including petroleum naphtha and compressed liquid hydrocarbons such as butane, isobutane, propane and propylene.” [2] Superficially, the purpose of this section is to avoid accidents resulting in fires that may endanger the lives of manufacturing operators, the business, and the neighbors. To ensure local safety manufacturers usually take every precaution available as is required by the Authority Having Jurisdiction (AHJ). These precautions can be explained as a 2-pronged approach to eliminate the possibility of fire or explosions. The first prong is making the entire extraction space a Class 1 Division 1 (C1D1) room. The classification of C1D1 room is defined by the National Fire Protection Association, as stated in NFPA 58, Liquefied Petroleum Gas Code. NFPA codes, standards, recommended practices, and guides, are developed through a consensus standards development process approved by the American National Standards Institute. A C1D1 space ensures all the air in the room is constantly being replaced and the entire space (including HVAC and electrical) is completely spark-free. In addition to these protections there is a solvent detector that turns on the emergency HVAC system when the detector senses the solvent level in the room approaches 25% of the lower flammability limit (LFL). The LFL is the absolute lowest amount of solvent that needs to exist in air with an ignition source to cause a flame. The second prong of this 2-prong approach is employing a trained operator to work on a certified, peer-reviewed, closed-loop extractor. Equipment is built specifically for this purpose, engineered to operate in a C1D1 environment with the highest safety standards. In the US the equipment and environment are regularly serviced and inspected for compliance by the AHJ and certifying engineer. As a result of all these protections solvent extraction is extremely safe and there have been no reported major injuries, incidences of fires or explosions in a regulated cannabis extraction facility to date.

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