When it comes to extracting methods, CO2 and Hydrocarbon extraction seems to be the most popular on the market. There are differences and similarities between the two solvents and today we will be reviewing some of these details.
Firstly, what is a solvent?
A solvent is:
Noun – the liquid in which a solute is dissolved to form a solution
Adjective – able to dissolve other substances.
In other words, it is the medium in which extraction occurs. CO2 and Hydrocarbons serve as the solvent while volatile terpenes and cannabinoids (including fatty acids and esters) serve as solutes (extracted/dissolved material).
Within the extraction process, these solvents are used in combination with heat, pressure, and time to draw out the desired chemicals from cannabis; they are collected and then post processed (purged/winterized) in order to create the desired end product.
The differences between the two solvents are so:
CO2 is considered extremely clean or “pure”, being deemed as “Generally Regarded as Safe” by the FDA, and leaving no residual chemicals within the end product. However requires consistent and thorough cleaning to prevent bacterial build up within the tank system.
Hydrocarbons which are petroleum distillates can potentially leave trace hydrocarbons within the oil; legally, according to the FDA, BHO and PHO products are allowed to have up to 5000 ppm of residual solvent within the final product. However with a proper purging process, residual levels of hydrocarbons can be removed quite effectively.
Both extraction methods require a substantial start up cost, however in different areas.
Within CO2 extraction, due to the extreme amounts of pressure used to contain the CO2 a well designed+manufactured closed loop extraction system will be the most expensive start up cost, running between 100-150K, not including additional post processing equipment such as a roto-vape or oven vacc.
While within hydrocarbon extraction, a system can cost anywhere from $25 – $60,000. In addition, due to its incredible flammability (butane can explode at concentrations between 2-8% in air), hydrocarbon extraction rooms must be blast-proof, which requires extensive engineering controls, ventilation and approval from the National Fire Protection Association (NFPA) in order to be in operation. Blast proofing can cost up to and over $100K.
However, assuming that the extraction equipment is professionally designed and assembled in a closed loop system there should be little risk of explosion in extraction. The benefit of such a system lies within the amount of time saved, BHO taking anywhere from 45-60 minutes to complete. While CO2 taking upwards of 8-12 hours, or even 24 if doing a cold extraction. This said, CO2 is less expensive than high quality (most pure) butane/propane, so long term its difficult to say which is more cost effective, hydrocarbons allowing for a faster output, while CO2 allowing for less expensive solvent material.
Processing – What’s the difference?
When using hydrocarbons for extraction we see how it’s extremely effective at stripping a large array of terpenes and the majority of cannabinoids from the starting material while leaving unwanted chemicals, such as pigments and chlorophyll behind. Afterwards, there is the simple step of purging the residual hydrocarbons out, or going further to agitate the oil into another consistency such as budder, or crumble.
While within CO2, due to its supercritical nature (acting as both a gas and fluid) it has the capacity of fine tuning the terpenes that it captures, capturing more aroma/terps efficiently, however also extracting more waxes and lipids in the process.
Generally speaking, hydrocarbon extraction tends to yield a greater amount of cannabinoids within its final product at around 80-95%, however due to the heating process it undergoes, you can expect a portion of the terpenes to be burned off, and thus have a smaller terpene count at around 0-4% when compared to CO2.
Within CO2 extraction, while working within a closed loop system where the CO2 can be recycled, multiple temp controlled runs (soft and hard run) within the same starting material can yield greater amounts of terpenes (around 7-15%) and yield cannabinoid percentages at around 75-80%.
So in short, CO2 is better for extracting a fuller spectrum of terpenes, while hydrocarbons are better in extracting cannabinoids. Both extractions provide a crude or raw oil that would most likely undergo additional winterization processes and pressure oven vacuuming.
As mentioned earlier in this section, hydrocarbons have more variety within its end product. Differing concentrations of nitrogen, CO2, and oxygen, are used to agitate the crude oil and cause the change in texture and aromatics we see among hydrocarbon products. Depending on this mixture of gases during the post processing the final product can be of a mono-crystalline form (aka shatter) or poly-crystalline form (aka wax/crumble).
However what are the actual expected yields of oil?
We spoke to a number of processors and even extraction equipment companies to determine what the greatest differences between CO2 and hydrocarbon extraction yields are. What we found out is that their yields are quite comparable and that the yield all depends on the starting material.
Starting Material – Trim or Untrimmed:
Within both solvents, the best quality flower with the least amount of damage or least processed starting material, the greater the yield. This is in order to preserve and capture the volatile terps and essential cannabinoids. To elaborate, “processed flower” brought to an extractor is somehow trimmed either by hand or by machine. In doing so, the starting material (flower) is tumbled and some of the terpenes are knocked off and dissipate into the air via the trimming process. In addition, machine trimming material in particular will increase the amount of surface area of a nug substantially and aggressively knock off desired chemicals. This allows oxygen to seep through, oxidizing the flower, further degrading its terpenes and cannabinoids content, resulting in a darker oil at the end of the process.
Within hydrocarbon and CO2 extraction for machine trimmed material, you can expect a yield of 4-7% of oil, with respect to the starting material weight. So if you had a starting amount of 100 grams than you could expect anywhere from 4-7 grams of darker oil after your run.
While if you had lets say A Grade Indoor Popcorn you could expect your yield to be closer to 10%
Therefore, the most suitable flower for extraction is full, untrimmed A-Grade Flower or A-Grade sugar leaf/Popcorn.
Within both CO2 and hydrocarbon extraction the general yields look like so:
Low grade – 4-8% Yield
Mid grade – 10-15% Yield
High grade – 20-25% Yield
*25% is a rarity within hydrocarbon extractions
Layered over this general scale is whether or not the material is indoor or outdoor.
Indoor Vs Outdoor
The differences between outdoor and indoor extractions are a few, mainly the amount of waxes and fats that are found within the crude oil, terpene content and cannabinoid levels. Outdoor flower seems to yield more waxes and fats, due to the environmental elements (sun, wind, insects, etc). However due to these same conditions, outdoor flower seems to have a broader spectrum and thus generally larger count of terpenes. This requires a more extensive post processing procedure for de-waxing, however can provide a more complete product that is truer to the plant.
The logic is that because the plant is being stimulated by external forces such as insects and wind, it responds defensively by producing a greater number of terpenes and cannabinoids that may not have been provoked to be produced if it were in doors.
Indoor flower can be grown in a manner which will produce extremely terpene rich flower as well however with less diversity within its profile, and because it grows in a controlled environment, it typically is higher in cannabinoids and lower in terms of waxes and lipids. This allows for a less time consuming post processing, and is great starting material for RAW CO2 oil which goes through minimal post processing, providing a terpene rich and balanced experience, or for BHO sugar wax where the color and aroma are key facets of the end product.
Ultimately, its truly difficult to say what extraction method is better. It’s not as if we’re comparing apples to apples, more like apples to oranges. When it comes to CO2 and hydrocarbons they’re just two different things altogether. Some people prefer CO2 and others prefer BHO/PHO.
Personally, I’m glad we have both options. As long as there are regulations and safety standards that are met and maintained, I’m happy to smoke on either.