In today's cannabis extraction market, manufacturers are continuously looking to improve their operations from throughput to expenses to quality of oil. In the pursuit of crafting the perfect product and scaling their business, manufacturers have turned to solvents to process high volumes of raw cannabis products.
The three most common and efficient solvents used in solvent-based cannabis extractions include light hydrocarbons (butane and propane), ethanol, and carbon dioxide (CO2) in its supercritical state, all of which are already used in pharmaceutical, agricultural, and petrochemical industries.
As the legalization wave continues and cannabis goes global, operators are looking for innovations in equipment, solvent, and workflow to optimize traditional cannabis extraction methods. Here, we pit one of the newest and niche extraction methods (R134a) with a classic method (CO2). In the world of cannabis extraction, is one method better than the other?
Understanding Solvent-Based Cannabis Extraction Processes
Solvent-based extractions occur in a laboratory setting using peer-reviewed closed-loop equipment capable of recycling and reusing solvents used during extraction. Each extraction type comes with different rules and regulations that vary by state relating to the storage of solvents, exhaust systems, gas monitoring, and other safety measures needed in a facility.
A variety of chemical solvents have made the fast expansion of the cannabis market and its diverse product spectrum possible. Today, consumers can enjoy everything from cannabis gummies to transdermal patches to suppositories, all because of cannabinoid extraction.
After every harvest, cannabis plant material is processed using a solvent-based or solventless method to remove the cannabis compounds from the plant. These compounds are the foundation for a wide range of derivative products including edibles, vape cartridges, tinctures, topicals, and extracts.
Solvent-based cannabis extractions, in particular, can handle a spectrum of raw cannabis products from high-quality, fresh frozen flower buds preserved at their peak freshness to aged trim with a lackluster color and aroma. Extraction efficiencies and results vary based on the following elements:
- Starting plant material
- Operator skill
- Desired end product
Light hydrocarbon extraction
Light hydrocarbon extraction stands out as one of the most effective and popular methods of extracting a full-spectrum oil replete with cannabinoids and terpenes. This process is capable of producing a wide range of extract consistencies and products ranging from THCA crystals to high-terpene full-spectrum oil like terp sauce. Hydrocarbon extractions require vacuum purging to remove the residual butane from the cannabis oils.
Ethanol is another popular extraction solvent, primarily reserved for the processing of high volumes of cannabis and also during winterization after CO2 and hydrocarbon extraction processes. Ethanol became a go-to solvent after the passage of the 2018 Farm Bill which legalized the production of industrial hemp with under 0.3% THC.
Carbon dioxide, when it has supercritical properties, is another common solvent used in the industry. CO2 is chosen for its efficacy and commonly used to make cannabis oil for vape cartridges. CO2 is considered more environmentally friendly and safer to use than the latter methods.
Tetrafluoroethane (R134a) is a hydrofluorocarbon used as a refrigerant in the automotive and HVAC industry. It has recently made a splash in the industry as an alternative to CO2 extraction. Its relative safety and efficiency at preserving the plant’s terpenes has piqued the interest of a cadre of cannabis processors looking to optimize their workflow.
Choosing the right method
Among the safest and highest-capacity processing methods for commercial cannabis processing, CO2 extraction and R134a extraction share many similarities and have a few differences in process, yield, and quality of the oil extracted.
All methods of extraction involve running processes at temperatures and pressures that can lower yield, delay the process, and increase overall costs. It is up to operators to determine the right procedures for their operation through trial-and-error.
For those considering CO2 and R134a for use on botanical substances, we have created the ultimate guide to break down the intricacies of each extraction workflow, their pros and cons, efficiency, safety, cost, and environmental impact. Is one method better than the other? The answer may surprise you.
What Is CO2 Extraction?
Supercritical carbon dioxide (CO2) extraction is one of the primary methods of producing a pure and potent cannabis extract and its derivatives. This method of botanical extraction uses carbon dioxide in its supercritical state, which has properties of a liquid and a gas. Because of this, CO2 can easily and effectively dissolve cannabinoids and terpenes like a liquid from biomass and spread through every part of the material like a gas.
In addition to its popularity among cannabis processors, CO2 extraction processes have been common in a variety of industries including the production of perfume, essential oils, beer, and coffee decaffeination.
The process uses carbon dioxide in its supercritical state, which is odorless, colorless, non-flammable, and non-toxic. The method takes advantage of the supercritical properties of CO2 which are better able to dissolve the natural oils of botanical substances.
During cannabis extraction, cannabinoids are removed using supercritical extraction, while terpenes are removed by running subcritical extraction processes that use lower temperatures and pressures which can take longer than the supercritical process.
CO2 is considered a tunable solvent since operators can fine-tune the temperature and pressures in the system to essentially target and extract their desired compounds all while reducing the amount of unwanted substances in the crude cannabis oil.
After the primary plant matter extraction process, processors may perform a winterization step that filters out the lipids and waxes with cold ethanol. If this method is used after supercritical extraction, a separate solvent recovery process must be used to remove the ethanol solvent from the cannabis oil.
What Is Supercritical CO2?
Carbon dioxide is a low density gas that must be pressurized for use as a cannabis solvent. At room temperature and standard pressure, CO2 is a gas. When it is cooled and/or pressurized enough, it becomes solid, also known as “dry ice.”
During the extraction process, CO2 gas is held above its critical pressure and critical temperature to reach a supercritical state that has properties of both a liquid and a gas, making it easy to completely soak and diffuse through every inch of the plant material.
Supercritical CO2 is a popular commercial solvent due to its low toxicity and environmental impact. The low temperatures used during the subcritical process allow operators to strip materials of their plant values without too many unwanted compounds. Altering pressures in the system can allow extractors to perform selective extractions.
How Does CO2 Extraction Work?
Since carbon dioxide is a low density gas, it must be pressurized to dissolve cannabis oil from the plant. The ground biomass is loaded in the extraction vessel and pressurized carbon dioxide is pushed into the tank effectively dissolving the natural oils of the plant and separating cannabinoids and terpenes.
Then, the mixture is pushed into a separate tank. Less Heat and pressure are applied to the mixture to boil the carbon dioxide from the oil extracted. Afterward, the solvent is turned back into a gas and recycled for reuse.
Depending on temperatures and pressures use, the cannabis oil may need post-processing to remove the fat, lipid, and wax content. This post processing method requires additional machinery and training to produce a pure and clean product.
When cannabis oil is extracted, it can be used to create a variety of cannabis-infused products including vape pens, edibles, extracts, tinctures, and topicals. CO2 is a popular alternative to hydrocarbon-based extracts for consumers worried about residual solvents.
Subcritical Extraction vs Supercritical Extraction
It is important to note a difference between supercritical cannabis extraction and subcritical extraction in a closed loop system. When running subcritical extraction processes, the steps remain much the same as in a supercritical method but use relatively lower temperatures and pressures to preserve certain compounds.
In this subcritical state, the liquid CO2 is able to dissolve the terpenes and other temperature-sensitive natural oils from the plant. The process is able to preserve them due to the lack of heat involved. While this process may be slower than a supercritical method would be and may produce a lower yield, it can create a product with a fuller spectrum of terpenes without the need for winterization.
CO2 extraction is one of the best, safest, and most efficient methods of producing a full spectrum oil. With the use of subcritical extraction and winterization techniques, producers can take their cannabis crude oil to the next level by removing the waxes and preserving the terpenes. Keep in mind, CO2 extractions are relatively slower than other methods, thereby, resulting in fewer runs per day compared to other processes such as hydrocarbon extraction.
Pure botanical extraction using supercritical CO2 is considered one of the safest methods for both processors and consumers. In the extraction room, running supercritical extraction poses relatively fewer safety hazards for operators compared to other methods such as hydrocarbon extraction since CO2 is non-flammable and non-toxic.
However, there is still a risk of asphyxiation if the concentrations of CO2 reach above a certain threshold. For this reason, CO2 processing facilities must use closed-loop extraction systems as well as alarms and sensors to alert operators when unsafe levels of the gas are present. Proper ventilation can reduce this risk.
On the consumer side, CO2 is considered safe for use in commercial extractions by the FDA. Food, beverage, and pharmaceutical industries turn to CO2 as a solvent because there is very little chance of leaving residual solvent in the end product. For this reason, many health-conscious consumers may turn to CO2 extracts out of all the solvent-based extracts.
CO2 extraction is considered the most eco-friendly processing method in the cannabis industry. CO2 is a byproduct of a number of industries, making it widely and easily available for producers. In addition, it is a non-toxic and renewable resource that can be reused in a closed loop system. It is also regarded as a green solvent by the American Chemical Society.
Equipment and Operational Costs
The high upfront costs of CO2 extraction systems make this method of production prohibitively expensive for some startups who do not have enough funding. CO2 extraction systems have the highest system prices compared to more budget-friendly ethanol, hydrocarbon, and solventless equipment like a rosin press.
On the more affordable end of the spectrum, a starting CO2 extraction system can start at about $100,000. CO2 systems also require more special training for operators to learn how to operate the machinery. In terms of the solvent itself, it is readily accessible and affordable compared to other solvents and even has higher storage limits than most cannabis extraction solvents since it is non-toxic and non-flammable.
Ultimately, CO2 extraction operations can be an expensive process and require a steeper upfront investment but for some businesses, the initial expenditure can be worth it due to the relatively low operating expenses. If processors have the budget and training required for this production method, CO2 extractions offer longevity and superior quality.
- Medium cannabinoid yield
- Sustainable and renewable solvent
- Affordable solvent per kg
- Tunable solvent
- High upfront investment for equipment
- Relatively high wax content
- Run times take longer than most processes
- Medium chlorophyll content
- Relatively low terpene contents in supercritical extractions
- May require winterization
- Requires specialized operator training and experience
What Is R134a Extraction?
One of the newest methodologies used to improve the efficiency of traditional extraction methods is through the use of tetrafluoroethane (TFE), also known as R134a, as a solvent. Cannabis extracts that are made using the R134a extraction method are known as post-winterized full-spectrum oils because they can produce extracts with under 5% wax content. In most cases, the end product can contain as little as 2% wax content.
Most cannabis extractions tend to focus on removing as much of the plant's primary cannabinoids such as delta-9 tetrahydrocannabinol (THC) and cannabidiol (CBD) without paying special attention to its terpene content, which is known to produce synergistic effects with the other bioactive compounds.
In a natural phenomenon known as the entourage effect, researchers believe that consuming the full spectrum of active ingredients over cannabinoid isolates or distillates can elevate the therapeutic effects while minimizing the adverse effects of the plant. In concentrates and derivatives, the preservation of more of these compounds can create a product especially fit for medical patients and recreational users.
R134a is an innovative and effective solvent that has been slowly growing in use among cannabis processors. It is used to preserve the plant’s full terpene profile to create full spectrum products for medical and recreational markets. R134a is an affordable production method that can create high-potency extracts with an exceptional flavor and aroma profile.
What Is R134a?
R134a is a type of hydrofluorocarbon (HFC) commonly used in automotive and residential refrigerants. If you are familiar with proper automotive air conditioning maintenance, you may know R134a as freon. Freon is a non-combustible gas used as a refrigerant in your air conditioning systems. It undergoes a continuous evaporative process that cools air that circulates through an air conditioner.
R134a is a non-polar solvent that can convert to its supercritical state at 213.9º F and 40.6 bar. Compare this with carbons’s temperatures and pressures needed to reach its supercritical state: 87.8º F and 83.3 bar.
Since this production method uses lower pressures using a nonpolar solvent, it can be a highly efficient process to use for cannabis extractions.
R134a extraction is non-toxic, odorless, inert, non-corrosive, and non flammable. It also does not form an acid when working with moist biomass.
R134a was created to replace the use of chlorofluorocarbon (CFC) refrigerants, which were banned in 1987. CFCs include chlorine that destroys molecules in the ozone layer. Unlike CFCs, R134a is a more environmentally friendly solvent than CFCs that does not deplete the ozone, although there are some growing concerns about its effect on global warming.
R-134a is commonly used in:
- Car air conditioners as a refrigerant
- Refrigerators and freezers as a refrigerant
- Aerosol cans
How Does R134a Extraction Work?
R134a extraction works similarly to CO2 extraction in that both extraction methods use a gas solvent and turn it into a liquid (or a supercritical state in CO2 extractions) to wash over the material and strip the plant of its active ingredients.
R134a extractions occur under low pressures and room temperatures in a closed-loop extraction system. Because the process occurs at room temperature, it produces no thermal degradation or a considerable loss of terpenes during extraction. R134a’s low boiling point (-15.34º F) essentially eliminates the requirements for a long solvent recovery process that can lead to a slowed process. At room temperature, the solvent can easily evaporate from the extract.
R134a is slightly pressurized and then pumped through the biomass to strip a significant percentage of the plant’s cannabinoids and terpenes. Then, the solvent is recovered in a separation tank, leaving behind a full-spectrum oil.
R134a is a small, inert, and nonpolar molecule that is able to easily and effectively pass-through a wide range of biomass material to extract oil-soluble compounds. Best of all, the use of this solvent can preserve the complete terpene profile of the biomass without destroying a lot of terpenes. For this reason, this extraction method is generally performed on fresh plant material with a naturally higher concentration of cannabinoids and terpenes.
Compared to CO2 extraction, R134a extraction is an easier-to-perform process that does not require as much operator training and still produces a high quality and yield of oil. It can be much more cost-efficient since facilities do not need as many technicians or systems, translating to low maintenance and labor costs. Not to mention, the solvent is easy to purge.
Research has found that R134a is better able to dissolve unsaturated carboxylic acids with a 20 fold reduction in the energy required to compress the gas compared to CO2 extraction under comparable conditions.
Because it does not extract solids from the biomass, the process does not require winterization after the primary extraction process. Winterization is the process used to separate unwanted fats, chlorophyll, waxes, and lipids from the crude extract, usually with a lipophilic solvent like ethanol.
In addition, this extraction method does not strip away water-soluble compounds such as chlorophyll, mold, and pesticides, producing a clean extract. R134a is a worthy alternative to traditional extraction methods due to its extraction efficiency, affordability, ease-of-use, and purity.
As a solvent, R134a is non-toxic and considered generally recognized as safe (GRAS) by the Food and Drug Administration (FDA). In addition, the European Union has approved its use as a solvent through EC Directive 2009/32, making it an effective solvent alternative in a burgeoning international hemp market.
In the production process, R134a vapor has no known effect on skin contact. In liquid form, the solvent can cause frostbite and eye damage if splashed in the eye.
Currently, there are no human studies on the exposure to R134a. Animal studies show that R134a has a low level of systemic toxicity. R134a has a low acute toxicity when inhaled. It has an approximate lethal concentration (ALC) and rats at 567,000 ppm in a 4-hour exposure window.
R134a is generally considered safe for human health when exposed to small amounts. In a commercial lab facility, R134a would properly be purged from the extract.
Equipment and Operational Costs
R134a extraction systems are relatively affordable compared to higher-priced CO2 extraction systems. R134a is also affordable compared to other solvents, making this process a good option for startups or those hoping to produce terpene-rich cannabis extracts.
In addition, R134a extraction does not require as much specialized training as supercritical CO2 methods. For this reason, manufacturers may reduce expenses on training, labor, and system maintenance.
Secondary Cold Ethanol Extraction
R134a cannabis extraction can benefit from using a secondary ethanol extraction process after the initial R134a extraction. R134a extraction is a new and efficient method that can preserve terpenes in a span of 10 to 15 minutes.
After this primary extraction method is complete, a secondary cold ethanol extraction takes about 30 to 60 minutes and is efficient at dissolving just the cannabinoids, eliminating the need to perform a distillation after these processes.
The result of the primary and secondary extraction processes can yield a complete cannabinoid and terpene profile compared to R134a extraction alone, capturing a wider range of lighter and heavier compounds.
Case Study: Extraction of Artemisinin
A 2006 report by Malaria Medicine Ventures (MMV) studied new technologies, including R134a, for the extraction of artemisinin, an herb used as a treatment for malaria. Traditionally, the primary plant extraction solvent has been hexane and petroleum ether due to their affordability. Supercritical CO2 has been considered as an alternative solvent to these solvents which have more safety hazards and can be harmful to the environment.
Researchers found that “extraction with [R134a] and ionic liquids was shown to be the most promising replacement for hexane extraction.” In addition, “extraction with [R134a] provides much cleaner extracts with higher concentration of artemisinin and, therefore, should lead to simpler recovery of artemisinin from the primary extract.”
Researchers concluded that “the process is economic, low-risk, and has low environmental impact, with the main concern being the need for tight control of the solvent inventory and of its recovery from the biomass.”
It is important to note that the same results may differ with cannabis plant material. Currently, this method of extracting cannabinoids and terpenes from cannabis biomass is not common in the industry. COMERG is one of the leading vendors of pure botanical extraction systems designed for R134a.
Despite its cannabis-friendly inherent qualities, this solvent is a greenhouse gas. Federal agencies have recommended discontinuing its use due to its contribution to climate change. In some cases, states have passed bans on its use.
In California, new vehicles will not be able to use R134a starting in 2021. In 2020, the state's ban on its use in marine flotation foam took effect. Needless to say, R134a’s future in the cannabis industry is up in the air despite its efficiency.
R134a initially came on the scene to replace a refrigerant that was causing too much harm to the ozone layer. Now, this innovative solvent may be responsible for worsening the climate change problem as well but in a different way. R134a has a global warming potential of 1,430 times greater than carbon dioxide.
While the effects are mitigated when working using a closed-loop system, R134a’s environmental impact and its staying potential in the cannabis industry is yet to be seen.
- Safe for cannabis extract production
- FDA-approved and qualified as GRAS (generally recognized as safe)
- EU-approved solvent
- High cannabinoid yield
- Low wax content
- Low chlorophyll content
- High terpene yield
- Low operator training requirements
- About 1,430 times as potent as CO2 as a greenhouse gas
- Not as many system options
- May need a secondary cold ethanol extraction to create a full spectrum product
- May not offer longevity in the cannabis industry due to the ban of its use
R134a vs CO2 Extraction Methods: Which One Is Better?
Is running supercritical extraction better than R134a or the other way around? Ultimately, the best overall extraction process for consumers and producers depends on a variety of factors including consumer lifestyle and needs and the desired product the producer intends to create. Here, we go over the most essential factors to consider when choosing between one type of extraction method over the other.
The process architecture of these two extraction processes are very similar, although CO2 stands out as the most common with plenty of room to scale operations if operators can afford the higher equipment costs. R134a remains a promising alternative or supplement to traditional CO2 manufacturing operations.
Finding the Right Cannabis Extraction System
A major part of producing a pure botanical extraction depends on the closed-loop extractor system used. While CO2 requires a larger upfront investment for its extraction systems, it boasts the capability of producing full-spectrum products. Operators have a wide range of system options to choose from for small, mid-level, and large commercial operators.
R134a extraction is a much more niche segment with much fewer system options compared to CO2 extraction. If operators want to produce higher terpene extracts at an affordable cost, especially for startups, R134a extraction can be a viable alternative to the more expensive CO2 systems.
CO2 and R134a Mixtures
Research has shown that using “hydrofluorocarbon solvents significantly increases the polarity of the super critical medium and significantly increases the solubility of a solute.” Using a mixture of CO2 and R134a solvents can reduce the amount of supercritical fluid needed and makes for easy solvent recovery.
Improve Your Cannabis Oil’s Color and Clarity With Media Bros
Inspired by the market potential and innovation in the industry, Media Bros aims to make cannabis extracts better. Our line of high-grade filter media and hardware improves the color and clarity of extracts made with CO2 and hydrocarbon systems.
Color remediation technology in cannabis uses a variety of filter media to remove the chlorophyll and pigments from any quality oil without negatively affecting the yield. Our line of filter media products include:
- CRX: CRX is our flagship filter media capable of removing undesirable pigments with negligible reductions in cannabinoid and terpene yield. CRX’s granular size is compatible with high-flow and low-pressure systems. It is ready to use out of the packaging.
- CRY: CRY takes the CRX approach up a notch with 1.5 times the embedded silica content for seriously tough colors and aged biomass.
- CR2: CR2, designed for use in CO2 extraction processes, removes the bitter taste found in many CO2 extracts, to produce a better tasting and looking product.
Take your cannabis manufacturing operations to the next level with color remediation technology from Media Bros. Request a sample of our filter media to start producing the highest quality extracts.