Sara Krostag   |   August 19, 2021

Solventless Cannabis Extraction Methods

Exploring the various methods of solventless cannabis extraction.
Freelance journalist and US Navy veteran based near Lake Superior. After 12 years of electronic intel and repair, she acquired an MS in Health and Wellness. She now pursues her passion for helping people through the use of natural medicines…

While solventless extraction methods are known for high yield and practicality, they may also be safer for the environment, extraction facilities, and the human element involved in all aspects of the industry, from grower to consumer.

Popular cannabis products such as shatter, rosin, hash, budder, and hemp oil are end products of an extraction process, commonly through hydrocarbon or alcohol-based solvents (butane, propane, or ethanol).  These methods are not only expensive, but they are also dangerous. The use of solvents in a cannabis extraction facility may present exposure to harmful dust and vapors, fire, explosions, or even asphyxiation from CO2 exposure.

What is Solventless Extraction?

Solventless extractions refers to any type of mechanical extraction method performed without the use of solvents. Water is widely known as a universal solvent; however, it is a misnomer among extractors when used in this manner.  Due to the nature of the cannabis plant, water may be used as a medium rather than a solvent to separate plant matter from trichomes.  While some terpenes may dissolve in the water during the process, at no time are resin heads dissolved completely.

Solventless vs. Solvent-Free

A concentrate obtained through solventless extraction methods such as hash or rosin is much different than an extract labeled “solvent-free.”  This term refers to a product extracted using a solvent but later distilled to remove residual chemicals.

The Pros and Cons of Solventless Extraction

Recent studies show solventless extraction methods can be viable, more environmentally friendly alternatives to conventional methods.  Solventless extraction methods can produce a better quality extract with a higher yield more quickly.

Pros

  • This practice does not require solvents, which can cause damaging ozone levels and pollute water supplies by releasing volatile organic compounds (VOCs).
  • Due to potential hazards, only specific solvents are permitted in Colorado, although all (except CO2) release VOCs when they evaporate. The disposal of solvents by allowing them to evaporate or pouring them out is prohibited. Solventless extraction is easier to control and dispose of waste products. 
  • Hydrocarbon solvents are byproducts of petroleum.  Many hydrocarbons, including petroleum products and byproducts, can be found on the United Nations List of Dangerous Goods.  As described by the name, solventless extractions require no solvents.
  • Many high-quality industrial rosin presses are easy to use and available for $3,000- $10,000. They require minimal supplies and are less expensive compared to traditional methods.  The same quality CO2 extraction unit can cost $200k+ upfront.
  • Solventless extraction shows fewer hazards throughout the entire process and passes that onto the consumer by eliminating the risks of residual solvents in the end product without additional testing.
  • Solventless rosin can be produced using freshly harvested or cured cannabis flowers, kief, water hash, and trim, although the result will vary based on the material used.

Cons

  • What goes into a solventless extraction will come out of a solventless extraction.  The quality of the result will depend directly on the quality of plant material used.
  • All cannabis flowers are not created equally when it comes to solventless extraction. Certain cultivars can offer a higher yield than others.
  • Solventless extraction does not remove contaminants during the process.  If the plant material is contaminated, the same will hold true for the end product.  Contamination includes mold, mildew, heavy metals, pests, and pesticides.  All products must pass state-level testing before they are allowed to reach the consumer; excess contaminates would cause a failure.
  • While water is a relatively safe and stable medium for solventless extraction, reverse osmosis is recommended.  Tap water may contain contaminants, while pre-existing pesticides in distilled water are concentrated in certain processes (ice-water hash).
  • Cannabinoids and terpenes are heat-sensitive.  Some processes involving high heat or high pressure may damage or degrade the whole plant profile.

Solventless Extraction Methods

  • Microwave-assisted extraction (MAE) generates heat by using microwaves to interact with polar compounds (water and plant matter) to accelerate extraction and improve yield synergistically. While there are two types of MAE (solvent/solventless), the solventless method is required to extract volatile compounds. Relatively new MAP™ technology uses water (and ethanol) to isolate critical compounds in the biomass and focus energy, reducing extraction time to minutes.
  • Ultrasonic Assisted Extraction (UAE) uses a combination of water and sound waves to break down the cell walls in cannabis to create an emulsion that can be easily reproduced.  UAE may be combined with other extraction methods to create more potent concentrates and is often specified in U.S. Pharmacopeia monographs to extract active pharmaceutical ingredients from carriers for uniformity and potency testing.
  • Solventless THC-A is created by taking terpene-rich rosin and re-pressing it at very low temperatures through a 25-micron screen. This process separates the high-terpene sauce from crystallized THC-A.
  • Rosin Presses use heat and pressure to extract cannabinoids and terpenes.  With advances in rosin press technology, this technique can be used from beginner to commercial operation.
  • Subcritical Water Extraction keeps water in a liquid state under pressure at temperatures less than 374°F.  This process is still under investigation; however, research shows subcritical water extraction yielded more components than hydro-distillation (HD) and organic solvent extraction under ultrasonic irradiation.  Some techniques could be considered pressurized hot water extraction (PHWE).
  • Cold Water Extraction relies on ice, water, and agitation to extract concentrates while cleanly preserving cannabinoids and terpenes. This process avoids high heat or pressure that may potentially damage the original plant profile.

Cannabinoids can be extracted in acidic or neutral forms, depending on the process.  If the preservation of terpenes is important, a method involving lower pressure and heat is needed.   With many different solventless methods, the end-product characteristics must be considered before building or converting an extraction facility into a solventless operation.  With that in mind, any shift away from using solvents, organic or otherwise, may improve safety from facility to consumer while protecting the environment.

 

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