What is the Best Extraction Technique: CO2 extraction or ethanol extraction?

There are many different methods of extracting cannabidiol (CBD) or tetrahydrocannabinol (THC) and other cannabinoids from biomass. Each extraction method uses a different solvent to pull oils out of the biomass. While each method carries its pros and cons, supercritical CO2 extraction has emerged as the leader for demanding customers while driving high throughput and low operating costs, with the best quality, purity, and consistency oils produced. The following table compares the pros and cons of CO2 and ethanol extraction methods: 

Table 1. Comparison of Solvent and CO2 Extraction Techniques

Parameter

Ethanol Extraction

Supercritical CO2 Extraction

Organic Oil

Organic ethanol required.1

No special requirements, approved organic solvent.1

Cannabinoid Recovery

50-80% typical cannabinoid recovery including carbon scrubbing. Method may require carbon to remove chlorophyll. Carbon absorbs THC and CBD which lowers recovery. Carbon is a high cost consumable.

85-95% typical cannabinoid recovery. No carbon required.

Solvent Recovery

Ethanol is expensive and therefore needs to be recovered.  Typically, 90-95% recovery of ethanol leads to high operating costs.  Losses come from ethanol remaining in biomass and in the extract.

No need to recover CO2 other than recycling within a run or batch due to low expense of CO2.

Reuse of Extracted Biomass

Biomass extracted with ethanol is hazardous waste until the ethanol is removed to negligible levels, may be flammable and/or toxic due to type of ethanol used. 2,3 Transportation is typically regulated.

Biomass extracted is clean and is a source of food grade essential amino acids. Transportation is not regulated.

Winterization

Winterization may be avoided if extraction is at < -20oC leading to high energy expense.  Warm ethanol extractions need to be winterized.

Winterization may be avoided with subcritical extraction.  However, extraction is much slower at low pressure.

Safety

Significant fire hazard risk for indoor deployment.4

Inert. No fire hazard risk.5, Static and asphyxiation risks are mitigated with proper install.

Infrastructure Cost & Requirements

High cost for hazardous building occupancy and special room classifications and limitations.4,a

Minimal requirements. May operate in industrial building (F2) classification.4

Equipment Cost

$2-3M USD for 1 ton per day

$3-4M USD for 1 ton per day

Operating Cost

High variable costs and overhead due to ethanol cost, losses of ethanol, consumables, reduced recovery, high insurance premiums, hazardous waste disposal, and energy costs.

Very low variable cost for CO2. No difficulty getting business insurance.

Scalability

Scalable easily to 10 tons per day in less than 450 m2 with hazardous (H2,3) occupancy, with about ~7000 amps, 230V, 3 phase cooling capacity and C1D2 special rooms.6

Scalable easily to 10 tons per day in less than 450 m2 in F occupancy with ~2400 amps 230V 3 phase.

Solvent Sourced Cross Contamination Risk

 Herbicide, pesticide, solvent contamination,  extraction byproduct contamination and build up risk.b

CO2 is not generally used across lots.  No risk of cross contamination.

Solvent Sourced Cross Contamination Risk

 Herbicide, pesticide, solvent contamination,  extraction byproduct contamination and build up risk.b

CO2 is not generally used across lots.  No risk of cross contamination.

Cost of Solvents

Food grade ethanol is safest and comes little to no chemical contamination risk but with higher cost. Specially denatured solvents are less expensive but carry a myriad of non-food grade contaminants.7

Low price per kg.

Terpenes for full spectrum flavor and aroma

Lost during processing.

Harvested during processing.

Environment

High carbon footprint to produce ethanol, tons of cooling capacity needed to cool to <20oC, and dispose of hazardous biomass waste after processing.

Byproduct of existing industrial processes, non toxic, non eco toxic, renewable, recaptured.8 Considered a green solvent by the American Chemical Society.

 a. Limits on the amount and storage of flammable solvents in addition to specific alarm lights and deflagration alarms and detectors, emergency phones and alarm systems with 24-hour third party monitoring, alarm levers every 150 ft, setbacks from property lines or other adjacent occupants, automatic and special sprinkler systems, fire distance offsets, deratings on maximum solvent volume for multi-story, emergency power for vents, fail safe electrical systems, spark proof venting, certified equipment for hazardous locations, and explosion control plans.4,9 The use of CO2 as an extraction solvent does not require any of this infrastructure since there is no limitation on the amount of CO2 a factory can have on site.4

b. Most importantly, ethanol derived chemical contaminants10 that remain in the extracted oil after removal of the ethanol, may increase the risk of safety and health for the consumer. For example, some of the residual contaminants listed in the specially denatured ethanol recipes have a higher boiling point compared to ethanol and are not removed from the oil during distillation.  Furthermore, solvent analysis for contaminants are not always included in a typical certificate of analysis.

The table shows that in terms of every factor except capital equipment cost, CO2 extraction has advantages over ethanol as the extraction method.  Taken collectively, CO2 extraction as a method leads to DRASTICALLY lower operating costs.    

It’s All About Operating Costs

The following table shows why CO2 is such an attractive business proposition compared to ethanol technology:

Table 2. Estimated Difference in Solvent Cost for a 1 ton per day Ethanol and CO2 system.

  Ethanol CO2
Approximate Equipment Cost $2,000,000 $4,000,000
Required Solvent Start-Up Cost $7,000 $500
Solvent Loss Cost per Day $3,500 $115
COMPARISON    
1 Year Solvent Loss Cost $1,260,000 $42,048
10 Year Solvent Loss Cost $12,260,000 $340,000
  1. Biomass throughput is 1 ton per day processing to distillate. 
  2. All costs are approximate and in USD.
  3. Costs of infrastructure, biomass disposal, revalidation costs, and energy are neglected in the analysis.
  4. 5% ethanol lost per day at 1 gallon ethanol/lb of biomass extraction ratio.  Assume no carbon or filters are used. 
  5. Cost $35/gallon for food grade ethanol.  Reduce figures to $12/gallon for denatured ethanol. Does not include shipping. 
  6. Cost of CO2 in bulk delivered is about $0.04/lb.

With the highest cannabinoid recovery levels and low operating costs, CO2 extraction is usually the best choice for your manufacturing equipment foundation to serve multiple market segments.  

Get your copy of the Critical Analysis & Comparison of Ethanol & CO2 Extraction White Paper Here


REFERENCES:

  1. Guidance & Instructions for Accredited Certifying Agents & Certified Operations | Agricultural Marketing Service https://www.ams.usda.gov/rules-regulations/organic/handbook (accessed Dec 8, 2019).
  2. eCFR — Code of Federal Regulations- EPA Hazardous Waste https://www.ecfr.gov/cgi-bin/retrieveECFR?gp=&SID=c94567294dff611654af7a3944a91d69&mc=true&r=PART&n=pt40.28.261#sp40.28.261.c (accessed Dec 15, 2019).
  3.  Hazardous Waste from Cannabis Extraction - Extraction Magazine https://extractionmagazine.com/2019/08/14/hazardous-waste-from-cannabis-extraction/ (accessed Dec 15, 2019).
  4. Chapter 3: Use and Occupancy Classification, Building Code 2015 of Utah | UpCodes https://up.codes/viewer/utah/ibc-2015/chapter/3/use-and-occupancy-classification#3 (accessed Dec 8, 2019).
  5. CGA P-1-2015 - Standard for Safe Handling of Compressed Gases in Containers - 12th Edition https://webstore.ansi.org/standards/cga/cga2015-1531002?gclid=CjwKCAiA27LvBRB0EiwAPc8XWflJxH6MAC74YxV5upUoi5lt6OakcaPK5L_mu7CrSSu5CMXTjcG9mxoCrikQAvD_BwE (accessed Dec 8, 2019).
  6. 2006 International Building Code https://www.optasoft.com/applications/codes/2006IBC/HTMLHelp/414.htm (accessed Dec 8, 2019).
  7.  eCFR — Code of Federal Regulations- TTB Alcohol and Rules for Specially Denatured Alcohol https://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&sid=fc3be5d2e97afdd4aed5fb7b5c26309c&rgn=div5&view=text&node=27:1.0.1.1.17&idno=27#se27.1.21_1112 (accessed Dec 8, 2019).
  8. Brunner, G. Applications of Supercritical Fluids. Annu. Rev. Chem. Biomol. Eng. 20101 (1), 321–342. https://doi.org/10.1146/annurev-chembioeng-073009-101311.
  9. Chapter 9: Fire Protection Systems, Building Code 2015 of Utah | UpCodes https://up.codes/viewer/utah/ibc-2015/chapter/9/fire-protection-systems#903 (accessed Dec 8, 2019).
  10. eCFR — Code of Federal Regulations https://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&sid=3f34f4c22f9aa8e6d9864cc2683cea02&tpl=/ecfrbrowse/Title07/7cfr205_main_02.tpl (accessed Dec 8, 2019).

 

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