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Understanding Solvent Density in Supercritical CO2 Extraction: Optimizing Efficiency and Compound Solubility

Supercritical CO2 extraction is a widely used method in the cannabis and hemp industry for extracting desired compounds from biomass. While the conventional focus has been on pressure and temperature, the concept of solvent density plays a pivotal role in determining extraction efficiency and selectivity. In this article, we will explore the significance of solvent density in supercritical CO2 extraction, its impact on compound solubility, and how it influences the overall extraction process.

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Solvent Density: The Key Measure

When discussing supercritical CO2 extraction, it is essential to consider the relationship between pressure and temperature, which ultimately determines solvent density. By combining pressure and temperature, a single measure, solvent density, can be used to set equipment parameters and develop extraction methods. This approach simplifies the optimization process, providing a clear metric to work with.

Compound-Specific Solubility

Solvent density plays a crucial role in targeting specific compounds during supercritical CO2 extraction. By manipulating the solvent density, different classes of compounds can be selectively solubilized or avoided altogether. Understanding the solubility characteristics of target compounds helps in developing extraction methods that maximize efficiency and yield desired results.

CBD Oil CO2 Extraction
CBD Oil CO2 Extraction
  • Terpenes and Cannabinoids: Solubilizing monoterpenes and sesquiterpenes without co-extracting plant waxes and cannabinoids is achievable at solvent densities between 0.250 g/mL and 0.300 g/mL. Plant waxes solubilize at approximately 0.400 g/mL, while cannabinoids start to solubilize within the 0.450 g/mL range.
  • Solubility Factors: Each cannabinoid exhibits its own solubility, with CBD and CBDa generally having higher solubility than THC or THCa. Solvent density influences the extraction rate, and higher densities can accelerate the extraction of compounds with increased solubility.
  • Balancing Quality and Efficiency: Optimal solvent density depends on the desired extract quality and extraction efficiency. Running at higher solvent densities can enhance extraction speed, but it may also extract undesirable compounds like chlorophyll degradation products. Finding the right balance is essential to meet specific processor requirements.
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Tailoring the Solvent for Different Needs

Supercritical CO2 extraction offers flexibility in tailoring the solvent for specific extraction goals. Whether prioritizing high biomass throughput or high-quality crude, the solvent can be adjusted accordingly. Understanding the trade-offs between extract quality and extraction speed is vital in achieving the desired results.

The solvent density plays a critical role in the extraction process and affects the overall efficiency and quality of the extraction. Here are some considerations regarding solvent density in CO2 extraction:

Top 7 considerations regarding solvent density in CO2 extraction

  • Supercritical vs. Subcritical CO2: CO2 can exist in three states – gas, liquid, and supercritical fluid. In CO2 extraction, the solvent can be operated in supercritical or subcritical conditions. Supercritical CO2 is used for higher extraction efficiency, as it exhibits both gas-like and liquid-like properties. The density of supercritical CO2 is higher than subcritical CO2, which means it has better solvating power and can extract more compounds.
  • Density and Solvating Power: The density of CO2 affects its solvating power, which is its ability to dissolve and carry away the desired compounds from the botanical material. Higher CO2 density generally results in increased solvating power, allowing for better extraction of the target components.
  • Pressure and Temperature Influence: CO2 density is influenced by pressure and temperature. As pressure increases, the CO2 density also increases. Similarly, at higher temperatures, the density of CO2 decreases. Adjusting these parameters can help fine-tune the extraction process and optimize the solvating power of CO2 for specific target compounds.
  • Extraction Efficiency: The density of CO2 impacts the extraction efficiency, which is crucial for commercial applications. Higher CO2 density allows for a more efficient extraction process, reducing the time and energy required to extract the desired compounds.
  • Selectivity: In some cases, increasing the CO2 density may result in enhanced selectivity, where specific compounds are preferentially extracted while leaving undesirable components behind. This selectivity can be controlled by adjusting the density and other extraction parameters.
  • Safety Considerations: Higher CO2 density implies higher pressure in the extraction system. Safety precautions must be taken to handle high-pressure CO2 to avoid any potential hazards.
  • Product Quality: The density of CO2 affects the solubility of various compounds. Extracting at optimal densities can result in higher-quality products with better flavor, aroma, and bioactive compounds.


Solvent density is a critical parameter in supercritical CO2 extraction that significantly impacts the efficiency and selectivity of the process. By considering solvent density as a key measure, it becomes easier to optimize extraction methods and target specific compounds of interest. The flexibility and selectivity of supercritical CO2 as a solvent are valuable assets, provided they are leveraged with a deliberate understanding of compound solubility and extraction goals.

Read More: Supercritical carbon dioxide