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Optimizing Biomass Grind Size for Efficient Supercritical CO2 Extraction

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In the marijuana and hemp industry, the significance of biomass grind size often goes underappreciated when aiming to maximize extraction efficiencies. Despite being described qualitatively, the grind size is a quantitative variable that plays a crucial role in developing robust extraction methodologies and ensuring production-scale reproducibility.

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The Influence of Biomass Particle Size on Extraction Efficiency

Controlling biomass particle size is not solely about managing an input variable; it significantly affects extraction efficiency and, consequently, extraction time. Peer-reviewed literature highlights the direct correlation between particle size and extraction efficiency.

Key points to consider:

  • Increasing Extraction Efficiency: Smaller particle sizes enhance extraction efficiency up to a certain point. Studies on seed oil extraction, such as soybean seeds, have demonstrated substantial yield differences between various particle sizes. For instance, a reduction in particle size from 0.81mm to 0.25mm led to a massive 46.7% increase in extraction yield.
  • Impact on Diffusion Resistance: Reducing particle size decreases intra-particle diffusion resistance and increases the overall surface area available for solvent diffusion. This reduction in resistance facilitates faster and more efficient extraction as CO2 can diffuse more easily into the cellular matrix.
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The Limitations of Finely Ground Biomass

While grinding biomass into a finer consistency may seem ideal for faster extraction, there is a limit to this dynamic. Finely ground biomass, particularly with resinous compounds like cannabinoids, can lead to potential issues such as solvent channeling and particle clumping.

Key points to consider:

  • Solvent Channeling: When the material is ground too finely, solvent channeling can occur, creating pathways through the biomass. This results in uneven extraction, where areas in contact with the diverted solvent flow are fully extracted, while areas outside the channels experience reduced extraction rates.
  • Potential Clumping: Finely ground particles may also clump together, hindering the uniform flow of solvent and further compromising extraction efficiency.

Benefits of Supercritical CO2 Extraction and Optimal Grind Size

Supercritical CO2 extraction offers distinct advantages over other solvents in terms of grind size flexibility and product quality preservation.

Key points to consider:

  • Minimizing Product Quality Changes: Unlike solvents with higher polarity, supercritical CO2 allows biomass to be ground to the optimal particle size without concerns about cell lysis or co-extraction of degradation products like chlorophyll. The flexibility of supercritical CO2, achieved through solvent density modulation, ensures consistent output quality across different biomass types.
  • Determining Optimal Grind Size: Processors can determine the optimal grind size by using appropriate grinding equipment capable of producing specific particle sizes. Building extraction kinetic curves and conducting consecutive tests with the same biomass, varying the particle sizes, will provide insights into the optimal grind size for efficient extraction.
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Biomass grind size significantly impacts extraction efficiency and completion time in Supercritical CO2 extraction. Processors must recognize the quantitative nature of grind size and conduct optimization tests to ensure maximum efficiency. Neglecting this variable can result in unnecessarily prolonged extraction times or reduced yields. By focusing on quantitative data and thoughtful consideration of grind size, processors can enhance their extraction processes and achieve more consistent and efficient production.