Carbon dioxide (CO2) plays a vital role in keeping natural plant oils flowing. Processors who rely on supercritical CO2 to extract plant oil understand the key advantages of the high-pressure process: It is precise, effective and versatile.
Plant oil extracts, including derivates such as hemp-based oils and hemp-based cannabidiols (CBDs), are important ingredients for numerous products, including various dietary supplements and food additives. Plants may contain a number of useful compounds beyond the primary plant oil, and supercritical CO2 can often extract other compounds, including terpenes, separately in the same batch process.
Better Extraction
CO2 is a non-polar solvent due to the symmetry of its bonding, so it is ideal for extraction. With the supercritical extraction process, raw plant parts are loaded into the extraction unit, and pre-pressurized liquid CO2 is pumped to the extractor at roughly 800 psi or more. The extractor drives the CO2 to a supercritical (SC) state, which generally means above 1000 psi. Plant oils and other organic compounds are usually extracted between 1200 and 1400 psi (depending on the plant and the target molecule because different molecules volatilize at different pressures).
Most large plant-oil processors use either supercritical CO2 or ethanol for extraction, but only CO2 offers this versatility to easily extract additional compounds. Hydrocarbon solvents sometimes used in plant oil extraction such as butane and propane may contain byproducts that can complicate the extraction process and render the extract unsafe. By contrast, CO2 is available in high-purity grades for consistent, high-quality extraction.
Higher Crop Yields
Beyond plant oil extraction, CO2 is also important on the cultivation side. It fosters plant respiration and growth and may help some growers add an extra growing cycle and increase crop yield. Integrated operations can feed plants in their greenhouses from the same CO2 tank that feeds their SC extraction units.
Value-Engineered Pressurization Equipment
Supercritical CO2 extraction operations require a consistent high-pressure supply of liquid CO2 to the extraction units. Messer’s high-pressure CO2 units feature a highly efficient pneumatic design and are an important part of our supply solution. While mechanical pressure-pumps typically require 220V or 440V power, Messer’s unit requires only a 24V signal and an air compressor (which may already be available on-site) to keep the CO2 ready for delivery at > 800 psi.
Because the CO2 pressurization unit is pneumatic, there is no motor controller trying to adjust the pump speed. When the operator opens the valve to use the CO2 for the next batch, it does reduce the pressure of the CO2, but the air pressure on the other side of the piston drives the pressure up again, and the CO2 continues to move. There’s no preparation to start using the CO2 again, no on-off cycling, it’s simply ready to use.
Of course, the value of CO2 solutions for plant oil extraction and cultivation will continue long after the immediate crisis.