The choice of extraction material and method usually follows the farming practice. Large scale agricultural producers focused on cost will harvest using machinery which cuts the plants at the ground level, and then grinds up the stalks, stems, seeds and flower into “aerial parts” which can be found on some labels. CO2 is then passed through the aerial parts under pressure and temperature to extract the terpenes and again at a higher temperature to extract the cannabinoids. CO2 is great for selectively extracting parts of the plant. It is also used to remove the caffeine molecule to decaffeinate coffee and and to dry clean clothes. The upfront cost is high, but it's cheap to run and easy to scale - ideal for mass production.
Horticultural growers are more focused on plant quality, and want to preserve that quality through to the final product. Hemp flower (bud) grows sticky glandular hairs call trichomes, and this is where most of the precious cannabinoids, terpenes and flavonoids are located, not the “aerial parts”. It is also why marijuana consumers smoke the flower / bud, and large, sticky smelly buds are prized. To preserve the trichomes / quality, the delicate flower should be hand harvested. Some solvents (butane or hexane) shouldn’t really be used, but organic alcohol is a natural and highly effective solvent, produced by the plants and for the plants.
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