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Hemp has been purposely grown and harvested since 8000 B.C. The crop was essential for fiber and food. Since 2012, the products and sales derived from the hemp industry in the United States increased by 600 percent. The plant-based fiber and by-products are commonly used in foods, industrial applications, personal care products and textiles. Processing the plants is an interesting process and depends on individual parts of the plant.

Harvesting

Seeds are acquired four to six weeks after the plants being shedding pollen, which typically occurs sometime around the middle of August. The fiber is commonly ready three months after planting. Combines equipped with specific cutting tools are used during harvest.

Once the plants are cut, the stalks must lay in the field and rett for up to six weeks. The time frame provides sufficient time for pectin to escape and the fibers to loosen. As the plant’s leaves deteriorate they are occasionally turned. The plants also emit nutrients back into the soil. Other retting processes might include immersing the stalks in water or exposing them to enzymes to break down and loosen the fibers. After the allotted time, the stalks are baled and stored in a dry place until the moisture content is at or below 15 percent.

Processing the Fibre

Running the stalks through a pair of top and bottom rollers separates the core or short hurd fibres from the longer bast fibres. The fibres are then cleaned and carded according to the desired fineness. The fibres might also be cut and baled again. Following the carding process, the fibres undergo further steps. When planning on using the fibre or textiles, the plant is steamed and exposed to chemicals to remove the binders that hold the fibers together. The plants typically yield 3.5 percent of their weight in fine or dry line fibre and one percent in the coarser dry tow fibers.

Processing the Grain

Once harvested, the seeds are cleaned and dried thoroughly before storage. The seeds are hulled using crushing mechanisms to remove the hard outer layer. Hemp oil is extracted from the seeds using mechanical cold pressing. The oil might also be extracted using ethanol, hexan or liquefied carbon dioxide as a solvent, which produces higher yields. The oil must not be exposed to heat, light or oxygen once obtained.