Hemp Glossary

Bast fiber, or just bast, is the stringy fiber that makes up about 25 percent of the hemp stalk. It is located in the phloem, the layer between the core and the outer skin, and is harvested via a retting process that separates it from the hurd portion of the plant stem.

There are two categories of bast fiber, primary and secondary. The primary bast fibers are the most valuable part of the stalk. They make up 70-90% of the bast. They are 5 to 50 mm long, have a high cellulose density (50-70%), and are low in lignin (4-10%). They have been used for centuries to make paper, rope, canvas, textiles, plastics, and much more.

The secondary bast fibers make up 10-30% of the bast, are high in lignin, and are much shorter than primary bast fibers, only about 2 mm in length, making them much less desirable.

Hemp biomass is all the plant material remaining after the seeds and flowers are harvested. Basically, anything not used for human or animal food, like the stalks and leaves, are considered biomass.

Hemp stalks contain an inner core called hurd, or hurd fiber. It is a short fiber (about 0.5 mm long) that is high in lignin (20-30%) and is used to make animal bedding, fuel, bioplastic, and construction materials, like insulation, acoustical tiles, hempcrete, and much more.

Pyrolysis is the process of applying high heat to solid organic material, or biomass, in the absence of oxygen. In the case of hemp, pyrolysis can be used to expedite the decomposition of hemp stalks to produce fuels, industrial feedstocks, and other uses.