When you hear the word hemp, you automatically think of cannabis. Essentially, they are the same plant, so confusing hemp for marijuana is an understandable mistake – but a mistake, nonetheless. Yes, they are both derived from and classified under the Cannabis sativa plant, but hemp is very different from marijuana in terms of chemical makeup, cultivation, and uses.
Hemp has been grown industrially for thousands of years to produce paper, textiles, food, biodegradable plastics, and much more. While the hemp plant does contain tetrahydrocannabinol (THC), the primary intoxicating component in marijuana, it does not have a high enough concentration of THC to actually get you intoxicated.
What it does have in high amounts is cannabidiol (CBD). Like THC, CBD is psychoactive, but the extremely low concentration will not induce any sort of narcotic high.
Apart from its medicinal use, the hemp plant is also largely utilized to make hemp fiber.
So what exactly is hemp fiber? As the name suggests, hemp fiber refers to the fibers that grow on the outside of the hemp plant’s stalk. It is completely natural, and in the age of sustainability, this proves to be a great substitute for other fibers or fabrics. Its growing popularity suggests history repeating itself once again as hemp was one of the first and most common plants to be made into fabric about 10,000 years ago.
Hemp fibers grow up to 15 feet in length and are extremely durable. A few years ago, archaeological excavation in the ancient city of Çatalhöyük, Turkey, found a baby skeleton wrapped in hemp fabric, which goes to show how long they can last.
The plant itself, Cannabis sativa L., is usually tall and branched. It is high in fiber and grain, as opposed to its sister Cannabis Indica, which is short, densely branched, and has poor fiber quality.
Hemp Fiber Harvesting and Extraction
Hemp fiber is generally grown in a temperate climate. It requires about three and a half months with 10-12 inches of rainfall to grow adequately. Hemp plants are also thermophilic and heliotropic, meaning that they need a good amount of warmth and sun, without which seed production and bio-mass are compromised.
Originating in Central Asia, it is now grown in a number of countries ranging from Canada, USA, France, Italy, Germany, Philippines, and India, to name a few.
Plants cultivated for fiber are densely sown and grow up to 2-3 meters tall. They are best harvested soon after they reach maturity, which is shown by full blossoms and shedding pollen of the male plants. The male plants blossom faster than females and do not produce as much fiber. Most female hemp fields include some male plants scattered amongst them. This is so that the male plants release pollen for the female plant to produce seeds. These seeds can be used for more crops and also sold as food.
As opposed to marijuana plants, hemp plants can be grown outdoors and more densely – those cultivated for oil can be grown among 40-60 other plants per four square feet, and those cultivated for fiber can be grown with 100-120 plants per four square feet.
Hemp farmers use the crop rotation technique, a practice that involves growing a variety of crops in one area across a sequence of different growing seasons to avoid pests and diseases and to increase the use of soil nutrients.
While harvesting, they are usually cut a few inches above the ground, ideally with a sickle or machete. Hemp harvest equipment such as a disc mower or sickle mower would work even better. The stalks are then chopped and allowed to dry for a while. The hemp stalks contain two types of fibers – bast fibers and hurd fibers. Bast fibers are long and found in the bark, while hurd fibers are short and found in the stem.
Hemp Fiber Processing
Hemp fiber processing does not require many chemicals but could use other materials such as synthetic fibers and resins, depending on the product that is to be made. The fiber is made from the stalks and undergoes a multistep process to deliver a satisfactory outcome of the yield.
Retting is a process that involves the use of microbes and moisture to dissolve the tough cellular tissue of the hemp stalk. The process is done by microorganisms on the stem, in the soil, or by special enzymes.
The pectin or chemical bonds holding the stem together are broken down to enable easier separation of the bast from the core of the plant. It is also known as ‘controlled rotting’ and requires a skilled hemp farmer to oversee the process. There are three main types of retting:
Field or dew retting:
Field or dew retting is the only type of retting that can be done on-farm, while the other types require some sort of special facility. It is done by spreading the hemp stalks on the ground, so they are exposed to rain and dew. They should be cut as close to the ground as possible.
The plants are laid in the field for 4-6 weeks, during which the bacteria on the plant’s surface will break down the outer layer. For even retting, they should be turned over when they start changing color from green to pale yellow and must be picked up at the right time to avoid over-retting.
The retting is over when the color of the stems changes to a slightly dark beige with small, dark spots. This type of retting is inexpensive but usually delivers poorer quality fiber compared to other types of retting.
Water retting involves soaking the dry hemp stems is bacteria-filled water tanks, ponds, or rivers. The water softens the outer layer of the stalks and promotes the growth of more bacteria to speed up the process. This type of retting produces a higher quality of fiber though it is more expensive.
It is done by either natural water retting in slow-moving waters like ponds, bogs, or streams or by tank retting in concrete vats. In double retting, a process that produces extremely high quality, excellent fiber, the stalks are removed from the water before the retting is finished, dried for a few months, and then retted again.
Chemical retting uses acids and special enzymes to break down the components of the bast fibers. They are boiled in treatments consisting of chemicals like Sodium Hydroxide, Sodium Chloride, Sodium Sulphite, Hydrochloric acid, and Oxalic acid. It is also a more expensive method and requires a hemp grower to properly manage the process.
Hemp decortication is the process that removes the tough, woody interior of the hemp plant and separates it from its soft exterior. The stalks are passed through fluted rollers to break the hurd into small pieces and separate the hemp fiber. This can be achieved through a machine called a decorticator.
The fiber then undergoes scutching, the mechanical removal of remaining hurd bits by beating the stems with a beech stick or passing through rotary blades. Modern decorticating techniques use steam explosion and ultrasonic breaking, two techniques that are not as harsh.
Hackling is when short and medium-sized fibers are combed out of the stalk. A special cutting machine is used to reduce the length of the fibers from 3 m to 650 mm. Any woody particles are removed and then aligned for spinning accordingly.
To further treat the fibers for a finer yarn, they are passed through a trough of hot water before being spun. This is known as wet spinning. It softens the pectin and allows for further separation of fibers. Dry spinning is also possible, but the outcome is coarser. It is also cheaper.
Hemp fibers are finally baled for long-term storage or transportation. Large, round bales work best as they allow for better drying and the hemp is not as tightly packed as in squares. They should be stored in a dry, less humid environment limiting any sort of water penetration to avoid mold. Using plastic net wrap and twine would further ensure its integrity.
Hemp Fiber Properties
- Though it is hard to bleach the naturally dark color of hemp fiber, it can be dyed in bright or darker colors and does not fade easily.
- The tensile strength of hemp fiber is greater than other vegetal fibers and twice that of cotton. This goes to show that it is far more durable and can be used for industrial products requiring a sturdier fabric.
- The hemp strands have microscopic alcoves, making them extremely breathable and absorbent. The fabric helps one stay cool in hot weather and also warm in cool weather due to the catacombic build-up, which allows air trapped in the fibers to be warmed by the body.
- The fiber has low elasticity, so products made with hemp fabrics retain their shape.
- The ecological footprint of hemp fiber is one-third to half that of US cotton, according to a 2010 analysis by the Stockholm Environment Institute.
- It is highly resistant to harmful UV rays and will not fade in the sunlight.
- It is quick-drying and prevents the growth of bacteria and mildew, making it anti-microbial.
- It withstands laundering – each time it is washed, the fibers become softer and finer. It also sheds a microscopic layer that avoids soiling and exposes a fresh surface.
- The fabric itself is fully biodegradable and recyclable, contributing to sustainability.
HEMP FIBER USES
Clothing and Textiles
Hemp fiber has been used for thousands of years to make fabric for clothes and textiles. The fabric has a number of advantageous properties such as UV protection, and its anti-microbial/hypo-allergenic benefit makes it optimal for sensitive skin.
They can be blended with other fabrics to increase durability. Sailors used the fabric to make canvas sails for ships (the word ‘canvas’ comes from ‘cannabis.’)
Industrial Building Material
Hemp fiber is less expensive than wood and also great for insulation. It has been used to replace wood to build breathable homes. Using more hemp fiber for building promotes the preservation of trees and, in turn, an overall better environment.
The most common and ancient use of hemp fiber is for paper. Paper made from hemp was first identified dating to the Western Han Dynasty, 200 years before regular paper making. It can substitute for wood fiber in pulp and paper production. It offers 4-5 times longer fiber and higher tensile strength, contributing to higher tear resistance. Hemp paper also prevents cutting down of trees.
Ropes and Cords
Some of the first ropes ever were made from hemp fiber. It is one of the best fibers to make ropes and cords due to its durability and is stronger than jute, linen, and cotton. It was also used for sail rigging and anchor cords.
Hemp has also been used to make shoes that are comfortable and sturdy instead of leather. Leather can be expensive, but hemp fiber is a lot cheaper, not as time-consuming, and does not harm animals.
Automobile companies like BMW use hemp fiber to reinforce door panels for better safety and lighter weight. They are more practical than cotton, and their length adds to the strength.
Many hemp producers recycle the fiber by removing dust and then packaging it. The dust can be pressed into pellets and utilized for fuel. The dirt and tiny particles of the core can also be used as a high nutrient soil additive.
Hemp fiber has been used for the production of many items throughout ancient history. Though its usage and popularity declined temporarily, it is slowly climbing back up with people finding new and inventive ways to make use of its properties.
Hemp’s versatility contributes to its annual growth rate of more than 30%. It will only continue to increase as people make the change to sustainable, eco-friendly products with little harm to the environment.