Background

Industrial hemp- simply known as hemp- comes from the cannabis sativa L. plant which contains 0.3% tetrahyrdocannabinol (THC) or less in the leaves and flower. Hemp belongs to the cannabaceae plant family that contains over 270 species and 11 genera and is often confused with cannabis plants that are uses as a source of the drug, marijuana; however, hemp does not have any psychoactive or drug properties and is often identified as an agricultural crop. In this section you will find the history and plant anatomy of hemp; including antibacterial properties.

History

Hemp originated in Central Asia, and has been cultivated as early as 2800 BCE in China. Hemp made it’s way through Europe in the Middle Ages and North America in the early 16th century. Early settlers often used hemp for rope, clothing, sailcloth, and oil applications. In the early 20th century, hemp was beginning to be widely used for paper in addition to rope, clothing and oil applications. Industrial hemp was on the rise and many believed it to be the “next billion dollar crop.” However, in 1937, the United States Government passed the Marihuana Tax Act, criminalizing marijuana and any plant in the cannabis plant family. Despite this, the bill was temporary lifted and government urged farmers to grow hemp to aid during the second World War. Henry Ford was also able to developed a prototype automobile that was made from hemp fiber and was designed to run on hemp bio-diesel in the 1940’s.

For the next 60 years, hemp was considered an illegal crop in North America. In 1998, the Canadian Government passed laws to once again allow the cultivation of industrial hemp and in 2014, the US Farm Bill was passed to allow hemp to be cultivated for research purposes in the United States. In recent years, there has been an increase in popularity and demand for industrial hemp to return hemp to the agricultural crop it once was. See Hemp Legislation more information on hemp legislation in North America.

Hemp For Victory

In 1942, industrial fibers were in short supply and were often imported overseas. In order to keep up with demand, the United States Government needed the farmers to grow as much hemp as possible to support war efforts during World War II. To encourage American farmers to grow hemp, the government released this video to explain to farmers the history of hemp and how hemp is grown and processed.

Marihuana Tax Stamp for a Wisconsin farmer.

Plant Anatomy

Fiber Background

Fibers can occur within the central growing stalk or stem of most plants in one of three forms:

  1. Core fiber:  Short, lignocellulose based fibers within softwood and hardwood trees and wood-like cores (pith) of other plants (such as bast fiber plants.)  Due to the short nature of these fibers, they are believed to be of limited technical interest to the envisaged project.
  2. Bast Fiber:  Long, strong lignocellulose based fibers that occur within a narrow band within the cross section of several plants.
  3. Straw Fiber: Left over from cereal straw harvesting such as wheat.  Straw fibers relatively have low strengths relative to the other stem fibers due to high content of weak hemicellulosic substances and thin cell walls with lower cellulose content.

Hemp has a very similar structure to flax as do most bast fiber plants.  Hemp has a wider stem than flax.  In essence, the bast fibers are structural fibers that work in tension to allow the plant to grow to significant height without buckling or bending and breaking.

The bast fibers themselves are composite structures.  Fundamentally there are 4 main chemical compounds present in bast fibers as follows:

  • Cellulose: Long chain polysaccharide (polymeric carbohydrates or sugars) molecules of high molecular weight.  Cellulose molecules are microfibrous at the nanometer scale.  Cellulose itself is stiff and of high tensile strength.  Cellulose molecules bond with themselves to form spiral-like mesofibrils or supermolecules of cellulose fibers.
  • Lignin: An amorphous, somewhat rigid, high molecular weight polymer of moderate strength that does not form fibrous structures.  Lignin occupies spaces between the cellulose mesofibrils and acts as a cellulose fiber binder.
  • Hemicellulose: Weaker short fibers of lower molecular weight cellulose-like compounds.  Some of the hemicellulose is found with lignin and aids in binding the strong cellulose fibers together.  Hemicellulose can bond with both cellulose and lignin.  The combination of cellulose, lignin and hemicellulose creates a single fiber tube inside which the cell vacuole is housed (the main living part of the cell.)  This tube is called an ultimate fiber and is the primary building block of the coarser bast fiber, which contain many ultimate fibers.
  • Pectins:  Weak, gummy, amorphous, polysaccharides of low molecular weight.  Pectins combine with lignin to form the middle lamella, a flexible, continuous binder phase that binds the ultimate fibers into flexible discrete bast fibers.

Hemp Plant Components

A hemp plant consists of four (4) main components; stalk, leaves, seeds and flower. The hemp stalk is tall, dense and strong with the capability of reaching over ten (10) feet tall. The stalk is composed of two layers, the inner layer known as hurd or shiv and the outer layer know as bast fiber. At the top of the stalk are the hemp flowers where the seeds accumulate, and all along the stalk are jagged palmate shaped leaves. See our consumer products section for the many uses of hemp.

Hurd & Fiber

Hemp stalk has a short brittle wood fiber core called hurd (shiv). Hurd are primarily used to produce technical fiber for construction and paper purposes. The outer layer of hemp stalk has structural long flexible fibers called bast fiber, which are used composites, textiles and rope purposes among others. Most technical fiber for reinforcement is manufactured from bast fiber, while various types of non-structural fiber, absorptive products and functional fillers are made from hurd.

Seeds

Hemp seeds are on average 1-3 millimeters in size and can be roasted, pressed, and eaten raw. Hemp seeds are used for food and oil purposes. Hemp oil is obtained from the seeds by pressing the seeds and is used to make industrial fluids, food oils, personal care products, and biofuel.

Leaves

Hemp leaves are palmate shaped and have approximately 3-9 long and slender leaflets. The leaves have a jagged appearance and range in coloration from bright lime green to dark green. Hemp leaves are often used for pharmaceutical and tea purposes.

Flower

The flowers on a hemp plant are small greenish-yellow flowers. Hemp plants have seed-producing and pollen-producing flowers. Seed-producing flowers are female and grow in a dense spike cluster at the top of the stalk. While pollen-producing flowers are male and grow in dense branched cluster. Hemp flowers have no industrial purposes and are only used for pharmaceutical purposes.

Antibacterial Properties

Hemp has been shown to possess antibacterial properties against a range of pathogenic bacteria, including B. subtilis, S. aureua and E.coli. These properties are contributed from cannabinoids, alkaloids, and other bioactive compounds of the hemp plant.

Hemp hurd, the woody core of the hemp stalk, has a high lignin content of 19-21% as well as high hemicelluloses content of 31-37%. In a series of test, it has been found that hurd has a strong antibacterial property against E. coli, bacteria found to infect the lower intestine, and the ability to restrain the growth of micro-organisms such as S. cerevisiae, B. licheniformis, and A. niger.

Additionally, the hemp stalk has also been found to have antibacterial properties against B. subtilis, bacteria that commonly infects the gastrointestinal tract, as well as S. aureus, bacteria that infects the nose, on the skin and in the respiratory tract. Furthermore, the stems and leaves of the hemp plant have also been found to have excellent antimicrobial properties against S. aureus. Hemp grown in the northern latitudes of the world has higher CBD compounds; leading to stronger antimicrobial properties. While hemp has antibacterial and antimicrobial properties, it however does not have antifungal properties.

Reference

Khan, B. A.; Warner, P.; Wang, H. Antibacterial Properties of Hemp and Other Natural Fibre Plants: A Review. Bio Resour. 2014, 9 (2), 3642–3659.