HEMP FIBRE

Hemp production is easy to achieve organically. Therefore many of the ecological problems in chemical farming of other fibres are obviated. Hemp quickly grows up to 5 metres in height with dense foliage which blocks weed growth. This means herbicides are not needed and the field is weed free for the next crop. Unlike cotton hemp does not have a high water requirement. The hemp plant has a deep tap root system which enables the plant ot take advantage of deep subsoil moisture, thus requiring little or no irrigation.

Hemp has been produced for thousands of years as a source of fibre for paper, cloth, sails/canvas and building materials. Natural fibre from the hemp stalk is extremely durable and can be used in the production of textiles, clothing, canvas, rope, cordage, archival grade paper, paper, and construction materials.

There are two principal types of fibres in hemp – bast or long fibres and hurds or inner short fibre. Traditionally hemp has been grown for its valuable and versatile high quality bast fibres. Bast fibres account for 20-30 percent of the stalk (depending on the seed variety, and planting density). There are two types of bast fibres:

·     primary bast fibres. Primary bast fibres make up approximately 70 percent of the fibres and are long, high in cellulose and low in lignin. Primary bast fibres are the most valuable part of the stalk, and are generally considered to be among the strongest plant fibres known.

·     secondary bast fibres. Secondary bast fibres make up the remaining 30 percent of the bast fibres and are medium in length and higher in lignin. They are less valuable and become more prevalent when the hemp plants are grown less densely, making shorter fatter stalks since they do not have to compete for light.

The production or extraction of the primary bast fibres has traditionally been a very labour intensive process, but recently an alternative fibre separation process has been developed using technologies such as ultrasound and steam explosion, which are much less labour intensive. Once separated the bast fibres are ready for spinning and weaving into textiles, or for pulping into high quality pulp. Bast fibres are ideal for specialised paper products such as industrial filters, currency paper, tea bags or cigarette paper.

Hurds are the short fibred inner woody core of the hemp plant. They comprise 70-80 percent of the stalk and are composed of libriform fibres which are high in lignin. Traditionally hurds have been considered waste as they are the by-product from bast extraction. The hurds are 50-77 pecent cellulose making them ideal for paper making. One acre of hemp can replace 4.1 acres of trees for pulp production. Although the fibres are shorter than bast fibres they are suitable for a range of products such as rayon, biomass fuel, cellophane, food additives, industrial fabrication materials and newsprint pulp.