fiber extraction methods from husk

 There are several types of fiber extraction methods from husk, depending on the technology and purpose. Here are the main types:

1. Manual Extraction

• Method: Beating the retted husks with wooden mallets or stones.

• Used in: Traditional or small-scale setups.

• Pros: Low cost, simple.

• Cons: Labor-intensive, slow, low output.

2. Mechanical Extraction (Decortication)

• Method: Using a coir decorticator machine to crush and extract fibers.

• Used in: Industrial or large-scale processing.

• Pros: High efficiency, faster production.

• Cons: Expensive machinery, requires power.

3. Water Retting

• Method: Soaking husks in water for microbial action to loosen fibers.

• Used in: Traditional settings.

• Pros: Natural process, low cost.

• Cons: Time-consuming, water pollution risk.

4. Chemical Retting

• Method: Using chemicals (alkalis or enzymes) to break down the husk tissues.

• Used in: Experimental or industrial research setups.

• Pros: Faster than water retting.

• Cons: Cost of chemicals, potential environmental hazards.

5. Biological Retting

• Method: Using specific microbes or enzymes in controlled conditions.

• Used in: Eco-friendly fiber extraction research.

• Pros: Environmentally safe, effective.

• Cons: Still under development, expensive setup.

Extraction of fibre from the Husk

Extraction of fibre from the Husk

Separating of the tightly bound fibres can be done by mechanical, chemical and biological means. Traditionally, the fibre from the coconut husk is extracted using biological means and it is known as Natural Retting. The Natural Retting practised in India consists is soaking the husk in water for a period varying from 6 to 10 months. According to the local condition, the method of retting varies from place to place. The principle involved is to steep the husks for retting in the saline water or brackish water or brackish mud in specially prepared enclosures.

Mechanism of Retting

The term Retting is a technical form of the word "Rotting" and designates the process of decomposition of the thin-walled tissues surrounding vegetable fibres leading to the loosening of fibres.

In principle, the retting process is based on the relative differences that exist in the susceptibility of the different constituents of the husk to microbiological decay. The process is usually aerobic for coir fibre. The retting, which consists of the soaking husk, facilitates easy separation of the fibres from the adhering tissues of the husk.

The retting proceeds in three stages.

Physical

Biological and

Mechanical

In the physical stage, the tissues of the husk swell under the water, and several substances, carbohydrates, glucosides, tannins, nitrogen components etc. are brought into solution.

During the first stage, the proto-pectinases break down the linkage of pectin with the celluloses and hemicelluloses of the cell wall without modifying the pectin molecule itself and convert insoluble proto-pectin to pectin. As the pectin is released, the surrounding liquid becomes slightly milky during retting; there is a fall in pectin, tannin and hemicellulose contents of the husk. The periodic replacement of the retting liquor considerably reduces the percentage of the substances in the husk and increases the rate of retting. The colour of the fibre is also improved by the removal of retting liquor.

During the course of the first few days of retting, the water gets distinctly brown because of the changes brought about by the atmospheric oxygen in contact with the extracted materials from the husk. A smell of hydrogen sulphide is noticeable in retting pits after about 30 days of keeping the husks under water; the mass of the husk becomes appreciably warmer, due to the temperature rise, the water becomes more turbid and a scum forms on the surface of the retting liquor. This is particularly noticeable where the retting is carried out in stagnant water. After about two to three months of soaking, gas formation, temperature, turbidity and smell increase. But after six months the water becomes clear and the gas formation and smell diminish. A major part of the husks get softened at this stage and the separation of the fibre is possible except for the hard tips of the husks and the inner layers of the exo-carp which require ten months or even more for satisfactory retting

Coir products

 

HUSK

HUSK 

 Structure of Coconut Husk 

There are 18 varieties of coconut palms, but the husks from three varieties only are suitable for coir production. The most important commercial utilisation of husk is for the manufacture of coir. Husks are also used as fuel, as surface and seedling pit mulch and for burying in coconut gardens as fertiliser due to the high content of potash.

 

A coconut husk with a fibrous husk(me so carp) is surrounded by a smooth outer skin, called ex-o-carp. The coconut is embedded in the husk and has been left intact. The hard shell of a nut is called the endocarp and contains the nutrient tissues called endosperm and the embryo. 

The fibrous mesocarp is an assemblage of numerous fibres in a ground tissue of elastic cellular cork-like material containing the binding agents, dispersed throughout the mass. The mesocarp is 1 to 1½ inch thick. The bulk of the ground tissue is made up of pectin, hemicelluloses tannin, other phenolic bodies and water-soluble substances. The elastic cellular cork-like material forming the non-fibrous tissue of the husk is called pith and accounts for more than two-thirds of the total weight of the husk.