The thickest and most resistant of all commercial natural fibres, coir is a coarse, short fibre extracted from the outer shell of coconuts. Its low decomposition rate means is a key advantage for making durable geo-textiles.
Coir is extracted from the tissues surrounding the seed of the coconut palm (Cocos nucifera), which is grown on 10 million ha of land throughout the tropics.
Coir fibres measure up to 35 cm in length with a diameter of 12-25 microns. A coconut harvest occurs once in 45 days. From 1000 coconuts it would be possible to extract 10 kgs of coir. Among vegetable fibres, coir has one of the highest concentrations of lignin, making it stronger but less flexible than cotton and unsuitable for dyeing. The tensile strength of coir is low compared to abaca, but it has good resistance to microbial action and salt water damage and needs no chemical treatment.
There are two types of coir: the more commonly used brown fibre, which is obtained from mature coconuts, and finer white fibre, which is extracted from immature green coconuts after soaking for up to 10 months. Mature coir fibres contain more lignin, a complex woody chemical, and less cellulose than fibres such as flax or cotton.
Coir is a material which is widely used to overcome the problem of erosion. When woven into geotextiles and placed on areas in need of erosion control it promotes new vegetation by absorbing water and preventing top soil from drying out. Coir geotextiles have a natural ability to retain moisture and protect from the suns radiation just like natural soil, and unlike geo-synthetic materials, it provides good soil support for up to three years, allowing natural vegetation to become established.
Uses of coir
Traditionally the coconuts were left to cure in water for several months (or in brine for a longer period for white fibres) then the coir was extracted. However with technology there is an increased use of coconut husk defibering machines.
Typically, white coir spun into yarn is used in the manufacture of rope and, thanks to its strong resistance to salt water, in fishing nets. Brown coir is stronger and more widely used than white coir. Applications include sacking, brushes, doormats, rugs, mattresses, insulation panels and packaging.
Recognition of coir for sustainable vegetation and erosion control arises from the fact that it is an abundant, renewable natural resource with an extremely low decomposition rate and a high strength compared to other natural fibers. Coir is woven into thick textiles which are applied like blankets on the ground in erosion prone areas. Geotextiles made from coir are durable, absorb water, resist sunlight, facilitate seed germination, and are 100% biodegradable. These blankets have high strength retention and a slow rate of degradation meaning they last for several years in field applications.
Coir is widely used in the upholstery industry, and it is a healthy substitute for processed synthetic rubber. It is also used as a combination with natural rubber and is used for filling up mattresses, automobile seats, sofas, settees, and seating systems. European automobile producers upholster cars with pads of brown coir bonded with rubber latex. Coir is used for insulation and finds application in panels, cold storages, food industry, etc.
A substitute to plywood, coir ply is an innovative product that when is added together with resin and limited pre-treated timber veneers. In India the product has been well accepted by the market as an alternative to plywood. Substituting coir for other timber products could also save a substantial amount of tropical trees being logged for this purpose.
Coir ply has all the properties of phenol-bonded ply with the added strength of fibre reinforced phenol bonding. It has high degrees of surface abrasion resistance and resists contraction/ expansion due to variations in temperatures.
The waste product from milling the coir is peat or pith which makes for high quality mulch and fertilizer. Coir peat compost developed from coir waste is an excellent organic manure and soil conditioner applicable to agricultural crops.
Production and trade
The coir industry is fully developed only in India and Sri Lanka, but economically important in Brazil, Indonesia, the Philippines and Vietnam. Coconuts are typically grown by small-scale farmers, who use local mills for fibre extraction.
Globally around 650 000 tonnes of coir are produced annually, mainly in India and Sri Lanka. India and Sri Lanka are also the main exporters, followed by Thailand, Indonesia, Malaysia, Vietnam, and the Philippines. Around 80 percent of the coir produced is exported in the form of raw fibre. Smaller quantities are exported as yarn, mats, matting and rugs.
India has made considerable efforts to promote coir industry including establishing an annual International Coir Festival. The efforts support the market expansion for coir and India hopes to further increase production by streamlining the fibre collection process to meet demand. Research and development efforts are continuing to focus on the use of coir in geotextiles and other new applications as the market shows promising prospects. Coconuts are grown in more than 93 countries in the world and therefore there is considerable scope to develop coir industry in further countries.
Much of coir production is done by small holders meaning production is scattered and at small volumes. Integrated farm level processing as a community/cooperative approach would help to facilitate greater availability of technology to process the husk and extract the fibre in volumes needed for industrial buyers. Since many of the developing countries growing coconuts are not utilizing coconut husk to produce value added products, providing such facilities can go along way to provide employment, increase the income of coconut farmers and reduce poverty and provide environmental benefits associated with use of the nutrient rich waste product.
A Common Fund for Commodities (CFC) funded project in Sri Lanka established a R & D and Training Center in a rural area to demonstrate best practices in coir processing. Improved production (increased quantities and higher quality) is to be matched with improvements in the working conditions and production environment currently prevalent, ultimately resulting in higher levels of profitability at the bottom-end of the coir production chain.