Fibres of the future

With the rising cost of petroleum-based fibres, natural fibres are once more in fashion but not only for their use in textiles. Synthetics may be able to match the physical characteristics of plant fibres such as tensile strength and durability but the environmental benefits of utilizing a renewable resource are becoming a major consideration with the development of plant fibres in the manufacture of plastics, replacements for fibreglass and insulating materials. Plant fibres are also being developed for the treatment of pollution: modified fibres can selectively absorb oil from water (see kenaf ), and another group of technologies involves fibres and have an ion exchange capability which are able to remove heavy metal ions, such as copper, chromium and zinc, from industrial effluent. Sisal and other natural products are gaining ground in industrailized countries In addition, fibres can be burnt under reducing conditions (limited oxygen) to form an activated carbon source which can be used as a filter - for instance, in the removal of colour (as in the effect of peat) from water.

Much of the current pulp and board production around the world is based on softwoods. However, institutes such as the Biocomposites Centre at the University of Bangor, UK, have focused much effort on the adaptation of conventional technology to suit non-wood feed stocks to make use of agricultural and process residues. In many countries, such residues offer the only untapped fibre resource which might be used to satisfy increasing demand for pulp. The use of fibres, such as hemp and kenaf, for paper processing is being explored and developed and hesperaloe ( Hesperaloe funifera ) - related to sisal and a member of the Agavaceae, native to northern Mexico - is also being considered as a new fibre crop for the US . Unlike, other fibres, hesperaloe is naturally white which eliminates the need for bleaching. In addition, it is drought tolerant and its long, thin fibres could command a high price in the paper industry. However, this species still poses problems for the US as it lacks frost tolerance and there are currently no commercial sources of seed.

Many fibre crops traditionally grown in the tropics can provide products (see hemp, sunnhemp and coir) other than fibre which are of importance to small-scale farmers and can provide additional income. Roselle ( Hibiscus sabdariffa L.), a fibre relative of kenaf, is used widely in beverages and food products and is reported to be an aphrodisiac as well as a remedy for hangovers and bilious conditions! And Giradinia diversifolia , the Himalayan or Nilgiri nettle (see In Print ), another stem fibre plant that grows wild in the high altitude forests of the middle hills of Nepal , produces the strong yarn used for making, amongst other products, the narrow headbands worn by porters. But young tender shoots are used for medicinal purposes, as well as a vegetable and for pig feed.

Some of the world's most important agricultural fibres are classified as bast fibres, such as jute, flax, kenaf, sunnhemp and hemp. But leaf fibres from banana and pineapple are of particular importance in some regions. Banana leaf fibre, otherwise known as 'Manila Hemp' or abaca is grown mainly on small, multi-crop farms in the Philippines where there are some 200 varieties in cultivation. The remaining production is almost entirely from Ecuador where, in contrast, it is grown on large estates. Certain cultivars of pineapple ( Ananas comosus L.) are also grown especially for fibre production; the fruits are removed to produce optimum yields. The leaves generate a strong, white, silky fibre which is used to produce the sheer fabric, or pinya, for the Barong Tagalog worn as national dress in the Philippines . And, like Pashmina from Kashmir , pinya cloth has gained international recognition. Sisal ( Agave sisalina ) continues to be an important leaf fibre in Africa and Asia but is also grown extensively on hill slopes and arid regions of India to arrest soil erosion. As a xerophytic plant, it is drought tolerant and its extensive root system helps to bind the soil. Sisal is also propagated easily using small suckers from the base of older plants.

Cotton continues to dominate global fibre production (18 million tonnes) and the most important fibre used in large-scale textile production. However, pesticide usage is high - almost 50% of the chemicals used in the US are on cotton - and harvesting of cotton in developing countries is highly labour intensive. With concerns about the rise in resistance to pesticides in cotton pests, organic and integrated pest management of cotton is increasingly being adopted. However with the development of new markets for fibres many cotton growers, particularly in the US , are considering the production of fibre crops, such as hemp or kenaf, which require little use of pesticides.

But, despite the development of fibres for new industries in the West, major fibres and a diverse range of minor fibres will continue to be of importance in the tropics for traditional uses. Many of these products are now familiar to international markets, including rattan furniture, which is no longer primarily harvested from the wild but rather planted by rural farmers for additional income. With the need for many farmers to diversify, the future potential of many fibres has yet to be realized.

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