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Jute is a true-blue environmentally-benign product

By Rathin De
Last Updated: Sunday 28 June 2015 | 11:25:17 AM

-- THE socioeconomic significance of jute cultivation lies in the fact that almost 10 million small and marginal farmers in India, Bangladesh, China, Thailand and Nepal are dependent on it for their livelihood. Equally important, jute is also an environment-friendly fibre when compared to artificial fibres like polypropylene (PP).

The jute crop occupies the land for 4-5 months of the year, and is commonly rotated with food crops like rice and potatoes. The plants shed leaves during the growing season, and if left on the field after harvesting, they enrich the soil with organic matter. Jute plants also improve the availability of soil nutrients by breaking the subsoil hard pan caused by continuous rice cultivation.

PP, on the other hand, is a thermoplastic produced by low pressure polymerisation of propylene with the help of certain catalysts. PP can be customised for particular uses by adding specific compounds to it. Some of these compounds contain heavy metals which are injurious to both human and animal health.

Another difference is that while PP requires mainly crude oil and vast capital for its production, jute calls for nothing more complicated or difficult to get than humanpower and land. The cultivation of jute plants contributes to the reduction of the "greenhouse effect" due to absorption of carbon dioxide from the air; PP is a pro-greenhouse warrior.

After harvesting, jute plants are defoliated in the field itself. Thereafter, jute stems are "retted" in water and the fibre is extracted. The traditional method is to ret the stems for 15-18 days and extract the fibre manually. Since this is time consuming, an alternative is to ret the outer ribbon without the woody stick. This is called "ribbon retting" and is widely practised in China. Ribbon retting requires half the normal quantity of water and takes much less time.

Jute appears to be at a disadvantage when it comes to waste water generated in the retting process. Retting is a microbial process to biodegrade the material holding the fibres in the stem. According to experts, no known toxic substances are released while retting. Since the operation takes place once a year, there is enough time for the organic residues to biodegrade with the help of solar radiation. Some organic residues also act as manure for aquatic vegetation that feed the fish population.

PP production generates far less waste water. The little there is, however, contains toxic substances like heavy metals which can be eliminated by complex chemical processes but not by biological treatment.

In order to soften the jute fibre, an emulsion of batching oil, water and emulsifier is applied to the raw fibre. Usually, petroleum-based mineral oil is used but India and Bangladesh have developed batching oil based on vegetable fat.

Through its life cycle starting from crude oil, each tonne of PP generates at least 5.5 tonnes of waste. The waste of jute production is the dry matter that cannot be used as fibre -- each tonne of dry fibre generates 4.5 tonnes of dry leaves and sticks. However, jute wastes cannot be compared with PP grunge, as dry leaves can be used as manure and sticks as construction material or fuel. The environmental impact of jute waste has to be regarded positively, while PP wastes contain toxic compounds, some of which are carcinogenic.

From the environmental angle, the disposal stage of the jute life cycle certainly stands superior to that of PP. These products are not biodegradable, and allow only partial decomposition by ultraviolet rays. At present, there are only 2 ways to PP waste disposal: disposal sites or incineration plants, neither of which is very attractive. In case of jute products, if the defined conditions are amenable to waste treatment, composting or producing biogas seems to be the most suitable method to dispose of jute products which cannot be recycled.

Jute products like geotextiles, jute-based paper pulp and jute composites can directly protect the environment. Jute geotextiles have proved effective in controlling soil erosion. If jute is used for making paper pulp, entire forests can be saved. A paper plant in Hooghly has used jute fibres to produce a variety of high value paper. Recently, a public sector organisation in Bangladesh has started using whole jute plants for producing pulp for industrial grade paper. The ongoing programmes for diversification need to be intensified in the tropical countries, where the climatic conditions are suitable for largescale jute cultivation.

---Rathin De is working with the International Jute Organisation in Dhaka, Bangladesh.

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