Role Of Organic Colours For The Sustainability Of The Environment

By Manas Bhaumik

Every living organism uses natural resources for its growth and prosperity. Humans are considered the best among them also depends on these environmental elements for their survival. The ancient cave painting, the discovery of remnants of dyed cloths in excavation sites of various civilization indicates that the art of dyeing with natural colours was age-old and has close relations to our civilization in every nook and corner of the globe.

 

The first scientific analytical explanations come from Newton’s light experiment with a prism where we were acquainted with the colours of the rainbow. Colours play an important role in miscellaneous needs in daily life, as well as emotional development and pleasure. In our natural resources, we get colours from plants, animals, microorganisms and minerals. The colours obtained from plants, animals and microorganisms are considered organic. There are more than 4500 plants from which we get natural colours. Although all plants possess natural colours which may or may not be useful to us. Some animals also provide excellent colours too. We also get some natural colours as a byproduct of an industrial process. Until the discovery of synthetic dye in the middle of 19 th century natural dyes flourished to a large extent.

 

The blue dyes obtain from indigo (Indigofera tinctoria), various red sheds from Madder (Rubia cordifolia), Brazil wood (Caesalpina sappan) Morinda (Morinda citrifolia) Safflower (Carthamus tinctorius) yellow colour from turmeric (Curcuma longa) Saffron (Crocus sativus), Barberry (Berberis aristata), Myrobolan (Terminalia chebula), Marigold (Tagetus erecta), Dolu (Rheum nobile), different shades of orange red obtain from Annatto (Bixa orellana), orange yellow from flame of the forest (Butea monosperma, Kamala (Mallotus phillipensis) were very few examples.

Different shades of colours may procure by increase or decrease of colorants or mixing of two or more colorants with different combinations.

 

Cochineal was an insect (Dactylopius coccus) originated popular red dye. The byproducts of Lac industry also produce useful brown red dye. The popular host of lac insects (Kerria lacca) is Sissam and Butea plants which are very much common in Indian subcontinent. Similarly red ocher, yellow ocher, charcoal black, azurites are few examples of mineral pigments found in nature.

 

The detail research on chemical aspects of this naturally occurred colour components from vegetable origin proves that natural dyes have a complex chemical constitution in comparison to synthetic dye. They are categorized as Indigoid, Anthraquinone, Napthoquinone, Flavonoid, carotenoid tannin-based dyes and others.

 

W.H. Perkin accidentally synthesised a mauve colour while preparing quinine from coal tar. This was the first synthetic dye in 1856. Next year he established his factory near London to produce synthetic dye commercially. Later several chemical and pharmaceutical industries were set up by different entrepreneurs to produce various synthetic chemical-based products.

Synthetic dye became highly popularized by its low cost, better fastness and variety of shades. But synthetic dyes are non-biodegradable, non-renewable resources and harmful mostly derived from petroleum resources. The fact was understood after one and a half centuries. The synthetic dyeing industries produce highly polluted effluent water which mixes with river and local water bodies. It directly or indirectly affects ecosystems, local population, wild animals, and even agricultural fields by irrigation of polluted water. Lack of interest in environmental importance or less interest in investing in effluent treatment plants ultimately affects the marginal communities, farmers’ livelihood, and a wide range of macro and microorganisms. But, synthetic dyes are still popular because natural dyes have some limitations too.

The natural dyeing processes are very tedious, with limited shade range and seasonal availability of dye resources, non-reproducible shade and poor fastness properties and are less suitable for industrial set-up.

 

The advantages of natural dyes are, that they are obtained from renewable natural resources like flowers, fruits, leaves, bark etc. The components of natural dye are easily biodegradable by microbial action, light or water treatment. The pomegranate rind, onion skin and safflower petals are byproducts of agro-processing industries. The leaves from deciduous trees are always renewable resources that can harvested without any environmental destruction. Apart from the textile industry, natural dyes are also used in food colouring (turmeric, saffron), pharmaceuticals, cosmetics (annato), painting, home décor craft items etc. In rural villages local artisan groups may produce dyestuff by locally available plant material for their traditional craft items.

 

Most of the dye-yielding plants have medicinal properties like Indigo, Turmeric, Myrobalan, Terminalia, Tagetus and many others. Cultivating these plants not only gets dye or medicine but also leads to higher carbon fixation in the form of biomass synthesis. Leguminous plants like Indigo help to fix nitrogen in the soil by nodule-forming bacteria in roots. The crop rotation by regular cash crops with dye-yielding plants may increase the fertility of the soil. The residues of plant parts after extraction of dye are also useful as green manure. Nowadays significance of natural dyes valued by traditional dyers and printers, selected ethnic communities, textile designers, various artisan groups, hobby groups and research institutions like Universities, NGO’s and museum communities. Their untiring efforts to popularize the natural dye to civic societies. Another important aspect is to prevent the loss of Indigenous knowledge and technique by documenting the natural dye-making process used by remotely located tribal populations, generation after generation.

 

To increase sustainability in this field some measures may be taken like the use of waste places for cultivation of dye-yielding plants because priority of land is always given to cereals or pulses. High dye-yielding varieties may develop by hybridizing, gene transfer and other modern techniques.

Biotechnological tools may apply to transfer dye-producing genes to fast-growing harmless microorganisms to resolve the issue of land availability. Try to avoid metallic mordant which contains heavy metals to fulfil global organic textile standards. These small-scale industries may be facilitated by providing infrastructural facilities and tax relief by the local government. Mass scale awareness of the importance of organic products among traders and end users.

 

To safeguard the environment of Planet Earth, Scientists, Industrialists, policymakers and users are paying more attention to renewable resources. Various national and international bodies are vigil to implement treatise on environmental safety and assess the progress of commitment of countries in a regular manner to reach the goal.

About The Author

Manas Bhaumik is a Scientist in Botanical Survey of India Industrial Section Indian Museum, Kolkata. His field of specialization are Taxonomy, Biodiversity and conservation of wild plants of Eastern Himalaya. About 55 research papers and 7 book chapters published in national and international pear reviewed Journals.

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