Blue jeans, green drive

In a first, scientists believe they’ve found a way to kill toxic impacts of the synthetic indigo dye — 50,000 tons of which are produced every year, the bulk goes into making our jeans. As indigo does not bind with water or textiles, a chemical process and a bleaching stage are required before it can be used. Tonnes of waste water after the process damage water bodies and destroy marine life. Here’s how making blue denim can become a less harmful process.

Denim starts off as white cotton…

Bales of white cotton are dunked into boiling vats with the synthetic indigo and bleach so that the dye binds to the cloth.


Turning it blue is a chemically polluting process…

Today, indigo is synthetically derived from petroleum for use by the denim industry. Waste products from indigo dyeing decompose slowly and colour water bodies. When disposed of untreated, it is toxic to marine life, drinking water and soil, and even corrodes pipes in water treatment plants.

RIVER OF INK:

China’s blue rivers have been extensively reported on since 2010, especially in industrial clusters where textiles and jeans are manufactured. Rivers near these factories turned a dark blue ink with a stench: a cocktail of dye, chemicals and detergent.

BLUE DOGS:

A dog with blue fur in Navi Mumbai’s Taloja industrial area, where strays mysteriously turned blue in August 2017. The dogs turned blue after swimming in river Kasadi, a dumping spot for industrial waste, including from a dye unit that was then shut down.

Now, a new process could replace the chemical agents

This biosynthetic method mimics the natural way plants produce indigo, but inside bacteria.

-Naturally derived from plants that have the colourless molecule indican

-When the plants are crushed, indican reacts with air to produce indigo

1. Researchers added genes to Escherichia coli bacteria to make them secrete indican, the source of indigo

2. Cloth is then exposed to the indican-producing bacteria in the presence of an enzyme solution

3. The colourless indican gets converted to soluble indigo capable of binding to cloth

FLIPSIDE

-The enzyme solution is expensive to make

-The process releases sugar molecules as waste, which would encourage growth of microbes in water bodies, depriving marine life of oxygen.

Text by: Anjishnu Das