The Water Footprint of the Blue Jean
Blue jean manufacturers will soon be adopting new techniques that reportedly reduce the water used in dying by 71-99%.
From growing cotton to dying it to laundering finished products, producing blue jeans consumes a large amount of water
We may think of that worn pair of blue jeans simply as an old friend, but may not put a lot of thought into how those jeans are made. In fact, a great deal of water goes into growing cotton, washing it, and dying it blue. It is estimated that 20% of industrial water pollution worldwide is associated with garment manufacturing, and 85% of that is associated with the fabric dying process. Each year, 1.3 trillion gallons of water is used for dying fabrics alone, and it’s estimated that the amount of water needed to grow, dye, and process the cotton for just one pair of blue jeans ranges from 500-1,800 gallons. Global production of cotton is estimated to use 222 billion m3 of water.
The water that is used to grow the cotton for blue jeans is considered “virtual water,” or water that is sometimes overlooked in calculating a true water footprint. The worldwide average water footprint to produce 1 kg of cotton is 10,000 L, but with sophisticated irrigation, cotton farming in the U.S. uses only 8,000 L/kg. In India, however, producing this amount of cotton requires an average of 22,500 L of water.
An illustration of cotton farming’s dramatic environmental impact can be seen in the disappearance of Asia’s Aral Sea. Water withdrawals for cotton farm irrigation are the primary reason for the draining of the planet’s fourth largest lake. And, pesticides used to keep cotton crops around the world healthy account for a large percentage of total global pesticide use.
Water Use in Denim Manufacturing
After cotton is removed from bales, it is carded (run through brushing machines), spun into yarn, and dyed, usually with a synthetic indigo. Large balls of cotton called “ball warps” are repeatedly dipped in a vat of dye, forming dye layers. The cotton yarn is “slashed,” or coated with a starchy sizing to stiffen it, then blue and white yarns are woven on shuttleless looms. The production already is water-intensive, but to make it even worse, after manufacture, some jeans are also prewashed or stonewashed.
The process creates compounds that must be disposed of. Chlorine is a byproduct, along with organic pollutants like dye and starch, which may be treated biologically. They shouldn’t, however, be discharged untreated into surface water because the oxygen needed to break down the pollutants would deny necessary oxygen from aquatic life. Yet streams do run blue in many areas where denim is manufactured.
Greening the Blues
Manufacturer Levi Strauss has compiled perhaps the most comprehensive estimate of water used throughout the life cycle of a pair of blue jeans. The company estimates that from farming to final disposal, one pair of its 501® jeans requires 3,781 L of water, including laundering.
The company also has launched an ambitious Better Cotton Initiative to reduce global cotton agriculture’s water footprint, with a goal of 100% sustainable cotton use by 2020, including the use of recycled cotton.
Making jeans with at least 15% recycled cotton creates a water savings equal to what the entire manufacturing process consumes. Levi Strauss also is adopting a pioneering laser dying method from Spanish company Jeanalogía that is touted to reduce water consumption in the dying phase by 71%.
Wrangler has also just announced that it will be adopting a new Dry Indigo® denim process for a line of jeans it will launch in 2019. The foam process is touted to eliminate 99% of the water used to dye denim. The process was developed at Texas Tech, with early-stage funding from Wrangler and the Walmart Foundation. Tejidos Royo, an environmentally minded fabric mill, expects to be shipping the foam-dyed jeans by the end of the year.