A lack of information and widespread greenwashing led Transformers to conduct the study, “A Reference for Water Consumption During Indigo Dyeing.”
On Thursday, the non-profit organization hosted a webinar to discuss the results of the study and how competing companies can work together to establish measurable and transparent data.
The objective of the study was to define, establish and validate a reference standard for conventional or standard dyeing of denim warps and equip brands with a benchmark to compare against suppliers’ data. Seven mills from four countries participated in the two-phase study: Naveena Denim, Crescent Bahuman, Soorty and Diamond Denim from Pakistan; Orta Anadolu from Turkey; Candiani Denim from Italy; and Advance Denim from China. Machinery support was provided by Morrison Textile Machinery and Karl Mayer, with additional technical oversight from Bluesign and DyStar.
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As the founder of the Kingpins denim supply chain trade show, Andrew Olah—who also founded Transformers—called how he would see one mill after another share information on their dye processes and how much water they saved. “That’s a selling feature, but nobody knew if it was true or not. We still don’t know if it’s true or not, but we now know after this report, what it probably is and how to figure it out,” he said.
The study found the average quantity of water used for washing and rinsing ranged from 15 to 20 L/kg for rope dyeing and 10 to 15 L/kg for slasher dyeing.
Though different types of machinery make it impossible to estimate the exact difference between slasher dyeing and rope dyeing, Transformer said experts believe the latter uses roughly 30 percent more water due to the need to clean the ropes thoroughly. Manual adjustments by operators as well as the level of automation and control systems can also lead to variability in water usage data.
Though there is no wrong or right decision when it comes to deciding on rope or slasher, Rashid Iqbal, Naveena Denim NDL’s executive director sales and marketing, said there are factors to consider. Rope dyeing offers high productivity, but slasher allows more versatility, which is important if a mill plans to run different warps, he said.
The report also raised questions about other dye techniques like foam dyeing. Introduced in a collection by Wrangler in 2019, the waterless technology continues to be offered by Tejidos Royo. Though it initially received a lot of attention from the industry, Olah said foam does not produce the volumes required to be an efficient alternative. “I do know that uptake on it in production is minor,” he said.
In terms of practicality, Paolo Leidi, Transformers technical director, said there’s no chance of foam dyeing, as it is today, to take the place of the regular dyeing methods. Instead, he urged companies to take the path of least resistance and focus on optimizing the processes that are currently being used at scale.
In the future, Olah said the foundation plans to study topics like wastewater, especially as every manufacturing country has a different standard of how the mill returns clean water.
And data gaps persist. Leidi said it’s important to measure the quantity of indigo that is wasted in the washing water because this is something that is underestimated by most mills. “This is indigo you’re throwing away… it’s money but it’s also polluting water.”
There also needs to be an analysis of water consumption in the pre-treatment of denim.
“I’ve visited so many mills in the world, and many mills are not equipped with suitable technical instruments on their machines to measure the quantity of water. There are simple instruments available, [like] flow meters or liter counters—very simple and very cheap instruments,” Leidi said. “But there’s still a lot of mills in the world that are leaving it to the operator [to decide] how much to open the valve or close the valve based on the feeling of the operator. This is something that should not happen.”
