A groundbreaking new report by the Transformers Foundation, titled “A Reference for Water Consumption During Indigo Dyeing,” is bringing long-overdue clarity to one of the most environmentally opaque stages of denim production. The study addresses the lack of standardized data on indigo dyeing’s water usage, challenging outdated figures and aiming to counter misleading environmental claims in the denim industry.
As sustainability regulations tighten—particularly under the EU Green Claims Directive, the UK Green Claims Code, and a wave of lawsuits in the U.S.—the need for transparent, measurable environmental benchmarks is more urgent than ever. Transformers Foundation warns that without such reference points, even well-intentioned sustainability efforts by mills can fall into the trap of greenwashing.
Key Findings on Water Consumption
The study revealed that water use during pre-dyeing is relatively consistent across denim mills. However, post-dyeing processes such as rinsing and washing showed significant variability, especially depending on the dyeing method used.
- Rope dyeing consumes 15 to 20 L/kg of water for rinsing and washing.
- Slasher dyeing uses slightly less, at 10 to 15 L/kg.
- With best practices implemented, these numbers could drop dramatically to 3.85 L/kg for rope dyeing and 3.40 L/kg for slasher dyeing, showing substantial potential for water savings.
Indigo efficiency—defined as the percentage of indigo retained on yarn—was found to be 93–95% for rope dyeing and 85–94% for slasher dyeing.
No “One-Size-Fits-All” Solution
The Foundation emphasized that the report does not favor one dyeing process over another. Rope dyeing, while more water-intensive, is better suited for high-volume production due to its efficiency and reduced waste. Slasher dyeing, on the other hand, offers more color variety and lower operational costs, making it an attractive option for smaller batches and cost-sensitive operations.
Global Industry Collaboration
The study was conducted in two phases with participation from seven leading denim mills across four countries:
- Pakistan: Naveena Denim, Crescent Bahuman, Soorty, and Diamond Denim
- Turkey: Orta Anadolu
- Italy: Candiani Denim
- China: Advance Denim
Technical and machinery support came from Morrison Textile Machinery and Karl Mayer, while Bluesign and DyStar provided additional technical oversight.
To ensure comparability, the study used fixed parameters, including:
- 100% cotton warp
- Ring spun NE 9 yarn
- Pure pre-reduced liquid indigo at 4% concentration
- No added chemicals
- Standardized testing for dry and wet crocking
Toward a More Transparent Denim Supply Chain
The report sets a new standard for assessing water use in indigo dyeing and lays the groundwork for more credible sustainability reporting across the denim industry. By anchoring environmental claims in data, Transformers Foundation aims to equip stakeholders—from mills to brands to consumers—with the knowledge needed to drive meaningful change.
