Unveil the carbon footprint of textiles dyed with different reactive dyestuff recipes from an industrial manufacturing perspective

The textile industry is inclined towards an unsustainable trajectory because of a variety of environmental issues stemming from the intensive use of water and energy during wet processing. As climate change has been regarded as the biggest health threat facing humanity and textiles’ color derived from dyestuff is closely associated with wet processing, this study focuses on evaluating the carbon footprint (CF) of textiles dyed with different dyestuff recipes and identifying the quantitative correlation between the CF and the mass of dyestuff inputted, to seek opportunities for improvement from the manufacturers’ perspective. 

The industrial CF of 25 cotton-dyed knitted fabrics with different reactive dyestuff recipes was assessed referring to PAS 2395 and the methodology of life cycle assessment, where the investigated phases include knitting, wet processing, packing, and sewage treatment. The primary data of assessed fabrics were collected by on-site investigation in a knitting manufacturing company in China. The functional unit is knitting, dyeing, and finishing 1 t of cotton. The mass of dyestuff in a dyeing bath for 1 kg fabric (MDB) was utilized to characterize different colors of textiles. A quantitative correlation between the CF of wet processing and MDB was established through second-order polynomial regression. 

Within the given system boundary, 1 t of cotton-dyed knitted fabric emitted an average of 7505.12 kg CO₂ eq, and energy accounts for the largest proportion. When white fabric without any dyestuff was included and excluded from the sample range, the maximum differences in CF between fabrics were 4437.90 kg CO₂ eq and 3546.55 kg CO₂ eq, respectively. Furthermore, with the consecutive increment of MDB within a certain range (0 ~ 5.41%), the CF of pre-processing shows a gentle downward trend while the CF of dyeing exhibits a trend of initially rising and subsequently declining within a certain range (0 ~ 1.37%) and then presents an upward trend. Interestingly, the CF of wet processing is affected by the alternation of its two major processes. The above results may reduce the absoluteness of the argument that “textiles with darker colors are less environmentally friendly.” 

Special attention should be paid to the contribution of textiles’ color to their CFs, owing to the substantial variations that exist in the CF of wet processing among knitted fabrics of different colors. The contribution of wet processing to global warming is impacted by multiple factors, including steam consumption, chemical usage, liquor ratio, and process time. This study may offer ideas for interdisciplinary research and point out the future direction for the textile wet processing industry to improve environmental performance.