How to calculate the amount of water needed to make a pair of jeans?

The MANGO Chair in Corporate Social Responsibility and the UNESCO Chair in Life Cycle and Climate Change at ESCI-UPF, analyse the water impact of a pair of jeans, from the cotton production to the transportation to the warehouse of an organisation.

In order to know the distribution of the use of water and reduce it, the researchers have developed a calculation tool for any organisation to obtain the results of the water footprint in a manufacture of a denim, applicable to other similar fabrics.

denim water footprint

Coinciding with the World Water Day, celebrated on March 22 every year at the initiative of the United Nations, the MANGO Chair in Corporate Social Responsibility (CSR) and the UNESCO Chair in Life Cycle and Climate Change at ESCI-UPF, publish the report “Calculation of the Water Footprint of a Product.” This study aims to determine the use of water (water footprint) in the manufacture of a pair of jeans for an organisation, “from the cotton production, denim fabric production, its manufacture and finishes in different areas, to the subsequent transportation to the warehouse of an organisation,” explains Xavier Carbonell, director of the MANGO Chair in CSR and responsible for the study. Based on this analysis, and with the objective to impinge favourably on the reduction of the impact on the use of water, the researchers have developed a calculation tool in Excel for any organisation to obtain the result of a product's water footprint.

The study focuses on circular economy, “in which the extraction of raw materials as well as the generation of waste is limited or eliminated,” highlights Carbonell. Thus, “it focuses on making more efficient use of water resources in the manufacturing process of a pair of jeans,” he adds.

Life cycle assessment of a pair of jeans (denim)

The study focuses on a very common clothing item, being one of the most sold, because of having access to data on the use of water easily and completely. Researchers at ESCI-UPF have focused the analysis on the part of the life cycle prior to its use by the consumer and its final treatment once it has been used and is unusable. Due to the great variety of jeans that exists, an average of the different weights of the fabrics has been made up to get an 'average pair of jeans' with a weight of 0.318 kg, reference base for the calculation.

The methodology used in the analysis includes the consumption of water in the different stages of manufacture. “The greatest impact on water is the one needed for the first phase of cotton cultivation with which a pair of jeans will be manufactured, which represents 68.8% of the total water impact. Therefore, the use of recycled fiber would significantly reduce the water footprint of the jeans,” explains Xavier Carbonell. The second phase focuses on the manufacture of the fabric, including spinning and weaving, and dyeing. The third step is the manufacturing of the jeans, which includes cutting, making, washing, tinting, labelling and packaging, and transportation and distribution.

Based on data on water consumption in each of the production stages of a pair of jeans, the water footprint has been calculated using the standard ISO 14046:2014, applying the GaBi1 software, which allows the creation of life cycle models of products and processes. Also, in order to offer a methodology of calculation in the textile sector, the researchers have created a simplified tool based on the Excel programme that “allows obtaining orders of magnitude about the use of water in different garments made with 100% cotton-based denim,” explains Jaume Albertí, leader of the Sustainable Construction and Energy Research Line at the UNESCO Chair ESCI-UPF and responsible for the technical analysis of the study.

“Once the use of water in the manufacture of a denim has been calculated, it would be convenient to apply it to other products with similar characteristics, such as T-shirts,” Carbonell emphasises. “Focused on the optimization of water use, this work lays the foundations for being able to take measures at different points in the production chain and distribution channels,” he concludes. With this objective, the researchers have made the report “Calculation of the Water Footprint of a Product”(text in Spanish) available to organisations interested in its application.

World Water Day

The ESCI-UPF UNESCO Chair “develops its scientific research and professional training activity joining forces with non-governmental organisations, public bodies, private sector and other research centres, both at national and international levels, to achieve the 2030 Agenda for Sustainable Development, approved by the United Nations in 2015, including 17 Sustainable Development Goals (SDGs),” explains Albertí. Among the 17 goals, the SDG 6 is intended to ensure availability and sustainable management of water and sanitation, balancing the water needs of society by 2030, in tune with the objectives of World Water Day. Furthermore, it connects with the SDG 12 aimed at “ensuring sustainable consumption and production patterns.”

Coordinated by UN-Water–the UN’s inter-agency collaboration mechanism– the World Water Day draws attention to the importance of water. This year's theme 'Nature of Water', focuses on exploring nature-based solutions to the water challenges we face in the 21st century, becoming aware that “water plays a key role in reducing poverty as well as in the economic growth and environmental sustainability,” as stated by the UN.


The UNESCO Chair and the MANGO Chair in CSR, both at ESCI-UPF, closely collaborate in research projects linked to the three pillars of sustainability: environmental, social and economic.



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