Life Cycle Assessment of a T-shirt

This article looks into the life cycle of a standard 100% cotton t-shirt. However, there is still some packaging and tagging to consider. Once t-shirts are produced in factories, they are usually shipped to retailers in cardboard boxes. When we purchase a t-shirt at the store or even online there are a few other materials used. When purchasing online your t-shirt product usually will arrive in a plastic bag. If you purchase in-person, at the retailer, your t-shirt will be placed in a plastic or paper bag upon purchase. In either scenario, your brand-new t-shirt will include a tag using paper and plastic.

As mentioned above the functional unit, or t-shirt, is made from cotton. In Figure 1 you can see the life cycle of the t-shirt starting from farming the raw material itself. Cotton is typically grown in the U.S., China, or India (Chang, 2017). Once grown and harvested the raw material is taken to a refinery, better known as a cotton gin. Here they cycle the raw cotton in various machinery that separates the fiber from stems and seeds. From here the cotton bales are sent to processing facilities usually in China or India (Chang, 2017) where the cotton fiber is spun and stretched into yarn and woven into fabric. Here it is also dyed, and washed before being transported to production factories mainly in Bangladesh, Turkey, China, and India (Chang, 2017). Factory workers measure, cut, and sew the cotton fabric into ready-to-wear t-shirts of various colors and sizes. From here the t-shirts are finally ready to be sold and are shipped to retail stores all over the world where the consumer can come in look at and purchase a t-shirt. With the use of a t-shirt comes care, which includes washing, drying, and ironing. Lastly, this garment usually goes one of two ways. It is either disposed of and fated to a landfill, or it is recycled by being donated to someone who can get more use out of it. Eventually, this t-shirt will end up in a landfill after its second, third or fourth life has come to an end.

Inputs & Outputs of the Manufacturing Process

Each part of the t-shirt's life cycle includes inputs and outputs within the process. Figure two outlines those of the manufacturing process of making a 100% cotton t-shirt. First, farming cotton (conventionally) requires inputs such as water, fertilizers/pesticides, and energy. In this case, energy encompasses physical human labor, and machinery used for tilling, maintenance, and harvesting. According to the WWF, a kilogram of cotton requires 20,000 L of water to produce (Newell, 2016). Also, the global cotton crop uses 8.2 million tonnes of chemicals between synthetic fertilizers and pesticides (Trent, 2020). The total energy used for one kilogram of cotton is 61.2 MJ (Cotton Inc., n.d.). The outputs of this step are the harvested cotton and also organic waste from the rest of the plant (leaves, stems). Additionally, we see negative outputs that impact our environment such as air pollution, chemical runoff that seeps into nearby water sources, and contaminated and eroded soil from tilling, fertilizers, and pesticides.

Next, the refining step that takes place at what is called a “cotton gin” includes energy as the main input. U.S. cotton gins use an average of approximately 126 MJ of electricity per bale (Funk et al., 2017). The product outputs include the cotton fiber bales themselves which are used for t-shirt making but also the cotton seeds and oil separated by the machinery. Cotton seeds are then used for livestock feed and cottonseed oil is sold for cooking purposes. The environmental outputs from this step are the emissions from the machinery used for refining.

From here the cotton bales move into a processing facility where they are stretched and spun into yarn and woven into fabric; then the fabric is dyed in different colors and washed. Here the inputs are energy (labor, and machinery), pigments, and water. The spinning process is responsible for 8.84 MJ/kg of electricity (Nigam et al., 2016) and the weaving process utilizes 20.88 MJ/kg of electricity (Moazzem et al., 2021). The dyeing and washing of the cotton fabric require 3.5-17 MJ/kg of energy (Moazzem et al., 2021) and 280 L/kg of water (Chapagain et al., 2005). Output products of this step include yarn and fabric. Environmental outputs include energy emissions from machinery as well as chemical runoff and air contamination from pigment pollutants such as cadmium, lead, chromium, and mercury (Chang, 2017).

Lastly in the manufacturing process is the production factory where yarn and fabric are used to make final products like the 100% cotton t-shirt. Here again, we have the input of energy mainly in the form of physical human labor and machinery together cutting, sewing, and packaging the product. This step requires 2.472 MJ of energy (Islam, 2016). Outputs include the t-shirts, but also fabric scraps and textiles that will end up in landfills. Additional outputs are emissions from powering the factory itself including the machinery (e.g. sewing machines) used for production.

Conclusion & Recommendations

The overall carbon footprint of one cotton t-shirt through its entire life cycle is over 2 kg of Co2 (Ro, 2020). This includes the manufacturing process which we mainly focus on in this paper but also the transportation between each step, the emissions from retail, and use/care of the product. The majority of emissions (52%) come from the use/care step when washing, drying, and ironing the t-shirt throughout its life (Van Der Heide, 2016). The overall water footprint to produce one cotton t-shirt is 2.7 cubic meters of water (Chang, 2017). The rest of the water footprint of one t-shirt depends on the use/care. The water footprint of an average household’s laundry is about 73 cubic meters of water per year (Chang, 2017).

To decrease the resource needs and impact of a cotton t-shirt, we can start by growing and using more organic cotton eliminating the chemical fertilizers/pesticides and their contaminants. Additionally, renewable energy such as solar, wind, or biodiesel could power machinery and facilities used for farming, manufacturing, selling, and using the product. Furthermore, using natural pigments would eliminate pollutants that come from synthetic dyes. We can also recycle fabric textiles from the cutting and sewing step to reduce material waste. Emissions from transportation and distribution can be reduced if the entire manufacturing process is done domestically. In the retail stage, plastic attaching price tags can be substituted with thread and plastic bags with paper bags or no bags at all. At home, end-users should reduce how often they use the washer and dryer by washing "dirty" areas of the t-shirt by hand when possible and always line drying. Ironing should be kept to a minimum as well by only doing so when necessary. As consumers, we can also look for organic or recycled cotton t-shirts and when we no longer want the item we should always donate it or give it another function like a rag for as long as possible.

References

Chapagain, A. K., Hoekstra, A. Y., Savenije, H. H. G., & Gautam, R. (2005). The water footprint of cotton consumption: An assessment of the impact of worldwide consumption of cotton products on the water resources in the cotton producing countries. Value of Water Research Report. Retrieved October 24, 2021, from https://www.waterfootprint.org/media/downloads/Report18.pdf.

Cotton, Inc. (2021, September 2). Plant-based biocompatibility. CottonToday. Retrieved October 25, 2021, from https://cottontoday.cottoninc.com/our-sustainability-story/microfibers/plant-based-biocompatibility/.

Funk, P. A., & Hardin, R. G. (2017). ENGINEERING AND GINNING: Energy Utilization and Conservation in Cotton Gins. The Journal of Cotton Science, 21, 156–166.

Islam, I. (2016). (dissertation). Energy consumption determinants for apparel sewing operations: An approach to environmental sustainability. Kansas State University. Retrieved October 24, 2021, from https://core.ac.uk/download/pdf/77977794.pdf.

Moazzem, S., Crossin, E., Daver, F., & Wang, L. (2021). Environmental impact of apparel supply chain and textile products. Environment, Development and Sustainability. https://doi.org/10.1007/s10668-021-01873-4

Newell, A. (2016, February 23). Quenching Cotton's Thirst: Reducing the Use of Water in the Cotton Lifecycle [web log]. Retrieved October 24, 2021, from https://www.triplepundit.com/story/2016/quenching-cottons-thirst-reducing-use-water-cotton-lifecycle/57196.

Nigam, M., Mandade, P., Chanana, B., & Sethi, S. (2016). Energy consumption and Carbon footprint of Cotton Yarn Production in textile industry. International Archive of Applied Sciences and Technology, 7(1), 06–12. Retrieved October 24, 2021, from http://soeagra.com/iaast/iaastmarch2016/2.pdf.

Ro, C. (2020, March 10). Fashion accounts for around 10% of greenhouse gas emissions from human activity, but there are ways to reduce the impact your wardrobe has on the climate. [web log]. Retrieved October 24, 2021, from https://www.bbc.com/future/article/20200310-sustainable-fashion-how-to-buy-clothes-good-for-the-climate.

TED-Ed. (2017). The life cycle of a t-shirt - Angel Chang. Retrieved October 24, 2021, from https://www.youtube.com/watch?v=BiSYoeqb_VY.

Trent, S. (2020, October 7). CLOTHES AND CLIMATE: IS COTTON BEST? [web log]. Retrieved October 24, 2021, from https://ejfoundation.org/news-media/clothes-and-climate-is-cotton-best.

Van Der Heide, J. (2016). How big is the carbon footprint of YOUR T-shirt? [web log]. Retrieved October 24, 2021, from https://www.tshared.eu/blog-of-tsharedeu/carbon-footprint.html.