Cotton, a natural cellulose fiber, and polyester, a synthetic polymer, are the two most dominant materials in the global textile industry. They present fundamentally different environmental challenges throughout their lifecycles. Cotton cultivation relies on agricultural resources, while polyester manufacturing is heavily dependent on fossil fuels. A comprehensive assessment must compare the impacts of growing a natural fiber against the industrial synthesis of a plastic-based fiber.
Sourcing and Initial Production Footprint
The initial stage of material sourcing establishes a clear divergence between the two fibers. Cotton begins as a plant, necessitating the use of arable land and creating an ongoing demand for agricultural space. Conventional cotton farming can strain soil health and has historically contributed to land degradation. Organic cotton, while requiring approximately 30% more land due to lower yields, promotes significantly better soil health by avoiding synthetic inputs.
Polyester is a derivative of crude oil and natural gas, tying its existence directly to the non-renewable fossil fuel industry. The process of creating polyethylene terephthalate (PET) is entirely industrial and does not require agricultural land. Its sourcing footprint centers on extraction sites and petrochemical refineries, where crude oil is refined into the necessary chemical precursors. This reliance on petroleum as a feedstock is the material’s largest resource drawback.
Water Use and Chemical Pollution
The water footprint of cotton is overwhelmingly larger than that of polyester during the fiber production stage. Growing one kilogram of conventional cotton fiber requires an average of approximately 10,000 liters of water, primarily for irrigation in arid and semi-arid regions. This excessive water demand can lead to significant water scarcity and has been linked to ecological disasters.
Conventional cotton farming is one of the most chemically intensive agricultural operations globally, accounting for a high percentage of the world’s total insecticide and pesticide use. These agrochemicals and synthetic nitrogen fertilizers create toxic runoff that pollutes local waterways, leading to eutrophication and poisoning ecosystems. Polyester production contributes to water pollution through the chemical byproducts and heavy metal catalysts used in its synthesis. Both fibers share a common problem in the downstream process of dyeing and finishing, which is responsible for a substantial portion of global industrial water pollution.
Energy Intensity and Carbon Emissions
Polyester production is inherently energy-intensive because its raw material, petroleum, and its entire manufacturing process are fossil fuel-based. Significant energy is required to extract and refine the crude oil, and even more is consumed in the high-heat polymerization and extrusion processes. This reliance results in a substantial carbon footprint, with virgin polyester fabric often emitting around 8.95 kilograms of carbon dioxide equivalent per kilogram of material.
The carbon footprint of conventional cotton is also considerable, though the sources of emissions differ. Primary energy demands come from the heavy machinery used for planting and harvesting, the electricity needed to run irrigation pumps, and the energy-intensive manufacturing of synthetic nitrogen fertilizers. Fertilizer production is often cited as the single largest contributor to cotton’s total greenhouse gas emissions. Choosing organic cotton can reduce the farming-related carbon output by over 45% due to the avoidance of synthetic fertilizers.
End-of-Life: Biodegradation and Microplastic Issues
The final fate of the material after disposal presents the most distinct difference between the two fibers. Cotton, as a natural cellulosic fiber, is fully biodegradable and will decompose relatively quickly, often within a few weeks to five months under optimal composting conditions. Even when treated with common dyes or finishes, cotton microfibers have been shown to biodegrade significantly in aquatic environments, meaning they do not contribute to long-term plastic pollution.
Polyester, being a form of plastic, is non-biodegradable and can persist in landfills for centuries. More concerning is its role in microplastic pollution: every time a polyester garment is washed, it sheds thousands of microscopic plastic fibers. These microplastics are too small for many wastewater treatment plants to filter out and consequently enter rivers and oceans, where they are ingested by marine life. Furthermore, recycling polyester garments is complicated because most clothing is a blended fabric, such as a cotton-polyester mix, which current mechanical recycling technology cannot effectively separate without severe quality degradation.