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The European Textile Services Association (ETSA), which seems to be a lobby group, has a (2012) brochure that claims (among other things) that

Polyester/cotton blends have a lower CO2 footprint [than 100% cotton]

When measuring the CO2 footprint from cradle to cradle, workwear made of a polyester/cotton blend emits 10% less CO2 than 100% cotton workwear. The figures below take the following into account: fibre production, production of fabric and garments, use and laundering, distribution and disposal

enter image description here

This brochure is based on a comprehensive Life Cycle Assessment published by the Danish Technical University.

*Source: ‘Life Cycle Assessment - Berendsen Profile Workwear.’ Master Thesis by Morten Søes Hansen and Jesper Krarup Holst, 2002, Danish Technical University, in cooperation with Berendsen.

Now a Master thesis doesn't strike me as the ultimate word on this matter (and it's also from two decades ago), so is the claim that polyester-cotton blends have lower CO2 footprint than pure cotton consistent with other studies on this matter?

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  • 2
    Note that "polyester" covers a number of different chemicals, some produced from "natural" sources, some synthesized from petroleum. Hard to quantify the "footprint". Commented Dec 3, 2020 at 17:53
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    From the graph it looks like all the difference is in the laundry costs. That sounds very odd to me. I cannot find the source online which makes it hard.
    – Dave
    Commented Dec 3, 2020 at 19:57
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    @WeatherVane - that may suggest that the disposal of the 100% cotton has a very small negative kg CO2 equivalent cost, so was moved to the left
    – Henry
    Commented Dec 4, 2020 at 2:01
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    The chart suggests the largest effect is laundry. This might be the case if polycotton uses a lower temperature to wash, or less water, or does not need so much ironing, when compared to the same item made of 100% cotton. Certainly washing instructions vary by material, so it is not an insane idea.
    – Henry
    Commented Dec 4, 2020 at 15:22
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    Sounds like fake news. Does "fiber production " count the production of xylenes ? Does it count the production of terephalic acids from xylenes ? Does it count making polyester from terephalic acid ? This is source for the bulk o polyester . All polyester is made by very similar processes. Commented Dec 4, 2020 at 15:36

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Yes, cotton-polyester blends have a lower CO2 footprint than 100% cotton.

According to "How Bad are Bananas?: The Carbon Footprint of Everything" by Mike Berners-Lee (ISBN 9781846688911), producing a pair of jeans has a carbon footprint of 6kg CO2, versus nylon trousers which generate around 3kg CO2. Factoring in longevity and energy used in washing and drying the garments over their lifetime he estimates that "nylon trousers are less than one-tenth as carbon intensive as jeans."

(Not a direct answer to the question, since it asks about the difference between cotton and polyester-cotton, and not denim and nylon, but a difference of 10% definitely seems feasible.)

An additional graph from the book:

The annual carbon footprint of buying and washing clothes.

Berners-Lee's source for much of this is the paper "Life Cycle Assessment environmental profile of cotton and polyester-cotton fabrics".

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  • "Quick drying. No tumble drying." Does that graph imply that if you have polyester clothes you don't tumble dry them, and then go on to compare it to clothes that are tumble dried? Commented Dec 18, 2020 at 20:38
  • It’s not completely clear how frequently Berners-Lee assumes the clothes are tumble dried but it is considered: “if everything I wore were equivalent to my jeans, my clothing footprint would be 45 kg CO2e per year for the garments themselves plus around the same again for washing and more than double again if I use a dryer. But if everything I wore were equivalent to my nylon trousers, I could cut my clothing footprint to just 7 kg per year, or 16 kg including laundry.”
    – mjs
    Commented Dec 20, 2020 at 2:11

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