All things environmental

Musings about the environment and all it touches, from education to city planning

My old UBC shirt

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My old, old shirt. You can still read “Bio-Resource Engineering, UBC. ERTW.”

I have a golf shirt from my UBC grad student days, one that the bio-resource engineering students designed for their class. This was well over twenty years ago – the program long since defunct – but I keep wearing the shirt.

But surprisingly, the shirt is still in fine shape, and that is the intriguing part. I must have washed this shirt 200 times. Some t-shirts I have worn for fewer years are thread-bare, worn-out with holes.

The worn-out shirts, it turns out, are made of cotton, and only cotton. My UBC shirt, by contrast, is a fifty-fifty blend of cotton and polyester.

Polyester? Yuck! The synthetic material has a bad reputation: it’s made with toxic oil products, it’s energy intensive to make, it doesn’t breathe, and it’s all-around uncool.

Could it be that that reputation is unwarranted? Clearly, a pure polyester fabric is not comfortable, and doesn’t breathe well. But used in a blend, it’s brilliant.  It gives clothes a longer life; so though it does take more energy to make polyester than cotton, if the garment is going to last much longer, things balance out.

But does making polyester take that much energy? It takes about 125 megajoules of energy to synthetize one kilogram of polyester fibres. It only takes 14 to make a kilo of organic cotton, and about the same for hemp and flax (linen). Wool is a bit more energy intensive, at 63. But if you’re going to use ordinary cotton, as opposed to organic, then you need about 55 MJ/kg (all those pesticides make a big difference!). And if your polyester fibre is made from recycled plastic (the common end use of all these recycled water and pop bottles, made from PET, which is another name for polyester), then you’re saving half the energy cost (66 MJ/kg).

The New Scientist magazine fielded a question as to why we consider cotton more comfortable. J. Robert Wagner answered that

Cotton is comfortable as it has a high amount of moisture regain, generally about 7 to 7.5 per cent. Moisture regain is the amount of moisture that the fibre will absorb, expressed as a percentage, starting from a bone dry condition when placed in an atmosphere of standard temperature and humidity. This means cotton can absorb our body moisture and give us the sensation of being cool. In contrast, polyester, a synthetic that many fabrics are made from today, only has a moisture regain of 0.4 per cent and will feel hot, sticky and clammy, especially when the humidity is rather high.

That is true in general – but then moist cotton gets heavy. Long-distance runners have long ditched pure cotton for synthetic blends. Still, if you’re not going to be sweating in it for a long time, cotton feels nicer.

But cotton’s ability to wick moisture is also its undoing when it comes to drying. A cotton/synthetic blend dries faster. This adds up if you count how many drier loads a typical family needs in a year; there are considerable energy savings to be made just in the choice of fabric. (This is something that travelers know well – shirts and underwear made with blends dry in your hotel room quickly, so you can pack light. Travel stores sell light ropes made of a bungee-like material, because backpackers use them to dry their clothes.)

Answering the same question in the New Scientist section, Brian Bennett noted that cotton has less abrasion resistance than synthetics, and therefore doesn’t last as long. He added:

Cotton’s advantage in absorbing water is also a disadvantage, in that more energy is required to dry it. While this may not be a problem in the summer, when garments can be dried outside, during the winter the extra heat required is significant. Making synthetic yarns is clearly an energy-intensive business. However, this energy may be less than the extra energy required to dry cotton, taken over the lifetime of the garment. Clearly this additional and hidden energy use should be considered when clothes are designed. Unfortunately, it is frequently overlooked by manufacturers, who go for the easiest option, with long-term implications for the climate.

Uh, Mountain Equipment Co-op, the 100% cotton shirt I bought in your store is already starting to fray, five years later. Kudos for using organic cotton – but could you maybe look into adding a bit of polyester to your fabric? It would actually be more, not less, environmentally friendly.

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Written by enviropaul

February 28, 2016 at 9:57 am

2 Responses

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  1. I’d like to see this same analysis done for wool, specifically, high end NZ Merino wool which many athletes/travelers are switching over to due excellent wicking abilities, fast drying times and low-impact environmental properties. Lasts longer than cotton, too.

    Jo-Ann Svensson

    February 28, 2016 at 12:02 pm

    • Excellent comment – I’ll see if I can dig up some info on that material.

      enviropaul

      February 28, 2016 at 4:22 pm


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