Cotton uses about 23% of the world’s insecticides and 10% of the world’s pesticides, according to the Sustainable Cotton Project and Pesticide Action Network North America. On average 200kg of nitrogen is added to the land for every tonne of cotton picked. 33% of this is lost into the atmosphere, though 98% of this is harmless, the remaining 2% is nitrogen dioxide which is 300 times worse as a greenhouse gas than carbon dioxide.
Meanwhile, polyester is created from petrochemicals and requires twice as much energy to produce as cotton does to grow. However the total cost for producing a cotton shirt and a polyester shirt is about the same, at 3.25CU (a Carbon Unit (CU) equals 1 kilogram of carbon dioxide released into the atmosphere).
So is cotton or polyester best?
Of course, it depends! The difference between the two is more apparent over the life of the garment. Polyester can be washed at a lower temperature (40 degrees Celcius as opposed to 60), dries more quickly and usually doesn’t need to be ironed. Therefore it contributes approximately around half of the CU a cotton garment does. You could of course wash your cotton items at a lower temperature, hang them to dry and not iron them, then there is no real difference.
[Via: BBC Focus Magazine]