Australia is the leading wool exporter, and a leading cotton exporter.
So which fibre is more climate friendly?
Calculated by Emma Hakansson, verified by Faunalytics
Australian wool CO2e emissions:
One study (Brock, Graham, Madden, & Alcock, 2013) of sheep on a farm producing wool and meat (because the wool industry is a part of a slaughter industry) found that total emissions were 24.9kg CO2e per kg of greasy wool.
This is not including ‘meat’ in the breakdown, so more emissions come from these sheep, but this is allocated specifically to the wool per kg.
This study looks at sheep in a breeding ewe enterprise bearing 19 micron wool. The Australian Wool Exchange informed us via email that such wool would be used for a light knit, fine outer layer jumper of 300-400g.
The study also reports a conversion rate of 68% when cleaning greasy wool to produce usable fibre.
These emissions do not include scouring / processing emissions, but only on farm.
In an email from the Australian Wool Exchange:
‘Ok 19um is a light outer layer- say a fine knit men or ladies jumper.400-300g. 19 micron wouldn’t be considered something you could wear next to skin’
Using a conversion rate of 68% per the study, and using a 350g knitwear garment per email:
68% yield of usable clean wool per kg greasy wool
= 1/0.68 kg greasy wool required to produce 1 kg clean wool
= 1.47
1.47 kg x 24.9kg CO2e
= 36.6kg CO2e for 1kg clean wool
36.6kg CO2e x 0.35kg = 12.81kg CO2e for 350g Australian wool jumper
Australian cotton CO2e emissions:
Cotton CO2e emissions on farm = CO2e emissions from chemicals + electricity + fertiliser + on-farm fuel + other pre- and on-farm items = 1,360.4kg CO2e / tonne of cotton lint in 2019
(in drought, lower yield, higher emissions)
*The table above is screen-grabbed from this report, with red annotation showing the on-farm only processes calculated in the 2019 paper used in our calculation. This table does not clearly indicate that the metric is kg CO2e / t, but the text referring to it indicates this.
0.00035kg jumper x 1360.4 = 476.14g of CO2e for one Australian cotton jumper
From this we learn that an Australian wool knit sweater emits about 27 times more greenhouse gas emissions than a cotton knit sweater.
Note that the emissions involved in both wool scouring and cotton processing are not included in these calculations, only emissions associated with the production of useable fibre (clean wool and cotton lint) itself, which would then be processed.