"Environmental impact" formula is totally subjective and unscientific. You could easily create another one which would put mentioned bags in a different order.

"Environmental impact" formula is totally subjective and unscientific. You could easily create another one which would put mentioned bags in a different order. For example cotton bags critique often involves mentioning how much water is needed to produce it. But is it really a problem on the planet mostly covered by water? By tweaking the formula you can put cotton bags where you want on list like that.