Others have already alluded to this, but we should just go ahead and completely ignore the 20,000 use figure for an organic cotton bag. I have no citations to back this up and even so I can say with complete confidence that the environmental impact of 1 organic cotton bag is not equivalent to producing, printing, boxing, and shipping ~300lbs of HDPE.
Study was in Danish but with a few translations it looks like their metric was overall environmental impact. I suspect one of their metrics was severely over weighted. This makes me question the rest of their findings as well.
Sorry about this being my first post, I may partake in more conversations on this forum, but I tend to just read and not participate in online forums. However, this is a topic that is very interesting.
There has been several studies, as has now been mentioned here.
Here is the Danish one:
https://www2.mst.dk/Udgiv/publications/2018/02/978-87-93614-73-4.pdfPage 80: "In order to provide a comparable performance to LDPE in all impact categories, the number of
reuse times for cotton and composite bags increased to thousands of times"
And the British one:
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/291023/scho0711buan-e-e.pdfPage 7. A cotton bag would need to be reused over 300 times to equal the environmental impact of a single use grocery plastic bag. Even paper bags require 7 uses. Who uses a paper bag 7 times?
The data seems pretty well studied and clear. That single use bags have far less environmental impact than reusable bags. Unless you are like the poster above who has used the same bags for decades, of course. But the problem is, most people don't. So for every person that doesn't use a cotton bag 300 times, you are just adding more uses to those that do to offset environmental impact. The numbers get out of control, fast.
I see some "US is so stupid" comments here, but these are studies from other countries that show bag bans are counter productive.
Personally, I have mixed feelings. I don't like any single use items in general. But, plastic bag bans seem to be pointless, and probably harming the environment more than helping. I think we are focusing on the wrong things. Picture the average shopper at the grocery store with a cart full of groceries. A single packaged item in their cart will have more plastic and harmful material than all of the bags used to bag up their order. When I hear about bag bans like it's going to save the world, I just can't help but picture a cart full of groceries in massive amounts of single use plastic, foam, and paper products.
In light of data suggesting reusable bags have more environmental impact and the tiny amount of plastic actually being used compared to all of the single use packaging, it seems like plastic bag bans are more a feel good measure that most likely does more harm to the environment than good, while at the same time taking focus away from very real changes that we could be focusing on that would make a real difference.