[sirwitti]

After reading through the results of parent's [1] I'm wondering: Are they simply comparing environmental impact of the bags?

If so the numbers might be misleading because if someone buys a plastic bag the number of reuses is very limited. Let's say you buy 10 plastic bags a year for 5 years as compared to reusing 1 cotton bag in the same time period.

This would mean that in order to compare the environmental impact of both scenarios over that timeframe you'd need to divide the numbers of the cotton bag by 50 (10 plastic bags for 5 years) to get comparable results.

If this logic is correct this would mean that you'd need to reuse a conventional cotton bag 142 times and an organic bag 400 times over 5 years to get the same impact.

These numbers sound quite reasonable/realistic to me, assuming other people use their cotton bags as often as we do.

[parsimo2010]

The problem with these studies is that you can't just correct the impact of a cotton bag, you also need to correct the impact of the plastic bags. [For me at least] The estimated impact of plastic bags is also wrong, so two wrong estimates aren't going to lead to a correct conclusion unless you get lucky. While plastic bags might get re-used only once, and cotton bags might be more durable, but that isn't the only thing to consider.

I re-use nearly all of my plastic bags, but only once. They have limited durability but wide applicability. Cat litter, trash bins in bedrooms and bathrooms, and bundling up oily paper towels in the garage. My waste management service requires that I bag all my trash, and I use my plastic bags from stores for this. If I switched to cotton bags for shopping I would still need plastic bags for my garbage, so if I switched I would actually be hurting the environment. There's no way I'm using cotton bags to bag up my trash and cat poop. I wouldn't be opposed to biodegradable bags from the supermarket though, as long as it isn't something that I have to pay extra for.

I know that not everyone re-uses all of their plastic bags, but how many people like me does it take before the world is worse off? Now we're shopping with cotton bags and buying a box of plastic bags to throw our garbage in? What is the loss rate of cotton bags? If I lose one per year am I losing them before getting to the break even point?

[scotty79]

> If this logic is correct

It is not.

If canvas bag costs 7000 plastic bags then you have to use it 7000 thousand times like you would use a plastic bag to get the same impact. It doesn't matter how often you use it.

If you divide 7000 by 50 you are just saying you have to use canvas bag like you used 50 canvas bags, 140 times. Since you got 5 years of groceries out of those 50 bags you'd need 5*140 years to get 140 as much of utility out of canvas bag.

[dredmorbius]

The question is what the all-in costs are. Specifically, manufacture is not the. full lifecycle, and plastic persists in the environment for decades, if not millennia.

Alternatives which balance modest production costs, greater ruse, and biodegrade more quickly, can come out on top.

[scotty79]

Many multiple use bags are thick plastick or have thick plastic inner lining. They have less plastic than 7000 "single use" plastic bags but they don't have 0.

I hope we won't let most of our trash to persist in the environment for millenia.