Disposable Mask Footprint Calculator

A cloth mask pays back in about a month of daily use, and the disposables are polypropylene.

Reusable item

What it replaces

Times used a week

Clear

Uses to break even32.2Reusable cloth mask against disposable face mask

How long that takes4.6 weeks0.09 years at 7 uses a week

Making the reusable one1.9 kg CO2e

Each disposable0.059 kg CO2e

After 100 uses, reusable1.9 kg CO2eunchanged — it was all spent at the start

After 100 uses, disposable5.9 kg CO2ethe reusable is ahead by now

Carbon is one axis and not the one plastic bags are usually criticised on — their real problem is persistence and marine litter, where cotton does well and they do terribly. Whatever you already own, use it until it falls apart: its footprint is already spent, and replacing it starts a new debt.

The formula

uses to break even = reusable footprint / disposable footprint

Reusable is not automatically better

A cotton tote takes roughly a hundred times the emissions of a single plastic carrier to make, so it has to replace about a hundred of them before it is ahead. A paper bag is only two or three. The reusable option wins if and only if it is actually reused enough, and the number is far higher than most people assume.

Different impacts point different ways

Carbon is one axis and it is not the one plastic bags are usually criticised on. Their real problem is persistence and marine litter, where they perform terribly and cotton does not. A cotton tote used ten times may be worse on carbon and better on litter than the bags it replaced, and both statements are true.

The honest conclusion

Whatever you already own, use it until it falls apart. The footprint of the bag in your cupboard is already spent, and replacing it with a better one starts a new debt. This is the least satisfying and most reliable environmental advice there is.

How much to trust a footprint

Life-cycle figures for the same product routinely differ by a factor of two between studies, because deciding what to count — the farm, the packaging, the shop, the drive home, the disposal — is a methodological choice rather than a measurement. The numbers here are central estimates from published meta-analyses. They are reliable for comparing one option against another, which is what people actually use them for, and not reliable to the second significant figure.

The other thing worth keeping in view is scale. Individual choices matter and they are not where the emissions are: the difference between the best and worst quartile of beef producers is larger than most people's entire dietary footprint, and that is a question about agriculture policy rather than about shopping.