If you're going to store your passport (or anything) in a zip-lock bag for a long period, maybe just sprinkle in some baking soda? Mould doesn't like dry, alkaline conditions.

Yuck! Save one of those little packs of silica gel used to keep food dry and use that instead? Looks more legit than some random white powder.

"Looks" more legit, and is far more woo-woo.

Those little packs are completely useless if they've been exposed to open air for a few hours. I swear, 99% of the population think those packets reverse the laws of thermodynamics somehow, pumping an infinite amount of water without work.

I'll go with the chemically-valid, physics-valid, non-random white powder.

Well then store them in an airtight container? Better than just tossing them.

Bake them first, 120°C (250°F) for a few hours. They're reusable if the water is baked out.

Not much better. They're tiny and ecologically rather bland.

A white powder residue found on your passport by security just might result in a delay.

I carry yeast, flour, and oil with me to the airport to demonstrate proving if necessary. On the off-chance that the white powder is not in fact baking powder - after a trip to South America for example - I use self-raising flour (harina leudante) cleverly switched into a plain flour packet.

With this many steps might be just easier to not put the passport in water then weekly maintenance jobs :)

If you’re setting a weekly reminder, then every 4th week you should wipe down the outside cover and inner card with a spritz of vinegar (better than windex) and then air dry for a few hours.

(I’m not seriously suggesting this)

No! Not all passports have the thick inner cover US ones have.

So you're suggesting putting the passport into some sort of protective package before wiping it down? :D