Wet diaper - put in a small opaque bag with the handles tied - you can get them by the 100 on Amazon.
Messed diaper - ziplock or other sealing freezer bag and then one or two small bags. They still smell even then - but it helps a bit.
Then everything into double bin bags - and not too much weight in each one. Then in the rubbish / trash.
Outside wet diaper - hopefully never messed outside - put into a supermarket bag and seal it and then put in any bin - ideally not right at the top - and one with a lid that birds and mammals can't get at so easily.
If you accident outside and end up messing unintentionally I don't know - I haven't had one yet, and I'm really not looking forward to having one.
If you're concerned about someone finding the "evidence", it worked well for me to bag it (in a grocery bag) and then drop it in a public trash can somewhere along my commute - for example, a gas station or a store with the bins out front.
I buy cases of black plastic shopping bags. You can hardly see through them and they come in a box of one thousand, so you can double or triple bag if you feel you need or want to. Also does an alright job of keeping the smell down pretty decently for the messy diapers you're throwing out.
When you take it off, roll it up, wrap in a big black bin bag, tape it up. Repeat. Put in plastic bag. Walk to a public dustbin (in the park or wherever) and then chuck it.
Its lengthy but works nicely.
I still feel bad about this: when I was young and first starting, I didn't want my parents to find them so I stuffed them into a soft drink cup, put the lid on with a straw sticking out so it looked like a normal drink cup, then went down the street and dropped it into a storm drain at the curb. So awful, and probably a great way to have it found by someone cleaning it out in the future, along with stinky diapers. I thankfully only did that one time.
If they're plain white, I would drain it into the toilet as much as possible, bundle it up tight, place in middle of bathroom trash can (not against the sides where someone could see when taking out the trash) and camouflage it with bundled up toilet paper. I only do this with wet diapers though since any urine smells wouldn't be suspicious in the bathroom trash. Also it's very unlikely that someone will rummage through a bathroom trash can.
Only throw one or two per trash load though otherwise the added weight would be a dead giveaway.
I do this because we don't have an outdoor trash. If you do however, it's much better to throw it out there.
I wonder how can you hadn't your own ways to rid them, are you still live with parents or your house is too spacious to be easily seen by others?
For me personally have my own trash, so I just put it on that because my room always closed and nobody knows that diapers.
There's some ways to you get rid your diapers, why you don't have your own idea.
The thought of using a black bag seems counter productive because adult stores are the ones that wanted "discrete" black bags so customers purchases could not be easily seen, but they scream look at me I'm "discrete" and everyone Is interested, although I am not dumpster diving for any color bag period, but others can't resist the impulse to investigate, the yellow nappy sacks are also that same level of "discrete" , I use regular Walmart specials , whatever the varied color be , there is less provocation to be interested in the contents, at home I also use just a plain garbage bag because it don't matter how fancy you go any sanitation worker will know a bag of used diapers by weight and squish Ness, I don't care if my garbage guys know I wear diapers, and I seriously hope anyone without a disposal strategy that has a problem would take advantage of using the can of there local IC , I throw out a ton of diapers so if someone were to add a few no one would be the wise or care.