My kitchen trash can smelled even with a fresh bag in it. I bought the scented bags, I sprayed it, I took the trash out more often. It always came back within a day.
The smell was not coming from the bag. It was coming from the can.
Where the Smell Actually Lives
Under the bag, at the bottom of the can. Every bag leaks a little, or drips when you lift it out. That liquid pools at the bottom, under the next bag, and sits there for months.
In the rim and under the lid. Splashes dry on the underside of the lid where you never look. In a pedal can, the hinge area is worst.
In the plastic itself. Plastic absorbs the oils that carry smell, so an old can holds its own smell even when clean and dry.
Putting a fresh bag into a can with old liquid at the bottom is the reason it smells again by the next day.
The Proper Clean
Take it outside and rinse it with a hose or fill it with hot water.
Half a cup of dish soap and half a cup of baking soda, hot water, and leave it an hour. Slosh it around so the sides and rim get wet.
Scrub the rim and the underside of the lid with a brush. This is the part that matters and the part everyone skips.
Rinse, then dry it completely. In the sun if you can — the UV kills what the soap missed. A damp can will start smelling immediately.
Do this every couple of months, not once.
Then Keep It From Coming Back
Put something absorbent under the bag. A folded sheet of newspaper, or a sprinkle of baking soda, or a couple of used dryer sheets. It soaks up the drips before they pool. This one change does most of the work.
Wrap the wet things. Meat trays, fish, chicken skin, coffee grounds, onion ends. Wrap them in newspaper or a small bag before they go in. Almost all trash can smell comes from a small number of very wet items.
Freeze the worst of it. Keep a bag in the freezer for raw meat packaging and fish, and put it out on collection day. Sounds excessive, works completely.
Do not overfill. When the bag is stuffed past the rim you cannot close the lid and you tear the bag lifting it out.
What Does Not Work
Scented bags and air fresheners. They add a smell on top of the smell. Within a day you have both.
Bleach. It kills bacteria but does not remove the residue that is feeding them, and it does not touch absorbed odor in the plastic.
A new can. It will smell the same way in six months unless you change what you put in it.
Start Tonight
Lift the bag out and look at the bottom of the can.
Whatever is down there is the thing you have been smelling.
