Why does rotting garbage give off a bad smell?

Rotting garbage emits a bad smell primarily due to the breakdown of organic materials by bacteria and fungi. As these microorganisms decompose the waste, they produce volatile organic compounds (VOCs) and gases such as hydrogen sulfide, ammonia, and methane, which have strong, unpleasant odors. The process of decomposition also releases other byproducts that contribute to the foul smell, making rotting garbage particularly offensive.