Why does garbage smell?

Garbage smells bad

Garbage odors at home are nasty.  Have you ever forgotten to take out the green bin after dinner to wake up with rotten garbage smell in your condo or apartment? Even when you do throw it, whether it’s down a chute or into a bin, it does not just magically stop and you’ll still want to get rid of the garbage smell.  The reason for this is simple, it has started to decompose and bacteria are breaking down all the organic matter into simpler molecules while also releasing gases into the air.  The gas is what smells.

the science of why garbage smells

Aerobic Digestion - with oxygen

There are two ways that garbage will decompose, either aerobically or anaerobically.  That is to say in the presence of ample oxygen or not, respectively.  A forest floor or a public park would be examples of aerobic decomposition of material, while a tied-up bag or garbage in a dumpster would be an example of anaerobic digestion at work.


Aerobic digestion leaves very little to no smell as it is a slower process that fully consumes all the organic matter.  In this form of decomposition organisms consume the carbon and turn it into CO2 and the nitrogen turns into more cells for the organism.  This process takes time to churn through the material and produces heat as the breakdown occurs.  This is the process used in backyard compost and occurs naturally in forests.

Anaerobic Digestion - without oxygen

Anaerobic composition works differently, by limiting the oxygen – such as waste that is in a sealed bag or at the bottom of a dumpster, it forces the material to break down into different, often smelly compounds.  Most of the compounds contain sulfur or nitrogen, the former tending to be very smelly in small amounts while the latter generally needs larger concentrations to be noticed.  Anaerobic composition accelerates in a warmer environment as the bacteria is more active, explaining why garbage smells worse in the summer. 


Anaerobic composition of garbage is the prime reason why buildings smell, as the garbage is all in bags that get thrown down the chute and layered high, the bacteria sets to work. Garbage is picked up regularly so these gases are not in volumes that would cause physical danger, but it is nasty.

 Where does the smell go once it has been created? Well, most often it goes right back up the chute where the garbage was dropped into through a process called the Stack Effect which is a subject of a past blog. https://www.airfixx.ca/why-do-chute-rooms-smell/

Pro-Active Odor Control