Compost Smells Bad: How To Fix Bad Smelling Compost

Compost Filled With Food and Soil
apartment composting
(Image credit: Joyce Grace)

While compost for the garden is wonderful, a compost pile can occasionally get a little smelly. This leads many gardeners to wonder, “Why does compost smell?” and, more importantly, “How to stop compost smelling?” When your compost stinks, you have options.

Does Compost Smell?

A properly balanced compost pile should not smell bad. Compost should smell like dirt and if it does not, there is something wrong and your compost pile is not properly heating up and breaking down the organic material. There is one exception to this rule and that is if you are composting manure in your compost pile. This will commonly smell until the manure breaks down. If you wish to suppress the smell of composting manure, you can cover the pile with 6-12 inches (15-30 cm.) of straw, leaves or newspaper. This will reduce the smell of composting manure considerably.

Why Does Compost Smell?

If your compost smells bad, this is an indication that something in the balance of your compost pile is off. The steps to composting are designed to help break down your organic material faster and, a side effect of this is, to stop compost from smelling bad. Things like too many greens (nitrogen material), too little aeration, too much moisture and not being mixed well can cause a compost pile to smell badly.

How to Stop Compost Smelling

At the heart of it, stopping your compost from smelling comes down to fixing what is making it smell. Here are some fixes to some common issues. Too much green material - If you have too much green material in your compost pile, it will smell like sewage or ammonia. This indicates that your compost mixture of browns and greens is off balance. Adding brown materials like leaves, newspaper and straw will help bring your compost pile back into balance. Compost pile is compacted - Compost piles need oxygen (aeration) to decompose the organic material properly. If your compost pile gets compacted, the compost will start to smell. Compost that has too little aeration will smell putrid or like rotting eggs. Turn the compost pile to help get air into the compost and stop the bad smell. You may also want to add some “fluffy” materials like dry leaves or dry grass to help keep the pile from over-compacting again. Too much moisture - Often in the spring, a gardener will notice that their compost stinks. This is because due to all the rain, the compost pile is too wet. A compost pile that gets too wet will not have enough aeration and the effect is the same as if the compost pile was compacted. Compost that is too wet will smell putrid or like rotting eggs and will look slimy, especially green material. To fix this cause of a smelly compost pile, turn the compost and add some dry brown materials to absorb some of the moisture. Layering - Sometimes a compost pile has the right balance of green and brown material, but these materials have been put into the compost pile in layers. If the green material is isolated from the brown material, it will start to decompose incorrectly and will start to give off a bad smell. If this occurs, the compost pile will smell like sewage or ammonia. Fixing this is only a matter of mixing the pile a bit better. Proper care of a compost pile, such as turning it regularly and keeping your greens and browns in balance, will help your keep your compost pile from smelling.

Heather Rhoades
Founder of Gardening Know How

Heather Rhoades founded Gardening Know How in 2007. She holds degrees from Cleveland State University and Northern Kentucky University. She is an avid gardener with a passion for community, and is a recipient of the Master Gardeners of Ohio Lifetime Achievement Award.