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We get this question from GEOBIN Composter customers frequently: Should my compost bin smell bad? The answer is no—compost should smell earthy, like dirt, even when it’s actively decomposing food and other organic material. 

Why Does My Compost Smell Bad?

Composting is all about maintaining a healthy balance of organic material and proper ventilation. When that balance gets thrown off or there’s not enough oxygen circulating, the contents of your bin will rot rather than properly break down into compost. When this happens, your compost pile may begin to smell unpleasant. The good news is there are ways to combat these offensive odors.

Why Your Compost Smells Like Ammonia

To effectively heat up and decompose, compost needs the right ratio of brown (carbon) and green (nitrogen) materials. For the GEOBIN Composter, we recommend a 3:1 ratio of browns to greens. Sources of carbon include dried leaves, twigs, cardboard, and sawdust, while nitrogen-rich materials include food scraps, grass clippings, and coffee grounds.

If you notice the smell of ammonia coming from your compost bin, it could mean that there’s too much green material. Balance your compost pile by adding some carbon-rich material. Carbon is the energy source for your compost—without it, your food waste will improperly decompose and release excess nitrogen in the form of ammonia.

Reasons Your Compost Smells Like Rotten Eggs or Garbage

• Your compost pile is too compacted or lacking oxygen: Composting is an aerobic process, which means it requires the presence of oxygen. If your compost pile becomes compacted, airflow will be restricted. You can correct this by mixing up the pile and adding some “fluffy” material, such as dried leaves. This will create air pockets throughout your compost pile which will provide the microorganisms with the oxygen required to break down the organic material.
• Your compost is too moist: This is common in spring and fall when there’s an increase in rainfall. When your compost is too wet, it will lack the aeration required to properly decompose the organic material, causing the smell of sulfur or rotten eggs. Introducing more brown material will help soak up excess moisture and eradicate these bad smells.
• Your compost pile is not layered properly: When layering your organic material, sometimes the greens can become isolated from the browns. If this happens, the green material will begin to rot and emit a foul smell. You can fix this by mixing up your pile so the browns and green work in unison to produce nutrient-rich fertilizer.
• You added meat, fat, or dairy to your compost: These materials release putrid odors as they break down. They also attract unwanted pests, like rats and flies, so it’s best to avoid adding these to your composter.

If you follow these simple steps to maintain your compost pile, your garden, and the environment, will thank you.