An Ammonia Smell From Compost

Too much nitrogen waste may cause ammonia odors in your compost bin.

For most newbie composters (and their close neighbors), a heap of organic waste that reeks of ammonia probably isn't what they had in mind when they started turning household and yard waste into nutrient-rich finished compost. If your compost heap or bin suddenly seems to have morphed into an ammonia-breathing monster, take heart -- this is a fairly common composting problem that you should be able to fix and prevent with proper compost care.

Composting Bacteria

An ammonia smell coming from compost may indicate that a population of anaerobic bacteria has invaded your compost heap or bin. Biodegradable compost waste typically breaks down as a result of activity from aerobic or oxygen-loving bacteria, which need air to survive and thrive. If your compost waste becomes tightly packed or extremely wet, these microorganisms cease microbial activity and often die off because they don't have access to oxygen. When this happens, anaerobic or oxygen-hating bacteria begin growing and reproducing. As these oxygen-hating bacteria break down the compost matter, they produce an assortment of foul-smelling gases, including ammonia.

Excessive Nitrogen-based Waste

Overloading your compost heap or bin with too much nitrogen-rich waste, such as grass cuttings, food scraps or animal manure, could also be the cause of ammonia smells. The heap's population of aerobic bacteria works quickly to break down waste, but in the presence of excessive nitrogen-based materials, they often won't be able to process it all quickly enough. Left to languish too long without being decomposed, excessive nitrogen gets released into the air as colorless, pungent-smelling ammonia gas, according to Cathy Cromell, author of "Composting for Dummies."

Solution

Getting rid of the unpleasant ammonia odor coming from your compost waste requires that you get serious about properly managing the compost. Reduce the percentage of nitrogen-rich waste by adding additional carbon-rich waste to the compost; common sources of carbon-heavy matter include straw, sawdust, dead leaves and shredded newspaper. Once you've added the carbon waste to the compost, stir and mix the waste with a manure fork to introduce a fresh load of oxygen and boost microbial activity from the aerobic bacteria. When you feel the waste, it should be about as moist as a wrung-out kitchen sponge. Continue maintaining the compost waste on a regular basis, aerating it once every seven to 21 days to help ensure the ammonia smell doesn't return.

Prevention

In addition to regular compost maintenance, knowing the role different types of biodegradable waste play in the composting process helps prevent potential ammonia smells in your compost. Carbon-rich waste (which typically includes dry, brown materials, such as dead leaves, newspaper, cardboard, straw and sawdust) gives composting microbes energy, while nitrogen-rich waste (which typically includes wet, green materials, such as horse or cow manure, fresh grass cuttings, vegetable peels, seaweed and freshly pulled weeds) enhances their growth and reproduction. In order to keep your compost's population of aerobic bacteria alive and well, you'll need to provide the microbes with a mix of these two kinds of waste. As a rule, about one-fourth to one-half of the waste in your compost heap or bin should come from nitrogen-based materials, while the rest should be carbon-heavy waste.

References

• "Composting Inside and Out"; Stephanie Davies; 2011
• "Composting for Dummies"; Cathy Cromell; 2010
• "The Complete Compost Gardening Guide"; Barbara Pleasant, et al.; 2008
• University of Illinois Cooperative Extension: The Science of Composting