What common composting mistakes cause foul odors?
Written by
Liu Xiaohui
Reviewed by
Prof. Martin Thorne, Ph.D.Bad odors in compost indicate serious failures in the process that must be corrected at once. The sulfur odors of anaerobic decomposition will occur, and the ammonia odors indicate a surplus of nitrogen in the pile. The causes are poor handling. These can be corrected readily with appropriate treatment. The pleasant odor of healthy compost should always be an earthy one, like that of moist forest soil aged in the woods.
Rotten Egg Smell
- Cause: Anaerobic decomposition from waterlogged materials
- Fix: Turn pile immediately; add coarse browns like wood chips
- Prevention: Install drainage layer; cover during heavy rain
Ammonia Odor
- Cause: Excess nitrogen from too many greens
- Fix: Incorporate shredded cardboard or dry leaves
- Prevention: Maintain 30:1 carbon-nitrogen ratio; layer carefully
Sour Vinegar Smell
- Cause: Acidic conditions from excess fruit waste
- Fix: Add crushed eggshells or garden lime
- Prevention: Limit citrus; balance with brown materials
Prevent smells by building your pile properly. Start with 6 inches of browns, then 3 inches of greens for layers. This lasagna-like method allows for air movement and consistent decomposition. Keep the moisture of the pile like a sponge that has been wrung out, so that no water runs out, but it is on the verge. I can tell how mine is doing by taking a handful and squeezing it in my hand. Water will trickle slowly out between my fingers.
The frequency of aeration will determine the effectiveness of odor prevention. Turn with a pitchfork once a week. Shift outside materials into the hot center. This will ensure an even distribution of microbes. The temperature should reach 130-150°F to kill pathogens. Piles that are colder than 100°F often become odorous.
The right materials are paramount in preventing chronic odor issues. Never use meat, dairy, or oily things that attract animals and insects. Bury kitchen scraps under adequate layers of brown material. As much as possible, cut everything into 1- to 2-inch pieces to facilitate the breakdown process. Such methods will lead to an efficient aerobic decay, without any odor.
Approach a consistently odoriferous compost heap with a methodical mind. First, check it for moisture and rectify it if necessary. Secondly, consider the carbon-to-nitrogen ratio and adjust it. Finally, inspect the size of the pile and the aeration. Most odor problems are rectified in one to two days by following these suggestions. Your compost should brighten up and assume the character of fine, earthy humus.
Read the full article: Choosing the Best Compost for Gardens
