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Composting Should Not Stink

A short lesson on the difference between aerobic and anaerobic decay

If your composting tumbler stinks, it has become anaerobic. Keep a supply of dried leaves, hay, straw or shredded paper nearby for immediate relief.

A Bay Weekly reader cornered me at Christopher’s in West River, complaining that her compost pile stinks. She was composting in a rotating drum on an elevated stand. Her complaint: the contents in the drum were slopping wet and the odors so strong that her neighbors were complaining.
    She admitted that she had not read the directions on the drum. “What difference would that have made?” she wanted to know.
    The instructions for enclosed composting systems clearly state that when odors are detectable, add dry matter such as shredded newspaper, dry leaves, straw or hay to absorb the excess water.
    Composting is an aerobic system, which means that the microorganisms digesting the organic matter require a minimum of five percent oxygen. As composting progresses, moisture from decomposing vegetable matter is released into the atmosphere. Closed composting systems such as rotating drums or enclosed bins do not have sufficient ventilation to release that excess moisture into the atmosphere. Thus, moisture condensates on the inside walls of the container and accumulates in the organic waste being composted. When the moisture concentration within the organic waste exceeds 60 percent, oxygen is excluded and the system becomes anaerobic. When the organic waste becomes anaerobic, objectionable odors are generated by the anaerobic digesting organisms. Other by-products from anaerobic digestion are acetic acid and methane.
    The ideal moisture concentration for composting is between 45 and 55 percent. As most vegetable waste such as cucumber, potato, carrot, watermelon, squash, cabbage, lettuce, etc. contain between 80 to 95 percent water, it does not take much to overwhelm the system with excess moisture.
    Enclosed composting systems should be checked two to three times weekly and turned. At the slightest odor, add dry material and turn several times to incorporate it into the wet. Continue adding and turning the unit until the contents feel moist but not wet. At the proper moisture content, composting materials should feel like a moist sponge. If you can squeeze moisture from a handful of composting material, there is too much water. You can help rid some of the excess moisture by leaving the door open, but make certain that you shut it before turning.
    I used composting drums for developing formulas for composting garbage. Garbage tends to be dry, making it necessary to add water in addition to phosphorus and nitrogen. I was able to compost garbage in 30 days, and the drums often developed temperatures of 180 degrees. I turned the drums daily.
    Drums are useless in the late fall, winter and early spring. However, during the normal growing season, they are very efficient when managed properly.
    If your composting unit stinks, it is because you have allowed it to become anaerobic. Keep a supply of dried leaves, hay, straw or shredded paper nearby for immediate relief.


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