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Compost Odor

Compost Odor

One thing that is surely hurting the composting industry is compost odor. Large composting facilities start off with the best intentions but often people soon start complaining about the smell. Public concern over composting facililty odor can also put planned projects on hold if the developer and city planners do not incorporate a proper level of odor control into their facility. Compost odors in small scale compost piles, heaps or bins are easy to eliminate with weekly maintenance, but for large scale facilities a more advanced method is required.

The Three Compost Odors

The three odors that are most unpleasant to humans are ammonia, hydrogen sulfide and volatile fatty acids.

  1. Ammonia – Ammonia is generated by the build up of nitrogen in an area that does not get enough air, this is called an anaerobic condition.
  2. Hydrogen Sulfide – Anaerobic conditions also produce hydrogen sulfide which smells like rotten eggs. Compost compaction increases levels of hydrogen sulfide in an active compost pile.
  3. Volatile Fatty Acids (VFA)Microbial decomposition under anaerobic conditions produces volatile fatty acids in the form of a vapor or liquid.

Compost Odors – Causes and Solutions

Compost Compaction – Be sure to churn and add bulking material to compost such as bark mulch, to prevent compost compaction which increases the level of anaerobic activity.

Low Temperature – Cold weather causes compost compaction.

Too much moisture – Plastic compost bins tend to build up excessive moisture, so if you have a homemade bin, make sure to allow proper ventilation by drilling holes in its sides.

Improper C/N ratio – The carbon to nitrogen level in a compost pile requires balance. What I like to do is have two barrels of “leveling” materials on hand. One barrel of browns (shredded leaves) and one barrel of greens (grass clippings) to mix in as needed.

If you are new to composting do not get too lost in the details, just remember the above simple tasks and you will get a feel for what works for you. Compost odor is the easiest way to determine if you are doing your maintenance correctly and remember, properly composted material smells earthy fresh.


Posted in News by admin on February 7, 2006.

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