- Describe what causes bad smells in compost
- Perform a smell test to evaluate compost
Decomposition in the composter is most active during the thermophilic phase when temperatures move north of 113 degrees. The bacteria, fungi, insects, and others are actively breaking down organic material to create that black gold. Or at least, that is what is supposed to be happening.
If the material in the composter gets too wet, too compacted, not aerated enough, or is degrading too rapidly that could “smell” trouble. A simple smell test will indicate a problem, usually marked by a sour smell, very sharp odor, or a whiff of ammonia. This is the indication that the composting process has gone from aerobic to anaerobic, creating the perfect conditions for the bad bacteria to take over.
It doesn’t take any special talent or years of honing your skill to make a proper smell test assessment. It will hit you in the face before you know it.
When the composter is balanced and the process complete you should be able to take a handful of compost, give it a sniff, and notice only a predictable earthy smell, like that of rich soil.
Teach the Teacher
Tools & Materials
- Earth Cube
- Disposable Gloves
- Sour smell
- Sharp odor
- Earthy smell
Introduction (10 minutes)
Begin the lesson by describing the various smell profiles that could be present in the composter. Explain to the class how those smells are created and the steps to correct it.
Activity (20 minutes)
Open the access port on the Earth Cube. Have each Student put on gloves and grab a handful of compost and give it a smell test.
Discussion (10 minutes)
Any discernible smells or odors? Are they good or bad? What do we need to do to remedy the issue? Make note of the condition of the compost and how it might affect the smell (ie. too moist, too dry, not hot enough, too much green material, etc.)
Assessment (5 minutes)
Use the following questions to assess the Students before and after the lesson. Tally the responses of the group in the Assessment Tracking Log for comparison:
- By a show of hands, how many of you think you can test compost by smelling it?
- Now that you know what to smell for, how many of you think you can use the smell test effectively for assessing compost?
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