Listing of bacterial classes common to composting. (View information on composting organisms.)
Psychrophiles are bacteria that flourish at low temperatures. These bacteria prefer temperatures of approximately 55 degrees F, and will slowly decompose your compost even at temperatures of 0 degrees F.
Mesophiles are bacteria that thrive at temperatures in the 70-90 degrees F range, and survive temperatures of 40 degrees F to 110 degrees F. These aerobic bacteria do most of the work of decomposition.
The work of decomposition raises the temperature inside the pile. When it's too hot for the mesophiles, the thermophiles take over.
Thermophiles are bacteria that work in the high-temperature range from 104 degrees F to 200 degrees F, but prefer temperatures of 105–140 degrees F. The high rate of decomposition will turn the mixture of organic materials in your pile to a uniform deep brown color.
Thermophilic activity quickly raises the temperature in the pile to levels that kill most weed seed. In the home composting arena, we look for three to five days with pile temperatures of 131 degrees F or higher to manage weed seeds. By turning the pile, you can introduce fresh oxygen to support the aerobic activity and expose all organic material to the high seed-killing temperature.