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Moist leaves & grass reached 150F (66 C) in only 2 days in a simple home-made insulated  composter.
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Compost Temperatures

Moist leaves & grass reached 150F (66 C) in only 2 days in a simple home-made insulated  composter.

I made an experimental compost system consisting of one trash can placed inside a larger trashcan with the gap filled with Styrofoam in order to reduce heat loss. The system was placed with its cylindrical outer surface on four casters so that the system could be rotated about a horizontal axis to promote mixing. The system was rotated by hand a few times a day. I also used a Styrofoam lid.

I charged the system with a mixture of garden leaves and fresh grass cuttings and added water to give enough dampness without making the material sodden. The inside temperature, measured on the axis with a long-stemmed compost thermometer, showed a rapid increase followed by a decrease, as shown in the accompanying graph. No chemicals were added, so the temperature changes must have been entirely due to biological activity. Possibly a larger apparatus would give higher temperatures.

Paul Parent told me that 140 deg.F is high enough to kill weed seeds.  

According to my information, oxygen is used during the first days of a properly-organized composting as the temperature rises. Then, during the cooling period, bacteria fix nitrogen from the atmosphere.
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