Thermal Output of Decomposition


Scott Holloway


Can a compost pile spontaneously combust?  What is the temperature created in the core and on the surface of a compost pile?


Heat and Thermodynamics 

Energy cannot be created or destroyed, although in many processes energy is transferred to the environment as heat. 

Chemical Thermodynamics 

 Energy is exchanged or transformed in all chemical reactions and physical changes of matter 

Students know chemical processes can either release (exothermic) or absorb (endothermic) thermal energy. 

Experimental Design

Create two separate compost piles each made with different components and track internal temperature over time.

Independent variable

Compost material - leaves, sticks, sawdust, bread, soil and water.

Dependent variables

Temperature of the core of the compost pile


Compost pile with leaves, sawdust, soil and minimal water. (Compost pile A)

Compost pile with leaves, sticks, bread, soil and water. (Compost pile B)


2 - Styrofoam coolers

very dry leaves

small dry sticks

loaf of stale bread



6 - temperature probes


Build one compost pile in each cooler.  Place a temperature probe in center of pile, on surface of pile and on the outside of each cooler.  Record temperature daily.  After temperature falls, manipulate one variable in the compost pile to see what causes the temperature to rise again.

Sample data and graphs

Photographs and Movies