Thermal Output of Decomposition

Author(s)

Scott Holloway

Question

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

Standards

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

Series

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

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

Materials

2 - Styrofoam coolers

very dry leaves

small dry sticks

loaf of stale bread

soil

water

6 - temperature probes

Procedures

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

References

http://en.wikipedia.org/wiki/Composting

http://web.extension.uiuc.edu/homecompost/building.html

http://whatcom.wsu.edu/ag/compost/fundamentals/needs_temperature.htm

http://compost.css.cornell.edu/physics.html