An avid gardener composts her wastes near the back of her property, away from her house. She moved the compost heap out there because it sometimes heats up enough to smoke. When asked why it heats up so much, she answers, simply, “Because the second law of thermodynamics says so!” How does the second law of thermodynamics explain her compost smoking?

Question

a. Gardeners will often set their compost heaps on fire first to accelerate the rate of decomposition. According to second law of thermodynamics, ash and carbon form and smoke is given off.
b. The second law of thermodynamics says that energy in a system is always increasing. This increase in energy includes the energy in compost heaps. As the energy increases, heat is produced.
c. The breakdown of compost involves a transformation of energy from chemical bonds in the decomposing organic matter. The second law of thermodynamics says that there is no 100% energy transfer, so some of the energy is lost to the surroundings as heat.
d. The gardener is incorrect and her garden compost heap has nothing to do with the second law of thermodynamics.

Answer 1

c. The breakdown of compost involves a transformation of energy from chemical bonds in the decomposing organic matter. The second law of thermodynamics says that there is no 100% energy transfer, so some of the energy is lost to the surroundings as heat.