ASU-Ask A Biologist-EXPERIMENTS AND STUFF

Composting

Microorganisms in action!

Get yourself a large pile of grass clippings (best results are a foot or more wide and a foot deep) and a thermometer (the kind with a probe at the end of a wire is the best). Start with fresh grass clippings and measure the temperature at the surface of the pile of grass and in the middle of the pile. Repeat your temperature measurements every day for 7 to 10 days and also record the appearance of the grass clippings. You should be able to detect a temperature difference between the surface of your grass clippings and the center of the pile. Which do you think will be hotter? How big do you think the difference will be? Where is the heat coming from to make the difference? Can you think of a way to test your answer? After a week or ten days, what seems to be happening to the grass clippings?

(Edward Birge, Associate Professor and Chair, Department of Microbiology, Arizona State University)