Tom Rhodes, manager of the Mushroom Test Demonstration Facility, outlines the process of growing mushrooms.

Mix compost. Rhodes mixes up six to eight tons of straw-bedded horse manure, 300 pounds of dried poultry manure, 300 pounds of dried brewer's grain, and 300 pounds of gypsum.

Manage the pile's decomposition. The mixed compost is left in a heaping pile to begin decomposition. It is then turned three more times within a week by a large machine that churns the pile like a giant eggbeater.

Pasteurize the compost. Once the compost has reached a proper state of decomposition, the pile is transferred to a separate room to sit for 48 hours at 132 degrees Fahrenheit. Then it is pasteurized by raising the air and compost temperature in the room to 140 degrees F for 2 hours. It is then gradually cooled over the next five days to about 85 degrees F.

"Seeding" the spawn. The crew introduces mushroom spawn -- resembling grain pellets -- into the compost, a process similar to planting seeds into soil.

Growth. The mixture is placed in 4-foot-by-4-foot trays, covered by a layer of peat moss "casing." The mushroom trays are then placed in a succession of darkened rooms with controlled temperature and carbon dioxide levels as the crop grows and is eventually harvested.