A heap heats from inside. The outer layer stays cool and the core can go anaerobic. Turning moves the outside to the inside and lets air back in.
For the long method ICAR-DMR turns on day 6, day 10, day 13 with gypsum, then days 16, 19, 22 and 25, and fills on day 28: 7 to 8 turnings over 28 to 30 days. The short method runs outdoor Phase I for only 10 to 12 days before a tunnel, and the bunker method finishes in 6 to 8 days with forced air.