Last fall I built one with only hay. It turned out okay. It needed to be more consistently moist. You can really add any organic matter to them. The microbiology will “digest” the organics and in turn you receive a high quality compost.
Discussion
So am I just looking at lined wire mesh with vented pipes in the middle for airflow? Keep moist, and any organic matter I add will degrade into compost? (Leaves, sticks, shavings, etc?)