This is the reason I do not keep big herbivorous tortoises any more. The droppings are huge (about the size of a house-cat for a 15-incher), they smell sort of bad, but most importantly they get smeared all over an indoor enclosure by the plastrons, where they become hard as cement on both the enclosure and the tortoises. (Outdoors, which for me means the summer, no problems. Indoors, a huge headache)
A partial solution is to keep them on Dri-Tek tile indoors(used in restaurants, etc. to keep personnel off slick floors) which you hose down daily, or get used to the idea of buying hay by the bale, and then mucking it out like a horse barn.