Our cats are mostly outside cats. The boys (Hillard, Harry, Bullett, and Lorenzo) are definitely outside. Lorenzo cannot be trusted in the house at all, Harry is trained to go straight to the bedroom when he comes in. Bullett and Hillard seem to be ok but always go out when then need to go. The girls on the other hand seem to need to be in. Is it the privacy? Tabby goes in the box if it is clean but has intentionally gone on the rug. Adah goes in the box if one is clean and available. Otherwise it is unpredictable where she will go. As a result, we have shifted from clay litter to pine-bark mulch. We get the mini-nuggets. The regular pine bark is to large. And the ground pine mulch is too fine. There is too much track out even though it is more absorbent. With the mini-nuggets, cat can keep her feet clean and cover if she wants to without too much getting out of the box. Except for Adah who is too energetic with the covering.
We go through a 2 cu-ft bag per week. This is with changing each box after each use. To get rid of the stuff, I put it around the trees and in the garden. No need to fill up the landfill.