Hm! We too use clay (because my god, after using pine I was so monumentally sick and tired of finding tiny bits of sawdust from one end of the house to the other,) and this is a good thought. I wonder about several things, however, such as whether or not airborne or waterborne pathogens would be a concern, and oh my yes, it would stink to high heaven. I've read some about composting cat waste, though. I wonder what principles would cross over, there.