What I can put on the ground of a dirt basement to absorb cat smells?
I’m not sure I entirely understand your situation. If your cats are using your basement as a litter box, it’s going to be extremely difficult to manage. You can cover the floor with baking soda or clay litter and it will absorb the odor, but you’d still have to clean it out very regularly (every few days) or the smells will overwhelm whatever you throw down there. Eventually their waste will finish decomposing and stop smelling, but that could take weeks or months. What you could do is put an ozone air purifier down there if the basement is properly enclosed. That will kill the odors pretty effectively. If your basement is large, you might need more than one. But the best solution is to not let your cats use the basement that way. Either train them to use a litter box which is easier to clean, or make the basement floor unappealing buy covering it, at least with some kind of plastic tarp so that they won’t be tempted to use it. I’m not sure this helped, but good luck!!