I've started using ONLY espresso pucks on our poop trays (bc I have a lot of espresso drinkers in my house and a young adult son who sprung for a nice espresso machine!). I think it smells much better than normal used grounds and the consistency is great. I've read articles, used coffee still has quite a bt of caffeine, but they don't eat it.the pucks you should just be able to break apart with your hand. They are very finely ground coffee that had steam blown through them essentially, which makes them stick together a bit but otherwise pure coffee (VERY rare you will find me calling sbucks coffee so enjoy !! )
Aaron