I can't believe how long I used catsan for before changing over. Especially in the summer, you could smell the wee after a couple of days. I really think with Cats Best, it pays to be generous and fill the tray really deep so proper clumps form. Apparently, you can compost it - I tried flushing it but found it blocked the toilet so I bin it now. In the winter, it goes on the wood burner.