It's not perfect but if you're looking for a natural product to replace clay litter, I choose Yesterday's News.  It absorbs urine but doesn't clump.  Stir it daily to contain the smell.  Remove the "lumps" daily; more difficult since the litter is brown.  Replace it weekly (I have 2 cats.)  There is some tracking but the pieces are large and easy to find.  So what makes Yesterday's News better?  I tried Feline Pine (non-clumping).  Urine dissolves the pieces into powder which is tracked all over.  I also tried World's Best but the smell was uncontrolled.