I'm just on my first sack of Megazorb and think it's fantastic. Am a gardener too and a good by product of having buns is I can use it as compost, which I couldn'with sawdust or cat litter. I have 2 buns, with 2 litter trays each and I haven;t even got a third of the way through my sack but maybe I'm mean with it as I line the trays with newspaper but only use a handful or two of Megazorb.
Then again, I tip out the entire trays and disinfect twice a day (I have spare sets of trays so as one is drying, one is in the hutches). And I've not noticed any smell whatsoever. I reckon if it can absorb horse pee it can easily manage with whatever my buns are doing! I also lay some straw or hay and a little dried lavender over it.