Lime is simply finely ground limestone. Hydrated lime is heated, which changes it chemically and makes it more reactive. Way back when, sometimes farmers made their own hydrated lime over big wood fires. Incidentally, hydrated lime is what's sometimes used in conjunction with portland cement to make concrete. I think mainly what lime does in the privy is dry things out and render the environment toxically alkaline. Without bacterial growth, you shouldn't get any odors. Lime is very, very cheap if you go to an ag place like the farmer's coop. There's not much cheaper out there than rocks. Steve Tyree In a message dated 8/19/2005 1:14:07 PM Central Daylight Time, penokee@cheqnet.net writes: I'm still wishing I knew what it was we used on the river trip. Not sawdust. I thought it did something chemically to dessicate the #2 or something. I do think it was lime or something in combination with lime. And I vaguely remember reading a murder mystery (or was it the book Helter Skelter years ago) wherein a corpse was dissolved with lime (see now we're really getting indelicate!), so maybe there's something to it, chemically. Or maybe the lime is now known to be worse than the original material you're trying to dissolve.