WarMovies, if not for the water... the portable toilets in RV's and many travel trailers are a small form of vault toilets. They both hold the waste in a container until pumped/dumped out.
We are holding our annual local geocaching event this April at a new park here in Louisiana, that they say has the first composting toilets in the state.
I'm interested to see how this goes, as there may be 75 people at this thing.
Do you have any experience with these kind of composting toilets?