One of the things that many people find yucky about composting toilets is the fact that one is basically sitting on top of a box of poop. Different companies deal with this in different ways; Envirolet has a trap door you operate with a handle to hide the stuff. MullToa has a clever toilet seat that opens doors when you sit on it. Sun-Mar has a step because you sit up really high.
The Australian company Nature Loo has a different approach; their composting unit is separate from the toilet and is installed in a space at least 2'-4" below the floor. It is a really simple system without trap doors or moving parts:
Nature Loo’s split-system composting toilets are batch process toilets which come with at least two composting chambers. Fill one, put it aside to continue composting, and put the second chamber into use. When it’s time to change chambers again, the contents of the first chamber should be well and truly composted. You then remove the compost, put it on your garden or bury it, and re-use the chamber.
This is a a wonderful feature if you are using the toilet continuously. But even with all that distance between the person and the poop, they advise in their FAQ, when asked "Can I see the compost pile?"- they answer "it is best to not position a light fitting directly above the pedestal."
Like most composting toilets, it has a fan to ensure that air is sucked down through the toilet and out through a stack to eliminate smells. Unlike any others I have seen, it actually has a battery backup for the fan in case of power failures. It is a really simple system, really Clever stuff from Nature Loo, which unfortunately does not appear to be available in North America. Found in Renew Magazine.
In my recent review of composting toilets I showed a couple of versions of North American composting toilets that have separated the bowl from the composting mechanism, so that at least is available here.