The choice of a toilet was a tricky one.  I didn't want to be mucking around with chemicals, and "black" tanks of stinky gloop, so I started looking around to see what boaties used on their yachts.  I came across a composting toilet from the USA which used Peat Moss as the composting agent and the only high tech bit on it was a standard computer type 12v ventilation fan.

The 'trick' according to the supplier is to keep the liquids and the solids separate. If you mix them together you get a stinking mess. So this design has a catcher at the front for all the liquids, and a separate area for the solids underneath. This means that blokes can't wee standing up!!  You must sit down for everything, although if you are a man and you are camping you're much more likely to go behind a bush than anything else.

It is made of some lightweight resin material and all the fitting are stainless steel.

The tank at the front holds the liquids and can be emptied separately from the solids.

I built a false floor at the same height as the shower base for the toilet to sit on. Any water splashing from the shower will run back into the shower base.

By the way, the brand of the toilet is "Nature's Head" and this is a link to their website: NaturesHead

You can see the thick clear hose and a wire at the RHS back, which is the ventilation tube and the power to the 12v fan. The opening/closing flap which is under your bum obviously needs to be opened up when you're using the toilet, but it is normally closed to keep things a bit more airtight (and so you don't have to look down into the pit of poo!).  The 2 holes at the front are where the wee drains into the bottle at the front.

This is how it looks with the flap closed

There is a rotator on the side to mix it up, in the solids department. You start things off with 5Kg of damp peat moss, and every time you do a poo you give the handle a few turns to mix everything up.  When it fills up (once every 2 or so months apparently) the whole base unclips for emptying. I can bet that it's going to be MY job to do the emptying.....

And because the toilet is in the bathroom, I got a waterproof toilet paper holder.