The composting toilet is a custom built one using the principles of providing a large area for the solids (i.e. shit) to spread, a continual movement of air to assist in the decompostition process and a seperate area for liquids (i.e. piss and runny shit) to accumulate and evaporate. 

The end result is a fibreglass box built around a bastardised Thetfords cassete style toilet. 
 
A fairly hefty piece of stainless steel mesh provides the base for the crap to sit on and a 12 volt computer fan runs continually to draw air over the pile and the pooled liquid and blows the smelly air out a rooftop stink pipe.

In this picture, the computer fan is inside a flange in the PVC pipe and is just out of sight on the top left of the picture.
The exhaust vent for the waste gasses  folded flat for travelling and extended while we are stationary.
The sides and back of the compost toilet were created with ply then all the inside was fibreglassed.
The chequer plate outside cladding then went on with inspection hatches included to facilitate the removal of solids and liquids when nesessary.
Photo showing the plywood and fibreglass box before the modified Thetford cassete toilet was fibreglassed onto it.
The almost finished toilet - it just needs some more fibreglassing on the outside to pretty it up and to further water proof it.
Di gives it a "test drive".