The initial use for composting toilets was for houses in Scandinavia. The toilets allow waterless and low effluent systems to be put into locations where water based septic systems or aerated treatment plants are required, with much higher water requirements and the requirements to treat quantities of sewage.
The best composting toilet systems for houses with permanent residents is the large tank systems as these do not overload if the house experiences larger than normal regular use, or the shock loading of parties.
The systems are best designed into the plans of the house so that the best use of slope is obtained. Alternatively, a cellar is required as the systems gravity drop the toilet wastes.
It is also important to consider that without greywater going into a septic system, there is needed a greywater treatment system in the house design. This has much les loading than a septic system effluent system and there are a variety of innovative designs available to re-use the household greywater.