Incinerating toilets have been common to marine vessel applications for nearly a century and offer another alternative to the conventional toilet for reducing water consumption. They function by using a powerful electric furnace to incinerate the waste while venting to the outside. Human waste is mostly water and the remaining waste ash is very small in volume and completely dry and sterile. After as many as 50 uses, only a half-cup of ash may remain. At sea, this is simply flushed with seawater to the ocean but on land this inert ash can be disposed of by a conventional flush to the sewer system, put with conventional trash, or composted and dispersed to the land. Incinerating toilets offer the convenience of much reduced maintenance and much greater compactness compared to the more commonly used composting toilets and are better are reducing the residue of prescription drugs to inert material. They also eliminate the need for a leach field or septic system for urine and run-off processing. But this comes with the trade-off of requiring much more energy in operation, being much more expensive, and being fairly complex machines more prone to break-down.
The Utilihab Incinerating Toilet is a unit adapted from marine and industrial forms. Electric and propane fired versions are available as well as stand-alone units and multi-toilet central incinerator units which link conventional low-flow toilets to a macerator pump, blackwater storage tank, and central incinerator unit located in any convenient utility space with outside wall or roof access for venting. Aside from a roof vent, only cold water supply plumbing for a low-flush cycle is needed. This can also be supplied from a raised gravity-fed water storage tank. Operation is otherwise identical to a conventional toilet.
[Note: see EcoJohn brand incinerating toilets as possible off-the-shelf option]