Compost toilets do work. They are approved by NSF and plumbing codes. They do not need a septic tank to opperate. They are basicly odor free. I would say they are fully odor free, but any device for removing feces (including a regular toilet) is subject to ambiant odors. Some odors are left over after the use. All odors associated with the composting however are under a slight vacuum and kept from the room, by the design of the toilet and the composting process.
Check out www.envirolet.com