A self-contained composting toilet quickly separates and evaporates the liquid/water component, and composts the solids.
The Sun-Mar Excel NE, a well-known brand and model of self-contained composting toilet, this one requires no electricity. Other models, for AC or AC/DC operation, are more efficient in evaporating liquid. List: $1,695. Sounds great, but there are some detractors who criticize price and performance of this and other brands of similar units.