I would think that given the amount of energy required be it wood, propane or other, it makes no sense to dispose of waste in this way. I believe the best method will be to keep liquid and solid waste separate. As long as your sewer is a gravity system you can put the liquid down the drain. This will get rid of that portion AND keep your J traps full keeping sewer gas out of your home. Disposal of solids will be dependant on personal living arrangement...IE country, city, time of year, current local situation.

JAB