This is really quite a safe way of handling waste despite its unsavory reputation. It will last about 5 years for a family of five in full time use. A small handful of lime dumped into the cavity will do wonders to help the enzyme action. You just need to put it some distance from your well (if you have one), and place it downhill from your spring. When it gets filled up, build a new one. They are really quite easy to build, provided you stockpile the materials, or cut them yourself later.
You need a 4' x 4' x 5' deep pit. A wooden box (pressure treated if possible) must be constructed in the pit, leaving an inch between the slats for drainage. You make a reinforced 7' x 7' concrete slab with integral rings on the top and the sides so you can move it later. You build an outhouse building over it, with a toilet box, and a vent or ventilation slates in the sides of the building. When it fills up you drag the whole structure to a new spot and cover the hole over with fill that you took out to build it in the first place.