The Amish use outhouses. Properly built — odor-free and fully hygienic.
Pit
1.5x1.5 m, depth 1.5-2 m. Reinforce walls with boards or stone — prevent collapse. Bottom — earth (contents compost naturally).
Cabin
Wooden, 1.2x1.2 m, height 2 m. Bench with opening. Lid on opening — keeps out flies and odor. Door with lock and window for light.
Ventilation — The Key
Pipe from pit upward (above roofline). Black — heats in sun, creates draft. Air pulls from pit upward, odor exits. Screen on pipe — against flies. This solves 90% of the odor problem.
Maintenance
After each use — handful of lime or sawdust (suppresses odor, speeds composting). When pit is 2/3 full — fill with earth, dig new one. After 2-3 years, contents fully composted — usable as fertilizer for trees (not vegetables).