If you want to build your own compost toilet there are a few options. A pit latrine compost toilet is the cheapest, simplest, easiest option and suitable for a small group of people to use.
In this composting pit latrine design, when waste has filled the first pit, the latrine is moved over the second pit. The first pit converts to compost and can be emptied to fertilize fields. Credit: E4C Solutions Library
A pit latrine generally consists of three major parts: a hole in the ground, a slab or floor with a small hole (aprox 25cm) with a toilet box / seat over it, and a shelter. The pit is typically at least 3 meters (10 feet) deep and 1 m (3.2 feet) across. The distance from groundwater and surface water should be as large as possible to decrease the risk of groundwater pollution. When the pit fills to within 0.5 meters (1.6 feet) of the top, it should be either emptied or a new pit constructed and the shelter moved or re-built at the new location.
A basic pit latrine can be improved in a number of ways. One includes adding a ventilation pipe from the pit to above the structure. This improves airflow and decreases the smell of the toilet. It also can reduce flies when the top of the pipe is covered with mesh (usually made out of fiberglass). Other possible improvements include a floor constructed so fluid drains into the hole and a reinforcement of the upper part of the pit with bricks, blocks, or cement rings to improve stability.
Here is an advanced pit latrine with urine divider. This twin-pit VIP latrine system offers a long-term solution as the compost can be dug out at some stage without having to move the whole toilet. The urine divider
Ventilated Improved pit latrines receive excreta in the same fashion as those of the simple pit latrines, by direct deposition through a squat hole or a pedestal seat. The liquid part infiltrates into the surrounding soil and the faecal solid are digested anaerobically, gradually accumulating and eventually requiring emptying the pit for further use.
Importance of urine separators:
Too much liquid means the compost will go anaerobic (lacking oxygen) and different bacteria will result. These bacteria give off methane and other offensive smells and make the whole process very unpleasant! A urine separator is the answer, thereby diverting urine away from the deposit container. These are more easily used by women than men as they are generally designed for the sitting position. However men can aim more accurately but do have to be instructed/educated to do so! Either that or sit down to pee. The male pee issue is important as too “meny!” will result in anaerobic conditions, so signs/instructions/alternative urinal facilities are essential. It’s really a cultural thing which we all need to work at, especially the boys!