In case anyone needs to make simple composting toilets in a place that allows it, here's an update on the simple direct-drop outhouse toilets we have been using happily at a school in Ladakh for over ten years. We have 50 - 150 people residing at the school at a time, and each of these toilets serves 10 - 20 people. The climate is cold desert, and biomass is very scarce so traditional compost toilets have always been an important addition to field soil.
Ours are slightly improved over the traditional ones. They consist of a double chamber underneath, with a large single user's room upstairs. We use one manure chamber for a year, throwing a shovelful of cover material down after each use; and then in the spring we close the holes on top of the current chamber to leave it to compost, and empty the chamber that has been standing unused for a year.
The manure chambers are large, designed to fit cheap common doors, so they are about 3 feet (1 m) wide, 8 feet (2.5 m) high, and 6 feet long (though smaller would be fine for fewer people). There are two user holes above each manure chamber, to utilize most of the 6 foot length. We line the door with a plastic sheet from old torn greenhouses. Because we're on a hillside, access to the upstairs user rooms is from ground level uphill, and the manure emptying doors are at ground level downhill. We usually empty the chambers in winter or spring and leave the pile nearby for secondary composting before carting it out to the gardens and trees later.
About one in 10 chambers that we empty seem to have gone anaerobic and stink, so starting last year we've laid a perforated pipe at the bottom of the empty chamber protruding out the bottom of the door, and started with a few feet of dry autumn leaves. I hope that prevents this.
Cover material and additional items:
- The traditional local composting toilets simply use garden soil, kitchen stove ash, and barn diggings.
- Our garden soil is too sandy, so we bring truckloads of dry clayey silt from nearby once in a while. But if you use only clay, it will be very hard to dig out afterwards, so we mix it with organic material.
- Sawdust is available free in summer from lumberyards, but in winter local people pay for it as heating fuel. It tends to come mixed with shavings, which often don't decompose adequately.
- We use the diggings from the cowshed sometimes in winter, when smell won't be an issue. In summer it seems to smell; probably the combination with humanure makes it too nitrogen-rich.
- We have a wood-fired oven so we get a little ash that goes in from time to time.
- We feed all our food scraps to our cows. I wanted to put things that cows can't eat into the toilet: eggshells, meat-tainted food, mango pits and spoiled food, but local people find it repulsive to put anything food-related in the toilet, so we put those in the wood-burning oven instead.
- Toilet paper, newspaper used as toilet paper, other waste paper, and tampons all decompose without a trace. We do have to pull out lots of plastic liners of sanitary napkins from the compost; cultural norms mean that our girls won't do it if boys are in the area, so we've had to separate the emptying of the toilets for boys and girls.
- I went a little compost crazy and threw some old worn out jute mats and gunnysacks down, crumpled in the bottom of a newly used chamber. They didn't decompose very well, and when we removed the compost after two years, they were soggy and black, and not nice to remove.
We haven't had excessive fly problems but there are some flies, so we have added simple fly traps. Drill a one inch (2 or 3 cm) diameter hole in the manure removal door and attach a large clear plastic container outside. Put covers over the user's holes when not in use, so the flies see light only from the fly trap. They fly towards the light into the plastic container, and don't want want to go back into the dark, so they stay there and die. It doesn't get 100% of them but it does catch quite a lot and reduces the number flying around.
We put a sign in each toilet with a paragraph about how composting toilets are eco-friendly and don't waste fresh water, etc., and how to use them. I also made a poster of the Nutrient Cycle cartoons from the Humanure Handbook and put it up in the toilets.
If I were to design these toilets for a private house, I would make the manure chambers just as tall (6 or 8 feet) but much narrower. The three foot width and 6 foot length means that a lot of the cover materials falls to the sides, and there is always a mound in the middle. If the chamber were narrower, the cover material would cover the deposits better. It might be good to put a perforated pipe standing up in the corner of such a tall narrow chamber.
We have added a seat over the hole in one toilet, but local people mostly prefer to squat. We made a seat out of wood, very heavy and stable. Later we made one by cutting a hole in a plastic outdoor chair with a soldering iron, and covering between the front legs with a sheet of metal to prevent splashing.
It's rather a lot of work to empty the toilets once a year in the spring, a half or whole day of work for an average of ten to 15 people at a time. But it's worth it to get the compost and not to waste any water in this desert, and even more, for our students to see why we prioritize it and don't install water toilets.
You can see more about our solar heated and solar powered campus at www.secmol.org
PS All praise to Joe Jenkins! Thanks for the books you sent to our library!