We now have compost toilets in four of our houses and I’m hoping to convert the regular ones into compost toilets over the next year or two. First off, I need to convince Khady and the other Senegalese here. For me, this is odd – they see compost toilets as being quite disgusting, whereas in actual fact there is virtually no odour, the compost comes out dry, crumbly and again odourless. Compare that to a typical African toilet that is often disgusting enough to make one wretch.
The typical system here is to make a soak away cess pit that the sewage pipe runs into from the toilet. In our case the builders stupidly ran the shower pipe into it as well, not realising the average westerner uses a heck of a lot more water whilst showering than the single bucket an African would use. The cess pit is a square or rectangular hole lined with concrete blocks and made into a cement chamber with some holes at the bottom for liquids to soak away. My builders proudly divided the shower side from the toilet side, although quite what the point of that is, I’ve no idea. As water levels in the ground rise and fall with dry and wet season, so does the water level in the cess pit. Sewage quietly rots away and an air-pipe allows any gas build up to be released. With regular use it should never fill and if it does, a chopped up chicken carcass can be added (flushed down the loo I presume) and the resulting decay introduces the bacteria required to break down the sewage.
The problem with this system is that plenty of cleaning products as well as soap/bleach etc are flushed down. Although we have situated cess pits far more than the recommended 20 metres from the well water source, there is a danger sometimes of cross contamination.
So, for these reasons I decided to give composting toilets a try. I’d experienced them at an eco lodge in the Gambia and had been pleasantly surprised by how little odour there was – in fact there was a mildly sweet smelling aroma. No water is required and one simply throws in some dry organic matter after you’ve been. We use wood chip collected in sacks for free from a local carpentry workshop. Every now and again we add ash from fires – this is good for killing any insects.
The design is simple. We make a low brick wall with two chambers. There’s a wooden top into which a toilet shaped hole was made and toilet seat attached. An air pipe leads up and out. The reason for two chambers and seats is as follows: you start on one side (half fill it first with your organic matter), then depending on usage a few weeks/months later when full, close it and move to the second chamber, leaving the first to compost. Angle the floor downwards slightly and have an outflow pipe for liquids at the low end. Run a pipe out the back. Dig a trench into which the pipe – which you can perforate, flows. Fill the trench with shells, pebbles or whatever you have locally, then plant bananas nearby which will go crazy in the nutrient rich soils.
Once the second chamber is filled, empty the first – we put this into a deep hole that we’ve dug, then leave this to rot for a further six months or so (add a bucket of water every day as well as any other compost if you like), before adding it to the garden.
There’s only one problem I’ve encountered here – Africans don’t use toilet paper – they find the idea as disgusting as we find the idea of using our hand. Instead, they wash with lots of water which can cause a problem for compost toilets. I’d be interested to hear from anyone that’s found a solution to this one.
I’ve leant a few lessons:
1. Put mosquito netting over the air pipe to prevent flies entering and breeding.
2. A black pipe outside heats up in the sun and creates a strong airflow sucking up any odour – before realising this there was a faint ammonia smell in the mornings.
3. Rather than make the tops of the two chambers the same with two holes and two toilet seats, make one solid and one with the hole, so you can swap and make it clear which side needs to be used. Seems obvious, but I didn’t think of it until I saw it at Footsteps eco-lodge in the Gambia.