The main benefit of building your own is that you can do it cheaply, especially if you have the materials lying around already.

The basic DIY design has two chambers, but you can buy toilets with one chamber. We think the two-chamber model is better for DIY, because it gives the contents of each chamber at least a year to break down with no fresh material added. The new material will contain more nutrients, liquids, salts and ammonia, which means that worms can’t be added, and pathogenic material may be leached into the compost you are about to remove. A chamber is used for one year while the contents of the other one are decomposing.

A seat is situated on a platform over the chamber in use. The seat can be removed when the chamber is full and re-situated over the empty chamber; the full chamber is then sealed and allowed to decompose for at least a year. You could also have a seat on each chamber, so that it doesn’t have to be removed – but you’d have to make sure that you can’t open the lid of the one that isn’t in use.

There has to be some sort of hatch to empty the finished compost, a vent to take away odours and moisture, and a fly-catcher is recommended, just in case.

Our very basic design has no fans to remove smells and vapours, no electrical elements to heat the waste, no paddles or mixers to turn the pile, or to knock the top off the pile – and it works. There’s not enough room for a detailed description of how to build your own compost loo in this short guide, but you can find it in our book and online course.