Composting toilets can be expensive things if you choose to buy the fancy all-in-one devices. Most aren’t much more than a seperator seat to keep the pee and solids apart, with some sort of fan to dry the solids a bit, and keep any smells to a minimum. Usually pee is piped away to a container someplace. The good news is that you can put in a seperator for £30 and get yourself a bucket. Our own model uses just such an arrangement – the pee goes direct into a 2 gallon container which gets emptied every couple of days (soon it’ll be piped into something a bit bigger and outside); and the rest into a container which we line with newspaper and empty every 2 weeks. Just add sawdust as you go and there won’t be any problem with odours.
Technically its a compost loo, not a composting loo, as the composting takes place elsewhere – we have a very seperate plastic composting bin in which waste will sit for a good long time until it has broken down fully – the extra carbon in the form of sawdust and paper will take care of that.
The seperator and loo seat are screwed to a removable panel (above) which hides all the lovely containers. You do need to keep a close eye on the liquid levels, to prevent any potentially nasty overflows, but otherwise it is all pretty easy to deal with.
This is the first indoor compost loo we’ve made – the lovely outdoor ones are here  and we’ll be building a new one here soon to save folk always having to come into the house. Plus the view is going to be stunning, believe me.
Incidentally, we like our bathroom for other reasons, primarily that it contains so much recycled stuff. From the freecycled tiles on the wall, to the old cast iron bath from a house refurb in Belfast, to the sink that came from a garden, and the panelling made from old bits of roof joist.