A compost toilet is a dry or waterless toilet, i.e. one that doesn’t
use water to take the waste somewhere else; it also allows natural
processes to produce useful compost, after a resting period depending
on the type of toilet.
DIY compost loos
There are usually two chambers – one
in use and one resting. A typical toilet would use one chamber for
a year, then change to the second chamber and allow the first to
decompose for a year before emptying.
They don’t smell, as long as there is a vent pipe, and a drain
to take away excess liquid. A handful of a soak (straw or sawdust
etc.) is dropped into the toilet after each use. This is because
bacteria like to eat a balanced diet of carbon and nitrogen, and
as human waste contains a lot of nitrogen, if they don’t get
enough carboniferous material (like sawdust, straw, hay, shredded
paper) they will give off excess nitrogen in the form of ammonia,
which makes the loo smelly. Also, the soak allows oxygen into the
pile, and absorbs liquid. This allows the pile to decompose aerobically
to produce nitrates, phosphates and sulphates. Without a soak, the
pile will decompose anaerobically and produce methane, ammonia and
hydrogen sulphide – all smelly and not very useful.
Human pathogens don’t like conditions outside the human body,
so almost all will be dead after a few hours. Only one type of roundworm
egg can survive a year-long decomposition period, but even though
it is a tiny risk, we recommend using the compost on fruit trees
and bushes, not the vegetable garden.
off-the-shelf compost loos
You can also buy off-the-shelf toilets with
one chamber - for inside or outside use.
what are the benefits?
solid waste is dealt with on site, and doesn’t have to
be treated with chemicals in sewage farms, or end up in waterways
water – you don’t have to use one resource (pure
drinking water) to flush away another (fertilizer)
matter is allowed to go back to the soil where it belongs, improving
soil structure and nutrition
chemical cleaners or bleaches are used in the toilet
don’t contribute to the sewage sludge that is often dumped
in landfill, or more controversially, put on to agricultural
long as the decomposition is aerobic, there will be no greenhouse
low resource use – no pipes are needed to transport waste
to a sewage farm, and no truck needed to remove solid waste
can I do?
installing a compost toilet: there are many different
types that you can buy:
Separett or Air Head
: buy from our partner Eco-Toilets
- the Separett looks like an ordinary loo, and the Air Head is small enough to be used in a camper van or boat
small; electricity used to evaporate liquids; distributed in
UK by Eastwood Services - 01502 478165
make their own twin-vault loos with stainless steel urine separator
- or you
can build your own. This will work out cheaper, and there is no
need for electricity in a basic unit. The components of a basic
unit are two chambers, platform, vent, hatch, and removable seat. Our book explains how to do it.
Going on a course might be a good idea too.
a compost toilet: a compost loo is not a flush-and-forget
system. A DIY compost loo needs to be checked every day to see that no problems
are developing. If necessary, an ingenious fly-catcher can be made
from a glass jar and a little cone made from perspex. Ensure that
there's a bucket with 'soak' (e.g. sawdust) next to the loo. To
stop a ‘peak’ developing, it may have to be ‘knocked
every couple of months with a rake or hoe either via the hatch or
seat - this may not be necessary though. After the toilet has been
used for a year, remove the seat and blank off the hole. Attach
the seat to the second chamber. One year later, empty the first
chamber and move the seat back.
The procedure is different for various kinds of manufactured toilets. See here for a detailed, step-by-step guide to getting and using a compost loo.
- information, books, links, courses, etc.
of this factsheet (pdf)
outdoors? many people imagine that a compost toilet must be situated
outdoors, but if done properly, there will be no smells, and an
indoor toilet will be much more comfortable
in this case vent pipes from each chamber meet to vent any smells
above the gutter line
the Air Head
toilet is small enough to be used in a camper van or on a boat
emptying the chamber: after using the chamber
for a year, then allowing it to rest for a further year, it can
be emptied via a hatch. The texture and smell is the same as bag
compost bought from a garden centre