Building a Basic Compost Toilet

by James Reid

Geoff-Lawton-Online

Humanure, which one is it — embarrassing waste product or invaluable, free fertiliser? Heh, what do you reckon?!

The human body has within its waste products (faeces and urine) pretty much all the suitable nutrients needed to help grow the food we need to keep ourselves healthy and well fed. Everyday we produce this free fertiliser and flush it down the toilet when it could be being collected, managed correctly and transformed into truly amazing compost. Right now most of us live within a broken loop consisting of:

chemical fertilisers — grow food — eat — discard — pollute…

… when, with the aid of systems such as composting toilets, we could be in a closed loop of:

humanure compost — grow food — eat — excrete — compost (and round and round it goes).

I could talk more of the amazing facts and benefits of humanure but I’ll save that for another time and instead go into detail of what composting toilet system we currently use here for the volunteers that visit our site in Scotland.

Late last summer I decided to register PRI Tap o’ Noth as a WWOOF host site as I realised just how many extra hands were needed to get this place up and running. Knowing that I was going to have volunteers visiting throughout the year I thought that it was time to spruce up the static caravan that I inherited with the property and get it ready for eager WWOOFers to call it home during their stay with us. That meant improvements to kitchen, sleeping and living spaces and also the toilet. There was a horrible old chemical toilet on board which is not the sort of thing that is wanted around here, so, with great glee, the first reason and opportunity to build a compost toilet arose!

Over the years I’ve had many an idea and plan of what type of compost loo construction I would like to build — wheelie bin toilets, tree bog, etc., etc. — but for the caravan it was decided that a simple yet effective (and quick with the first WWOOFer arriving soon) toilet design was needed. I got myself a copy of the classic ‘Humanure Handbook’ by Joseph Jenkins which became my bedtime reading for the next few days and, once I realised that I had most of the construction parts needed around me, I set about building the Jenkins style bucket system toilet. This is a simple design which uses a 5 gallon plastic bucket housed in a wooden box to collect the ‘waste’ (resource). It is treated in the same way as other compost loo designs in that, once you have been to the toilet, a scoop of saw dust or other suitable carbon-rich material is dropped on top of your deposit. Once the bucket is full (which of course all depends on how many users there are) it is removed from the wooden box and taken to a specially designated humanure compost bin (more on that below) where it is emptied, the bucket contents covered and the bucket washed out, cleaned and returned to the box.

So, following the helpful design found in the Humanure Handbook, I began the job of making the wooden box which houses the collection bucket and of course the toilet seat. Luckily I had all the timber needed just lying around the farm and quickly measured, cut and screwed the box together. A hinged lid was then made and fitted to the box with a circular hole for the bucket to fit through. For the bucket I decided to sacrifice one of my fermenting buckets as it was the right size and good and sturdy (also has measurements on the side which, who knows, may come in handy?!). Then any normal toilet seat can be attached to the box and – ta-da! – a ready and waiting compost toilet.


Box made and hole being cut


Hole cut and bucket ready


Toilet seat attached and ready to use


The finished toilet in place in the van

The Humanure Hacienda, or, in our case, the Humanure Hovel


The humanure compost area (cover material bay on the right, in- use compost bay on the left)

 Right. So your bucket is full of humanure and there is a WWOOFer jumping from foot to foot outside the toilet door desperate to get in. It’s time to empty… the bucket.

But where? Well, you don’t want to just put the bucket load into your regular garden/kitchen waste compost bin as humanure contains a lot more possible nasties than regular compost ingredients and needs to be left alone to compost down, possibly for up to two years in this climate. So, a dedicated humanure heap is needed. Jenkins’ book has a design he has called ‘the Humanure Hacienda’ (again, check out the book for plans). I roughly followed these plans, building again with reused materials and came up with a ‘rough around the edges’ version I call the Humanure Hovel. It’s essentially a compost bin (in my case made from wooden pallets and corrugated iron) with an attached ‘cover materials’ bay which is roofed to keep the cover material (straw, woodchips, garden waste) dry, but also to collect and divert water to a water butt to then wash out the collection bucket (the wash water returned to the heap too).

The bucketload of human waste is emptied into the middle of the heap (which already has a generous layer of cover material acting as a biological filter) and then a fork of cover material is added on top of your bucket load. Just like any other compost heap your humanure heap is left alone to compost down when the bay is full to the top. Another bay can be added to the system and the process starts all over again. Fast forward a year or so and hopefully you should find that the humanure has turned into amazing rich, full-of-worms compost which can be added to the soil beneath food trees and shrubs (it is recommended by some that you avoid using humanure compost on vegetables).

So where are we in this process? Well, we have had a handful of volunteers using the compost toilet in the caravan since it was built late last year and so far have almost filled one bay. This has happened quite quickly and I think maybe folks have been adding a little too much cover material (both in the bucket and in the heap) in the misconception that you need a lot of material to mask any odour or hide their embarrassment! So far we’ve had no complaints from users and only a few raised eyebrows from onlookers who have not given it a go yet. Yes, it is a simple and no-nonsense in-your-face design (it’s a bucket that you shit in and empty!) but it really makes you aware of just how much ‘waste’ (resource!) we make and that this ‘waste’, that we usually flush down the toilet with a bucketload of drinking water and forget about (and let someone else deal with), is in fact an amazing growing medium that we can use to improve and build soil.

Plans are already afoot to build another compost toilet, this time an outdoor building close to the caravan. I’m interested in the idea of a Tree Bog and hope to have one or two of these built before the year is out. For now we’ll keep the bucket system running as, with most simple designs, it works a treat and certainly makes you think about your waste (RESOURCE!).

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5 thoughts on “Building a Basic Compost Toilet

    1. I’ve read most medications will break down to their components in a composting system and be greatly diluted anyway. These things usually get into your permaculture system via animal and poultry manures and composting of bought foods as well.

  1. Nice job. Here is another suggestion. Use a urine diverting seat, and drain the urine (it is sterile) into a small pit outside, or even into the gray water system. Put a 12 volt fan (about 3 watts) on the box, and exhaust it outside the building. This sucks air into the toilet, dehydrating the contents rapidly, and exhausting moist air out of the building. Now, once poop starts to dry out – it loses all odor. It shrinks drastically, increasing capacity of the bucket. Line the bucket with a compostable plastic bag, and emptying becomes a very quick job, not unpleasant at all. You will not have to add any organic matter whatsoever (also greatly increasing capacity). A deep cycle RV battery and small solar panel will suffice for the electricity.

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