Project 6
Compost Toilet (2010)
Summary and Lessons Learnt
A simple yet effective design for catching wasted nutrients and saving wasted time in the garden. This
project has been a talking point during Open Days and greatly improved the rhubarb and currants but
has not been taken up by the family other than me, so some work to go fully integrating it into the house
system is required. As a design it fulfilled my brief, but not the families so it was good learning
experience on how to accept feedback and PR permaculture!
Ethics
Earth Care- The motivation for this design was to create a sustainable alternative to a flushing toilet for
use when in the garden, to catch nutrient, especially nitrogen from urine for fruit crops.
People Care- This has improved my efficiency when working in the garden and is pleasant and satisfying
to use! Not sure the family would agree!
Fair Share- A real talking point and opportunity to share my knowledge if not my urine! Abundant fruit
crops appearing will be shared in the form of jams and fruit wines however.
Criteria and Principles Demonstrated
The framework for this project documentation came from thinking about Holmgren’s Principles and
applying them to the design process and thinking that evolved over time. The main principles
demonstrated include Accept Feedback and Self-Regulation, Obtain a Yield, Catch and Store Energy,
Produce No Waste, and Observe and Interact. The design required periods of Observation and
Evaluation, and has been a Rolling and Incremental design.
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Compost Toilet Design by Alison Ensor
Compost Toilet
A handy outside loo to stop me having to go back to the house when I’m working in the
garden had been on my wish list for some time when I started this diploma. Walking back to
the house for a pee takes a few minutes each time but it’s a distraction and I often lose
momentum and start doing some house job instead. I have been peeing in a bucket in the
polytunnel as neighbours walk past which is not good in a relatively see and hear through
polytunnel!
I’m also very conscious of the wasted nitrogen leaving my permaculture circle. My newly
planted willows have been very slow to get going when left to their own devices, despite
being mulched and watered, probably due to my rather sandy soil. So I thought maybe I
could utilise the unused resource of my own personal waste. I like the idea of a bottle of
urine as a liquid feed for my hungrier summer crops too.
Having just got rid of my compost bins to practice composting kitchen and garden waste
directly on the soil I was not keen to be handling buckets of unpleasant stuff in another
separate composting area, so I wanted a very low maintenance in-situ set up. It also had to
be odour free and pleasant enough not to put off the rest of the family as I wanted to use
this as an experiment for developing a suitable system for inside the house. I’m quite happy
to save my morning ablutions until I’m down the garden letting the poultry out each
morning but the rest of the family are not that excited about the idea for some reason.
So as this is something of an experiment, I’m loath to spend much if any money on the
whole thing until I have some idea whether the design is feasible or will actually be used!
Requirements Summary
 To provide a handy garden loo
 Collect urine for fruit/veg fertiliser
 Provide nutrient for willow fuel crop and basket weaving materials
 Low cost, waste materials at least for trial
 In-situ system, ie no separate composting area
 A pleasant experience to entice the family to use it hopefully!
 Provide learning experience to develop a design for an in-house system
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Compost Toilet Design by Alison Ensor
The Design
The most obvious choice to meet the above was to build a compost toilet with a urine
separator, that required no handling or moving of the dry material. A tree bog perhaps? But
I didn’t fancy building a large raised platform which would require more resources than I
currently had. So I have adapted the tree bog idea to be more like a garden privy, where by
the whole set up is temporary and easily moveable to a new position.
‘The Garden
Throne’
The structure sits over a 60cm hole in the earth. After each year the whole structure (which
is lashed rather than nailed together) can be shifted along 1 metre and willow planted over
the newly capped hole beneath.
The grass beneath the floor will have been killed by the light exclusion from an old butyl
pond liner, allowing the willow to get away without competition when planted surrounding
the previous year’s hole. The butyl liner will also prevent the pallet and box from rotting
from ground moisture or splashes from the toilet, and allow cleaning. I’m hoping it will also
prevent flies accessing the pit but observation will show if this works.
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Compost Toilet Design by Alison Ensor
Trellis on the rear may make the whole structure look prettier but time will tell if I can grow
any annual climber up this north facing side. I shall make trellis from grown willow if
possible.
I thought perhaps a hand washing system might be useful using captured, filtered rain
water, accessed by lowering the tube from the overflow pipe. Painting the plastic bottle
black will prevent the water from turning green and might allow some solar heating of the
water in the summer (when the loo will be most in demand!) In freezing weather I’m not
usually down the garden. If the roof fails to catch enough water, rain water from other
butts can be used to top up the bottle.
Principles Employed in the Design Process
This design came from observation of my behaviour and thinking about the materials I
had to hand and the most suitable location. The design also evolved over time through
trial and error. Using Holmgren’s Key Principles as a framework has helped me to
understand and document this journey.
Observe and interact
For 6 years I’ve observed my walking up and down the garden to have a pee and found it
frustrating as a waste of energy and focus.
Digging pits for clay in this area (for the clay ovens) I’ve noticed that the soil is very sandy
for the first 50-60cm and then meets a kind of sandy clay and even after heavy rain there
does not appear to be a water table at this depth. There is no water course nearby.
My intention is to observe how quickly a 60cm pit fills up and if it is not full within one year
then I can dig a shallower hole next time. The 1 year cycle would be ideal for the purpose of
establishing new willow each spring.
The structure is only lashed together to enable easy movement each year but I built the
structure for several weeks before I furthered the design to check its durability and it
happened to withstand some severe SW gales. Time will tell!
The site I have chosen faces our hedge and the rear of a neighbours stable block which is
never accessed except for when we maintain the hedge, so it’s pretty private. The area in
front of this hedge is pretty poor for winter crops due to lack of light (shading from the
stables in low sun months) – so as only half productive land I thought I’d give it over to
willow.
Catch and store energy
Clearly the whole purpose of this design is to catch the fertility from my pee and poo and
enable me to catch more energy from the sun in the form of willow and comfrey biomass.
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Compost Toilet Design by Alison Ensor
The structure also catches rainwater from the roof and saves my own energy from walking
back to the house.
Obtain a Yield
I’m getting a fertile pit every year, a bottle of liquid feed every fortnight perhpas, willow for
fuel every 3 or 4 years, willow for basket weaving and next year’s planting once a year. I’m
also getting some peace and quiet down there!
Self-Regulation and feedback
This system will only work if I choose to go outside, rather than use the house loo.
Integrating a house composting loo (which will be a bucket type) will require more selfregulation on my part(guess who will be emptying the bucket) and some on the part of the
family to actually use it. To enable the integrated system to work will mean me taking note
of all feedback and adapting accordingly.
Renewable Resources
The building materials for the structure are all recycled waste, except for a previously
bought plastic flat roof sheet, unused from the previous house (about 10 years old, a great
testament to my hording wisdom) and a bought plastic toilet seat with urine separator (on
ebay). I tried adapting a plastic bottle to collect urine but failed to catch anything. This seat
is weather proof, hygienic and an effective wee collector – and can be reused in future
iterations of the design if needed. Even the plywood box for the seat started life as a duck
house!
Produce No Waste
The system is made from waste materials and turns a previously unused ‘waste’ into lovely
willow and food crops. I’m also saving the water that would have been used to flush the
toilet each time I go.
Multi-Functional design
The main functions of the design are to provide a private toilet area for the garden and
capture nutrient for willow and veg production. The design also provides a hand washing
facility and potential vertical growing space. It could also act as a place to dispose of dog
waste in a more useful way than the current hole in the ground in the garden (which is too
shady for willow planting). In the future it could act as a teaching resource for potential
course attendees and at this point in time it’s a learning resource for me and my family!
Relative Location
The location of the toilet within the main veg area serves the purpose of saving time whilst
gardening, and fertilising a future willow coppice spot. The site is walked past every
morning when opening up the geese, so is ideal for capturing the moment! Its location
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Compost Toilet Design by Alison Ensor
behind the neighbour’s stables means it is secluded and wind protected and also downwind
of the seating area next to the pond, in case there is any smell problems.
Implementation Diary
September 2010 – Main structure built from reused pallets (originally intended for new
compost bins) and nylon string for easy untying. Trellis thing not going to happen!
October 2nd – survives major storm. Extreme winds failed to blow it down, very pleased
with design and placement in lea of neighbours building.
October 8th – Design completed apart from hand washing part. Using small amount
rainwater collected from roof, to rinse separator part of loo seat to prevent slight smell. OK
other than that.
The pallet structure is lashed
together (so I can dismantle easily
if need be) and is lined with old
carpet, looks a little rough but
strong! Open side facing private
hedge and the stable block rear.
Seat with urine separator and pipe
leaving left to bottle – see above
Hand washing tube inserted in overflow
blue pipe. Filter basket can be just seen in
top of black bottle.
October 20th –
First full bottle urine/water filled, emptied onto compost bin
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Compost Toilet Design by Alison Ensor
November 4th –
Second bottle full – approx. 4 litres per fortnight. Overflow to hand water working Ok but
careful not to push too far down pipe as you get a syphoning effect. No problems with
smells or any sign of flooding in pit.
December 2010 –
Severe snow and cold weather meant I have not been using the loo. Also the geese have
been transferred to the freezer so I am not walking this way every morning which means a
special journey is needed, not inclined if very cold or raining.
January 2011Weather still off putting , miserable and wet. Either I move the toilet closer to the chickens
but not keen due to privacy issues, or I need to introduce internal compost toilet to
augment the outside design. Preferred idea!
February 2011Using toilet again occasionally and structure still sound despite a winter of bad weather and
recent severe gales. I have decided to augment the system with a new toilet in the
bathroom, to increase nutrient capture for the coming growing season. Also have planted
several new trees and could do with the compost/feed to get them off to a good start.
Improvements on Design
April 2011
After 7 months of regular use the hole is only about 2/3rds full but I have some willow
saplings that I want to relocate so I need to move the toilet on this spring. Also, after talking
with my husband about why he’s not using the outside toilet I’ve decided to rebuild to
make it more ergonomic for his size, as currently it’s not comfortable for him being too low
and narrow (but perfect for me!). I’ve been saving bits of old shed and materials so it is
relatively easy to dismantle the temporary pallet shelter and build the new one above the
new hole.
June 2011 - New build loo finished
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Compost Toilet Design by Alison Ensor
The structure has been made more solid with sections of shed and taller and wider to allow
for my husband, though he still is reminded to sit with a slight head height restriction. The
whole structure looks more like a small shed so less ‘challenging’ for visitors to view and
even use occasionally! The roof has been made from off cuts of polycarbonate roofing
saved from the greenhouse project, so is very strong and windproof.
Note : - this picture was taken in October after this new design had been up 5 months.
There are 2 willow plants and 1 poplar planted around the old hole but the only one doing
well is the poplar. Other willow planted near the duck pond and in receipt of much more
water as a result has grown 10 times better. I have a feeling that this area close to the
hedge line is rather too dry for the willow even with regular watering of diluted urine. I
intend to trial more poplar (again grown as fuel crop) instead of willow in this spot when I
move the loo along again as it seems better suited for the conditions .
Also I intend to get rid of the water capture for hand washing as this has never been
successful (there is so much bird crap on the roof I rather not wash my hands in it!) and the
unit clogs with algae. I therefore intend to catch rain water from the roof and pipe it
directly to the coppice area- which probably means changing the guttering to the other side
of the structure and hence the direction of the roof slope!
Design Update 2012 – Just angling
the floor very slightly has enabled
run off from the roof to water
poplar sapling directly without any
need for guttering!
Notice urine collecting bottle.
Internal Compost Toilet Design – The Bathroom Box!
After the experience of winter but buoyed up with the thought of even more urine to help
my saplings get going, the internal compost toilet came even more of an interesting
prospect to get off the ground. The house offers no option for a permanent ‘drop through’
to a composting chamber type set up, so this trial was always going to be a ‘bucket and
chuck it’ variety.The design is as simple a urine separation system as I could make.
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Compost Toilet Design by Alison Ensor
The box will fit into our upstairs bathroom and is made from 9mm ply plus the same plastic
toilet seat as was used in the outside toilet design. This has proved very accurate at
collecting urine and is easy to clean –the whole seat can be lifted off in this design (along
with urine pipe) which means I can clean it under the bath tap. The only drawback is it
comes without a seat lid so I have made a box lid out of ply to fit over the entire seat,
including the gap at the seat base, to prevent flies getting in. I may decide to make the
same kind of lid for the outside toilet if flies prove a problem in the summer months.
The urine is separated off into a collapsible water container which is see-through so that I
can easily lift the hinged lid and see if I need to empty the urine bottle. The box allows easy
access to remove the bucket and/or urine container. The bucket will be emptied into the
hole of the outside compost toilet which is easy to get at by moving the outside toilet ‘box’
from off the hole in the pallet floor as this is not secured down.
The completed bathroom box – the jug of
water is to ‘flush’ the urine collection
section and hose after each wee otherwise
it can start to smell in warm weather.
Close fitting lid sits over the seat and
makes whole thing very discreet!
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Compost Toilet Design by Alison Ensor
Implementation Diary
April 2011
Using the internal toilet most of the time though still not convinced children – bucket needs
emptying about every 5 days to stop smells which do build up after this time. I’m emptying
the bucket into the outside toilet and this seems to be OK . Sprinkling urine on straw mulch
beds to encourage faster breakdown and feels better than just watering around fruit
bushes/trees.
Empty wee container every week – getting upwards of 5 or 6 litres a week
August 2011 –
Only using internal toilet for wee’s- Proving too smelly for number 2’s even if emptying
every third day which is a bit of a faff. Probably not using enough soak (loo paper and
cardboard) but the emptying itself is a nuisance and I’m just as happy using the outside loo
every morning. Still no sign of child use except once in an emergency during a house party
when all toilets occupied! Collecting masses of wee though and think runner beans love it!
Winter 2011/2012 – not using at all due to fact I have no need for urine in the winter
months. The outside loo captures enough to keep the compost bin active and to add to
straw mulch to encourage nutrient breakdown. Also still using outside loo first thing when
releasing chickens if weather not too bad (it has been much milder this winter) so that
ablution is taken care of! Will start up again in the spring when things start growing and I
need the nitrogen.
Project Evaluation
Having gone through several seasons and a few design iterations I feel I have given the
internal and external compost toilet a fair trial, and have come up with positive and
negative conclusions from both systems.
The External toilet
Successful aspects of the external toilet trial have been
1.
2.
3.
4.
5.
6.
7.
The external toilet is still in use after 16 months
Pleasant to use, no smells and can bird watch whilst on the loo!
No fly or rat problem
No flooding of the pit has occurred
Windproof despite the worst of weather
Provides plenty of urine in the growing season
Talking point!
Not so successful parts of the trial and my suggested improvements
1. The family totally unconvinced and only I’m using regularly, the teenagers not at all,
and my husband is happy to wee directly on the garden if he’s outside anyway. He’s
perhaps used it for the other once or twice a month when working outside at
weekends .
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Compost Toilet Design by Alison Ensor
 Resign myself to this and carry on leading by example!
2. The willow hasn’t really taken in this situation
Try using poplar instead and watering directly from roof. I don’t want to move the
toilet to a more willow suitable area as this has proved a good place in terms of
privacy and wind protection.
3. Hand washing not successful , water dirtier than hands!
 Unnecessary, I’m either working in soil or going back to house after opening
chickens so wash hands anyway.
The Internal Toilet
Successful aspects
1.
Fantastic amounts of urine collected during growing
season – 5 litres a week!
2.
Great when water gets turned off and can’t flush!
Not so successful parts of the trial and my suggestions
1. Only partial use due to the smell build up quite soon.
 Source more pleasant to use soak as have been reluctant to bring
messy straw into house, eg source cheap mdf-free sawdust? Or buy wood shavings
for horses? Trial and if still not working only use for urine collection.
2. Found emptying and cleaning of bucket a hassle so more inclined to use outside loo,
except when weather cold.
 Crucial point of whole experiment, will only work as far as I can be bothered to
make it work and place nutrient capture over ease of flush toilet!
3. The inside loo has not provided alternative to outside loo, as I don’t have enough
need for urine in winter
Use on a straw bale over a bed in winter to generate compost for spring use? This
might give me the incentive if I see a lovely pile of straw bale compost appearing.
This project had the following requirements at the outset which I feel have been met.
 To provide a handy garden loo
 Collect urine for fruit/veg fertiliser
 Low cost, waste materials at least for trial
 In-situ system, ie no separate composting area
The following have only been partially successful
 A pleasant experience to entice the family to use it hopefully The outside is more pleasant than the inside, but neither have been accepted by
the whole family. I will try again with wood shavings to see if better soak will
counteract the smell problem.
 Provide nutrient for willow fuel crop and basket weaving materials
Still to be judged on performance in following years with increased rainwater
directed onto area and/or use of poplar instead.
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Compost Toilet Design by Alison Ensor
 Provide learning experience to develop a design for an in-house system
The outside loo encouraged me to build the internal one, yet the two systems are
quite different and not sure I’ve cracked the internal one yet!
Overall the success of this project is dependent entirely on the user’s motivation to
overcome the ease and habit of a flush toilet. I am more motivated that the family because
I need the urine but in the winter my motivation goes down too.
If we had no alternative toilet then this would be a perfectly serviceable solution , because
the family would just get used to it. Whether the outside hole in the ground system would
work if the whole family was using it constantly I doubt, due to the scale of waste created.
It would then have to become a composting system.
In terms of collecting nitrogen for the garden though I am a committed wee separator. And
as a handy outside toilet whilst working in the garden it has proved invaluable. With these
two aspects being the projects primary motivation, judged against this criteria alone it has
been a success.
Conclusions - 2013
What I have learnt from this project is a lot about self-regulation. Of all the projects I have
undertaken this one has required the most change in behaviour to make it a success,
precisely because there is already a useable flush toilet indoors! Changing existing people
behaviour is an interesting aspect of the requirements that I will really need to think about
and build in to any future design. How to recognise the level of ingrained attitude, how to
challenge and bring about change? How to prevent slippage back to ‘normal’ behaviour as
opposed to more environmentally aware one? Most of all, how to give ownership to the
whole family/set of users and not just the permaculturally inspired ones!
As an evaluation of the design process I used, Holmgren’s Principles provided a framework
for explaining what I had done in retrospect, but it does not give the same stages of the
process that OBREDIMET does for instance. Most of my thinking for this project was done
standing looking at materials I had to hand and pondering on my site and my own habits.
Often when designing I just follow my nose without thinking of the design framework
process – unravelling this into a diploma write up then requires a lot more formal thinking
afterwards. Holmgren’s principles do enable this but the actual design process is more easy
to explain if using a proper structure.
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Compost Toilet Design by Alison Ensor