Sunday, April 2, 2017

Composting toilet systems

When I started my Earthship project in sunny Tasmania a big question for me was: to compost or not to compost?

When I weighed up all the benefits that a composting toilet provides, I was sold on creating one.

As with most things in life, plans don't often reflect the results and in my case I didn't end up with one composting toilet...

I built two!

Before I describe the practical aspects of construction I would like to talk about the benefits of composting your poo.

* compost toilets use zero water.

* composting your poo creates soil.

* compost toilets can be located away from your house.

*you'll never have to clean your toilet bowl again!

Let's look at these points in order one by one:

* Every time we flush a toilet we take an average of six litres of drinking water and add shit to it before flushing it to a chemical treatment plant in order for it to be pumped into our precious oceans whereas composting toilets use zero water.

* Poo = soil, that's right! after a year composting, poo turns into completely safe, rich, beneficial soil!

* Storing feces inside the home doesn't really make sense so why not have the toilet located near enough to be convenient but separate to the house?

* Lastly, with a properly designed composting toilet system, a large metal or plastic tube can be used to separate the seat from the catchment meaning that nothing touches the sides meaning there is nothing to clean.

now let's take a look at the two different designs I built from a practical angle.

The first model was a tried and true design involving several wheelie bins and some very basic plumbing.

wheelie bin toilet with a garden shed as shelter.
A really good design is the wheelie bin toilet. basically the wheelie bin is set up under a box with a hole in it and a standard seat.

Generally the larger bins are used and accessed from under the toilet block, in the above version of mine I used the medium size bin and the access is from lifting the lid and opening the door at the bottom.

solids sit in the bin and liquids drain into a leech field through a tap and garden hose at the bottom of the bin.

Straw is added before use and a short bit of ag pipe is fixed inside to stop the tap and hose becoming blocked.

After every "deposit" a high carbon material is added such as sawdust, charcoal/ash or shredded paper or a combination of these.

The carbon helps the feces to break down and also helps with any smells.

When the bin is full it is simply wheeled outside and closed and a new bin installed, after a year the bin is emptied where soil is needed. (only about a third of the contents are left in the bin after the thermophilic process has taken place.)

I like the wheelie bin compost toilet because there is no direct dealings with the feces and urine.


Clivus Multrum composting toilet

My second toilet build is a commercial model which costs around the $4000.00 mark. 

The Clivus Multrum composting toilet is expensive, it stays in place so the material has to be shoveled out and it requires a bigger area for installation.




Based on the description above you are probably wondering why I chose this type of toilet and why I even bothered to build a second toilet?

Firstly I picked this one up from a local tip shop for only $55.00!
Secondly I needed a council approved system for my building permit.




The Clivus Multrum is buried and plumbed in to my septic tank for liquid drainage,(also installed because of council requirements) and it takes food scraps as well as human excrement, has an outlet for a fan and because of it's holding tank size does not require emptying very often (depending on how many people are using it regularly).

Because I buried the unit, what better material for a retaining wall than... you guessed it, car tyres!


my good friend Lisa pounding tyres around the subterranean tank


The project is still in progress and I will update this post as it nears completion...
Stay tuned.

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