We recently visited a house with the most beautiful wheelie bin compost toilet. It’s designed to be inside the house, is smell-free, beautiful (in my opinion) and super easy to use. All the good things.

The wheelie bin’s hidden with a timber framework that opens up so you can roll the bin out when needed. 

Making a wheelie bin compost toilet is nothing new, we’ve seen and done it quite a few times in various locations across Australia. I think the first time I saw it done was around 2002 at a cranking music festival, since then I’ve seen them everywhere, from share houses to farms to urban homes . After trialling *many* compost toilet designs over the past 15 years this is by far my favourite DIY version. Mainly because it’s the easiest to use – specifically, you don’t have to handle any poo buckets at all and instead of lifting, you just wheel the full (heavy) bin out of the way and replace it with a new one when ready.

So how is it done?

There are quite a few variations in how to build a wheelie bin compost toilet, for this blog I’m outlining how these people did it for their context. They used a smaller 120 litre wheelie bin so it would fit inside their house. Often bins are placed *under* a house that’s already raised off the ground, so people usually use full size 240 litre bins. This wasn’t an option here.

The main thing you need to do is add a false floor (for aeration and drainage) and a drainage pipe to the wheelie bin (to get the wee out of the bin).

To create a false floor, these folks used spacers which are really strong plastic supports that hold up a metal frame. Unfortunately they forgot to take a photo of the metal frame they made, but they used some strong recycled mesh (you need to make sure it wont bend under weight) they found at the local tip shop with 2 inch holes and covered it with porous garden shade cloth that lets the liquid through but no solids.

Looking into the bin, you can see two spacers ready to support the false floor. You can also see the drainage hole covered with shade cloth. 

The drainage pipe to get the wee out of the bin is made by drilling a hole into the bin as close to the bottom of the bin as possible. They used half inch and 3/4 inch poly fittings to create the leak-proof joiner bits (that’s my non-technical term for them). On the inside they also covered the pipe with additional shade cloth *just in case* any solids do make it through the false floor. You really don’t want the pipe to get clogged and have wee backing up in the toilet.

The drainage pipe covered with shade cloth with a spacer next to it.

The half inch and 3/4 inch poly fittings used to create a leak-proof join.

On the outside of the bin they added a ball valve tap (you can see its red handle below) and connected it to a standard garden hose that runs out through the floor*. The ball valve means that when the bin’s full and you need to move it, you simply turn the tap to off to prevent any wee coming out while you’re wheeling it out.

*Once out through the floor the hose connects to a blue line poly pipe that runs under ground and into an infiltration trench down hill – more on that soon. 

The drainage pipe leaving the bin

To prevent any smell occurring two things are done. The first is a small amount of sawdust is added every time someone does a poo (not wee), this strong carbon ingredient counters the rich nitrogen poo – neutralising it.

In addition to this they added a small fan that’s built into the lid of the toilet, so you don’t even see it (unless you lift it up like I did). This is a standard 240 volt bathroom fan, these guys are connected to mains power but you could also use a fan connected to a 12 volt solar system if you’re off-grid.

The fan hidden under the lid  Me trying to take a photo showing how the whole lid can lift up. The fan is at the back of the lid, directly below the blue cylinder (which is functioning as a splash back for wee. 

Where does all the wee end up?

Great question. After leaving the house, it travels in a pipe under ground downhill into a subsurface infiltration trench that runs on contour for around 20 metres. We’re told that this trench is a large empty cavity that’s created with a plastic framework that’s wrapped in geo fabric to prevent any soil getting in.

Downhill of this hidden infiltration trench are some fruit trees who happen to love the nitrogen-rich wee seeping into their root zone. All these trees are thriving.

My feet, standing on top of the very invisible infiltration trench.

One of their happy fruit trees getting ready to fruit. 

One more really important detail for this design.

Is that they included a door in their bathroom so they don’t have to wheel the full bin through their kitchen to get it out of the house – how clever. Instead they wheel it straight out the bathroom door and a further 1.5m to a flat holding bay where it sits for up to 12 months. In this time they’ll put some compost worms into the bin to help process the humanure, turning it into a beautifully smelling compost that’s eventually added onto their orchard.

The act of composting is one of my favourite things to do and think about. Whether you’re composting food scraps, garden waste or your own poo, it’s all doing the same thing… Harnessing a waste product that’s ultimately becoming pollution in the mainstream waste system and turning it into a valuable resource. You’re turning it into a solution that feeds depleted, or hungry soils that can then support nutritious food production or, feck – even just to support a healthy planet! Composting is the act of supporting life, long beyond our own.

Fantastic resource

• The Humanure Handbook which you can download for free on their website!