Archive for ‘September, 2017’

The Wheelie Bin Compost Toilet

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

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The Home Composting Project

Over the past year we’ve been working with the City of Hobart to deliver The Home Composting Project. This was a multi-layered, creative education campaign that supported people to compost their food waste at home instead of sending it to landfill where it releases harmful methane gases into the atmosphere.

There were three layers to this project:

  • The first was focused on “passive education” that happened through installing large-scale public artwork in the city educating people how to compost.
  • The second layer was all about “active education” which took place through hosting two free home-composting workshops in Hobart.
  • The third layer was advising the City of Hobart in updating their website to include information on how to compost food waste at home.

But why?

Current figures indicate that up to 47% of Hobart kerbside bins are pure food waste[1] – this is both a big environmental and economic problem and a big opportunity. Environmentally, the main problem is that once food waste is buried in the ground it becomes anaerobic, eventually releasing harmful methane gases into the atmosphere.

“Methane is a potent greenhouse gas 28 to 36 times more effective than CO2 at trapping heat in the atmosphere over a 100-year period.”

Hello climate change and a plethora of social, environmental and economic challenges. We think it’s best to avoid this at all costs, hence turning the problem (food waste) into the solution (healthy compost to return to the soil).

To do this we worked with a group of households to (a) teach them how to compost, and (b) record how much they composted over one month to determine its effectiveness in keeping food waste out of landfill. They each received identical “compost kits” that made accurate data collection possible.

The outcomes for this brief, but effective project Include:

While the outcomes you can see above might appear modest, the power of this model is that it’s easy and affordable TO SCALE UP to be a highly effective approach to help keep food waste out of landfill.

Cost projections show that by investing in an educational program that’s free for the public to access, you could potentially divert hundreds (and eventually thousands) of tonnes of food waste from landfill per year and save tens (and eventually hundreds) of thousands of dollars by reducing processing fees.

A second layer to the project

Involved collaborating with local artist, Rachel Tribout, to create three large compost billboards that were displayed in central Hobart for 3 months. They were educational, beautiful and big – with the largest one measuring 7.8m x 2.3m.

A very happy me with the smallest of the 3 billboards

The third & final layer to this project

Was focused on working with the City of Hobart to update their website to include some educational information, supporting people to compost at home. This involved making easy-to-download flyers from the billboards and making them permanently available to the public as you can see below.

The City of Hobart are now exploring the feasibility of having a kerbside collection service specifically for food waste to further decrease the percentage of it ending up in landfill.   However as outlined in their Waste Management Strategy, this wouldn’t mean support for home composting disappears – rather it would be one of a range of approaches. We’re fans of not putting all your eggs in one basket so support this approach to turning this current pollution into a soil-loving solution.

  • Did you know: The City of Hobart have a unique and quality composting facility where they currently compost green waste that the public give them. Once composted this is then sold back to the community and while not certified organic (the inputs are too variable), it’s currently the best quality compost we’re aware of commercially available.
  • Thanks to the City of Hobart for funding this project – we loved it.

Some references & resources

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