A waterless dry composting toilet is a water saving, safe, ethical, non-smell, non-wasting recycling, life giving, natural waste system. Fully treating human manure safely to produce plant fertiliser. 30,000 litres of water is saved per person, per year, compared to a flushing toilet. See related: Waste Systems post.
Humanure Handbook, by Joseph Jenkins see: https://humanurehandbook.com/
Or https://www.permaculturenews.org/2008/09/18/humanure-handbook-free-download/
Building a Wheelie Bin Composting Toilet
Building see: https://www.permaculturenews.org/2018/12/21/how-to-make-a-compost-toilet/
This Toilets most likely need to be positioned next to external walls. To enable wheelie bins positioning and access underneath them. Unless a basement space grants access.
Bins are swapped in/out once or twice per year depending on use. Full bins are removed and left to compost for 6 to 12 months. So spare empty standby bins are needed for swap in whilst compost matures in full bins
Wheelie Bins
Underfloor ground clearance or a pit will need to be dug, to house 2 wheelie bins per toilet, as 1 empty is stored spare adjacent, ready for swap in. With space outside for a ramp down with maintenance access to the lid/chute and plumbing infrastructure.
- 120L: 930mm H, $80
- 240L: 1060mm H
- 360L: 1100mm H, $162, bigger the better.
Underfloor Bin Access/Pit
Underfloor bin access space or pit, would need to be:
- 1930mm, 2 bins Wide (~680mm x2), per toilet, with one in use and other standby spare. Or alternatively the 2nd bin needs to be housed nearby and wheeled in upon swap.
- Optionally additional space may be required for liquid storage tanks or thier plumbing.
- 1930mm Bin and Chute minimum Height, possibly allowing for:
- 1100mm bin height,
- 300mm chute lid clearance
- 420mm floor and joists, supporting the toilet above and it’s hole. This may be substituted with a thinner concrete slab with plumbing chute inserted during construction.
- 10mm for flat paved or slab floor, with external bin floor area walkway clearance leading to a ramp.
- ~1m External walkway path and ramp needs to allow for bin width, it’s turning and person pushing it in/out space.
Electricity: 12v , 6amp (80 watts) electricity supply is needed for
- Inline fan exhaust to roof, continuously running. With soundproofing considerations. Connected to lid to create negative air pressure in bin. Solar chimney Matt black pipe to aid convection.
- Heat pad for compost acceleration. Alternatively underfloor solar heated hydronic heating or sand battery could be used under bins.
- Water pump(s), unless liquids may be gravity fed down hill.
Liquids: require plumbing flow out, ideally gravity fed. Or worst case tanked and/or pumped out.
- Pit rainwater drainage to avoid flooding. Rainwater run-off can be filtered and run through other pipes to clean them.
- Blackwater waste water from Composting Toilet Bin at pit ground level.
- Urine diverted from Composting Toilet at bathroom underfloor level, to Urine storage tank downhill/in-ground, for periodic pumping for compost fertiliser.
- Grey water waste water from bathroom sink, shower and bath, at bathroom underfloor level. Standard grey water plumbing.
Ventilation, no smells.
Negative pressure ventilation is created by a continuous fan extracting air from the bin and expelling it up above the roof line.
Ventilation dries out and oxygenates manures keeping the mix, with carbon matter, a good aerobic compost.
>90cm diameter wide pipe should be used as a chimney vent pipe, that extends at least 60cm above the roofline.
An inline 12v fan (ideally IP66 rated), solar powered with small overnight battery power, to continuously exhaust air.
A Shelley Cloud smart wifi relay controller with PIR switch could be used to optimise on fan/battery use. Scheduled so it runs at likely peak times in the day with breaks, and triggers with PIR.
A Whirley Bird cowl can use winds to help exhaust air.
A solar chimney can be used by painting the top half of the exhaust pipe Matt Black, placed in sunlight, which increases solar thermal absorption, naturally creating air convection within the pipe on hot Sunny days.
Flush Materials
Initially the large bin may be filled with 20L of sawdust (carbon matter) and a cup of good compost. Lightly damp.
A few cups of Sawdust, leaf matter, coconut coir, or dried small chopped hay/straw, (carbon matter) is added, after each deposit. Even toilet paper helps. This mix helps the humanure become good aerobic compost, avoiding anaerobic conditions which may produce unpleasant smells.
Dry Wood Ash is also effective in absorbing smells.
Cleaning
Vinegar spray can be lightly used in toilet bowl and chute if there are any unpleasant odours. Especially in Urine diverting toilets.
A handheld Bidet spray can be used to not only wash ones behind after deposit, but also the toilet bowl and toilet brush can be used.
No Smell?
- Negative pressure Ventilation expels smells above the roofline. It dries out and oxygenates manures keeping the mix, with carbon matter, a good aerobic compost.
- Heavy carbon matter flush Materials for nitrogen absorption, helps the humanure become good aerobic compost, avoiding anaerobic conditions which may produce unpleasant smells.
- A urine diverting toilet, reduces saturation of the humanure pile with nitrogen rich urine, and this helps to further avoid anaerobic conditions.
- Light spray of Vinegar in bowl and chute, neutralises smells.
- Cleaning the bowl when needed, with a handheld Bidet spray.
Cassette Box Compost Toilet
See: Cassette box composting toilet
Currently experimenting using low cost, heavy duty 100L storage bin that can be slid in/out for swaps. Reducing ground clearance or pit depth needed. Multiple bins can be cheaply setup and stored away for extended periods when full. Better suited for low use toilets or holiday homes visited infrequently.
Prototype 1
100L box from Bunnings
Commercial Composting Toilet
EcoFlow Clivus Maltrum @ $4k https://ecoflo.com.au/blog/how-often-do-you-have-to-empty-a-composting-toilet
The Clivus Multrum™ High Profile, has
- 3 – 6 full Full time users (Residential/Continuous)
- dimensions 760 (930mm incl. handles) mm W x 700mm H
- It requires Min clearance below joistsClearance below floor: ↕ 750mm
- Clivus Multrum™ High Profile = 120L chamber.
- For 2.5 people, you could expect to empty this every 3-5 months or so, depending on usage. Which is a swap out/in of spare bin.
Q&A
How much waste is produced?
The average human produces 125 g of solid waste per day. In a four-person household, that’s half a litre every day, continually breaking down as it decomposes. 240L theoretically caters for a family of 5 for a year.
Will it smell?
If the variables of the system are managed correctly (heat, water content, bulky additives to prevent compaction) then no, the compost will not smell. Ventilation fans are available to further assist.
How long does the composting process take?
It depends on those variables (primarily temperature), but anything from weeks to months. Finished compost is like humus, a dry earth-like substance that is rich in nutrients.
What can be added to compost?
All organics are fine to add, from vegetables to garden waste. Just make sure the compost doesn’t get too wet, too dry, or too compacted. Some people add worms, a process called vermicomposting.
How can I use it when it’s finished?
There’s a lot of information out there on which plants are most suitable to fertilisation by compost but all areas of your garden will benefit, although you may not wish to use it for growing food.
Is it really safe?
Yes. It is recognised by the World Health Organisation as a viable method of managing human waste. If the conditions are right, the composting process will eliminate the pathogens in your waste. In an absolute-worst-case scenario, if your compost is only for personal use: you could only catch something you already had.