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On the subject of smells…

Kildwick Waterless Composting Toilets On the subject of smells…
Kildwick Waterless Composting Toilets On the subject of smells…

First written in 2016 (needs updating, but mostly relevant/correct)

No Smells? Not Quite!

Compared to a chemical tank (whether pump out or cassette), the smells from a composting system are mild and rarely unpleasant. Most compost loo users will tell you enthusiastically that there is no smell. That, of course, isn’t entirely true – there are very few things that have no smell at all. What we mean is that, compared to a chemical tank (whether pump out or cassette), the smells from a composting system are mild and rarely unpleasant.

But… having said that, there is the potential for putrid pongs if no one looks after things, so here are some of the things to be wary of and the solutions and ideas that users have come up with.

The liquids container

Urine is sterile as it leaves the body and only starts to smell once bacteria get to it. However, the little blighters are ready and waiting! One of the advantages of a waterless system that I have found is that urine without any added water (bringing with it some bacteria)  seems less likely to smell (that’s a personal observation rather than evidence based I should add!). However, whatever you do, it will acquire bacteria and start to decompose and smell. Going cloudy is a good indication there are bacteria at work. The Kildwick ‘Delta-10’ urine container is made from antibacterial plastic which slows down bacterial growth, smell and the formation of bacterial ‘sludge’.

Pong Prevention

  • A good quality container – not all plastics are equal (see ‘Delta 10 comment above) and a cheaper option may start to degrade which allow scale to build up and provide crevices for bacteria to settle in. If you are using a found container such as old milk containers then you may find that it’s a good idea to start a new one every few weeks, scrub the old one out and consign it to the recycling.
  • Empty the container regularly:
    • Daily or at most every 48-72 hrs
    • Rinse thoroughly.
    • Leave it upside down to drain and completely dry. The rationale behind this is simply that bugs can swim but they can’t fly. Doing it before going to bed gives it overnight to dry.
  • Suggestions for cleaning substances include:
    • Bicarb and warm water.
    • Any ecological bathroom/loo cleaner.
  • Suggestions from a variety of users for things to use to help treat/manage/avoid any smells are:
    • Nothing, just a good emptying and washing regime.
    • Add any of the following: 1-2 tea-spoons of sugar (or  the closely related substance, Coca Cola), vinegar, Napisan, a little bleach – apparently breaks down very quickly and is reported to keep the urine clear and non-smelly.
    • Bio blocks in the filter –  these are often used in public urinals and prevent scale as well as smell. Note: Li Loo supply these with kits currently, hopefully replacement stocks will also be available via the website
  • But… however thorough you are with your rinsing and drying you will eventually get some scale and a bit of a whiff in the container. Then it’s on with the Marigolds and get to work with the Vim (or similar) and a brush to give it a good scrub out. Do it every couple of weeks and you shouldn’t get to that point. And I don’t know a single user who has forgotten, or not had time, to empty it and come back to a pongy pot at least once…
  • Do a thorough nose check and clean on solids bucket changeover days when the box (or Airhead/Separett)  is empty and you can get at everything. Give the diverter a thorough wash and polish, especially underneath and round the rim, check the base or undertray and any corners.


That moment when there is a definite whiff of old wee…


  • The users – had any male visitors who thought that the ‘everyone sits down. Yes, even you with the willy!’ rule really doesn’t apply to them?
  • Any spillage? Evidence of wee getting around the solids bucket or on to the base of the loo? Li-Loo custom built loos have a fibreglass tray in the base. Puppy pads, nappies or incontinence sheets could serve the same purpose and help to avoid any spills soaking into the wooden base where it will be more difficult to get rid of.
    • Note: if you find spillage on more than one occasion you might need to revisit the positioning of the diverter and/or hold a family seminar on how to sit on the loo!
    • See also trouble shooting in the next section about wee getting into the solids container.

Solids Container

The most common smell adjective used among composters is ‘musty’ which often than not refers more to the cover material than the contents provided but, generally as long as you add plenty of cover material it won’t smell and if it does, adding some more cover material will solve it. There are other guides available on the subject of cover material and you may need to experiment to find the best for you.

The best material if you aren’t composting is medium-sized sawdust (ideally hardwood) but softwood ok. If the shavings are too coarse they don’t cover enough, if too fine, they just soak in and don’t cover and aerate (Colin Ives – who has tested a great many cover materials).

Filtered Ventilation

We have developed an internal filtered recurculating ventilation system that doesn’t require any holes drilling in your wall/roof[/inset-right]Here are suggestions from current users for cover material that help to ensure your loo remains pleasant to passers by:

  • Scented animal bedding – this one has had mixed responses, some find it imparts a pleasant aroma (lavender was the one under test), others found it sickly.
  • Small animal meadow grass (rabbit bedding hay) has a nice dried grass smell about it. My favourite – always add a layer before anyone on a research visit arrives.
  • Coffee grounds are said to be a good odour neutraliser – and they might as well be composted as clog up the sink.
  • A sprinkle of talc – Colin’s wife, Maria, found that a nearly full bucket had a bit of a whiff so sprinkled a little talc. Also useful if visitors are expected, just in case…
  • Chopped orange or other citrus peel imparts a cheerful aroma.
  • And finally, resist the temptation to make the bucket last as long as possible – the looser and more varied the contents, the less likely it is to smell and the quicker it will start to compost.

[inset-left]Ventilation,Powered ventilation systems are a ‘nice to have’, rather than essential[/inset-left]Note: commercial composting loos come with a fan that tries to dry out the contents but also acts to vent any smells. With daily use, there is little time to dry out the contents – this happens more if the toilet isnt used between weekends, for example.  You can fit a fan to a DIY loo but the oft repeated instruction that composting loos ‘must’ have a fan is a myth. Good management and an open window in the bathroom work just as well and use less power.


If you are getting ‘toilet’ sort of smells  it suggest that anaerobic digestion is taking place. The most likely reason for this is that urine is getting into your solids bucket and it’s starting to behave like sewage. This doesn’t matter, as long as there is enough cover material to soak it all up but it will fill the bucket more quickly and you did go to the expense of setting up that diverting system so it might as well do the job you paid for. Several Airhead users have reported this as a problem and solved it by slightly tilting the whole unit forwards. There have also been reports of some of the commercial diverters as leaking backwards because they have no lip at the back to encourage the liquid forward to the tank. This was the starting point for Colin to design the vastly superior Li Loo diverter. If you have one that is causing problems the tilt forward approach might work or you might like to consider an upgrade!

Other than that – just add more cover material…

And Finally…

Cover-Right!,If you find that there are residual unpleasant smells, you may need to look at the type & quantityof cover material you use[/inset-right]What you eat and drink will have an impact – plenty of water will result in straw coloured clear and non smelly urine. A diet that is high in fibre and low in fat will produce stools that are bulky, easy to pass and as unsmelly as is possible!

However, that isn’t easy for everyone and there will be users living with a long term condition such as Irritable Bowel Syndrome (or a short term gut illness) or who are on a medication that affects the state and smell of urine or stools.  Those aren’t a barrier to composting but might need a little more work finding the right cover material. There are users with experience who can advise and guide you so feel free to ask in the forum or Facebook group.

And if you encounter a problem we haven’t mentioned or a solution we haven’t spotted please let us know and we’ll add it in.

Thank you

Kate Saffin/Colin Ives

With thanks to:

Maria Mathews

Sue Lees

Alan Wildman

Isoult Tibby Cattistock

Sarah Louise Jasmon

Jo Lambert

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