Frequently Asked Questions (FAQs)

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Can compost toilets be free-standing?


If the toilet includes a bottle then it can go pretty-well anywhere as it’s self-contained. Furthermore, Kildwick toilets all have a leakproof enclosure to prevent accidental overflows from damaging your floor or box base.

In some situations it helps to have fan ventilation to remove excess damp from the toilet – in which case you may need some 12V (DC) or 110/240V (Mains, AC). The fan power requirement is only around 1/2 Watt.

If you want to have external urine or solids tanks then, clearly, you’ll need to add extra plumbing and/or containers beneath the toilet.

What to do with toilet paper?

What you like!

Ok, so you have choices.  With most paper you can, of course, put it straight in the compost bucket along with the poo – it will compost down with it but there are two caveats:

  • It will speed up the time taken to fill the bucket.
  • It’s hard to ‘cover’ toilet paper with sawdust which results in three further issues
    • The toilet may smell more than usual as the cover material ‘rolls’ off the paper
    • The poo beneath the paper doesn’t get its ‘full-measure’ of sawdust as the paper diverts it to the sides
    • Toilet paper can look worse than poo covered in sawdust!

Of course, these may not be issues in your situation but if some/all are then read on…

There are alternatives to putting the paper in the bucket.

  • Use a ‘family cloth‘ – basically a washable cloth ‘eco’ alternative to toilet paper – see the link.
  • Have a separate ‘pedal-bin’ (or similar) with a paper bag in it and put used toilet paper in there (as the Greeks do).
    • We recommend folding the paper on itself to capture the poo inside which will neutralise any smell in the way that adding cover does to the poo in the bucket.
    • If you have a stove then you can burn this bag of toilet paper – just squirt (or add a few drops) of some ‘kitchen oil’ spray as a low-volatility accelerator to get it burning well.
    • If you don’t have a stove then just put the bag out with normal domestic refuse.
  • A compromise would be to:
    • Put ‘poo’ paper in the compost bucket but put the ‘wee’ paper in a separate bag for burning or binning.
    • Allow guests to put the paper in the bucket as asking infrequent users to separately bag the paper may be one step too far :-)!

Do I need ventilation?

Yes…and No!

Lets start with the No…

A well-managed compost toilet should produce little more than a musty-wood smell.  If some urine gets in with the solids then the sawdust will usually soak it up. If, however,  too much urine gets into the solids then it may be that not enough sawdust can correct it so it may start to smell. If this happens then it may be worth emptying the bucket and starting afresh if you don’t have a fan.

Now to the Yes!

Some people find even the musty wood smell unpleasant (but still not as bad a cassette toilet/pump-out tank smells!). In this case  a low-volume (quiet) fan should extract the low-level smells.  If you are getting higher levels of smell then see the previous paragraph and deal with the smell – at source – rather than just moving all the smell outside with a big, noisy, energy-sucking fan!

The other factor is that in many small bathrooms there is insufficient airflow to remove the extra air moisture that a bucket and bottle of warm, moist, material will create.  In this case a low-speed fan can expel the extra humidity created in the toilet box.

When a fan is not much use…

To get the most from a fan the flow of air generated should be well controlled – otherwise you may just be extracting normal bathroom air and leaving the toilet air … in the toilet!  A well-designed toilet ventilation system will use a low-volume (quiet) fan to maximum effect extracting the humid air from the toilet with low energy and noise levels.

Carbon filter or extract outside?

If you are going to use a fan then the most efficient approach is to vent the air outside. Kildwick offers a wide-range of ventilation options to make external venting simple but there are some circumstances where ducting air outside just isn’t possible and the sis where a carbon filter/fan can be useful.

A carbon filter uses specially ‘activated and impregnated’ carbon granules that ‘adsorb‘ volatile compounds (smells) from the air passing through them. It’s important not to ‘rush’ the air past the carbon or it’ll not get adsorbed and so matching fan speed to carbon depth is important. For a quiet bathroom, Kildwick has done the calculations and tests for it’s ‘Interceptor’ super-quiet carbon filter / fan assembly which sits neatly inside the toilet.

Carbon can only adsorb so much and, therefore, it needs to be replaced periodically – how long this takes depends on too many factors to even estimate!

What do I do with the wee and poo that the toilet ‘collects’


In ‘developed’ counties, urine is relatively ‘benign’ and would not normally contain bad diseases, parasites etc. On this basis, it can be emptied almost anywhere that other people don’t walk, play etc. Grass verges, under hedges, around tree bases stored and diluted as an excellent fertiliser. Of course you can always pour it down toilets, drains or Elsan points! 

If you are using strong medications then be more careful where you put it and don’t put it around fruit bushes, trees etc. Composting urine with the poo is more likely to neutralise the chemicals as microbial action is very effective. See this article about composting and medications


Options are fewer for poo than for urine but much better than what you can do with them mixed together. Simply put, the options are composting or bagging/binning

  • Composting. This is where the carbon cover material comes into its own. Poo and sawdust (or other carbon based mix) composts very well if mixed and if it doesn’t get too dry or wet! Poo, by itself, will break down but it takes longer without the carbon. The UK’s Environment Agency generally recommend two years but a well-managed humanure compost mix can get most of the way there in as little as six months.  Once composted to at least this level it can be buried to finish off.
  • Bagging & binning. In the UK, it is legal to bag & bin solid waste /but/ this must be done responsibly.  Key ways to ensure responsible disposal are
    • Use bags that are obviously not domestic refuse – absolutely not black bin-bags
    • Use bags that are appropriately marked up for sanitary use – stripes and words highlighting that it may contain human waste to prevent others (inc those at the recycling centres) from opening them. Kildwick provides properly marked-up bags for its customers.
    • Do not put in dog-poo bins or picnic bins – only proper domestic refuse containers.
    • Do not over-fill bags – they may split and contents spill out
    • Double-bag – for security against splits. Use two sanitary bags that have the same markings

How long will the solids bucket/tank take to fill?

People really produce very low volumes of poo!

The average is around 300g/day and most of that is water (around 80%) with the balance being mostly poorly digested food and bacteria.  A 20L solids bucket can last one person up to around 40 days, two people 20 days and so on. Whilst toilet paper can be added into the solids bucket it can dramatically reduce bucket fill time so, if you can, separately bag the paper and bin or burn. Perhaps allow guests to put paper in the solids bucket as ‘binning’ it may be one step too far 🙂

How long will a urine bottle take to fill?

If you are using a bottle to capture the urine then how long it takes to fill depends on how many people are using the toilet, how much they drink, how hot the outside temperature is and whether other toilets are used. Clearly a lot of factors!

In general, allow 1L-2L per person per day and don’t leave it longer than four days before emptying as it may start to smell

Do you compost the urine?

Generally, no!

Urine can be added to the contents of a compost bin if it gets dry but it can be flushed, drained, poured over grass, poured under hedges, around tree bases or diluted (8:1) and used as a liquid fertiliser. So many choices!

How soon will ‘it’ compost down in the toilet?

Usually it won’t!

Composting takes time and, unless you use the toilet infrequently, it’ll probably fill up before it composts. The exception may be with a ‘long-drop’ toilet which has a larger container beneath the toilet hut/cabin.  Most ‘compost toilets’ are actually ‘compost collecting toilets’ – that is, you collect the solids, add some carbon necessary to the compost process (see another faq) and then add to an external larger container to actually do the composting…called ‘secondary compost containers’.

Do I have to use sawdust on Poos?

Usually, yes!

Some toilet manufacturers claim their toilet has some magic which means that they don’t need any additional material added. This is neither true, nor acceptable to the UK’s Environment Agency.  Why not? Urine diversion is not 100% effective and poos can be loose/runny leading to the build up of raw sewage in an open container…not pleasant, or safe. Having a turbo-charged fan may move the smell somewhere else (your neighbours) but the real problem persists.

Tell me again…Why don’t they smell bad?

Most toilet systems mix the pee and poo together creating a dangerous sewage gloop. Bacteria that thrive in an airless environment (Kildwick Waterless Composting Toilets Frequently Asked Questions (FAQs)  anaerobic bacteria) feed on this gloop and generate gasses that smell very bad. Cassette and pump-out toilets suffer badly from this problem and need strongly scented chemical to cover it up.

When you keep the pee and poo apart you have two simpler ‘products’. Urine can start to smell after 4-5 days but can easily be disposed of down toilets, drain, grass etc. Poo can be covered in sawdust which helps to dry it and also neutralises the smell. Poo can be easily composted or ‘bagged & binned’ (read more in another FAQ)

How do they work?

Kildwick Waterless Composting Toilets Frequently Asked Questions (FAQs)
White Kabin with Mid Oak Seat


The simplest compost toilet to use diverts the urine into one tank and the solids into another. This so-called ‘urine-diverting’ compost toilet keeps the pee from the poo which are each easy to deal with (see another faq) whereas combined they are a dangerous, smelly, ‘gloop’.

Kildwick urine diverters are unique in that they are made from a special antibacterial gelcoat which dramatically reduces smell and stain issues of plastic toilets & separators.  They are also a breeze to keep clean – the surface is super-hard & shiny and easier to clean than a ceramic toilet!

Kildwick Waterless Composting Toilets Frequently Asked Questions (FAQs)
Pink Glitter Seat and Klassic Urine Diverter

We also do ‘glamour’ separators – a mixed glitt

Kildwick Waterless Composting Toilets Frequently Asked Questions (FAQs)
Green Glitter Separator in Kildwick Kabin composting toilet

er base under a hard, shiny, antibacterial surface. We offer a range of colour mixes from simple silver/black to this ‘barbie’ pink :-)!   Adding a tough of glitter disarms those who may be concerned about using a ‘new’ style of toilet!





Do they smell?

Not much and certainly much less that cassette or tank (pump-out) toilets.   A well-managed compost toilet should result in a damp wood smell…like a forest floor. Not unpleasant and certainly not sewage…all without chemicals!

For the final element of confidence, a low power (quiet) fan can be used to vent the remaining gentle smell outside. Kildwick offers a versatile ventilation system that makes venting outside (in inside with a carbon

Kildwick Waterless Composting Toilets Frequently Asked Questions (FAQs)

filter) as simple as possible.