Centralised Composting Toilets

Looking into the world of composting toilets and the choices I could make to upgrade my humble sawdust toilet is a real eye-opener.  It is nice to know there are so many toilet composting systems to choose from.  That means there must be more and more people opting to use them.

There is still an awful lot of stigma around the whole subject of compost loos, primarily I suppose because people are scared of what they will be confronted with when it comes to emptying them.  Using a manufactured composting toilet means only dry matter is stored and you only ever get to see it when its completely decomposed and looks like soil.

You want to help the environment and use less water, but don’t want to wander around with a bucket of poo every few days, so the commercial waterless toilet seems the right choice.  But, lets be honest, they look a little less sleek than your conventional WC.  That’s probably why most people who choose them, do so because water is an issue at their holiday cottage or cabin.  Looking at all the testimonials it seems most customers of the popular Sun-Mar Compact Self-Contained Composting Toilet do not have them in their permanent home.  Necessity seems to be the reason most people choose a waterless toilet, rather than choice. I guess that’s because no matter how efficient and easy to use they are, they do still scream ‘composting toilet’, due to the bulky nature of their design.

Choosing a centralised composting toilet system means the actual WC part of the whole enterprise can look an awful lot more like an ordinary toilet.  All the waste storage and composting takes place downstairs out of site.  So the toilet you sit on looks very much like any other (though without the cistern).

Using a centralised dry compost toilet means the storage capacity is greater.  This means you have to remove completely composted hummus even more rarely than with a self contained version.

The system works in exactly the same way.  A vent pipe with fans draws odour and moisture outside while allowing oxygen in to speed up the decomposition of the organic waste.  An overflow system is desired so that any build up of liquid can be diverted to a soak-away, septic tank or sewage system.  This is rarely likely to be needed as the fan should easily promote the evaporation of all liquid.  But in times of extreme cold and heavy use, it is better to have this option available.

The drawback with these systems is the amount of space they require.  Many of the toilet composting units are not particularly bulky, but they must be situated directly below the toilet itself, so that waste matter falls from one to the other.    The units range in size but start at only around 2 x 2 x 3 feet which isn’t very large.  The issue is having space underneath your toilet for it.  If you do have some spare space underneath your bathroom this is ideal, here we’d end up with the composting unit in the kitchen which really isn’t that appealing at all.

Another key point is that you can have only one WC per composting unit.  So these are still always going to be  Eco way of dealing with human waste more suited to holiday cabins or small residential homes.

It seems the only way people can forget they’re using a composting toilet is to hide every trace of it away from the bathroom.  So the centralised dry composting toilet is probably the future as far as waterless toilets are concerned.  I will have to mention it to MrDB…

For a more self sufficient future

8 Responses to “Centralised Composting Toilets”

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  1. What about the cost of running such a toilet or is it a one off cost?

    It sounds stupid but even a conventional toilet costs money to flush… not that i’m advocating on skimping on that! but I guess using sawdust in a toilet would be cheaper or not?

    anyway sounds like a good alternative if it can be used as compost.

    • It depends what your water bills are like. But if you can stop paying for mains sewarage you should make great savings with a sawdust composting toilet. Perhaps more importantly you will definetely save resources whether or not you save cash

  2. you never think something as simple as a compost toilet could be so complicated
    good luck with getting it set up, i’ve seen a few and they worse amazingly well

  3. Hi Mrs DB

    I live in Spain too and am wondering about making a compost toilet on our land, which in some ways would be great (my husband is a carpenter = lots of sawdust; we have lots of fruit trees that need manuring in autumn) but I’m still worried (perhaps purely due to conditioning by my hygiene-obsessive mother!) about the spread of illnesses…two hippy camps near us both had cholera because their human waste al ended up in a river…yuck. Anyway, not an issue for us but still, is it totally safe using your own poo on your food??

    • Hi Medina,

      The key to recycling human poo is firstly not to let it run off untreated into any water ways and secondly to let it completely compost before spreading on the land. Once it’s been through the compost heap, human waste is completely safe. And, if you’re still feeling a bit concerned just spread the finished compost on your land the season before you want to plant. The worms and bugs will mix all the goodness from the compost into the soil, breaking it down even further. Even soil contains some ‘nasties’, so regardless of whether or not you’re fertilizing with humanure you should still be washing hands and veggies!

      In some places they use fresh night soil directly onto the land as fertilizer but for me that’s a step too far, I’d rather know any pathogens have been destroyed by the heat of the compost heap. If you’re in Spain too, just think about leaving the compost for longer so that every batch has one summer season to be completely baked before you use it – nothing can withstand summer on a Spanish compost heap – its just too damn hot!

  4. Almostgotit says:

    My in-laws have a cabin high in the Wyoming mountains which is totally off-grid. This means water from a hand pump (or using the new solar pump!), wood heat, propane-powered fridge, and a COMPOSTING TOILET. Things are very dry up there, which help immensely with smell. The waterless toilet looks like a regular one, but operates with a little flap that opens (flushes) things into a receptacle under the cabin. The cabin itself is above ground, and the toilet installed near an outside wall, so it’s a cinch to empty the receptacle once a year or two. The compost action is encouraged by throwing a handful of peat moss (e.g. sawdust?) and some powdered microbes in the toilet once a day or so. The good part: there’s so little moisture or heat at that altitude that odor is rarely an issue. The bad part: there’s so little moisture or heat at that altitude that composting itself CAN be an issue. Not with this toilet though, apparently. The only thing I’ve noticed is that when there is a large crowd of people in holiday or weekend attendance, folks are encouraged to remember the outdoor pit toilet too (which is emptied professionally with a big vacuum-hose truck every few years… as I said, natural composting hardly occurs there. Not to mention the fact that as the entire place is built on a granite mountain, it’s hard to make pit toilets very deep…)

    The soil from the compost toilet is innocuous looking and odorless, but not yet pathogen free, and therefore never used on any food crops (which won’t grow there, in any case), but just spread around the the grateful alpine trees in the area.

  5. Jonny Lyons says:

    Human Waste is never safe to use on food crops, even after it’s been completely composted. Fruit trees are O.K as the crop doesn’t have any contact with the ground, but otherwise it’s a big NO! There are projects in Africa which aim to supply toilets to villages to increase the amount of land available to farm, as well as for health reasons.

  6. Kate says:

    I beg to differ with the previous comment. If anyone is interested, head over to The Humanure Handbook website. The author has been growing food Safely for his family for over 20 years.

    You can find everything that you ever wanted to know about composting human poop, in the book which is available to read as a free pdf.