Composting toilets

[FerlasDave]

I’m looking to get some advice on composting toilets.

Work have asked me if I could put some on the fields for summer camping groups that we might have in now. I’m happy enough building the structure but I understand there are a few different options in terms of how to capture the waste, anything from a “long drop” to a cut down plastic barrel.

Does anyone have any experience or tips that would be useful? Are there any regulations I need to be aware of? Appreciate any suggestions or links you have.

 

[Broch]

Well, you'll see mine when you camp over

 

[FerlasDave]

I’ve booked onto a one day course at the CAT down in mid wales, which should give me a head start in what I need. I think it will have to be a fairly robust system to support 300 kids for a season.

 

[Broch]

That sounds good.

In composting schemes, robustness is down to the number of facilities implemented as much as anything.

I can't remember what type of system CAT were lauding; maybe more than one now. The problem with the traditional composting loo was that the wet had to be kept separate from the solid - not easy to do with kids (hard enough with adults). The 'tree bog' is a combined system and easier to manage - but it does all come down to numbers using it. Tree Bogs have been put into off-drainage camp sites.

 

[Tony]

I'd be interested in any resources online that give a how to...

 

[Broch]

I've got sketches of the system I put in; I'll tidy them up and put them on here.

However, a tree bog relies on having growing shrubs or trees around it. Some people plant willow or hazel around them but in a healthy woodland setting that is probably not necessary.

 

[FerlasDave]

@Broch I’m not sure if they only have one system or a few now. By the sound of it talking to the guy on the phone they had means of explaining a few at least.

The information I found online here @Tony was pretty good but very basic.

Composting Toilets - Centre for Alternative Technology

A composting toilet treats sewage onsite, recycling nutrients into useful fertiliser. Get free tips and advice on composting toilets.

cat.org.uk

 

[Broch]

It does look like it's a traditional compost loo they are using - i.e. dry/wet separation. Depending on where you're putting it that may be what you need to do. A tree bog needs mature trees or new growth around it.

Ours has been in a few years now and has needed no maintenance or intrusion at all. It has never smelt either. But, then, the most people using it has been eight over one weekend. I think I would build extra units and open and close them every few days if I had a lot of people using them over long periods of time. You also need access to plenty of wood shavings.

Here are a couple of links to other peoples implementations:

Tree Bog

A Treebog is a form of water-less toilet which can have a wide range of species - both trees and wetland marginal plants planted around it. Effectively, it is a system for converting urine and...

www.sustainability-centre.org

Tree bog

A Treebog is a form of compost toilet which has willows and other nutrient-hungry plants planted around it. The faeces is held in a chamber open to the air which allows it to decompose rapidly, feeding the trees around it. Unlike a conventional compost toilet, a Treebog is usually not emptied or...

permaculture.fandom.com

 

[ManFriday4]

I compost the poop of 180 people on a 10 day camp every year. We use a 2x3×5m box with 4 cubicles using sawdust. It's a semi wet system in that we allow for some urine in the system. We don't use urine separators because they are difficult and unpleasant to clean. We have Strawbale urinals too. At the end of the 10 days we all the urine bales to the box & leave it for a year at the end of camp the box is 5/7th full and after a year that is reduced to 2/7ths full... IPhone don't compost!

I kid you not we found an iPhone in the compost.

The most important math for composting is you need 30 parts carbon to 1 part nitrogen 30:1. Human poo is mostly carbon and the combination of the urine with the poo is roughly about 39:1 with enough water too. The addition of greenwood sawdust from a local lumberjack slows the system down a bit but that's OK..

I will post a design to my foot album tomorrow.

This is pretty much what i said a few weeks ago when i gave a talk on it..

Still wondering how that iPhone got in there..

 

[Broch]

Still wondering how that iPhone got in there..

I tell everyone that uses ours that what goes down stays down

 

[ManFriday4]

Correction that 39:1 should say 30:1.

 

[ManFriday4]

Correction that 39:1 should say 30:1.

I tell everyone that uses ours that what goes down stays down

If you make a deposit it's a long term investment you might see it after a year if it isn't biodegradable.

We use the compost to plant trees, but there is so little after a year.

I did a calculation based on a survey of our campers of roughly how many poos/ day were they small medium or large: small being a few Quails eggs, large being the size of a loaf of bread. To calculate volume and then built the box bigger..

The toilet is twinned with one in a Pakistan Refugee camp!

 

[SaraR]

I've always thought that the loos that come with the instructions to not wee when you poo must have been designed by a men-only team...

 

[Ystranc]

A close fitting toilet seat on the pedestal as well as a fine mesh cover at the top of the air vent pipe to exclude flies. Including bio-char (or fine bits of charcoal that are otherwise useless) in the soak can promote bacteria being able to break down waste.

 

[Broch]

It's interesting, but we have never had flies in our tree bog. It would be impossible to make one fly proof anyway as the concept requires the sides to allow maximum feasible air flow - typically two layers of chicken wire stuffed with straw.

 

[Broch]

This is a rough sketch of the one I installed in 2017; the tall plastic waste bin (the type you can get for an office or similar) is vital for clean, smell-free, operation. The worst smell that we get is a 'compost' smell; a bit like when you open a new bag of commercial compost. Obviously, the design would have to change for a flat area.

It turned out almost as planned

 

[Tony]

, thanks for that...

 

[Ystranc]

This is a rough sketch of the one I installed in 2017; the tall plastic waste bin (the type you can get for an office or similar) is vital for clean, smell-free, operation. The worst smell that we get is a 'compost' smell; a bit like when you open a new bag of commercial compost. Obviously, the design would have to change for a flat area.

It turned out almost as planned

View attachment 77855

View attachment 77856

So you compost directly to the ground, not an enclosed cell that gets rested for a year and then emptied after a year?

 

[Broch]

Yep, that's the 'tree-bog' principle - theoretically, it never gets emptied. The 'mound' reduces quite quickly in the unused periods. The bacteria, fungi, invertebrate, and trees take out the nutrients. Wood shavings (a small amount per visit) balances the nitrogen/carbon to improve the composting process. However, I have assumed that at some stage I will need to dig it out (in my case from the rear), but that is years off based on the current situation.

It only works where there are plenty of trees or where trees can be planted. They are often surrounded on three sides by new willow growth.

 

[Ystranc]

Yep, that's the 'tree-bog' principle - theoretically, it never gets emptied. The 'mound' reduces quite quickly in the unused periods. The bacteria, fungi, invertebrate, and trees take out the nutrients. Wood shavings (a small amount per visit) balances the nitrogen/carbon to improve the composting process. However, I have assumed that at some stage I will need to dig it out (in my case from the rear), but that is years off based on the current situation.

It only works where there are plenty of trees or where trees can be planted. They are often surrounded on three sides by new willow growth.

Very tempting…fit it and forget it with very low maintenance