Small composting toilet

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Small composting toilet
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Treacodactyl
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Joined: 28 Oct 2004
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Location: Jumping on the bandwagon of opportunism

Posted: Thu Mar 10, 11 8:53 am Post subject: Small composting toilet

I've been thinking about the feasibility of using a composting loo in a garden shed or garage. Privacy is not a problem but space would be. So, would it be feasible to have a small self-contained composting loo that could be tucked away, then pulled out and used when required?

It would be ideal if I could buy something like a self-contained camping toilet as I think more people would use it. However, a quick google suggests they are around the ï¿½400 mark so it looks like a home-made one would be the way to go.

I'm thinking, a wooden box to contain a bucket, a seat on the top and then a lid with a reasonable seal. That doesn't sound difficult but will an average builders bucket be large enough? Without going into too much detail how long would it take the average person to fill up a black bucket? I'm mainly thinking about how much saw-dust would be required after each use. I suppose I'd have to find somewhere to complete the composting process - any ideas?

Barefoot Andrew
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Joined: 21 Mar 2007
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Location: In the 17th century

Posted: Thu Mar 10, 11 8:54 am Post subject: Re: Small composting toilet

Treacodactyl wrote:

Without going into too much detail how long would it take the average person to fill up a black bucket?

Such images

Lorrainelovesplants

Joined: 13 Oct 2006
Posts: 6521
Location: Dordogne

Posted: Thu Mar 10, 11 9:17 am Post subject:
Can you also use ash from the fire to sprinkle on top after every visit? Granted we dont get a lot of ash from a wood burn,but is this not another way to completely use it up?

sally_in_wales
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Joined: 06 Mar 2005
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Location: sunny wales

Posted: Thu Mar 10, 11 9:25 am Post subject:
Offhand, I think the ones at Ginkotrees use what are essentially 5 gallon brewing buckets as recepticals, half full of straw, then you put a handful of sawdust on top after every visit. When full, they go on a special compost heap.

Bulgarianlily

Joined: 01 Jun 2008
Posts: 1667
Location: South West Mountains of Bulgaria

Posted: Thu Mar 10, 11 9:34 am Post subject:
we use a lot of sawdust in ours, it is a 15 liter buckets and it gets emptied every two or three days for two people, but then it is the only loo we have. You don't have to worry about making it too airtight as the sawdust covers and prevents smells.

cassy

Joined: 04 Feb 2008
Posts: 1047
Location: South West Scotland

Posted: Thu Mar 10, 11 10:23 am Post subject:

We use 50 litre ex-mango chutney barrels, in a wooden box with a conventional toilet seat on top.

For 2 people full-time plus occasional visitors, we 'produce' 40 litres of material a week. This is for 1 person's urine and 2 peoples faeces.

Once full, the barrel is emptied into a 0.9m3 composting bin. We fill 3 of these a year, so 1.35m3/person/year. We intend to leave the bin to compost for 2 years to be on the safe side in case we don't achieve good thermophillic composting, so we will need 3 sets of 3 bins (we're currently filling set 2). We have decided not to separate off all the urine, to add nitrogen to help to break down the sawdust but you would produce a smaller volume if you did.

Costs - the main costs have been the composting bins ~ï¿½100 to make one set of three. We could have used pallets, but in case anyone ever complains, the composting area looks clean, tidy and rat proof. They're made with 4" x 1 1/2" timber with felted rooves. The barrels were ï¿½7.18 each delivered; timber and hinges for the toilet box was ï¿½36. We have a plastic dustbin beside the compost bins which stores a cheap watering can for rinsing after emptying and a plastic brush.

In total it cost approx ï¿½370 for everything, but it should all last years and years.

We buy big bales of sawdust for horse bedding which is cheap and nice to use but we've still to find out how it will break down.

Hope that's not *too* much information.

Treacodactyl
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Joined: 28 Oct 2004
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Posted: Thu Mar 10, 11 10:51 am Post subject:

Thanks for the replies. I can cope with as much information as possible but I know a few more delicate members might not. I'll draw the line at scientific measurement of some of the finer details though.

Hopefully it'll just be solids as I will collect and use urine separately. I know a compost toilet shouldn't smell so shouldn't need to be air tight but as it'll be in a garage used for other tasks and I'd like to keep flies out etc I'll aim for a reasonable seal.

Looks like the only problem will be composting. There will not be any space in our garden but I do have plenty of space in our woodland which is where the final compost will be used. However, I'm not sure if I'll need to abide by any specific animal waste/composting rules. I'd also like to compost our dog's waste at the same time so I would need to do that properly to kill off any bugs.

cassy

Joined: 04 Feb 2008
Posts: 1047
Location: South West Scotland

Posted: Thu Mar 10, 11 11:08 am Post subject:

It might be easier to use the bucket lid as a seal when not in use, to avoid fly infestation. We screwed the toilet seat on to the plywood top and recessed the toilet seat hinges to allow it to sit flush on to the toilet seat, removing the rubber bumpers. It's an ok fit, but not a perfect seal. The plywood is hinged and that section lifts, taking the toilet seat and lid with it, for fitting and removing the barrel.

Nicky cigreen

Joined: 25 Jun 2007
Posts: 9886
Location: Devon, uk

Posted: Thu Mar 10, 11 11:10 am Post subject:
how much sawdust are you getting through a year?

cassy

Joined: 04 Feb 2008
Posts: 1047
Location: South West Scotland

Posted: Thu Mar 10, 11 11:47 am Post subject:

We didn't start out using the bales last year; we were getting free sawdust from a local sawmill in variously sized bags but I reckon it would equate to 6 bales per year (I'll keep a closer count this year).

That's 1 bale per compost bin as soak when empting the barrels and 3 used as soak and cover material in the barrels as they're being used.

The bales are 43cmx37cmx78cm (0.12m3) and cost ï¿½7.25 + vat.

So for a year, ï¿½43.50 plus vat.

We're hoping to eventually use our own sawdust.

sally_in_wales
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Joined: 06 Mar 2005
Posts: 20809
Location: sunny wales

Posted: Thu Mar 10, 11 11:52 am Post subject:
anyone using shredded paper in theirs in any proportion? Looking at the amount of junkmail I seem to put out for recycling or letters etc that get shredded, it might be usable as a soak layer in the bins mixed with sawdust?

cassy

Joined: 04 Feb 2008
Posts: 1047
Location: South West Scotland

Posted: Thu Mar 10, 11 12:02 pm Post subject:

We tried some shredded paper but it was not very good as a cover material IMHO and didn't prevent smell. We didn't try mixing it, but it could be useful as soak in the compost bins as you say.

If anyone is wondering how much space a composting toilet would take up in the bathroom, ours is 70cm wide, 47cm high and 62cm deep. This includes a compartment for soak material, so you could reduce the width to 49cm and you could reduce it further if you used a smaller diameter bucket and less robust carcassing (ours is built to withstand a nuclear attack

). There are some lighter weight models in Chapter 6 of The Humaure Handbook.

Ginkotree

Joined: 26 Jun 2008
Posts: 2956
Location: south west wales

Posted: Sat Mar 12, 11 11:34 pm Post subject:

The straw does break down very well,better than paper at the bottom of the buckets. Brewing buckets seem to be a very comfortable sitting height and have tight lids for when transporting the bucket to the compost site.,I add well rotted manure with worms to the composting units and adding shredded nettles can also aid the process .
The 'Sealing', I think is not necessarily in the lid closing tightly but in the covering of the "Offering". In all the years of running the bin method I have not had a fly or smell problem if the covering is done properly. Somehow, this stops smells and flies.I suspect flies would be attracted to uncovered "offerings" On days when we have many visitors I use grass cuttings rather than sawdust as there is so much extra bulk being added to the bin in one day. the Loos tend to smell of grass cuttings.Most visitors are generous with the sprinkling of grass so everything works well...Most folk are really pleasantly surprised and have said it is better than using some public conveniences.
We also place bunches of herbs in the room which is simply there as a Nice thing to do but not necessary.
We have spring water to rinse the bins and once clean I leave them in the sunshine to air.

Bulgarianlily

Joined: 01 Jun 2008
Posts: 1667
Location: South West Mountains of Bulgaria

Posted: Sun Mar 13, 11 4:43 am Post subject:

The sawdust breaks down into lovely compost BUT we don't collect the urine seperately and I think that if you did this the compost would be too dry to rot down. I think the urine is needed for it's nitrogen content also in the mix. Otherwise you would have to add some green stuff at some point. There is NO fly problem as long as there is sawdust on top. We have been using this system for the last four years. The other thing you need is to have a bucket cleaning area well set up. I wish I could find a stainless steel bucket of the same size (with a lid for removel) as the plastic buckets eventually smell themselves as they build up scratches that can't be well cleaned and we replace ours yearly.

How do you move the big 50 liter buckets?

Lorrainelovesplants

Joined: 13 Oct 2006
Posts: 6521
Location: Dordogne

Posted: Sun Mar 13, 11 10:01 am Post subject:
Those who have already installed these...could you give suppliers website/contact details? We are ready to do this in April!

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