What are compost toilets?
Compost toilets are dry or waterless toilets, i.e. one that doesn’t use water to take the waste somewhere else; it also allows natural processes to produce useful compost, after a resting period depending on the type of toilet.
Outdoor compost loo, by the Thunderbox Collective.
DIY compost loos
There are usually two chambers – one in use and one resting. A typical toilet would use one chamber for a year, then change to the second chamber and allow the first to decompose for a year before emptying. They don’t smell, as long as there is a vent pipe, and a drain to take away excess liquid.
A handful of a soak (straw or sawdust etc.) is dropped into the toilet after each use. This is because bacteria like to eat a balanced diet of carbon and nitrogen, and as human waste contains a lot of nitrogen, if they don’t get enough carboniferous material (like sawdust, straw, hay, shredded paper) they will give off excess nitrogen in the form of ammonia, which makes the loo smelly.
Compost loos don’t have to be outdoors; if done properly, there will be no smells, and an indoor toilet will be more comfortable.
The soak allows oxygen into the pile, and absorbs liquid. This allows the pile to decompose aerobically to produce nitrates, phosphates and sulphates. Without a soak, the pile will decompose anaerobically and produce methane, ammonia and hydrogen sulphide – all smelly and not very useful.
Human pathogens don’t like conditions outside the human body, so almost all will be dead after a few hours. Only one type of roundworm egg can survive a year-long decomposition period, and even that’s not going to survive washing and cooking. But even though it is a tiny risk, you could use the compost on fruit trees and bushes rather than in the vegetable garden.
A tree bog is a type of outdoor compost toilet with nutrient-hungry trees planted around it. Solid and liquid wastes are simply deposited into a hole in the ground, and the tree roots absorb the nutrients.
Another, simpler compost loo system is based on Joe Jenkins’ ‘humanure’ idea. It’s low-cost, extremely simple and it works. The downside is that there are buckets to be emptied. Here’s an article about some friends of ours who used the humanure system for many years.
Vent pipe: in this case vent pipes from each chamber meet to vent any smells above the gutter line.
Off-the-shelf compost loos
You can also buy off-the-shelf toilets with one chamber – for inside or outside use.
What are the benefits of compost toilets?
Main benefits
-
- the solid waste is dealt with on site, and doesn’t have to be treated with chemicals in sewage farms, or end up in waterways, where it causes pollution and algal blooms
- saves water – you don’t have to use one resource (pure drinking water) to flush away another (fertiliser)
- organic matter is allowed to go back to the soil where it belongs, improving soil structure and nutrition
Henry Moule’s earth closet almost became the standard Western toilet in the 19th century.
Other benefits
- no chemical cleaners or bleaches are used in the toilet
- they don’t contribute to the sewage sludge that is often dumped in landfill, or more controversially, put on to agricultural land uncomposted
- as long as the decomposition is aerobic, there will be no greenhouse gas emissions
- no electricity needed
- very low resource use – no pipes are needed to transport waste to a sewage farm, and no truck needed to remove solid waste
The Air Head toilet is small enough to be used in a camper van or on a boat.
What can I do?
Installing a compost toilet
There are many different types that you can buy. Here are some examples:
- Separett or Air Head: see Eco-Toilets – the Separett looks like an ordinary loo, and the Air Head is small enough to be used in a camper van or boat
- Rota-loo: plastic, several chambers on a turntable, fan
- Biolet: small toilets, some models electric, some not; distributed in UK by Wendage Pollution Control
- Clivus multrum: one large chamber, vent with fan
- Sun-mar: small; electricity used to evaporate liquids; distributed in UK by Toilet Revolution
- Natsol: make their own twin-vault loos with stainless steel urine separator
There are many more, with new models coming on to the market each year – do the research to find which model might suit you best. Alternatively, you can build your own. This will work out cheaper, and there is no need for electricity. The components of a basic unit are: two chambers, platform, vent, hatch, and removable seat. Our book explains how to do it. Going on a course might be a good idea too.
A HepvO valve is the simplest way to convert a conventional urinal to a waterless one.
Using a compost toilet
A compost loo is not a flush-and-forget system. A DIY compost loo needs to be checked every day to see that no problems are developing. If necessary, an ingenious fly-catcher can be made from a glass jar and a little cone made from perspex. Ensure that there’s a bucket with ‘soak’ (e.g. sawdust) next to the loo. To stop a ‘peak’ developing, it may have to be ‘knocked every couple of months with a rake or hoe either via the hatch or seat – this may not be necessary though.
Waterless urinals work well with compost toilets, as urine can be used as a completely-pathogen-free fertiliser, and it stops the compost toilet from becoming too wet. Waterless urinals can be adapted for female use too. Some compost toilets are designed to separate urine from solids.
Emptying one of the chambers.
After the toilet has been used for a year, remove the seat and blank off the hole. Attach the seat to the second chamber. One year later, empty the first chamber and move the seat back. The material from the chamber will be indistinguishable from bag compost bought from a garden centre if it’s done properly. We’ve taken compost from a compost loo and from a garden centre to events around the country, and people couldn’t tell the difference.
The procedure is different for various kinds of manufactured toilets. See here for a detailed, step-by-step guide to getting and using a compost loo.
The specialist(s) below will respond to queries on this topic. Please comment in the box at the bottom of the page.
Patrick Boylan has had a long-term interest in the environment. A graduate of the Trinity College Dublin Botany Department in 1998, he founded Toilet Revolution in 2012. Patrick has researched manufacturers the world over, and Toilet Revolution have hundreds of composting toilet installations around the UK and Ireland.
We'd love to hear your comments, tips and advice on this topic, and if you post a query, we'll try to get a specialist in our network to answer it for you.
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Rob Chambers, composting said on May 13, 2016
Just implemented a new design that has been used for hundreds of years. It’s rather troublesome because the maintenance is somehow tedious but I think it’s worth it if you’re aiming for a low-impact living. Plus you get sweet compost and no waste is wasted. 🙂
Rob, gardener & compost expert at http://www.gardenersserviceslondon.co.uk/
Anne Chapman said on October 10, 2016
Has anyone heard of compost loos catching fire? We own a small bit of land in Cumbria and had built a compost loo there, using a natural rock outcrop – you walked into the toilet at the top of the rock outcrop and the toilet was over a drop of a couple of meters, with the deposits being retained by timber sides. It had been there some years and was just used intermittently. However, in July this year we visited and found it had burnt down – all that was left was a few blackened bits of timber, and not much of that. One possibility is arson, but it’s a pretty out of the way place and there’s no other evidence of people being around, such as rubbish left there. Is it possible that it has spontaneously combusted? The loo seat may have been left up and if the wind was in the right direction it may have blown up through gaps in the timber and perhaps led to the compost etc. catching fire? Once it got going the structure would have acted like a chimney, and the whole lot burnt. The surrounding vegetation is pretty much unharmed. Has anyone known of something like this happening before?
Dave Darby said on October 11, 2016
I’ve never heard of it and I think it’s pretty unlikely. First, the decomposition would have to be anaerobic to give off methane, and so would have to be waterlogged or in a sealed container. If it intermittently used, with timber sides, it wouldn’t be waterlogged. Then there would have to be a spark or a fire – maybe someone throwing a finished cigarette down the loo. But it’s quite difficult to start a fire, and there almost definitely wouldn’t be any methane produced anyway, so I’d say arson was a lot more likely than spontaneous combustion.
Ollyoop said on December 21, 2016
hi i’ve seen systems that seperate the urine from solids. is this necessary? or can it all go into the one tank?
Dave Darby said on December 21, 2016
It can all go to the same place as long as there’s a drain at the bottom. If it gets waterlogged, it will become anaerobic and smelly. So there needs to be a drain, or a urine separator, or try to wee somewhere else (on a straw bale is good – turns to compost eventually), or a waterless urinal?
DiHammill said on February 18, 2017
Hello, Im looking into either bought or home-made compost loo for our tipi site teaching sustainable living and want to know if we made our own (we would rather go for a bought one but the prices are dear) – what is the vessel people use for he chamber? A wheelie bin with holes in sat in gravel with eg. willow growing would that do – say two next to each other to allow the one chamber to compost while the other is in use? Chamber advice please!? Di
x
Dave Darby said on February 20, 2017
You could certainly use a wheelie bin, as long as there’s a drain, as you say, and as long as straw, sawdust etc. is used to add carbon. Then when it’s full you could wheel it somewhere to break down for a couple of years.
Or – you could just dig a pit (as long as it’s more than 10 metres from a watercourse. Liquids will drain away, cover it over when full, and if you want to, you can dig out the compost after a couple of years.
Patrick Boylan said on February 20, 2017
There are a couple of differences between the off the shelf toilets and the home made. Venting. It’s important to get the vent flue to come directly out the top of the container to minimise odours, as opposed to coming out the side. Thermal Insulation, if you want the material to break down in the toilet then the compost pile will need to be above 13 deg C. This can be tricky to achieve as you must try and get an air tight seal between the top of the container bin and the underside of the toilet seat support. If you don’t all the heat will be lost and the compost will chill. But this may not bother you as Dave suggests you could just allow the material to break down over a couple of years and use a number of new containers. The off the shelf version overcomes these issues. On the idea of digging the pit, I think this is a risky option. The problem is that the base of the pit should be 1.5m higher than the high water table level. The high water table level is the level of the water table after a long rainfall event. If you don’t get this clearance, faecal matter could get on to the water table and contaminate drinking water for several months.
Graham Suddick said on May 9, 2017
Here is a UK company making eco loo’s: http://www.kildwick.com/
icarus said on August 28, 2017
The one important item missing from these toilets is a chimney pipe. It connects to the waste can just below the lid. Its purpose is to draw air into the toilet pan and thence out up the chimney . The result of fitting a chimney is that there is no odor even with a poorly fitting lid as air is constantly drawn into the toilet, Even when you lift the lid there are no nasty smells rising from the pan
icarus said on August 28, 2017
whoops just read the earlier post where Patrick has covered this excellently
icarus said on August 28, 2017
if your house has mains sewerage connection is there any legal obligation to use and pay for it or can you cap it off and notify the water authority their service is not required ???. I have commenced disconnection from the drainage system . Roof rainwater now is pumped to a storage tank with an overflow that finally terminates in a soakaway.
Patrick Boylan said on August 29, 2017
Sounds like an excellent system you have installed there. Is the rain water harvesting system got a mains top up for dry periods? I assume you have a water meter which is reading near to zero so is it the standing charge you are trying to avoid?
icarus said on August 31, 2017
I didnt want to top up from the water mains and at approx 1kg per litre i opted for ground level storage outdoor tank.I use a dual shower pump and pressure switched expansion tank to feed water at 3 Bar to house for good shower and working taps with no plumbing changes After pump supply goes through double check (1 way) valve to a tee The water meter feed goes directly into a second double check valve outputs through an electrical solenoid valve then to second leg of the tee.The output of the tee or feeds the whole house( apart from filtered drinking water taps fed solely by water meter). My supply conforms to uk water regs as it is isolated from supply water mains . to use rainwater electricity is supplied to the dual shower pump to use mains water the electrical supply is removed from the shower pump and connected to the solenoid . This can be done by a change over switch or relay . .My storage tank a recycled 1200L IBC has a float switch about 2cm from the bottom to automatically switch over to mains water when the tank is emptied to its last 50 L. . I worked in electronics industry, having escaped from the family plumbing and building business .There is no need to build a controller from individual electronic components as float switches and relay driver boards are available ready made at low prices . I just box them into nice looking electronic controllers. I am willing to supply full parts lists wiring diagrams and supply sources for UK if anyone wants to build their own controllers Yes I want to avoid the standing charges
Dave Darby said on August 31, 2017
Wouildn’t mind having a look. Are you happy for us to make them public in the rainwater harvesting section? We’ll acknowledge you.
Patrick Boylan said on September 1, 2017
Yes, I’d be interested in having a look too. You mention that the tank is topped up by the mains though – Anyway at the end of the day the correct body to ask is the water authority that sends you the bill and see what they say as there is no hard and fast rule for this around the country.
One thing to mention is that if you are showing in the rainwater you could be at risk here. The problem is legionaries disease which you can inhale as the water becomes an aerosol in the shower. Storing water at ambient temperature is quite likely overtime to develop legionnaires (https://en.wikipedia.org/wiki/Legionnaires%27_disease)
icarus said on September 5, 2017
hi sorry for delay ,I have been on holiday to Norfolk. The water main never tops up the tank it goes through a double check valve then an electrical solenoid connects it directly to the house when the stored water is low as ,sensed by a float switch. A second double check valve on the output of my pumped stored water prevents any water from the mains feeding back through the pump and into my stored water .. The water authorities state that no other water must be in contact with the drinking water supply . Full compliance is achieved by using the double check valves . To be compliant even a tap for a garden hose should be fed through a double check valve so that there is no contact between the stale water in the hose and the supply which could occur if the hose was turned on with a shut off sprayer on the other end. . I will happily post pictures and plans including circuit diagrams if anyone wants them .
EEK! I hadnt considered the legionnaires risk!!. Thanks Patrick- the first idea that come to mind is chemical based chlorination then feed the shower through a cheap charcoal filter.
Patrick Boylan said on September 6, 2017
Heyup, i wouldn’t be an expert on legionaries treatment. I suggest you post a question on http://www.susana.org/en/ . The level of knowledge on this blog is PHD ++, really knowledgeable people. Cheers; P
icarus said on September 6, 2017
thanks will do , I wish i had a cellar to put the water storage tank in but it has to survive outside . At the moment everything connects together with push fit piping and the mains water and high pressure output is in john guest plastic pipe so it is fully demountable The tank presently is right in the middle of the path . I am stripping and re-building the system into a small purpose built shed and putting in some proper trenches so the pipes dont freeze in extreme weather the pump could be run at low speed to circulate water round the system as moving water doesnt get cold enough to freeze . In 2 or 3 weeks time when it is all back together visitors would be welcome . I live in North west Leicestershire . I tend to be a hoarder and dont do tidy- there are quite a few part finished projects in the workshop.Sorry i sent this posting off topic ..On the toilet side i think if i started with the top half of a porta potty toilet added a press button to squirt a measured volume of waterto wet the walls to stop things sticking to the pan and a fine spray hose to clear away reluctant packages . the result would be a sealig trap flushable very low water volume toilet. Its a problem getting enough time to build prototypes to test all these ideas..
Patrick Boylan said on September 7, 2017
Heyup, hate to self promote ! haha but there are a range of pre made composting toilets that you can see here https://www.toiletrevolution.com/composting-toilet/ . This one is the top seller https://www.toiletrevolution.com/products/composting-toilet/separett-villa-9000/ but this one can be connected to a water supply to micro flush the urine channel https://www.toiletrevolution.com/products/composting-toilet/eco-dry/ but that one does need space below the floor for a container. I suspect you’re more inclined to make one yourself – but good to review the existing technology to inform your ideas.
icarus said on September 8, 2017
the reasoning behind building my own toilet was that the ones i had seen were over complicated way over priced and quite ugly!. The ones i have briefly looked at on your web site look well designed beautifully made competitively priced ,The best of all though is to be offered such a superb range of products by what is a dedicated superbly knowledgable expert company- they look fantastic ! . If i was paid by a competitor . to give adverse criticism the only thing i could write would be “This company should be known to many more people across the whole uk”.
icarus said on September 10, 2017
patrick ,Wow that is one superb crapper collection they look well made and reasonably priced .The inclination to make my own is waning , congratulations on an excellent range of products . I will be enquiring soon .
Colin Ives said on September 16, 2017
The UK’s major manufacturer of urine-diverting compost toilets is now Kildwick which is in North Yorkshire. They have a wide range of toilets and components to build your own. You could do with adding them to the main list of compost toilet providers. They offer models similar in functionality to AirHead, NaturesHead and Separett
icarus said on September 17, 2017
there are many suppliers but how good is their technical advice?
Ian Barker said on November 27, 2017
We are doing a self build and have planning permission for a straw-bale bungalow with composting toilets and are going through the building control full plans approval process. We have some experience of Humanure Handbook style composting (which has worked well for us), but we plan to build a 2 chamber system under the bathroom built in to the bungalow and vented via the buildings HEV system. Our building control officer seems rather skeptical about composting loos and wants us to adhere to ANSI/NSF 41:2005 (mentioned approved document G) which is an international standard for manufactured composting toilets and not very easy to apply to a one off built system. Having contacted the Environment Agency they have said that we can use composting loos but have said that the “Liquid effluent fraction i.e. urine, needs to be stored in a sealed tank and collected by a waste contractor for disposal at a sewage treatment works.”. Apart from the fact that the urine is the best bit from a plant food point of view we’re worried that once this goes through building control we’ll be digging up half our garden to fit storage tanks. We really want to avoid connecting to mains sewerage if we can – more than 30m away (albeit not much more) – as we’d rather not pay for a high impact lifestyle in order to live a low impact one. We know there are plenty of practical ways to deal with this, some of them outlined in Dave Darby’s book – bale urinals, soak-aways etc. and are very happy we can get something to work various ways from a practical point of view but building control want everything specified to a t and we don’t want to paint ourselves into a corner with the regulations. Can anyone help?
Patrick Boylan said on November 27, 2017
Hi Ian,
Thanks for the query – the project sounds very interesting. If the building control are looking for NSF certification you can use a Sun Mar or a Clivus Multrum, you can see the NSF listing on this page:
http://info.nsf.org/Certified/Wastewater/Listings.asp?TradeName=&Standard=041#new
The Clivus Multrum (.co.uk) units are more suite to parks and they are rated as such in x uses per day. The Sun Mar range (available from myself in Toilet Revolution in the UK) are rated in terms of numbers of persons for residential use. I suggest you contact both companies with the numbers of people you are looking to accommodate and see which units are suitable. Both Clivus and Sun Mar are not urine diverting toilets so the urine fraction will have soaked through the compost pile so I would call it ‘compost tea’ as opposed to urine as it will have faecal coliform in it. This will reduce the liquid output though, as much of the urine will soak into the pile, beevaporated off due to warm composting activity, and on electric sun mar units there is a heated evaporation plate to evaporate off excess liquids. It is still advisable to connect up the emergency overflow for power cuts and high usage (say a party for example). It is hard to estimate but even if you have to store excess liquid I would guesstimate for a residential situation that this would be way less than a 1m3 IBC (https://www.deltacontainers.com/reconditioned-ibc/plastic-pallet-reconditioned-ibc-containers.html) which could fit on in most gardens. All that said there are hundreds if not thousands of people in the UK using other technologies like the Separett, AirHead, Kildwik but I suspect they have not had to go through the planning process and they are retro fitting them. Queries welcome
Thanks Ian,
Patrick
Ian Barker said on November 29, 2017
Hi Patrick,
Thanks for the response. That and having a closer look at Multrums has helped me to work through what the Enviroment Agency Regulations are for disposal of compost etc. For anyone else wondering, I think they currently base their policy on ‘Regulatory Position Statement 36’. It tries to shoe-horn compost loos into being either septic tanks or cesspools based on whether the toilet separates “the liquid fraction” from the solids or not. You more or less need them to be in the septic tank category for disposal options. I had read this as: you have to separate the urine, at source as it were. But I think this can just means separating the leachate (‘compost tea’), as with Clivus Multrums (and others I guess).
BTW, buling Regs approved document G4 precludes using power to evaporate off the leachate (as with some Sun Mars) (not that we’d have the power anyway as we plan to be off-grid), but as you say the volumes are small esp. after natural evaporation from the generated heat. Hopefully, we can come up with our own design (with enough leachate storage internally) that will both allow Building control to tick enough boxes and work!
Thanks again,
Ian.
Patrick Boylan said on November 30, 2017
Hi Ian,
Thanks for highlighting the building reg doc. For reference here is it:
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/504207/BR_PDF_AD_G_2015_with_2016_amendments.pdf
Chemical and composting toilets
4.19 Chemical toilets or composting toilets may
be used where:
a. suitable arrangements can be made for
the disposal of the waste either on or off the
site; and
b. the waste can be removed from the premises
without carrying it through any living space
or food preparation areas (including a
kitchen); and
c. no part of the installation would be installed
in any places where it might be rendered
ineffective by the entry of flood water.
4.20 There are currently no British or European
standards for composting toilets. Appropriate
guidance can be found in ANSI/NSF 41:2005
as amended by Addendum 1:2007 Non-liquid
saturated treatment system.
4.21 Composting toilets should not be
connected to an energy source other than
for purposes of ventilation or sustaining the
composting process.
Just for clarity, the heating element on the Sun Mar (electric units) is required to sustain the composting process. It provides a base line temperature for composting to start. Composting is a bacterial process and does not start below 12 deg C. There is no heating plate on the non electric Sun Mar range.
Hope this helps,
P
Dave_M said on December 3, 2017
I’m starting to look into the idea of building a compost toilet and have just finished reading Dave Darbys’ book compost toilets which has encouraged me to continue the idea. I do have two main outstanding questions I’m trying to work through and would appreciate any feedback:
1 – Dog waste – any major concerns with adding this to the mix?
2 – The toilet would be built in an area with coldest temperatures around 15 degrees and warmest around 35 degrees centigrade. Any additional design features that may be useful for warm areas?
The project will start in about 6 months if it goes ahead. Look forward to any feedback, thanks.
Dave
Patrick Boylan said on December 4, 2017
Hi Dave,
With composting high temps are your friend in terms of sanitizing waste. The theory is that bugs etc in human and dog waste are evolved to exist at 37-39 degrees C, body temp for humans and dogs. So nice hot composting temps of 50+ are the business when it comes to killing them off – cool temps are less effective. Here is something i found on the topic https://www.motherearthnews.com/organic-gardening/composting-dog-poop-zmaz84sozraw
Cheers,
P
Dave_M said on December 5, 2017
Thanks for the reply, Patrick, I regularly get the (standard) compost bin up to 55-60 degrees C after digging it over, or after fresh addition of material, so hopefully a compost toilet will reach near the same once built.
Most of the information against using dog waste seems scaremongering rather than science, so I’ll go ahead and plan to use that too.
Cheers,
Dave
Dave Darby said on December 5, 2017
I think time is a factor too. Human / animal pathogens like being at human / animal body temperatures, but they also like being inside humans / animals. The longer they’re outside, the higher the percentage of them that will be dead. We have two compost bins that take about a year to fill, then rest for a year while we’re filling the other one. So stuff has between 1-2 years to break down. That’s a long time for pathogens to exist outside their body of choice, so I think it’s a tiny, tiny risk – much less than getting into a car, for example. We composted our cat’s poo when it was a kitten (he goes outside now). It turned into soil, we put it in the garden, and we’re still alive.
Dave_M said on December 21, 2017
Thanks, Dave, appreciated. I’m now thinking in the meantime of building a small construction to start composting the dog waste beside our standard compost bin. I’ll let you know in a couple of months how that goes.
I’m going to do a bit more research on a couple of thoughts that have occured to me but felt it worth putting here in case you experts already have answers:
In a standard toilet is there is anything on the market for catching human waste before it hits the water below, allowing you to transfer it to a composting container? Generally the toilet shape is too rounded to make any sort of fitting easy from the outside, but I did wonder about some sort of insert into the toilet which would allow you to catch in a paper lined basket but hopefully allow the majority of any urine to pass outside this. You could then remove the waste before a light flush for the urine, helping reduce water usage. We have standard UK shaped toilets here, not like some of the european ones with a flat area to check faeces before flushing. However with this whole idea there are probably cleanliness concerns with this too.
The other thought is picking up the dog waste in the garden, currently done in the very environmentally unfriendly way of plastic dog poo bags. For the best decomposition in the suggested dog poo decompostor, the material will need contact so need turning inside out as it is put in. Whats best for the plastic disposal afterwards – put it into the bin and leave it for the full year to wash and use again, or just remove and put into the trash? Or maybe I just need a special pair of dog waste collecting gloves.
Apologies if this appears a bit over pedantic / over thinking, but when it has health concerns I think it needs to be engineered out at the design stage.
Ann Beirne said on September 21, 2018
Hello
This might sound like a stupid question, but I have read some books on compost toilets and I am always amazed to read that you should use a urine separator, I think most people I know do wee and poo at the same time, I do when I do a poo so how the heck can you do separations at these time.
I am very impressed with compost toilets and would like to have and indoor one. My husband and I are very careful not to flush too often especially with the long drought this year.
Looking forward to the explanation
Ann
Patrick Boylan said on September 21, 2018
Hi Ann,
Yes, people do both at the same time. This is no problem using a urine diverting toilet. Basically at the back there is an aperture for solids and at the front there is a funnel for the urine. So, one sits down and does their business and the toilet the separation happens. Indoor versions (like the Separett Villa 9000) have a fan running all time to vents odours so they work really well indoors. Cheers
Helen said on October 16, 2018
Can you have a compost loo for just 2 people or do you need a large amount for it to work well?
Dave Darby said on October 16, 2018
Hi Helen
No, a compost loo for two, or even one is fine. The chamber can be smaller the fewer people it serves. Often, they’re ‘mouldering’ toilets rather than true composting toilets.
Nina Wilson said on October 16, 2018
One thing I have been unable to find out from all the sites I have looked at is what capacity do you need? ie. what is the “output” in cubic metres per person for year, allowing for adding scoops of sawdust.
Patrick Boylan said on October 16, 2018
Hello,
Yes, units for as little as one person are available. A composting toilet, where the waste breaks down to compost inside the unit is always rated in numbers of persons. In the case of the Sun Mar range which has NSF/ANSI 41 certification, the units are independently rated in user numbers. You can view the listing using the link below:
http://info.nsf.org/Certified/Wastewater/Listings.asp?TradeName=&Standard=041#new
The urine diverting toilet, which does not break the waste down inside the unit can also be suitable for one user. So minimum user numbers is not an issue.
I’m sorry Nina, I do not understand your query. Perhaps it is the user numbers query that is addressed above. The composting toilet is a waste disposal method, rather than a compost producing method although I realise these are sides of the the same coin. The standard (NSF/ ANSI 41) focuses on how many people can use it rather than how much composted material is produces… Hope that helps 🙂
Patrick (Toilet Revolution)
Dave Darby said on October 16, 2018
Nina – I think you might be talking about a self-built toilet? One person produces around 200 litres of faeces per year. Add the same amount of sawdust. But then the whole lot decomposes to about 10% of that volume. Aim for around half a cubic metre per person, and that will be more than enough. It can be used for more than one year then. See our book for more details on self-build – https://www.lowimpact.org/books/books_compost_toilets/
Nina Wilson said on October 17, 2018
Thanks Dave, that was the information I was needing. If you’re using it for compost then you need somewhere to store it until it is ready to go into the garden. So whether you’re using self-build or buying one, you need to know how much space you need to store the stuff.
Patrick Boylan said on October 17, 2018
Just for public information to the forum – Using the bought internal composting toilets, where composting happens inside the product, once the compost comes out of the toilet it is ready to go in the garden (not root veg) as it has broken down in the toilet. This is not the case with urine separating toilets that do not claim to break the waste down inside the product and yes the material must be composted somewhere else. The duration and therefore the volume of storage you need depends on some factors; the type of mulch (we like hemp), hydration, aeration, and if the composting bin is thermally insulated as composting needs 13 Deg C to start. Hot composting is much faster than cold.
Ann said on October 18, 2018
Hello Patrick
Just wanted to say thanks for the reply about how the separator toilet works, it has put my mind at rest, and we will certainly be looking into getting an indoor compost toilet.
I did try to use the reply button attached to your reply but nothing happened.
Ann