Human Waste Vermicomposting

Interesting message from Michelle:

We need to further process the human waste from our composting toilet!
I’ve read that vermicomposting could be the answer. Do you agree? Do
we need to make sure that the worms also get kitchen scraps? Also, we
are approximately in your USDA Hardiness zone (4 – 3ish) and want to
keep the worm bins in the basement but are concerned about the
temperatures they need to stay active.

I am so excited about all that I have learned on your site; thank you
for being so education-minded!

Hi Michelle,

I do indeed agree! Using Red Worms (or other composting worm species) to process wastes in a composting toilet is a great idea, and something a surprising number of people have done successfully. You definitely don’t need to provide them with food waste though – believe it or not, human waste is probably closer to the “ideal” food for these wigglers. That said, there’s no reason you couldn’t still toss the food scraps in the same system!

Your mention of “worm bins” actually leads me to believe you might be thinking about removing the waste from the composting toilet and adding it as “food” to a completely separate system (or multiple systems). In all honesty, this really isn’t necessary – you should actually be able to establish a thriving population of worms IN the composting toilet itself.

There are a couple of very important issues to consider though: 1) ammonia/salts (assuming this is not a urine-diverting toilet) and 2) pathogens. I recommend adding LOTS of bedding types of materials such as shredded cardboard on a regular basis. This will help to soak up excess liquid, keep things oxygenated, and just generally provide the worms with a much more substantial safe habitat zone. As for pathogens, while there has been considerable research demonstrating the effectiveness of vermicomposting as a means of destroying pathogens, I still recommend taking a cautious approach with any material removed from the system. You may want to further process it via hot composting before using it – and you may want to avoid using it as fertilizer for food crops (even with additional measures being taken).

It’s been shown that Red Worms hatching into a new environment are much better adapted for life in that environment than adult worms introduced from elsewhere. As such, you MAY want to start up a “regular” worm bin (assuming you don’t already have one) and then just transfer cocoons from it to your composting toilet. Adding a fair amount of habitat zone material (from your worm bin) – containing worms, cocoons etc – away from the main waste drop-off zone (lol) in your toilet holding tank could also prove to be a good stocking strategy. Whatever you do, don’t just toss in a pound of worms and hope for the best!
(Ever heard the expression “throwing your money down the toilet”?)

Regarding your temperature question – if your basement temps dip down below 50 F (10 C) you’ll likely see a pretty substantial slow down in waste processing speed. I would think that the composting toilet tank would stay warmer than the surrounding environment however – these tend to be fairly large, and the combination of nitrogen-rich wastes mixed with lots of c-rich bedding materials should result in lots of microbial activity (results in heat release).

Hope this helps a bit!

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  1. Timely post for me. I’m thinking about creating a humanure->vermicompost system at my new place.

    Is there any particular reason you are discussing doing the vermicomposting first and then thermophillic composting second?

    • Bentley
    • October 5, 2011

    Hi Neal,

    The only reason I mentioned the potential for hot composting after some initial vermicomposting is due to the assumption that the waste would be starting out in the composting toilet holding tank – likely better suited for vermicomposting than hot composting due to size and gradual accumulation of wastes. If all you did was allow the worms to process it for months, and then simply used it on non-food garden beds I think your chances of encountering pathogen issues would be very minimal, to be totally honest.

    My normal recommendation (for manures, and large amounts of waste in general etc) would actually be “pre-composting” THEN vermicomposting, since the latter process is a great way to finish off the material. This would likely work well if one were to use Joe Jenkins’ “Humanure” hot composting approach I would think.

    • Gordon
    • October 6, 2011

    We have been very successfully vermicomposting our 200L resting composting toilet bins for a few years now. With just the two of us it takes about 8-10 months to fill a 200L bin, so that is how long the worms get to work their magic. In general they have produced a fine brown loam after this period, but it does take some monitoring and sometimes some inputs. One of the keys to success has been to pay attention to getting the composting going in the bin while it is in use.

    We use sugar cane mulch as the filler in the toilet and damp this down with water from a spray bottle kept beside the toilet. Because it is such as simple system (a 200L recycled olive barrel, outdoors, with a ventilation structure built in that allows air to be drawn down through the mass then out and up to a vent) we are able to monitor the appearance of the top of the “mass” in the bin. Easy to see if it is getting too dry, for instance.

    About three or four times during the use period we use a stick or long-handled small garden fork to level off the mass, then cover it with about 50mm (2 inches) of compost from the compost heap. This introduces composting organisms (bacteria, fungi). We also make a point of adding mature fungi found growing in the compost heap to the active bin – and usually have a few crops of mushrooms come up on the mass, showing that they are doing their job below the surface. This provides the “pre-composting” that Bentley advocates, and helps to ensure that by the time the bins have to be changed over the mass has been fully composted.

    We also put in a bit of the top layer of worm castings from the resting bin, to introduce worms via eggs). Our experience with a range of vermicomposting systems is that Bentley is correct in saying that worm populations adapt to the food and medium on which they are raised. Usually by the time the bin is full there is already a healthy population of worms at work.

    It is necessary to make sure that there is an effective urine drain on the bin to stop it accumulating ammonia salts, and this then functions to drain off excess liquid during the resting vermicomposting phase – great stuff to make “tea” fertilizer, diluted about 5-10 times. I swear sometimes it seems like we can see the plants growing in response to this stuff.

    Also important to make sure that no one using antibiotics uses the toilet – plays hell with the composting process and possibly also the worm population.

    During the resting vermicomposting phase it is important that the mass is monitored to ensure that a) other organisms aren’t getting in there that might conflict with the worms, or become a problem in the surroundings. (Black soldier fly larvae are not a problem – they seem to co-exist with worms quite well, and to speed up the composting, as well as keeping away larvae from other species). It is important that the mass is ventilated – to prevent anaerobic conditions developing, but not so much that it dries out. We cover the top with damp newspaper layers, but don’t get too anal about checking regularly to see if they have dried out. We occasionally add the kitchen scrap bin to the top of the mass in the early weeks, just to encourage the worm activity in the top layer, but after a month or two the top layer will be worm castings, and all of the activity will be going on deeper down.

    In our climate (warm temperate, east coast Australia inland from Brisbane) an outdoor black plastic bin runs the risk of overheating in summer, so we wrap it in several layers of cream-coloured shade cloth in the hottest part of the summer. In winter the mass tends to generate its own warmth). The active bin is shaded by the resting bin in summer, so there is no need to insulate it – interesting too that one way to judge whether the composting is “going” in the active bin is to put a hand into the space in the top of the bin early in the morning – an active bin creates quite warm air above the mass.

    Hope this is useful.

    • Michelle
    • October 11, 2011

    Thank you so much for all this great info! I couldn’t have hoped that we can just use the bins on the composting toilets themselves. I feel like we’ve got step by step instructions…we’ll let you know when we have questions!

    • Jason
    • October 16, 2011

    While I think this is a fantastic idea if you live off the grid, I can’t say the same for those of us who live in urban/suburban areas that have city sewage services. No point in doing it yourself when the city will take your $%^& for $10 a month.

    Talk to someone like Gordon, and go look at their system, then put them on speed dial because the worst case scenario in this situation would be terrible inside a home. If you are looking to experiment, do it outside with the dog’s waste until you get a feel for it.

    • Jason
    • October 16, 2011

    Sorry to be a Debi-downer

    • Gordon
    • October 16, 2011

    @Jason: You have one good point – that being a living system a worm farm, no matter what it is based on – kitchen scraps, human waste or whatever – is subject to the impacts of a range of factors, and therefore can go down a path you don’t want it to. That is why it is important to do a lot of research on these systems before starting, and to manage and monitor pretty constantly, at least till you get a feel for the system.

    As for putting it inside a house, I wouldn’t recommend it, though we do have a commercial dry composting toilet system (SunMar – a Canadian company: installed in our bathroom / laundry for those times that it is too inconvenient to go outside. After a not too steep learning curve it has now been running very well for more than a year and yields a light, dry compost that is periodically taken out of a finishing drawer at the front. However I would not like to be relying on this as our only toilet, because if it does go wrong you have no alternative till you have fixed the problem. Nevertheless, there are a lot of these around the world installed in houses, holiday cabins, national parks, etc. Our local government housing approval authority was quite happy when we said we were installing a SunMar in the new house. And of course there are even more systems where the barrel is located outside the house or in the basement. The technology works – the waste gets composted. Adding worms to it, whether in the active or resting barrels, just helps to ensure that the end product will be a rich loamy soil that can be used immediately.

    Something like the system we build ourselves has been used by my sister for an in-house installation, but with the barrel under the floor of a fairly high-set house. This was in a densely settled trendy inner suburb and did not cause any problems to them or the neighbours.

    “No point in doing it yourself when the city will take your $%^& for $10 a month.” Maybe, unless you don’t want to add your contribution to the total waste of a valuable resource, or the pollution of waterways, or the financial and environmental cost of moving your waste to a processing plant and then processing and disposing of it. Or maybe you just want to take responsibility for your own life, as well as being able to use the product (a rich brown loam) to grow your own food.

    We each have to establish our own values and priorities, decide what is possible in our own situations, and be responsible for our own decisions. For a lot of us this means that we use composting toilets.

    • Jeff
    • April 2, 2013

    Would it be possible to introduce worms directly into the solid waste (no urine) without adding carbon? Harvey Ussery does this with horse manure as a method of growing worms to feed to his chickens. (He actually insists on removal of loose carbon [like straw] to make sure the pack doesn’t hot compost and burn out the worms.) But I’m not sure if the resulting compost is okay if you start with human waste instead of horse waste.

    • Bentley
    • April 2, 2013

    Hi Jeff,
    I remember being inspired by Ussery’s description of his greenhouse vermicomposting set up (having a worm bed below a removable walkway) in one of his Mother Earth News articles. I need to check back, but I could have sworn he hot composted the manure for a period of time before adding it. Even if not, he would be adding it over top of a large, established bed (so the worms are not being forced to move into the material right away). Important to also remember that horse manure is pretty fibrous carbon-rich stuff by manure standards – kinda like the “ultimate” Red Worm food/habitat all in one. Wet sludgy humanure (or dog manure etc etc etc) just wouldn’t offer a good habitat for the worms. I’m sure if sat outside in a heap for a period of time it would be great – but I’d be shocked if anyone had success using it solely (when fresh) as a food/habitat. With an established bed (as alluded to above) – especially one with excellent air flow – a LOT more is possible.

    • Jeff
    • April 2, 2013

    I’m getting the info from Ussery’s recently released “Feeding the Small-Scale Flock” book. He has bins divided into two 4×4 sections and fills half at a time, one side with worms working through the old manure, and the other side filled with fresh manure. As the one side gets fully composted, and the fresh side goes through any residual heating, the worms move over into the fresh side and he can harvest the old. Here’s a pertinent section from his book:

    “I filled the bins exclusively with pure horse manure from a neighbor who breeds and boards horses. Note that qualifier *pure*: if the manure is mixed with hay, straw, or pine shavings, it will heat up, as in a compost heapβ€”a disaster for the worms. Pure manure will not heat up, or only slightly so. It is an excellent medium for the worms. They live in this medium (using it as a bedding) while converting it (using it as feed) into castings.” -p.183

    Your note about the fibrous/moisture differences is well-taken. Human waste would definitely need to settle a bit before the worms would take to it. And it’s also rare to get it in 4x4x1 sized loads. πŸ˜‰ But my real concern is with pathogens. Does vermicomposting eliminate human waste pathogens? Or would you have to do hot composting and then feed that through the vermicomposting setup?

    • tokies
    • November 8, 2013

    i think maybe it would be better to use solider flies due to dampness of compost before it gets to the worms then use the worms to finish it all up

    • Samantha
    • January 18, 2014

    Great article! Looking to install a toa-throne type composting toilet, do you think it would work with the worm composting in the unit under the house? (warm climate) It usually takes 2 years some say before any product is expelled without worms, and there would be no urine separation, but would have organic material added at every use (mulch, scraps, toilet paper) and bedding or sawdust if moisture levels were to high. Wanting to base it off of systems like the ones shown here: but maybe modify it to accommodate worms, any tips and advice are welcome!

    • Randi
    • May 13, 2014

    I have been looking into this a lot now. And while there is little in the way of resembling a traditional toilet system here in America, the Australians seem to have perfected this system. It works just like a septic tank (there is a breathing tub type thing so the little guys can breath) you flush your toilet like normal it all goes down into a container like a septic tank (if you already have a septic tank they can convert it for you) the worms do their thing and then what is left is a “tea” that pumps out into your garden like an under ground water system. It is evidently safe to put of food crops and very beneficial to plant life. It requires no up keep, there is a compost shoot you can put kitchen organic waste in, there is no smell and no hassle. They will come out 6 months after the install to make sure everything is running to plan, and then you can have them come out once every two years, just to check up on it, or not. They also say there is no problem with medications in the human waste you can have your grey water go into it and it doesn’t affect anything, and while they recommend using earth friendly soaps, it is so diluted it isn’t a big issue. They make systems for small homes to large companies. You can leave for months at a time (suitable for vacation homes) or you can have a massive party and the system is never over burdened. A and A waste management in Australia is who is doing it (though there was a couple others) but we don’t seem to have anything like this in America, we don’t even seem to discuss it. I have looked at dozens of forums (American) and no one seems to even know anything about. Is there anything like this in America, why is there so much conflicting data between what people say you can do here, and what they ARE doing there (i.e. medications, must be a dry toilet, cant use the product on crops)?

    • Jo
    • April 11, 2018

    HI, I’m about to install a Sealand Dometic toilet (minimal water use) inside a seperate bathroom hut, with a separett urine diverter and Sun-Mar composting chamber underneath the building. I’m wanting to add tiger worms to the Sun-Mar to help composting times? Do you think this would work please? and what things would you change or monitor? Thanks for any advice you can give πŸ™‚ Im in New Zealand with moderate climate. Cheers JO

    • Bentley
    • April 12, 2018

    Hi Jo
    The advice I always give in this situation is to make sure you establish a SAFE worm habitat, hopefully off to the side somewhere in the unit. If the worms have a safe “home base” (emptying the contents of an active worm bin would likely work well – as long as that bin had plenty of good habitat material in it) to hang out in your chances of success will be much higher.

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