Human Waste Vermicomposting

Neal McSpadden
#1. October 5th, 2011, at 6:26 PM.

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?

Gordon
#3. October 6th, 2011, at 10:34 PM.

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
#4. October 11th, 2011, at 2:51 PM.

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
#5. October 16th, 2011, at 2:19 PM.

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
#6. October 16th, 2011, at 2:20 PM.

Sorry to be a Debi-downer

Gordon
#7. October 16th, 2011, at 11:42 PM.

@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: http://www.sun-mar.com/) 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.