I’ll try to put this as delicately as I can so as to not offend people’s sensibilities. Ahem…
I posted about this before, but it keeps coming up over and over when tiny/small houses and sustainable living are mentioned and I think there are a lot of misconceptions on the topic of sewage management. Some people have no qualms about using composting toilets and others have the “poo? Ew! I’m not touching that stuff” reaction. Well, technically, you were touching it all the way up until it… oh right, “delicacy” *cough*.
The gist of composting human waste
Waste is easier to manage when separated into solids and liquids.
Urine is actually quite easy to dispose of in that after collection and in fact can be directly released onto the roots of any ol’ tree (with some water added to dilute it so as to not overwhelm the root system if you keep to the same tree) since it’s rather sterile to begin with.
Many urine disposal systems for composting toilets follow a very similar setup to the typical septic system in that it is contained, diverted and released into the drain field. The containment is very small, because the system is only designed to handle urine and possibly gray water (from your shower or faucet).
As with regular septic systems, oils and grease are your enemy as they don’t decompose and just float to the top of the tank clogging the system if not suctioned out periodically. This follows the standard maintenance regimen of all septic systems.
More simple urine disposal systems involve a jug and a trip to the yard, but then there is a brief smell during the disposal. This dissipates rather quickly and you never need to worry about releasing to the same location overwhelming the vegetation. Most people tend to avoid this so as to not deal with “handling” or venturing out during a blizzard.
Solid waste needs a bit more attention.
This is really no different from leaf or other organic composting although you would need to keep the two separate since human waste needs more care before it can be used or handled. You can safely drop toilet paper in there as well and, best of all, not worry about clogging no matter how much of it you use since no water is used.
The key here, that it requires the action of aerobic bacteria which will rapidly decompose the waste vs the typical septic system which uses anaerobic bacteria and is far slower. The action of aerobic bacteria is odorless when implemented correctly and the end result can be used on your garden.
Once you go potty (and used a separate line for liquids), you would need to put a layer of sawdust or similar wood powder over the refuse so as to prevent odors from escaping and to provide a bed for the bacteria that’s going to work on it. More complex systems have automatic collection and aeration with a vent system that draws air over the refuse and out the vent, but these are expensive and tend to collect urine in the same container, prolonging the composting process.
The trick to getting this right is to make sure that it’s dry. Dry poo is easier to manage and doesn’t smell.
For this substance to go from poo to compost, it needs to be exposed to the bacteria for some time, the length of which will depend on how many people use the toilet and how often. A lot of DIY solutions involve a bucket, a small hand shovel with a bag of sawdust on the side… and that’s about it.
For something a little more advanced, I propose the use of a tilted 55 gallon barrel on rollers underneath the toilet floor which can be periodically turned manually or automatically by a motor.
Think of it as being similar to cement mixer. The barrel and the bottom of the toilet (the opening) can be enclosed with a 2 x 4 wall, which would create a tiny “compost room” with a door. This room can then be aerated by roof vent and possibly a small fan. The system can be setup similar to traditional bathroom venting system, except instead of the bathroom being vented, it’s the “compost room” with the barrel which would also draw air through the toilet opening preventing any odors from coming back into the dwelling.
By venting the “compost room” by fan, you may also be able to avoid placing a separate vent in the bathroom, since any moisture will be drawn into the “compost room” below and out the vent. But you would need to run this by the building inspector first.
Of course, this won’t be practical on existing structures unless you have access to a crawl space or, preferably, a proper basement and there’s nothing in the way below.
As with other composting solutions, this would require manual emptying from time to time of the bucket/barrel, but the good news is that once the composting process is under way, you’re dealing with odorless semi-composted waste and not just poo. You would still need to use gloves until everything is properly composted, but once it has, it’s just fertilizer.
Why would you even bother?
A full bath and a toilet flush are the biggest water wasters.
Even if you can justify a full bath for the emotional gratification, think about what happens when you flush an ordinary toilet. You’re just pouring water down the drain! There’s just no justification for it.
Even high-efficiency flush systems basically do the same thing so imagine what you could do with all that water instead (take a bath! LOL).
Besides that, there’s no guarantee just how much water we’ll have access to in the future. Our aquifers are being used at an ever-increasing rate and they aren’t being replenished nearly fast enough to keep up with demand. With a system like a composting toilet, you can tap into not just rain water, which will eventually end up in the aquifer after you’re done with it anyway, but also well water if you have access to a well without worrying too much even during a drought.
Rain water collection is the next best thing to a well in terms of water recycling and if the treatment and filtration are done right, you can truly save the well for real emergencies.
A composting toilet will go a long way to ensure you will have a safe and sanitary life in your dwelling without impacting our water resources as much.