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Humanure and Compost Toilets

An interesting discussion on Compost Toilets in the forum should probably be in this group, too.

Here's an excerpt, originally posted by Frost:

"We use a home-made composting toilet, based roughly on my reading of Joseph Jenkins' "Humanure Handbook", at our farm.

It's simply a shed over a deep hole filled with straw, which we "flush" with straw / sawdust / strips of newspaper. We don't separate - everything goes into the same hole. The shed doesn't cover the entire hole, so part of ot is exposed to the air and rain.

This has been perfect for a year but recently has started to smell. I suspect it was because it was too wet and lacked carbon, so I added lots of shredded newspaper and spread it out a bit, but so far this hasn't improved matters. Would appreciate any other suggestions.

FYI, we are in Ireland so it's not particularly hot..."

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Replies to This Discussion

Permalink Reply by Tim Kinney on November 24, 2012 at 9:10pm

I too read the Humanure Handbook. It's a great resource. Some people "flush" their composting toilet with a handful of Diatomaceous Earth. This keeps the compost sweet. Also, I'm wondering if the rainwater is such a good idea. Urine should provide more moisture than the compost needs. Commercial composting toilets often have heating elements to remove excess moisture. Also, if you can add a vent pipe which will thermosiphon air from the chamber, that might help. A small 12 volt computer fan could be tied to a small photovoltaic panel to increase the circulation, but that would be a more expensive proposition. Full disclosure; I have very little real life experience with composting toilets and most of that was sitting on one, so I'm one of those self-appointed armchair experts. As with all expurts, an ex is a has-been, and a spurt is a drip under pressure.

Permalink Reply by Tim Kinney on November 24, 2012 at 9:30pm

Also, you're Irish, so your poop is probably really stinky!

Just kidding!!! You shouldn't kid an Irishman unless you are one, and I are one. ;0)

Permalink Reply by Michael Levin on December 14, 2012 at 9:37am

Mycol Stevens has real experience with compost toilets. His is out of order. It would be interesting to hear what the problem is. Another compost toilet user is the Hostel in the Forest in Brunswick, GA.

Permalink Reply by Tim Kinney on December 15, 2012 at 2:04pm

It occurs to me that what some here are calling composting toilets may be closer to an old fashioned outhouse. This is not to disparage the humble outhouse. I spend half my time in the country, and half my time living with city utilities, so I'm in no position to cast judgement on a country mouse with an outhouse.

My point is that a proper composting toilet is different in several ways. Most importantly, a composting toilet isolates the waste from the ground water in some kind of containment. In a commercial unit,it's a fiberglass tank. In a home made one, it is usually a cast concrete tank. Secondly, there is some method of separating the liquids from the solids. This can be simple. the waste drops onto an inclined plane (ramp) with horizontal ridges. The liquids run down the ramp and collect in the tank, while the solids stay on the ramp and begin a slow slide toward the bottom. (Are any of you grossed out yet?) This gives the solids time to begin aerobic decomposition, while the liquids begin to evaporate.

There are several ways to speed the process. Air flow can be increased by adding a stack or chimney which carries air from the enclosure up and out. a breeze blowing across the top of the stack will draw air out of the stack. This has another advantage; the air getting drawn down into the tank at the toilet seat will keep any odor in the toilet. Air flow thru the stack can be increased by extending the stack higher and painting it black. It becomes a solar heater and the hot air rises. Another method is to add a small fan (like a 12v computer fan) to the stack.The air flow will enhance evaporation and decomposition.

Evaporation can also be increased by adding wicking (capillary action) or more commonly, by heating the liquid portion of the waste. If electricity is available, this is usually a small electric element. If a solar heater is to be used, some kind of circulation system is required, since the waste in the tank is the lowest point in the system.

I'm currently working on a workshop in the woods, and I plan to build a composting toilet in an outhouse. If I do, I'll photograph the building process and post the pics.

Happy pooping!

Permalink Reply by Michael Levin on December 15, 2012 at 3:08pm