Friday, April 27, 2007

Poop, Glorious Poop.

I promised I'd get back to personal green living this next time; so that's what we'll do. I still intend to deal with comments on previous posts; just a bit short on time at the moment.

Today's topic; everybody's favorite - poop.

Aha. I see you grinning and giggling out there. There should be a zen koan about why we so consistently find bodily functions amusing. "What is the chance of one square wiping?" perhaps.

Our own solution here in the Big Woods is a good one- and different I guarantee from anything you've seen yet. And possibly even applicable in urban situations; not sure. And just for extra fun; the thing didn't work out the way I planned it; it works far, far better.

Remember that I'm a biologist, and my father taught sanitary engineering (among other types). And it's probably significant that at one point in my life, my brother and I used to sneak into the nearby sewage treatment plant; to play with the tadpoles in the settling tanks, and sometimes catch a ride on the "merry-go-round" sprinklers. (Highly illicit activities.)

When we needed to do something more serious about our sanitation here, I was already familiar with both basic theory and practical engineering, on several scales.

So, Spouse and I built the THWASPCO. You can actually pronounce that, if you try; mostly it's intended as humor. It stands for "Three Hole Wind And Solar Powered Composting Outhouse." Actually; we more frequently refer to it as "the Potty House" these days. Once you've got kids, it's probably inevitable. I did the design; she did most of the construction, in this case.

There is a reason for every single aspect of the design; all to fit our circumstances.

A) poor- no money for a big septic project
B) poor - no money to add a room to the Little House
C) House is in the woods- on shallow soil
D) under the soil is : karst limestone - disastrous for leaking sewage; would make any standard septic installation much more expensive.

I'll tell you the outcome right away- we've had visitors come and try the "facilities" with substantial trepidation; only to emerge and blurt - "This thing should be in Better Homes and Gardens!"

If I can figure out how to get photos into this blog thingy, maybe I'll post some here. To describe it only with words would be a long process, and probably not as effective.

Here's how it works; and how it was conceived.

It's built into the side of a hill. The pits are made of concrete block, waterproofed; and with doors opening out on the low side. Entry is from the top of the hill; you can't even see the pit doors.

I made a guess as to how much poop 4 people and occasional visitors would produce in a year; then provided 3 pits for 3 years. The idea was, we'd use one pit per year; then move to the next one; leaving the first one with 2 whole years for the contents to break down; so shoveling it out wouldn't have to be icky; or dangerous.

The roof is mostly clear fiberglas; and the south wall is mostly salvaged school bathroom windows- the very nubbly glass you can't see through. This was to provide HEAT; both for comfort in winter; and to evaporate water, which is one of the big big problems with any composting toilet.

The seats (made of cherry wood, cut from our trees) close over the pits quite tightly. When the lids are down, very little air from the pits can get up into the room. Thermodynamics is also made to work in our favor- the pits, being underground, are usually chilly; the room, being heated, is warm- air pressure tends to move air from the room into the pit - the pits are provided with a "stack"- an 18" airduct, topped with a whirly thing, that is supposed to pull wet air up out of the pit, and let it blow away. (We've got a fair amount of wind- but I confess, there are days when the wind is not blowing; in which case it may get a little stinky. Mostly, though, visitors are amazed at how little odor there is.)

It's in the woods, about 100' from the house. Since it's under deciduous trees, it's shaded a lot during the summer; has much more sun in the winter. That's good; it doesn't get wildly hot in summer, and there are screened vents that we open to let out excess heat. But being in the woods- it does get less wind than is optimum for the pit vent. That could be fixed in a number of ways; but actually, it's not a big enough problem for us to worry about it.

Those are the basics. One other thing- "boys" in particular are encouraged NOT to pee in the outhouse; but to go feed a bush or tree when possible. That does a lot to decrease the excess water problem; but the water will have to be monitored in other sites, with other people. And yes, we DO use toilet paper- where we are, anyway, most of it comes from renewable tree plantations, not old forests; so we're not much worried about it.

Here's the surprise: in more than 20 years of use- I've NEVER had to shovel a pit out. Never.

WHAT!? I hear you say. Yup. The first time I was getting ready to get out the shovel; at the beginning of year 4 - I opened the lid on pit 1 to see how big a problem it was going to be- and lo, and behold- pit 1 was almost empty. When we'd closed it, 2 full years before, it had been pretty full. I did, as a matter of sense, top the pit off with dead leaves, and tossed some earthworms in to boot, just as we were closing it for good; so I expected pretty good breakdown and composting action. But I didn't expect it to be GONE. I was flabbergasted.

Here's my explanation for the miracle. Poop is... what? Mostly bacteria, actually; the beneficial guys from our intestines, who've been helping us digest everything- which means mostly - cellulose - and water. We provide warm air currents, to pull out water, and decrease stinkyness. The air currents also provide oxygen.

Given two years- the stuff broke down all the way to water and carbon dioxide- and just blew away. No pollution for the water table. Not much methane, I think; because it's aerobic at all times; methane is usually a product of anaerobic processes. Methane in case you haven't heard, is about 20 times WORSE than carbon dioxide as a greenhouse gas. Same output as the longed-for hydrogen car.

Basically, the Potty House just completes the composting cycle, totally; in 2 years. That's what will happen to any compost, eventually; it's just a matter of how long it will take. In this case, this seems like a great solution to the problems to me. Sure, it would be nice to take that carbon and sequester it somehow; but the practicalities there are lousy. This is easy- clean, comfortable (mostly). It's nothing like the dark torture chambers remembered by many, on the contrary; light, airy, with a great (safe) view of the woods.

So. What did I leave out here?


Chryss said...

Pictures--even a diagram if not a photograph--would be great... I doubt we could get away with this in suburbia, though we have septic now... hmmmm

Anonymous said...

Gee, I was about to build a septic tank, but I'll build this instead. Figure out how to get some illustrations onto the blog, and some dimensions, please. I am paying attention.

zane said...

Hey--just found your site...great system. It really is so easy. I just wrote about my family's composting toilet system on my blog ( We just need to let the bacteria and bugs do their thing...

Anonymous said...

Just wandered by and wanted to say thanks. Its these kinds of posts, informative AND proven (I'm getting tired of blogs that go on the "Well, we read this might work, go try it" approach) that bit by bit are leading my skeptical husband to agree to considering our options in the future. We're where we are for at least 2 more years - a quiet old neighborhood - but once we get more of the bills paid down, we're building in the country. (This is one big woods gal who is ready to go home!)

Thank you for all the work, and the attention to detail. This sounds similar to what my granda had outside the family cabin when I was growing up. The only real difference I can see is we had a 5 seater (bigger family) and we used 2 at a time. One for liquids and one for more.... well. Let me put it this way. One of the seats had a bookshelf built next to it. The other only the odd magazine!

Isle Dance said...

I hope we're lucky enough to see photos! I was considering a new indoor portable composting toilet. However, after watching someone else test it out for a few years, it appears to not be a solution that will work for me. Dang.

Anonymous said...

Been reading your stuff, Greenpa, for a while. Love it. About that magic disappearing poop, I got a word for you: rats. Out where you are, probably mice. Seen any evidence of them? Every spring out here in the exurbs we clean out our SunMar composting toilet out by the pool, and without fail, every year, rats or mice were in the drums and drawer, having a heated, stinky party all winter. My friend J has a guerilla poop-composting system in the city, and when she was turning her compost pile (complete with v. large thermometer!) in March, she found a whole pink litter of rats along one side. So check to see if there's any spoor from critters. I mean, besides humans. I suppose there's always The Humanure Handbook by Joseph Jenkens for folks who want to go deeper into the subject at hand...

Anonymous said...

More details, please! And it's really very easy to post photographs with your blogging program (go the help menu to see how).

1. how deep are your pits?
2. do you have a liquid run-off hose? Or is all liquid removal happening through the vent stack?
3. Do you have 3 separate vent stacks, one for each pit, or one vent stack connected to all three?
4. how are the 3 pits connected or separated?
5. how did you build the pits? Concrete blocks? But how did you waterproof them?
6. how cold does it get in your winter, and do you use the toilet then, when composting stops and you're essentially using a holding tank?

We use a self-contained composting toilet inside a cabin (we have electricity, but no water). In many ways, this works well. But I wouldn't go with a self-contained system again--it's too small. The remote systems seem to work better. Sawdust buckets also seem to work pretty well (sawdust plus buckets for the active business, and when the bucket is half-filled, you put it into a 3-section composting system outside--often just made of concrete blocks and screening, so water can't leach out. I don't have one, but several of my neighbors do).

Thanks for any additional info!

Anonymous said...

fantastic! i love the idea of sewage just wafting away.