The Power of Poo

Kitty playing in Toilet by dmansouri on FlickrI have wanted to write a post on human excrement management for awhile now.  I know it’s a rather taboo subject and some folks might be pretty grossed out but my real reluctance is that I wanted to gather more information.  However, my brother just sent me a great link to a Time Magazine article asking “Is it Time to Kill Off the Flush Toilet?”  (I prefer the title “Is it Time to Flush the Flush Toilet?” but I’m sure it would make every editor cringe.)  Apparently, I just missed the World Toilet Summit and Expo, which honestly sounds really fascinating to me and I’m sure I would have found answers to many of my questions and seen models I never could have imagined.

Still, I realize that I know a fair amount about poo and pee.  I learned about traditional wastewater treatment plants as part of my environmental engineering training.  I worked for awhile designing constructed wetlands for wastewater treatment as an alternative to traditional septic systems, which means I got to learn a lot about both.  I have never actually installed a composting toilet but I have used at least seven different models and I did take one class on how to design a particular model.  (I can’t remember the name but the creator was hoping that his name too would some day be as famous as “Crapper.”)  I have toured a farm that collects cow poo and uses it to create methane for electricity.  There are a lot of options out there for dealing with poo.

Back in the day, folks would do their business in chamber pots and then fling it into the street.  It was gross, unsanitary, and caused a lot of disease.  Flush toilets came around as an awesome alternative – press the magic button and all the waste is carried away through a series of underground pipes!  Originally, it all got dumped in the nearest river (“dilution is the solution to pollution”) but nowadays it goes to wastewater treatment plants where the water is partially cleaned before being dumped into the nearest river.  I say “partially” because it’s really hard (and expensive) to treat the water to a level where it’s really clean.

Even if wastewater treatment plants were really effective, it’s hard to escape the fact that flush toilets basically take clean water, mix it with human waste, combine it with mostly clean water (greywater) from our sinks and showers, and then send it to a treatment plant that uses a whole lot of energy to clean the water again.  We can take a lot of steps to reduce the amount of wastewater generated by installing low flow toilets and diverting greywater for other uses (if your state’s health code allows it) but perhaps it is time to think beyond the flush toilet, as many designers at the Toilet Expo did.

I personally believe that composting toilets are the way to go.  Composting is not new technology.  The British agronomist Sir Albert Howard worked with farmers in India in the 1930’s to compost human excrement and turn it into a safe form of fertilizer.  The key is to get the compost hot enough to kill off the bacteria living in the waste.  Nowadays we are paranoid about hygiene and so almost all composting books will tell you to never put feces in a compost pile but there is a lot of documentation out there on how to do it safely.  (I still have not read the “Humanure Handbook” but it has an excellent reputation as the Bible of composting toilets.)  Composting allows us to truly recycle our bodily waste and make it useful again.

However, the world seems very resistant to composting toilets and I can understand why.  There are a lot of taboos around poo and a lot of resistance to trying anything new.  Flush toilets are convenient and do a great job taking our waste out of sight and out of mind.  Composting toilets require a little more thought and most of them need to be emptied periodically, which is an intimidating thought for most people.  I believe this issue could be resolved by having some sort of servicing contract where a maintenance person would take care of that duty on a regularly scheduled basis.  Another big hurdle is health code requirements.  I understand that health department officials are trying super hard to protect us from disease and are extremely reluctant to allow anything new until it has a proven track record but I wish there were a clear path for getting new technologies approved.  I also wish there were better communication between the health departments in different counties and states so people didn’t have to prove the same technology in every county.

This is one of those issues where I feel like I don’t have any good options.  It would be illegal for me to install a composting toilet at home or even to reroute the greywater from our sinks and tubs into a constructed wetland.  (Indiana law says that all water going down a drain in a house has to be treated as “blackwater” and sent through an approved treatment system.)  Some days I dream of being a champion for better poo management, fighting for the right to install composting toilets in every home, becoming an engineering expert on alternative poo management.

Most days I feel like the best I can do is to focus on conserving water and maybe start peeing on my compost pile.  Urine is sterile so as long as I don’t scandalize my neighbors I think I could get away with it.  Building a composting toilet in the garage seems more risky, although I’m still tempted. Maybe I could start a guerilla movement.  We could have awesome t-shirts proclaiming the Power of Poo.  Wouldn’t everyone want one? this!

5 Responses so far »

  1. 1

    Abby said,

    December 2, 2008 @ 8:09 pm

    What about septic systems? I’ve been wondering about their relative greenness for a while, but when some cursory Googling didn’t turn anything up, I gave up.

  2. 2

    Maggie said,

    December 3, 2008 @ 9:26 am

    One of my early drafts of this post talked about septic systems but the post was getting ridiculously long…
    You may know the basics already but here’s the down and dirty on how septic systems work.

    All your wastewater (toilets, showers, sinks, washing machine) gets mixed together and sent into the septic tank. The septic tank is basically just a big concrete tank buried in the ground. Back in the old days, they were often constructed of bricks and therefore didn’t even hold water very effectively but nowadays they are pretty waterproof, like a swimming pool.
    Septic tanks have an outflow system that is designed to hold in the “floaters” and the “sinkers.” So all the solid stuff settles to the bottom and all the greasy/fatty stuff floats to the top and only the liquid part moves out of the septic tank. Generally, there is a healthy microbial community in the septic tank that eats the solids and the greases and transforms them into liquid waste so the volume of solids and greases stays about the same over time (e.g. solids move in, are eaten by microbes, and are replaced by new solids). But the microbial community can get overwhelmed, especially if homeowners throw stuff like bleach down the drain.

    So, the liquid part moves out of the septic tank and into what is called the septic field. The septic field is generally a series of parallel perforated pipes laid out in a gravel bed about a foot or two below ground level. The idea is that the water trickles out and is evenly distributed over a large area of soil so it can inflitrate into the soil (underground) and not oversaturate it. This movement through the soil will “clean” the wastewater by filtering out any tiny particles and allowing soil microbes to eat all the organic matter.

    There are a couple of issues. One is that the soil type makes a big difference in how the water flows. If it’s a tight clay soil, the water doesn’t infiltrate very quickly and can end up pooling, even to ground level. If the soil is very sandy, the water will flow right through without time for any treatment to occur. Another is understanding what is happening with groundwater. If the groundwater table is high, the wastewater can mix with it before it gets much treatment and then you have contaminated groundwater. A third has to do with soil saturation. If the soil is too wet, there isn’t enough oxygen in the soil to allow aerobic bacteria to eat the organic matter. Ideally you have anaerobic bacteria (no oxygen) doing their thing in the septic tank and aerobic bacteria (lots of oxygen) doing their thing in the septic field but if both places are super wet, there’s no room for oxygen.

    Basically, septic systems work pretty well in low density situations where the soil is a nice loam with a healthy microbial community and the groundwater table is a ways below the septic field and the area is free from flooding. Unfortunately, that probably only describes about a third of the septic systems in use today. Septic fields also tend to clog over time it’s not a permanent solution (I think I’ve heard 40-ish years but it’s one of those things that isn’t really tracked and you can’t really tel there’s a problem until you start smelling sewage in your yard).

    So determining how “green” a septic system is depends a lot on the site characteristics. But if we assume a site is pretty good for a septic field, I would say this is my order of preference:
    1. composting toilet with wetland system for graywater
    2. wetland system combined with septic system for everything (and logistically speaking, it probably makes the most sense to have a “cluster system” that collects and treats waste from several houses rather than putting one in each yard)
    3. septic system by itself (tied)
    3. traditional municipal wastewater treatment system that does not receive storm water (tied)
    4. properly designed outhouse (essentially a septic tank without an outlet; some microbial activity occurs but mostly the stuff just sits there)
    5. traditional municipal wastewater treatment system that also treats storm water – these systems tend to have big overflow problems when it rains, sending untreated or partially treated wastewater into rivers

    Did that help? Probably more than you wanted to know. 🙂

  3. 3

    Abby said,

    December 9, 2008 @ 10:11 am

    Thanks for all the info. Mmmm…more fodder for off-the-grid daydreams.

    Graywater systems are illegal where I live, but hopefully that will change before too long. As it is, there’s a town ordinance that requires houses to be built on at least 2 acres, partly to discourage McMansion developers, but officially to allow for space for a well and septic system (there’s no city water), plus room to redig either if necessary.

  4. 4

    Maggie said,

    December 9, 2008 @ 8:33 pm

    I think every community ought to allow graywater systems. Maybe some day.

    I’m not sure how I feel about an ordinance that requires 2-acre lots. It may discourage McMansion development (although I have seen some pretty ridiculous McMansions on bit logs) but it also encourages sprawl. Of course, if it were up to me I’d probably have super strict regulations that forced people to build dense but green ecovillages and be labeled as a goddamn communist hippy neanderthal or something along those lines. 🙂

  5. 5

    Abby said,

    December 10, 2008 @ 11:56 am

    If my neighbors were all goddamn communist hippies, I’d have much less of a problem living densely with them. 🙂

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