Energy & Sustainability
On Human Manure
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The above graphic is from a book that does not stink: The Humanure Handbook. Here’s a pdf version of this potential soution to water overuse.

As author Joseph Jenkins notes, “a single person using a Clivus (pronounced Clee-vus)
Multrum [specific type of composting toilet] will produce 40 kg (88 lbs) of compost per year while refraining from polluting 25,000 liters (6,604 gallons) of water annually.”

Make compost + save water = what’s not to like, right?

For starters, commercial models are way too expensive: often $1000+ per toilet.

Jenkins’ 5-gallon-bucket-of-excrement-and-sawdust method sounds like it works (plans here), but that’s rather labor intensive and may be difficult to convince your less-radicalized cohabitants to adopt. Septic systems are notoriously bad (both on your wallet and the environment), and alternatives like the pumice wick may or may not actually work.

What i want to do by end of year is create the following system:
-Normal high-efficiency flush toilets in house
-Solar-powerered pump(s) push blackwater to ‘cooking’ tank, to which household scraps are added (help increase carbon content to hit right carbon-nitrogen ratio) and water is allowed to boil off (prevent anaerobic environment from occurring for too long)
-Arduino regulates temperature via solar parabola and fan/vent at height (avoid smell) to keep solids at 113fahrenheit for 3 days –> kills all nasty bacteria to EPA standard by letting thermophilic bacteria dominate (see jenkins’ book p. 150)
-Resulting 3-day-old former poop/paper/urine then aged for a week or 2 in your normal compost pile to avoid colonization by salmonella or other nasties. (Poop should be smell-free at this point)
-Optionally, you can run this as a solar still to recapture (and even drink?) the water you distill off!

I estimate one can build this for <$500 parts and 40 hours time. Am I off the deep end, or does this just maybe make sense? Of course, it goes without saying that you should not try this without being prepared for the potentially malodorous consequences!

32 thoughts on “On Human Manure

  1. “And I seriously hope you don’t live upwind of me.”

    Nice way to skirt around the censored phrase “Not in my backy*rd” cliche ;-)

  2. your biggest problem is going to be maintaining 113F for three days with only solar as your heat input. Is this going to be a batch process or a continuous process stream? If batch, how many days storage before sealing off and cooking? 3 or more? I would design in some slack. e.g. if 3 days storage, utilize a 3 vessel system so each vessel has downtime. If continuous then I don’t think you can get the temp up and hold it without another source of heat.

    What about a digestor and capturing the resulting methane which could then be used to boil off the water. Have you seen the “Dirty Jobs” about “Poo Pots”? http://www.tv.com/dirty-jobs/poo-pot-maker/episode/950989/recap.html

  3. You know, back in the Dark Ages, people used to collect their excrement in buckets and then dump it in the forest. The thing is…they all died from the plague! You know why? Cuz they pooped in buckets! Geez. Get off your green high horse and come down here to the real world. We flush our dung out of the house in the twenty-first century. And we also bathe regularly.

    -Put

  4. Actually, I think they got the plague from rats. They got *cholera* from bad sanitation but that was slightly later, and mainly due to *not* dumping it in forests, but in the streets.

  5. @Put, poop *can* kill – there are lots of diseases/parasites carried in poop, like e.coli. Composting kills bacteria, parasite eggs, other nasties, if done right. Clivus Multrum toilets have been around for years, they’re very safe – great re-make potential! Some friends had a composting toilet 25 years ago, it didn’t smell at all. (Yes, plague was carried by rats, and fleas helped them.)

  6. I think your plan has some merit if you do the science to make sure that, as the folks above point out, what amounts to a biohazard is properly treated and sanitized. It can be done, surely.

    I would be very concerned about building codes, though. If you implement this system in your home, it might be impossible to sell your home later without tearing it out at great expense. Also, there may be laws regulating (prohibiting even) what you’re suggesting if you’re anywhere near an urban area.

    What I’m saying is, as part of your research I’d suggest looking at both building codes and local,regional, state, and federal laws relating to waste disposal. Better to let the legal beagles shut you down now than after you’ve built a working system and spent all that money.

    -JRS

  7. My wife and I have used the humanure system, a sawdust composting toilet, for the past 9 years. It DOES work.

    We first started composting our crap when we lived at a commune. This had about 75 residents, about 10 sawdust toilets and a Clivus Multrum (we said Cl-eye-vus, btw). The Clivus system did work, but was generally low in volume for the space it used- was used in batches, and required frequent messy work to keep running. The sawdust bucket was simple so long as everyone actually added sawdust.

    Now, my wife and I live off-grid in the high desert of Northern New Mexico. We have no well, all water in the area comes in by truck from miles away or else is caught from the roofs of enterprising residents. There are almost no flush toilets in an area about 100 square miles in size. Many residents do use pit toilets, which stink and attract insects and vermin. Many residents use commercial composting toilets, which are expensive and even the best can only handle two people.

    We have found the sawdust toilet to be far superior to either of these methods… it just works. It is extemely important to immediately cover any excrement with sawdust or another suitable substance. Then the bucket gets dumped into the compost pile (made of old pallets, slats help it breath), the compost pile gets rotted straw or more sawdust depending upon how its doing.

    Sawdust is really amazingly corrosive. We threw a dead rattlesnake (sans buried head) in there, and a month later the bones were still there and the skin but the flesh was gone. Poop goes away in under a year. The only time there is odor is if the stuff is not covered, even emptying the bucket isn’t very smelly. It is very important to rinse the bucket between “fillings” or else it does STINK, we use a pot of boiling water which gets dumped on top the pile to help keep it moist. A family of two at the home full time (ie, no outside jobs) needs to empty the bucket twice a week.

    I have serious doubts about using pumps, etc, with your system. They will eventually break and I doubt you can get the thermophilic composting to work right with that much moisture. Really, if you don’t wanna poop in a bucket then you should try the commercial composting toilets- these work best with a low power heater if you live on grid… these are used extensively (and in some places required!) in parts of Scandinavia. Sun-mars seem to work pretty well for some people I know.

    BTW, best thing to do with them pesky code inspectors and their ilk is move away from them, or else run em out… they really ruin the neighborhood!

    BTW2, when hiking the Appalachian Trail we found quite a number of outhouses with composting systems using bark and forest duff, then screening it out of the compost and reusing the decaying barks- this seemed to work very well too.

  8. I live in Portland and volunteer with a group called Recode. We’ve been working on gray water (water from sinks and showers) legalization and even that isn’t legal anywhere in the state of Oregon. I guarantee that if there are any codes at all where you live what you are proposing (Home blackwater treatment) will be illegal.

    Be very careful mixing solids into drinking water and then assuming that pumps and filters will continue to work properly. Oasis Design is a good resource for more information about gray water systems (some black water info too) and why you generally want to stick to very simple systems when you want the reliability required for a home treatment system. Art Ludwig of Oasis Design has a lot of experience with these issues and his books are some of the best on the subject.

    The bucket toilets work great by the way.

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Luke Iseman

Luke Iseman makes stuff, some of which works. He invites you to drive a bike for a living (dirtnailpedicab.com), stop killing your garden (growerbot.com), and live in an off-grid shipping container (boxouse.com).

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