Warning: the topic discussed below may not be everyone’s cup of tea.  Because so many people have asked about composting toilets, wanting to know some pretty detailed stuff, I do need to talk about human waste in a bit of detail below.

If you’d prefer to just to skip the potty talk and just read the upshot, here it is:

Composting toilets…

…do not require a connection to a private or municipal septic system, and are therefore often much, much less expensive to install and easier to use in a non-traditional (Tiny, Accessory, Off-Grid) home, even though the toilets themselves are more expensive than “traditional” toilets.
…do not smell.
…do require some maintenance (i.e. emptying), which can range from a few times a month to a few times ever, depending on the system.
…produce material that is excellent for flower and vegetable gardens.
…range in perceived grossness between “I never would have guessed it’s not a typical toilet!” to “You have a porta-potty in your house?”

Now, for the nitty gritty:

Maybe the most fundamental mentality change between contemporary global eco-consciousness and what came before is the desire to work with, rather than only against, nature.  Without much change in people’s lifestyles and desires, nearly everyone is on board with using the sun’s energy, harnessing the wind’s power, and taking advantage of wave motion.  On the slightly techier side of things, hybrid electric cars use residual wheel momentum to charge batteries, taking Newtonian waste and converting it to the electric equivalent of black gold.  Another “black gold,” at least in gardening circles, is compost.  Generally speaking, “compost” is nutrient-rich dirt that has recently decomposed and which is probably the most important “additive” for healthy, robust flowers and vegitables.  A swiftly growing percentage of Americans now have 3 pails under their kitchen sink:  trash, recycling, and compost – the last of these being where they toss banana peels, bread crusts, and nearly any natural material besides meat.

If those three pails happen to be neglected for a summer, opening the under-sink cabinet would reveal a trash pail that smells like death, a recycling pail that is no different than they left it, and a compost pail that is now full of sweet, frankly great, smelling soil – compost!  This is added to gardens often along with another miracle of decomposition – cow manure.   We’ve all driven through agricultural areas where the smell of cow crap, um, perfumes the air.  While some claim to like the smell, the uninitiated typically roll up their windows.  And, nearly everyone has used manure-based fertilizers for planting or gardening…  Notice there’s no poop smell?  That’s the magic of composting.


This leads us to human manure (or “humanure”, as Joseph Jenkins calls it in his similarly entitled, very famous book on the topic).  Human poop does have bacteria and other nasty stuff in it.  But, allowed to sit for a while, and ideally laced with a little bit of dirt, sawdust, or commercial “compost starter,” it stops smelling and becomes Black Gold, ready to be used in growing your tomatoes and other delectables.   So much has been written about this process – including Jenkin’s canonical book – that I won’t even try to add to the topic.  If you are interested, I urge you to browse some of the links I’ve included at the bottom of this post.

You may have noticed the words, “allowed to sit for a while,” in the above paragraph.  That’s all fine, but until then, will your bathroom/house smell like sh*t?  The vast consensus from those who own halfway decent composting toilets is “No!”  In fact, many owners of composting toilets can’t believe how bad their friends’ and family’s bathrooms smell when they are second in line to the loo.  I won’t comment on my own family, but I will say that this seemingly ironical issue does make scientific sense.  Most modern composting toilets (such as those we include as options in its DIY home kits) contain a fan that effectively sucks air (and the smells it contains) directly out from the toilet.  Without the air, there can be no smell.  It’s not like air fresheners which cover (often imperfectly) smells.  These fans  literally suck the stink out of the toilet.  This secret smell-killing weapon cannot be replicated with flush toilets because of the water in the tank, which is why that smell makes its way throughout your bathroom, even though you flushed.


This all being said, there’s for some people a unique downside to composting toilets – whether all-in-one units that are toilet and composting chamber in one or whether two-part units where the refuse is stored in a larger, separate tank outside or in the basement, they all need to be emptied every once in a while.  Depending on the system and size of the tank, frequency varies from 3-4 times a month for a family using an all-in-one “compact” system to a half-decade for those with two-part systems.  Because the process of composting reduces the volume of “material” in your tank, and because it doesn’t smell (remember from the three pails under the sink: composting, unlike sitting garbage, smells better as it decomposes), it’s simply a matter of emptying the tank when it’s full (Although, I wouldn’t push the limit too far, as you do need air in the tank for composting to happen.)  If you are emptying your tank monthly or more frequently, you either toss the fresh compost into your flower beds or hold it in a larger, outdoor container or pile (a compost bin/pile) for another few months before using it in your vegetable garden.  With a two-part system, the compost has sat long enough that it is “vegi-ready”.  If you have neither a the green thumb or a green property, I suppose you can just “throw out” your compost, though you’re wasting some good stuff that will just fill up your local landfill.  (If you are tossing your black gold, consider first donating it to a neighbor – just don’t light it on fire on their front steps!)

The other difference between “regular” toilets and the composting variety is that most of the latter are dry-bowl systems.  They are Teflon-y to be sure, but it’s still likely that, without the steps I mention below, you’re business might be known to the next customer.  While some fancier systems use foam flushing techniques that solve this issue quite well, you can alternatively use a spray bottle with natural soap cleaner.  Finally, some composting toilet bowls are black on the inside, which is a more, um, “artistic” way of dealing with the problem.

At this point, it’s also worth mentioning what you see if you look down into your composting toilet.  This depends on the unit.  The absolute most basic systems are similar to a porta-potty in this respect – you can see into the past, but in the composting version, the past now looks mostly like dirt.  Others are similar to airplane toilets (with or without water/foam flush) – there’s a trap door that closes the portal to what went down before.  (One brand, Separett, has a trap door that opens when you sit and closes when you get up, hiding your business even from you!)  Finally, two-part systems (separate tank) hold the waste somewhere else, so no issue there either.


Moving on to number 1, this stuff is even more potent as a fertilizer.  In fact, urine is primarily nitrogen, which is the main ingredient in commercial fertilizer.  The most basic composting systems don’t differentiate between liquid and solid waste.  However, most “modern” composting toilets separate the two (basically, there’s an area for each in the toilet bowl, located in such a way as to be comfortably used by both women and men.)  The urine either goes into a separate holding tank or directly to the outside of your home via a filter of some sort (at its most basic, we’re talking a little tube that pokes out the bottom of your house and goes into a hole filled with rocks in the ground).  Other systems, however, do need to be emptied from time to time, and there are many options depending on how often you are willing to empty the tank and how close you want to get to the liquid while do so.  And, again, if you have a green thumb, you’ll appreciate this super-fertilizer that you can just dump into your garden.  To think, it only cost the price of a Diet Coke!


Do I believe that Composting Toilets are going to replace septic systems in the near future – no, I don’t.  Throughout the world, however, countless gallons of fresh, clean drinking water is mixed with top shelf potting soil and the organic equivalent of liquid miracle grow – in the process rendering all three of these useless.  I personally hope that the composting ethos being employed by an increasing number of homesteaders, road warriors, tree huggers, and just, plain old conscientious citizens will trickle up to municipalities designing ways to improve the efficacy, cleanliness, and rationality of their town sewage systems.  In the meantime, home-based composting toilets are an inexpensive and fairly easy way to unplug but still tune in.

Thanks for reading, and feel free to post questions below.


(Co-founder, Homebuilt)

Resources for further information:

Wikipedia article on composting toilets:  http://tinyurl.com/plf5sg3
More on the non-stinkiness of composting toilets, by a scientist:  http://tinyurl.com/qfukvnw
Candide and pragmatic post by Tiny House owner & composting toilet user:  http://tinyurl.com/p8hv59z
Website of the humanure guru, Joseph Jenkins:  http://humanurehandbook.com/
Reddit discussion about whether composting toilets smell:  http://tinyurl.com/ndzdwnn
Scientifically validated explanation of urine fertilizer:  http://tinyurl.com/o4b2q95
Policy-based article on composting toilets by The Guardian:  http://tinyurl.com/ost5fko