5 Things You Didn’t Know About Composting Toilets

Energy & Sustainability Gardening Home Science

Your excrement contains the nutrients to fertilize and grow the food that feeds you. This was known and practiced from the dawn of agriculture until modern times.

Illustrated by Damien Scogin
Illustration: Damien Scogin

Then the use of chemical fertilizers made it possible to discard excrement into sewers instead of returning it to fields. The germ theory of disease made it seem desirable to do so.

Unfortunately, this has resulted in vast amounts of purified drinking water being used to flush soil fertility out into the oceans. In the oceans these excess nutrients cause “dead zones” from algae overgrowth and decomposition, which depletes the oxygen in the water. In these “eutrophic” areas, fish literally drown.

We now know it’s possible to eliminate pathogens by composting instead of flushing. We can return to the sustainable practices of ancient times without fear of disease, by using composting toilets. I decided to try it.

Ancient Roots

In 1905, American agricultural scientist F.H. King traveled to China, Japan, and Korea to study traditional farming practices there. He was very impressed by the absence of flies in those countries. Human excrement (“night soil”) and every other material that could decay was immediately collected and sold to farmers. The farmers carried it from the city to the countryside to compost it and use it for fertilizer. Flies had nothing to feed on.

There were stormwater drains, but no sanitary sewers — excrement was far too valuable to flush away into a river. King’s classic book Farmers of Forty Centuries, Or Permanent Agriculture in China, Korea, and Japan inspired the permaculture movement. It’s free online from archive.org, gutenberg.org, and others.

A Simple Composting System

Photos: Tim Anderson
Photos: Tim Anderson

The photo above shows a composting barrel, a Luggable Loo bucket toilet (about $20 at REI and other retailers), and a jug-and-funnel urinal.

I lined the 5-gallon Loo bucket with double paper bags and an inch or two of sawdust on the bottom. Toilet paper and more sawdust go into the Loo with each use. When it’s full, you empty it into the composting barrel.

To make the composting barrel, I got a bucket with an easily removed snap-on lid, and cut the bottom off it. Then I cut a hole in the top of a barrel and jammed the cut-off bucket into the hole. I cut a hole in the bucket lid for airflow, and stapled fine mesh screen over the lid to keep out flies.

After a while I got lazy and decided to skip the Loo. I Craigslisted a hospice throne and perched it over the barrel. I hold a pee bottle in front as an impromptu urine diverting system.

Peeing separately reduces the barrel capacity needed by more than half. It will take one person about a year to fill the barrel.

Urine Command

Urine is the safest of bodily fluids — typically it’s sterile. In most parts of the world it’s probably safer to have contact with urine than with the local water supply. Leptospirosis and schistosomiasis can be carried by urine, but if those diseases are in your area, it’s still usually better to apply urine to the soil or a compost pile than to flush it into a body of water.

The urine-diverting throne has a funnel in the front of the “drop zone” which carries the urine away to a jug for immediate use as an excellent fertilizer. This greatly reduces the volume of material that goes into the composter. The weatherstripping on the underside of the seat and lid is there to block insects. For a one-way valve, drop a ping-pong ball into the funnel; pee goes in, smells don’t come out. A water trap pipe from a sink with mineral oil in the upper part can do the same.

Adding carbohydrate-rich food waste (like bread or rice) to the jug will help the urea in the urine ferment into nitrates rather than volatile ammonia. If you smell ammonia, add more cellulose or carbohydrates. Peeing directly on a bale of straw is a popular solution. Carol Steinfeld’s Liquid Gold is an entertaining and informative book about urine as fertilizer.

What About the Smell?

My humanure barrel smells like damp sawdust. I love showing it to people because they always say, “That doesn’t smell bad at all!” Then I get to say, “That’s right. My sh*t doesn’t stink!”

Add sawdust to your bucket toilet until it smells nice. That’s a couple of handfuls of sawdust per use. At that point the ratio of carbon and nitrogen is perfect for the growth of thermogenic aerobic bacteria, which generate heat, CO2, and water. The long-chain nitrogen compounds that make feces stink are no longer being produced.

A year or two after the last addition to a humanure barrel, it will have composted down to one-quarter or less of its original volume and will smell like black dirt. It was the smell of a jar of finished humanure that won me over. That wholesome black-dirt smell was more convincing than any theories or books.

What About Germs?

Illustration: The Humanure Handbook, Joseph Jenkins
Illustration: The Humanure Handbook, Joseph Jenkins

The Humanure Handbook by Joseph Jenkins explains a system using a thermogenic compost pile in a straw-lined corral of old pallets. His table (above) summarizes the conditions for pathogen elimination. Germs die and become food for harmless bacteria in the hot, damp conditions of the pile. 

The World Health Organization provides data about pathogen survival in composting conditions in their “Guidelines for the safe use of wastewater, excreta and greywater”. At lower temperatures it takes longer to eliminate pathogens. Dry, cold conditions are the least effective.

When your barrel is full, set it aside for the sufficient time for pathogen elimination. (Most people won’t get the urge to mess with it prematurely anyhow.)

Illustration: tippytap.org
Illustration: tippytap.org

Freedom from Flies

When I first made my barrel I used window screen on the bucket lid. One hot day it became obvious I had an insect problem. Big, loud, black flies had gotten into the barrel.

I read the tales of woe from compost toilet users proofing their systems against “insect escape.” I made a new fine-mesh lid with no-see-um netting sandwiched between 2 layers of window screen. I added a few handfuls of sawdust to the barrel, put on the new lid, and shook up the barrel. A week later: no insects to be found. Triumph without chemicals!


It’s no coincidence that our bodily excretions are what plants need. We belong on this planet and fit perfectly with the plants that feed us. So remember, don’t put poop in a pipe!

13 thoughts on “5 Things You Didn’t Know About Composting Toilets

  1. skube says:

    Very interesting. I wish there were more photos of the final mechanical system. I also don’t understand how the meshing works. Doesn’t it keep solids from dropping into the buckets?

    1. Sam says:

      So the mesh is fixed to the detachable bucket lid. You remove the lid, dump in your latest excrement, then close it up. Waste goes in, flies stay out. I’m assuming the bucket-to-barrel hack was a way to get large quantities of night soil into the barrel at a time. I like this idea! Now to get the wife on board…

  2. Pat F says:

    Just to clarify, in non-third world areas when you flush, the actual excrement does not go into the rivers/ocean/whatever. It goes through the pipes to a treatment plant. And treatment plants are not using crazy deadly chemicals to remove the sewage from the water either. Treatment plants use very natural processes (settling, bacteria, aeration, vegetation…) to “treat” the sewage. This process leaves behind drinkable water that is discharged into the rivers/ocean/whatevers of the world. The discharges are monitored constantly and if the discharge gets out of spec, it recirculates back through the system.

    Don’t get me wrong, I’m all for the composting toilets. I think this is a very cool idea that could have a very positive impact on the environment. But sewage treatment plants shouldn’t be demonized. They are very good for the environment too.

    1. Ralph Wakefield says:

      My father used to collect “sludge” from a local treatment plant and spread it on our lawn aside from the occational volunteer tomato plants we had a very green lawn. He also inquired of a pumper truck that pulled in one day what he was doing? He was collecting the oil from the pond for cosmetics manufacturing.

    2. Jim says:

      If you live in the Milwaukee area you can still “poop in a pipe” and not feel totally bad about yourself! Where do you think Milorganite comes from?

      “Milorganite is composed of heat-dried microbes that have digested the organic material in wastewater. Milorganite is manufactured by the Milwaukee Metropolitan Sewerage District.”

  3. Everett Forth says:

    This says the average toilet flush is 3.6 gallons, and the average person flushes 18.8 gallons per day. That’s 6800 gallons of water per year saved per person!

  4. rose says:

    what can be used in place of sawdust if we don’t have a sawdust source?
    would leaves from the woods work?
    would dirt work?

    1. Karin Mandell Parramore says:

      I have used leaves, twigs, whatever is left over at the end of Fall. I have also used wood chips, free from the city, sawdust from a sawmill (hardwood is better, altho anything works) dirt, ashes, you name it. I feel like variety is a good thing–my pile breaks down super-fast.
      The only thing that did not keep the bucket 100% odor-free was coconut coir, a material many of my humanuring friends use and love. No idea why it didn’t work for me, altho I do eat a lot of fermented foods… :)

      1. rose says:

        Thanks Karin, I suspected any kind of material that decomposes would be an option as the trick is to cover the excrement completely allowing it all to break down in a plant nourishing pile of goodness! Just wanted to make sure :)

    2. Gunther Mueller says:

      You can use sphagnum peat moss from your local nursery, or big box “home center”. Unlike the past, the peat moss is now heavily-compressed into blocks to save freight costs. One compressed block, costs @$10, but weighs @40 lbs, and once opened, and allowed to un-compress, yields a huge amount of VERY thirsty absorption material. It does need to be “primed” with some bio-active material (soil from within 6″ of the top of the ground, or some already composted material). BTW, if you want to use sawdust, it is best to use “green” sawdust left from tree-felling/ stump-grinding, or from rough-cutting of unseasoned lumber. Dry sawdust, from mill-work shops, furniture factories, etc., will absorb moisture, but will not be very bio-active to start. Also avoid any sawdust from “pressure-treated” wood, which has basically been poisoned with chemicals SPECIFICALLY to retard any bio-activity (rot) in the wood. A small amount of PT sawdust can stop a compost pile cold… AMHIK.

  5. carllarsen says:

    while i like the idea, i can’t see the neighbors enjoying your trips to the compost barrel with a bucket of poop. or, if you live in an apartment, having a poop barrel on your porch or deck.

  6. Mungo says:

    We’ve used a composting toilet system aboard our shanty boat (and we live on it) for the last year and a half. Having experience with “backwater” systems on vessels, I’ll never have anything else BUT a composting system (ours is identical to the one pictured above). They just WORK, with very little effort, no smell, and no hassles.

  7. Daryl Foote says:

    This article is spot on in every way. After spending some quality time with my EcoJohn i’ll never go back to the water wasting splash toilets. I purchased mine from naturaltoilets.com. Thank you for this article!

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Tim Anderson

Tim Anderson is the founder of Z Corp. See a hundred more of his projects at instructables.com.

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