Composting toilet - Open Knowledge — LiveJournal
Jun. 28th, 2006
12:53 am - Composting toilet
On Feb 19, 2004, at 9:47 AM, LarenCorie wrote:
Personally I hate chemical toilets, but I insist on having a
toilet in my van, so I have developed a batch composting
toilet system, that I like enough that I even use in my
house, now. That is a subject for a different thread.
I'd love to know more about your toilet composting system.
I am slowly developing a system, which I hope I will be able
to sell over the Internet, but right now there are still a couple
of parts that I need to develop, before its ready for the market.
However, I can give you my opinion on how to put together a real
good system for a van.
Okay, first there are a variety of approaches used in the composting
toilet industry. I won't get into anything about the big systems, except
provide this link to "The Humanure Handbook" which is the bible
of residential composting toilets.
There is a list of parameters, which help define the design
of a system for use in vans, RVs, and boats. Size was critical.
So is the effect of the vehicle movement. There have been
a couple of systems designed for this market. Both were
much too large, for our purpose, and one even required a
step up, with the seat about 24" above the floor. Both
require nearly 5ft² of floor space. One system had a
clear-out door on the bottom-front, and developed leak
problems. Yuck! What I have designed is a "desiccating,
urine separating, batch type, sawdust, composting toilet"
That is the shortest description I can give. What that
means, will be explained below. I will tell you how to,
very easily, make your own van composter, which has
every function my fancy design has, except for the
urine separation function, and even offers a working
technique to achieve that.
Here is another very short description:
"All you have to do is, buy one of these, and vent it"
If you already have the bucket, you can buy just the seat:
BTW......These are very good prices. If you do happen to find
btter, please post them to the group.
Now, it really isn't quite that simple, but it is pretty close.
We can use the "Luggable Loo" as our starting point. Then,
to improve on the function of the basic bucket toilet, you
will need to do a few things.
1) Make a concerted effort to never pee in it. Not only does urine
make up a large part of human waste, and can be dealt with much
easier in a jug, it also makes a huge, very smelly mess, when you
mix it with the solid waste. That is one (a big one) of the many
problems with chemical toilets. Almost all of the smell is from
the mixing of the liquids and the solids. Your action of using
a urinal, can serve the same function as the separator does
in a urine separating composting toilet. A gallon jug makes
a great urinal. Guys can just remove the cap. Women can use
a funnel, or get one of these:
If you want to make a more elaborate system, you can
use a gallon jug, turned upside down, cut open, as a wall
urinal, with a drain tube, running from the spout, down
to a storage tank. A spray bottle of water makes a
very functional rinse/flush system. Put a couple of
drops of dish detergent in it to act as a wetting agent,
to facilitate better rinsing. (it contain glycerin) Once
urinal has been in a closed tank or bottle for about
two days, the few bad bacteria that were in it have
been killed, and it can safely be sprayed out onto
a lawn or dumped most anywhere.
2) You need a cover material, to sprinkle over the solid
waste, after deposit. Sawdust works very well. Wood fire
ash is excellent, too. That is what I use in mine. Wood ash
contains potash, which is a prime ingredient in fertilizer.
It is often added to compost piles. When it is added
directly to the toilet, it keeps the smell down, interferes
with flies, and speeds the drying process. BTW...put a
layer of ash or sawdust in the bottom, before using. By
using this cover material, you have changed your simple
bucket toilet into one of the most popular, and functional
types of composting toilets, a "Sawdust Composter"
If you are now thinking about that fly comment, a quick
spray with any flying insect spray will solve the problem
for days, if not weeks. The spray fumes will also never
spread in the van, because the toilet will be continually
vented to outside.
Now we have a system that will separate, and will cover,
and will begin to dry, and begin the composting process.
3) Add a strong plastic bag, as a removable canister liner.
Kitchen size trash bags are the right size. The pull-string
bags are probably the most convenient. The best color is
black. This is for two reasons. One is basic aesthetics. It
just looks better when you can't see into the toilet. The
other is so that flies can't see inside. If they can't see,
they won't fly in to find a place to lay their eggs. The
bags will allow you to deposit your "treasure" in a variety
of places. The best place is a compost pile, where it can
continue its natural return to the environment. You can also
dig a shallow hole to bury the waste, then put your plastic
liner bag into an adequately sized sealed baggie, to deposit
it without littering, at a later time. I just dump mine in a
secluded spot, back in my woods, and burn the bag. This
was the batch part of the formula. It allows a 'batch'
to be taken from the toilet, to continue its composting
process, while a new batch is being collected. A five gallon
bucket toilet, with attention given to separation, and use
of a cover material, will furnish you with as much as seven
weeks of full time use for one person, between batches.
A three gallon bucket allows you about 3½ weeks of use.
If your use is only part time, and the system is vented
to desiccate (dry) the compost, then you might go for
months before having to deal with the disposal part.
So, that is a "partially separatintg, batch type, sawdust,
composting toilet system" All we need now is........
4) Venting..........This is where the mechanical fidgeting
comes in. If you happen to have an old round shop-vac
around, that you can cannibalize for parts, you might
want to steal the flex hose, and the coupling, where it
attaches to the round canister. Those usually have an
inside section that sticks out a little, and points down.
That part can be used to hold the upper edge of the
liner bag (the rest of the liner bag will just overhang
the bucket, and be held in place by the seat/bucket
connection. That inner part of the shop-van connection
needs to be in a location were it will not get soiled, but
should optimize the removal of any unfortunate gaseous
discharges (don't ya just love the language ;O) Anyway,
"in loo" of using shop-vac parts (I couldn't resist that
one) you can make the vent hose out of whatever you
find, that will work. HD has a variety of vent tubing
for sale, and there are fittings in the plastic plumbing
section, that will fit the vent hose, and screw together
through the hole you make near the top of the side of
the bucket. The amount of airflow for continual venting
is only a couple of CFMs, but you will want more, for
when the lid is open. At least 10CFM.
5) The Fan...What I have is a "Nicro" Solar vent fan,
which has a small Solar electric cell, and a nine volt
battery, so that it will run a couple of days, without
sunshine. I even saw some little hand held cooling
fans, at the dollar store, which seemed appropriate.
You will need to figure that part out. This will also
provide your van with general stale air/humidity
exhaust, which brings in fresh air. The composter
could also be vented out through an air-to-air heat
exchanger, so the about half of the lost heat gets
transferred to warm the cold incoming fresh air,
or cool the incoming air in the summer. This will
keep you van smelling fresher than it did before
you installed the toilet.
6) If you downsize, to a three gallon bucket, it will
be closer to standard toilet height and, can more
easily store under your bed platform, or in a short
cabinet. Just open the door, pull the toilet out, and
have the paper dispenser mounted on the inside of
the door. Your urinal can store in the same place.
That is all there is to it. Mine is only different, in
that it has a stylish looking outer shell, that its batch
canister sets within. That shell is vented, and I am
developing the urine separation system, which will
require making special molds to cast the custom
pieces. Most of the differences are cosmetic, and
just dress it up for the marketplace. This is not
theoretical. I have been using this type of system
for many months as my only toilet. It also requires
no chemicals, or water, like the chemical toilets do,
And, it produces natural beginning compost, instead
of that nasty, vile, gagging, pollution that chemical
toilets create. BTW, the drying kills most of the
bad bacteria. Read "The Humanure Handbook"
and you will understand much better.
Passive Solar Building Design Since 1975
"Sandy Stone" <onestonefarm@h...> wrote;
> One subject I have never seen addressed is storage of the sawdust.
I am sorry. I put out that long post spontaneously, and
there is easily enough to the subject for a book, or more.
> Seems to me that a 5 gallon waste receptacle would require a second
> 5 gallon bucket full of sawdust. Maybe a 3 gallon container might do,
> but certainly no smaller than that. Storage space in a van is already
> at a premium, and that extra bucket for sawdust takes up a fair
> amount of room. I guess we could pack sawdust into a plastic lined
> cardboard box - that would help. Is there another more space
> efficient way to handle the sawdust storage?
Sawdust does take up a lot of room. In my mind, way too much room.
There is also a problem with procuring sawdust. Wood ash contains
potash, which is one of the primary ingredients in fertilizer. It is
also the ingredient lacking in compost, so it is a real natural to add
wood ash to the toilet. It is also an excellent cover material, and
stores in a much small space than sawdust. Only about a half gallon
of wood ash, is needed to cover a 5 gallon batch. That is a ratio of
10:1. You can store it in a can, or a bag, or you can keep it in a
dispenser with a shaker top, to sprinkle out the wood ash powder.
I prefer a one gallon metal can, with a snug fitting lid, and a small
scoop, which holds a few of ounces of ash powder. I never use a
> I have an old book titled 'The Toilet Papers' by Sim Van Der
> Ryn that details the history of human waste disposal. Particularly
> interesting is an 'earth closet' design from 1906. It incorporates
> a urinal that empties into an earth lined pan that is vented to the
Interesting......That must be one of the earlier documentations
of a urine separation system.
> The waste bucket itself is backed by a bottom-hinged door that
> opens to become a ramp, and the bucket slides down and outside,
> presumably to be emptied by one's lackey. But its best feature
> is the covering mechanism - equivalent to our flush device. The
> covering material (dirt, I think, or maybe sand) was stored in
> a cabinet mounted behind and above the waste receptacle. A
> lever on the front lowered the cabinet bottom and dry dirt
> flowed into the waste bucket!
The design of a system for a van is very unique. Size is a major,
and really the dominating parameter. The movement of the van
is a helpful aid in shaking down the compost and creating room
for more. Due to the movement, it is necessary to re-cover some
areas, later. It is necessary to optimize the cover material as
well. Wood ash takes up less room, for its ability to cover, than
other materials, like sawdust. It is also easier for a VanDweller
to replenish a supply of wood ash. Ash is available around any
place where people camp and build fires. My suggestion of a
"can" for ash storage, relates also to the ability to collect ash,
that may be still warm, and holds the potential of containing
live coals. The sealed metal can will extinguish any coals, and
alleviate any danger of fire..
There is another part of my 'system,' which I left out of
my opening long post. That is the separation of the paper
into a third container, with a sealed lid. I keep a plastic
grocery bag in that container. Those bags are small, and
easy to tie closed, and dispose of easily in a trash can.
This also keeps the 'compost' free of any manufactured
materials, so that it will return to nature far quicker.
Even with three containers, this system takes up only
as much room as a chemical toilet, yet it will go over
ten times longer, between emptyings for the same