Building a Dry Toilet
Preparation: 1 hour
Waiting: 1-2 years
Flush toilets take two valuable resources, clean water and nitrogen-rich human waste, and combine them to create a problem: sewage. Dry or “humanure” toilets combine sawdust and human waste, which is then composted to make soil. It’s a simple, elegant system that follows nature’s dictate that there is no such thing as waste.
A dry toilet uses no water, power, or chemicals, and it doesn’t require plumbing lines or septic tanks. This makes it perfect for off-grid living as well as situations where plumbing is not available. It's a convenient way to add an extra toilet to any house.
We’d be lying if we said it does not seem strange at first to use a toilet with no water, but you do get used to it quickly. If you’ve been raised with flush toilets, your most basic impulse is to make your waste vanish. Pronto. However, once you grasp the indisputable logic of the system, know firsthand that it does not smell, and have seen the contents transformed into sweet-smelling, clean soil through the power of composting, you'll never look at flush toilets the same way again.
You’ll Need
• Sturdy plastic milk crate
• 5-gallon bucket
• Toilet seat, complete with seat bolts
• Felt-tip pen or china marker (optional)
• Jigsaw or keyhole saw
• Utility knife
• 4 wood scraps or table legs
• 8 plastic cable ties
• Several gallons of sawdust and a bucket to store it in, and a scoop
Putting It Together
Scavenge
Find a milk crate and a 5-gallon bucket. Make sure that the crate is large enough to accommodate the width of the bucket. When you scavenge the crate, ask permission or be discreet. We know of someone arrested for scavenging milk crates behind a strip club, of all places. When the police finished booking the milk crate scavenger, the officer placed the paperwork in . . . you guessed it, a scavenged milk crate doubling as an in-box.
Attach the Toilet Seat to the Crate
Forage a toilet seat or pick one up at your local hardware store. Turn the crate upside down and attach the seat to one of the short ends. Be sure to center the seat. Slide the plastic bolts that come with the toilet seat through two holes in the grating on the bottom of the crate. Slip the nuts over the bolts on the inside of the crate, then tighten. Don’t overtighten.
Cut a Hole in the Crate
Lower the toilet seat so it sits on the crate. Lightly mark the position of the seat hole by making a few lines on the crate using a marker or china pencil, or scoring with a knife, using the inner rim of the seat as a guide. Now you know where the bucket will sit. Lift the seat and position the bucket upside down over the markings. Trace the outline of the top of the bucket onto the crate. Cut out the circle with a jigsaw or keyhole saw.
Ready-Made Composting Toilets
You can buy 5-gallon buckets with small toilet seats attached. Look for them at outdoor supply stores. Using one of these on a daily basis is not the most comfortable proposition—they're tippy—but it’s a good alternative if you won’t be using the bucket for long and don’t want to make a housing for it. You could fill one of these ready-mades with sawdust and store it away for emergencies.
Cut the Legs
The legs of the toilet support the crate so it sits flush with the top edge of the bucket. To figure out how long the legs should be cut, measure both the height of the bucket and the thickness of the crate’s bottom. Subtract that fraction of an inch representing the crate’s bottom thickness from the height of the bucket. The resulting number will be the length of the legs. The legs on our toilet are 13-1/2 inches long, but your measurements may vary, depending on the height of your bucket and the thickness of your crate.
Attach the Legs
The legs are positioned at the four corners of the crate, their ends braced against the floor of the crate. Attach them to the crate by threading cable ties through the plastic mesh of crate corners and tightening. Two ties, one high and one low, should hold the legs securely. If cable ties don’t appeal to you, you could bolt or screw the legs to the crate.
Operating Instructions
You’ll need a constant supply of sawdust to use as cover material. Ask around at wood shops and lumberyards for sawdust. Don’t use sawdust from chemically treated lumber, fiberboard, or plywood. This will be soil one day, and you don’t want those toxins in the soil. Sawdust works best in terms of coverage and odor control, though you can experiment with other carbon-rich cover materials, like chopped straw or hay. Whatever you use should be fine textured for proper coverage. Don’t use wood chips or wood shavings. They’re too “airy” and won't control odor well. Wood chips don’t compost easily, either.
Keep a covered container of sawdust next to the dry toilet. You’ll need a scoop for the sawdust. We splurged on a nice metal scoop. Kelly insisted that if we were going to poop in a bucket, we needed that touch of class. You could make a scoop by cutting the end off a plastic jug: Keep the jug handle intact and make the cut at an angle, to form a scoop shape.
Before the first use of the DIY composting toilet, put a deep layer of sawdust in the bottom of the bucket, about 3 to 4 inches. Do your business. The humanure toilet handles both solid and liquid waste. When you're finished, cover the deposit with a layer of sawdust. Try not to use too much sawdust—just enough to cover is plenty. Toilet paper can go in the bucket, but nothing else. Always keep the lid down when not in use. If odors arise, you’re probably not using enough sawdust. All you should smell is wet sawdust.
When the bucket is full, take it outside to the compost pile. Read on.
How to Compost Humanure
Compost is compost. All of the principles of composting that we described in this book apply to humanure composting. Like horse manure or chicken droppings, human waste is a nitrogen source. And like any other compostable manure, it can carry pathogens, but those pathogens are killed by both heat and time. Don't confuse humanure composting with the practice of using raw human waste as fertilizer, which would be dangerous. Remember, composting is a cleansing process—and a transformative one, as well. Composting turns everything to soil.
Expert humanure composters use their compost to grow food. They trust the power of composting, and they're experienced enough to know how to manage the pile to ensure its safety. We’d recommend that as a beginner, you only spread your finished humanure compost around nonedible plants and fruit trees.
For this reason, keep your humanure compost in its own, separate bin. The bin should be a closed-sided and lidded container to reduce the ick factor. A 50-gallon drum, metal or plastic, could be used, as could a big garbage can or a commercial compost bin. Unless you plan to move the bin, the bottom of the bin should be cut out or perforated with holes for drainage and to allow worms to get in. Worms will help purify the soil. If you're using a drum or garbage can, provide extra aeration by drilling two rings of small (1/4-inch) holes all around the top edge.
Because the pile is built up over time rather than all at once, humanure composting is a form of slow composting, with a little extra attention paid to temperature and aging. We’ll talk about these two factors as we go along. First, though, we need to talk about sawdust. Sawdust is an extremely carbon-rich material, much more so than dried leaves or straw. We talked about how composting is the art of balancing the earth, air, fire, and water elements. Sawdust is an earth element. It’s very “cool.” If it’s not balanced with plenty of nitrogen-rich material, it will make your compost pile cold and inert. Human waste is rich in nitrogen but isn’t quite “fiery” enough to balance all that carbon-rich sawdust on its own. This is particularly true if your household is heavy-handed with the sawdust when using the dry toilet. To provide the correct balance between earth and fire, you will need to add additional green stuff to your pile each time you empty the toilet bucket onto it.
This is the basic procedure for humanure composting:
• When you start a new pile, put a layer of something absorbent at the bottom of the bin, like straw or a bunch of dead leaves, to help aerate it and soak up extra liquid.
• When the toilet bucket is full, dump the contents on the pile. It’s not as gross as you’d imagine. The sawdust leaves a lot to the imagination.
• Rinse the bucket and pour the water into the pile. It helps to have a hose near the bin, as well as a dedicated swabbing brush. You can wash the bucket outside, using a small amount of biodegradable soap, and pour the wash water on the pile.
• Add an extra layer of “green” stuff to the pile. This includes kitchen scraps and coffee grounds and green trimmings from your yard, as well as other types of manure like horse, chicken, or rabbit droppings. A convenient concentrated source of nitrogen is alfalfa meal, which can be purchased inexpensively in large bags. Sprinkle a cup of it over the surface. That small amount carries as much nitrogen as an armload of greenery.
• After adding this layer, top the pile with a thin layer of dry carbon material, like dead leaves, dry grass, more sawdust, or even a layer of dirt, to control odor and discourage insects. Cover the bin.
• Repeat this process each time you empty a bucket.
You don’t have to turn this pile. Good news, huh? If you balance the four elements of earth, air, fire, and water, the pile will decompose on its own. By adding extra nitrogen, you’ve balanced earth and fire. The water element is moisture. Much of that comes naturally from urine and rinse water, but if the compost pile ever looks dry, add water. Air comes from the ventilation holes in the bin and airy materials like leaves and straw. If any one of these elements seems out of balance, take steps to correct it. For instance, if the pile seems soggy, add dry, fluffy material like straw or dead leaves to soak up some moisture. If it smells bad, you might have too much nitrogen, or the pile is insufficiently covered. The solution is the same—top with lots of dry stuff.
The fresh nitrogen from the toilet bucket and the greens will heat up as it decomposes. If you take the temperature of the top layer of the pile with a compost thermometer a day or two after a new addition, you should see temperatures of 130°F or higher. This will cool over time, and the lower portions of the bin will also be cool. But if the new additions hit 130°F, you can be sure that any potential pathogens (like parasites or E. coli) in the compost are being destroyed.
Time is also a great cleanser. Whether your pile is regularly hitting 130°F or not, it must be aged. When the bin is full to the top, put a lid on it and let it sit undisturbed for at least a year. Insects and smaller life forms will move in and finish the decomposition process. In the meanwhile, set up a new bin right next to it and carry on.
After a year, the contents of the bin should resemble soil. If they do not, take remedial action. Empty the bin. If the material still looks like it did when it went in, you probably didn’t add enough nitrogen. The sawdust kept it too cool. Shovel the compost back into the bin, adding a layer of fresh green material every 6 inches or so. The combination of fresh nitrogen and the mass of the pile should start the composting process again and generate enough heat to finish the pile.
Dry Toilet Concern: Pathogens in the Pile
The subject of pathogens in humanure is complex. In general, if no one in your household is carrying parasites or suffering from bacteria-borne intestinal diseases, your compost pile will not carry these things either—unless they are introduced to it via animal manure. Even so, hot temperatures and long aging will kill most everything. For a detailed discussion of these issues, read Joseph Jenkins’s Humanure Handbook. You can buy it in paper form, and he also offers it as a free pdf file at The Humanure Handbook. Also, remember these concerns are most pertinent if you’re planning to use the compost on food crops. If you plan to spread it around decorative landscaping or fruit trees, there’s little chance at all of any bad beasties coming back to you.