The simplest way to construct a compost toilet is to purchase a medical toilet seat and place a 5-gallon bucket beneath the seat to collect deposits.
Medical toilet seat
Two 5-gallon buckets
One plant pot that fits inside 5-gallon bucket
The simplest way to make a composting toilet for your home is to purchase a medical toilet seat (the kind where you can easily sit down to pee), and keep two buckets nearby. One bucket is for pee, the other bucket is for poop. Both buckets are layered with sawdust in between deposits. You can also purchase the Separette Privy Kit, which separates urine and feces for easy collection. This lowers the work load, eliminates odors, and makes waste composting simple.
Place the toilet seat over the buckets, and do your business as usual. Sprinkle a handful of sawdust into the bucket after each use. The urine your household produces is safe to use without treatment. When the pee bucket is full, dump it on the compost pile, or layer it in the garden as mulch. The nutrient-rich sawdust will enhance either garden or compost pile. Urine contains nitrogen, phosphorus, and potassium and makes an amazing plant fertilizer. Urine is typically sterile, and if separated from feces, can be easily and safely reused.
Urine can become contaminated if it comes into contact with feces. There are also a few diseases that can be transmitted through urine — leptospirosis and schistosomiasis (bilharzia), which are found almost exclusively in tropical aquatic environments, and typhoid, which is inactivated shortly after excretion. If urine has been contaminated with feces, or if it came from strangers who may carry these diseases, it should be purified before it is used. To purify urine, all you have to do is wait. Urine leaves the body fairly acidic and the pH increases rapidly until pathogens are unable to survive. This process takes from fifteen days in warmer Mexico to over three months in the chilly Scandinavian winter. Make sure you know the specifics for your location.
You can use urine directly by diluting it, one part urine to four parts water, and pouring it into the soil around your plants. Don’t use it on young seedlings, and water alternately with rainwater or city water to flush salts from the soil. Better yet, apply it before a rain. You can compost it and let it rot, or add it to your greywater system.
In the simple two-bucket system, the poop bucket is constructed slightly differently than the pee bucket. For the poop bucket, take another five-gallon bucket (which has a cover) and find a plant pot that fits within it. Usually the black plastic pots that come with small trees or large plants will fit perfectly. Line the bottom of that pot with about one inch of subsoil, packing it in so that it keeps the fecal matter from leaking out. This creates a block from any disease vectors escaping, but allows for a little bit of drainage. Add a layer of compost with live worms in it, about two inches deep. You can then start making deposits in the bucket, covering each deposit with a bulk agent, like wood chips or sawdust. Keep the bucket covered when not in use.
When the pot is nearly full (about three inches from the top) remove the plant pot from the five-gallon bucket, and add another layer of worm-rich compost. Plant a tree in the center of the pot, and let the pot sit in the shade under a tree for a few months. Keep it watered, but not drenched. This will keep any contaminants from leaking into the soil. Rodents don’t get in because they won’t dig through the subsoil. The trees love this soil, which has no pathogens because the worms have been processing it for the month or so it takes for one person to fill up the pot. After you let it sit for a few months, you can transplant the plant into the ground, or give it to someone you love.
This is a simple, indoor option that everyone can use. The basic mechanism is still the same; the only difference is that this composting toilet is inside, rather than outside, which makes it more convenient to use throughout the year. Urine is separated into one bucket and is put into the compost bin or diluted with water and used in the garden. Feces are separated into another bucket and allowed to decompose for a year before being returned to the garden.
The simplest backyard humanure setup: a medical toilet seat, a five-gallon bucket, carbon matter, your deposits and…voilà — compost!
You need three things to make this system work: a toilet receptacle, a compost bin, and carboniferous materials such as straw, leaves, or wood shavings to mix with the poop. Once the bucket of humanure is full, bring it to a dedicated compost bin, where it will be covered with straw or other carboniferous materials to aid the decomposition process. In this method, the heat of the compost pile is crucial. In order to instigate thermophilic (heat-based) composting, the compost pile needs to reach temperatures of at least 113 degrees F, or hotter. When it reaches this heat for a consistent amount of time, humanure will break down within months. Purchase a thermometer to track the temperature to make sure that thermophilic composting is taking place. This is the best way to ensure that any pathogens in the human waste are destroyed.
If you do not have the space to create a dedicated compost pile for humanure, you can seal the bucket of poop once it is full, and allow it to sit in a sunny spot in the garden for at least one year. To aid the process, this bucket can also be turned periodically the way you turn a compost tumbler. Make sure the bucket is tightly closed to inhibit insects or vermin from visiting. Once composted, this soil can be safely used in the garden.
We understand that not everyone lives in a place where this is feasible. Unless your apartment building installs a giant composting toilet in the basement (not impossible, and a great idea by the way), apartment dwellers with no yards will be hard pressed to comply with this shitty regime. Although North America doesn’t have a sewerless city (yet), there are a few sewerless buildings. One example is the public restroom at the Bronx Zoo in New York City. Faced with an exorbitantly expensive sewer connection, they decided to go sewerless, installing large composting toilets underneath the bathroom and using all greywater on the landscape. China, long familiar with the collection of night soil for fertilizer, has begun to standardize urban ecological sanitation systems and apply ecological sanitation principles on a large scale. In 2007, in the drought-ridden north, an “eco city” was built with modern urine-diverting toilets and systems for treating household wastes. The urine and feces — as well as kitchen compost — are collected from each home and processed in an eco-station, much the same way garbage and recycling are collected in parts of the United States. Large-scale ecological sanitation based on this model could be integrated into any urban environment.
But if you live in a place where you have a yard and a bit of extra space, you can safely compost and reuse your excrement to great effect. Humanure toilets are limited to situations where adequate and appropriate coverage materials are available. They are a knowledge-based sanitation system, sometimes referred to as “the thinking person’s toilet.” When properly built and managed, however, they provide a low-cost, hygienically safe, environmentally friendly, and pleasant sanitation option that produces a wealth of soil fertility.
Our biggest obstacles to recycling and reusing human wastes are neither technical nor health related, but simply in our minds. We live in a culture that hates and fears the body and the shadows of the body. Composting this story — the disconnection from our bodies, our fear of death, our separation from the world around us — is as important as literally composting our bodily wastes and reusing them as precious fertility for our soil.