My first experience with composting toilets dates back about 20 years. After putting it off as long as possible, I had to take a trip to the dreaded outhouse in a Washington state park. However, I immediately noticed that there was absolutely no smell. This was unlike any other “toilet” I had used, where the smell is usually unbearable. A small plaque announced that it was a composting toilet, producing natural fertilizer instead of toxic sewage. “Why didn’t anyone think of this before?” I wondered.
Turns out they had. In Europe, composting toilets have been around for generations. They are installed in homes, offices and government buildings, wherever a toilet is needed. Contrary to a popular misconception, there is no unpleasant odor if installed correctly. Americans have been much slower to adopt this technology. However, fresh water is becoming a scarce resource in many areas. It seems like a waste to dispose of gallons of pure drinking water every time we use a toilet. In 2005, Americans dumped 123 billion gallons of water, according to a US Geological Survey report.
Conventional wastewater treatment is sometimes impractical or too expensive. Septic systems have many potential problems, one of which is disposing of the contents in an environmentally sound manner. Composting toilets provide a viable solution in many cases.
A true composting toilet produces a safe, non-toxic end product that can be placed on landscape plants. No expensive or energy-intensive treatment is required, and no toxic sludge is produced. Best of all, once the unit is installed, it costs next to nothing to run.
The exact process varies depending on the composting toilet. It usually has a traditional-looking toilet seat and bowl, which sits above a storage tank. This tank can be incorporated as part of the toilet, or it can be installed under the bathroom in a basement or crawl space.
Some of the newer composting toilets separate urine from solids. This is a huge step forward in composting toilet technology. The relative lack of fluids in the storage tank helps eliminate the odor. Complete and rapid composting occurs easily. Further dehydration over time allows the solid material to shrink drastically (like a compost pile). A small urine-diverting composting toilet can have a surprising number of “uses,” meaning you don’t have to empty it often. The urine is diverted into a separate tank or drainage pit.
Most of the older designs contain the urine and solids in one tank. The water is evaporated with the help of electrical heat, with the same odorless results, at least theoretically. In practice, you have to be very, very careful not to introduce more liquid than the unit can evaporate. Peat moss, coir, biocompost starter, or other organic material can be added to the composting toilet to start and aid the composting process. In some restrooms, solids are rotated to speed up composting. With some simple homemade units, you simply cover the fresh material with a layer of sawdust.
Ventilation is required with all composting toilets. There will usually be a PVC pipe or small hose running from the toilet to an outside vent. A small, quiet fan is usually built into the toilet to ensure constant air movement. When the solids bin fills up, and this can take anywhere from a few weeks to years depending on the unit and how many people use it, place the already composted material in a suitable bin or container so it can “mature.” There should be little to no odor at this stage, other than a slight “earthy” odor.
How long it should sit is a matter of debate. It depends on the temperature. Many experts believe that 12 weeks at room temperature should suffice. Others recommend a 6-month preservative. Then it is safe to use the finished compost on flowers or other non-edible plants. If absolutely necessary, as a last resort, you can bag and seal the fully composted material and dispose of it in the trash.
Composting toilets require almost no maintenance and are impossible to clog. They are hygienic, economical in the long term and environmentally benign. As fresh water becomes increasingly scarce, we are confident that we will see widespread acceptance of this technology.