Modern composting toilets offer an environmentally friendly and odor-free method of dealing with human waste. There are many models available at different prices, each with advantages and disadvantages.
My first experience with composting toilets goes back about 20 years. After delaying it as long as possible, I had to make a trip to the dreaded outhouse in a Washington State park. However, I immediately noticed there was absolutely no odor. This was unlike every other “outhouse” I had used – where the smell is usually unbearable. A small plaque announced it was a composting toilet – producing natural fertilizer rather than toxic sewage. “Why didn’t someone think of this before?”, I asked myself.
Turns out they had. In Europe, composting toilets have been around for generations. Often called “waterless toilets”, they are installed in homes, offices and government buildings – wherever a toilet is needed. Contrary to a popular misconception, there is no unpleasant smell if installed properly. North Americans have been much slower to adopt this technology. However, fresh water is becoming a scarce resource in many areas. It seems wasteful to flush away gallons of pure drinking water every time we use a toilet. In 2005, Americans flushed away 123 billion gallons of water, according to a U.S. Geological Survey report.
Conventional sewage treatment is sometimes impractical or too expensive. Septic systems have many potential problems, not the least of which is disposal of the contents in an environmentally sound manner.
Composting toilets provide a viable solution in many instances.
A true composting toilet produces a safe, non-toxic final product that can be placed on ornamental 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 almost nothing to operate.
The exact process varies depending on the composting toilet. Generally you have a traditional looking toilet seat and bowl, which sits above a storage tank. This tank may be built-in as part of the toilet, or it could be installed below the bathroom in a basement or crawlspace.
Some of the newer composting toilets separate urine from solids. This is a big step forward. The relative lack of fluids in the storage tank helps eliminate odor. Complete and rapid composting occurs easily. Further dehydration over time allows the solid material to shrink dramatically (just like a compost pile). A small self-contained composting toilet can hold a surprising number of “uses”, meaning you do not have to empty it frequently.
Most of the older designs hold the urine and solids in one tank. Water evaporates with the aid of electric heat, with the same odor free results – at least theoretically. In practice, you must be very, very careful not to introduce more liquid than the unit can evaporate. Peat moss, coconut fiber, biological compost starter or other organic material is often added to the composting toilet to initiate and aid the composting process. In some toilets the solids are rotated, to speed up composting. With some simple home-made units you just cover fresh material with a layer of sawdust.
Ventilation is required with all composting toilets. Commercially available composting toilets use fans to dry out the contents and prevent odor. These fans are usually very quiet – 30 db to 40 db (which is between a whisper and a refrigerator in volume). They run all the time, 24/7. The fans pull air from the bathroom area, through the toilet and out a pipe to the outside. You never smell anything, even when sitting on the open toilet, because the fan is pulling air away from you. Any odor is exhausted, and it cannot waft up into the room.
When the solids bin fills up – and this can take between a few weeks and years depending on the unit and how many people use it – you empty the already well-composted material into a suitable bin or container so it can “mature”. There should be little or no odor at this stage, other than a slight “earthy” smell.
How long it must sit is a matter of some debate. It depends on the temperature. Below about 12 degrees Celcius or 55 degrees Farenheit composting will slow or stop. Many experts believe letting the compost sit for 12 weeks at room temperature should render pathogens harmless. Others recommend a more cautious 6 months. It is then 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 in the trash.
Composting toilets require almost no maintenance and are impossible to plug. They are hygienic, inexpensive in the long run and environmentally benign. As fresh water becomes ever more scarce we are sure to see wide spread acceptance of this technology.
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An excellent video on composting toilets can be seen here: