It used to be that people who owned composting toilets lived off the grid in hippie compounds or in underdeveloped countries. The toilets—which don’t require water or sewage systems—also were used for isolated summer camps, poolsides, boats and cottages. Today, composting toilets are a fast-growing trend in green building; you can even buy one at Home Depot or Ace Hardware. In Austin, Texas, composting toilets have been approved for household use (though the city must approve each site). A recently constructed 30,000-square-foot office complex at the University of British Columbia was equipped with composting toilets so the building did not need to be connected to the sewer system.
What is a composting toilet?
Composting toilets are well-ventilated containers in which human waste can decompose under controlled aerobic conditions, according to the Environmental Protection Agency (EPA). Natural bacteria and fungi—and in some cases peat moss, sawdust or other organic matter—break down waste and toilet paper into humus, a fully decomposed, odorless waste that is 10 to 30 percent of its original volume.
In self-contained units (the most common type), compost decomposes in a chamber attached to the toilet. More complex “remote” or “central” units move waste to a composter in another location (such as the basement or outdoors) to decompose. Regardless of the type of composting toilet you choose, fully decomposed humus must be removed and disposed of once fully processed. Fully decomposed humus poses little risk to handlers and, depending on local laws, owners can remove bins of decomposed humus themselves and bury it as a soil amendment or have a septic hauler remove it.
Advances in composting toilets mean they require less homeowner maintenance. Some composting toilets use minimal electricity or battery power, which can come from solar power, to fully automate all or nearly all steps required for decomposition. Composting toilets with multiple composting bins eliminate exposure to unprocessed composting waste. While one bin receives waste, a separate bin processes waste. Such systems can easily accommodate an entire family.
Choose your loo
Multichamber batch systems
Centralized, or multichamber batch systems, require less maintenance. They include two or more excrement bins; while one is in daily use, the other composts.
Pros: Each batch is able to cure fully without adding new excrement; these systems don’t require as much oversight as self-contained systems.
Cons: More expensive; some require users to add water to curing bin.
Single, self-contained systems
These simple systems, which require users to remove the humus from the bottom, are often used in small cottages or for camping purposes.
Pros: Urine keeps the process damp; simplest, cheapest option.
Cons: In single units, fresh waste is continually being added to partially decomposed waste. This means that some parts of the waste are more cured than others; uncured waste can have an odor and present health risks.
Look for a toilet that conforms to the American National Standards Institute’s standard for composting toilets.
Everything you need to know about composting toilets
How much do composting toilets cost?
For a year-round home, you can spend between $1,300 and $6,000 for a toilet that will serve a family of four. But keep in mind, you will save on water bills over the course of the toilet’s life (some offer lifetime warranties).
Where would I use a composting toilet?
Any home can have a composting toilet. Composting toilets are an excellent solution for homes that aren’t connected to the sewage grid, or where connection to the septic system is expensive or difficult. You can also install a composting toilet as a second or emergency bathroom in an outbuilding or basement.
Do I need a special permit?
You will need to comply with local building codes and regulations and get a permit. Call your city hall for details.
Can I use the compost?
Properly disposing of the final compost, or “humus,” is important. You can bury humus around trees and shrubs as a soil enhancement (never use humus on edible gardens) or have the compost removed to a treatment facility by a septic hauler.
How does a composting toilet work?
■ A composting bin (or multiple bins for batch systems) is connected directly or via pipes to a specially designed toilet.
■ Most composting toilets use no water. Micro-flush toilets use small amounts of water (about 4 cups per flush) and sometimes a battery or small amount of electricity to power vacuums.
■ Batch designs without a vacuum flush rely on gravity, so the composting bin must be on the floor below the toilet. Vacuum flush toilets don’t require gravity, allowing more flexibility in bin location.
■ An air inlet and exhaust system facilitate decomposition and release water vapor and other decomposition byproducts.
■ Composting material must be turned; some toilets have automated aeration systems.
■ For optimal composting, waste is heated with the sun or electricity.
■ Some composters drain excess liquid (too much or too little disrupt decomposition).
■ Final-stage humus is removed through a door.
Should you get a composting toilet?
■ It is more resource- and cost-effective to treat waste onsite.
■ Water is not wasted as a transport medium to flush toilets.
■ Harmful nutrient flows into rivers and oceans are eliminated.
■ Humus is safer than any wastewater treatment plant or septic system.
■ Batch system composting toilets are the most hygienic of all toilets if used properly; the natural bacteria that make compost kill viruses, bacteria and toxins in human waste.
■ Many systems allow users to compost vegetable peelings and garden trimmings with toilet waste.
■ Composting toilets require attention for proper maintenance.
■ Pests and odor problems can occur if not maintained properly.
■ Improperly maintained composting toilets are unsafe and unhygienic.
■ Composting toilets are expensive compared with low-flow models; however, they are less expensive than a typical septic system installation.
Annie B. Bond, editor-in-chief of Green Chic Cafe , is the bestselling author of five books: Better Basics for the Home, True Food, Homemade Detox Baths, Natural Flu Protection and Home Enlightenment.