Sonoma County Composting Toilet Project Approved

Sonoma County Water Agency Approves
Composting Toilet Pilot Project

On December 15th, the Sonoma County Water Agency Board of Directors approved a pilot project that will test “composting toilets” in Occidental. Composting toilets require no external water source and do not discharge to sewers, making them potentially well-suited for communities with limited water supply and sewer capacity. Currently, composting toilets are not permitted in Sonoma County.

“Many of my west county constituents are interested in composting toilets,” said Director Efren Carrillo, who represents Sonoma County’s fifth supervisorial district. “This pilot project will provide the data and analysis we need to tell us whether and how to move forward.”


Initially the pilot project will involve four households within the Occidental County Sanitation District. It will include the installation, monitoring, evaluation and, after the evaluation period, removal of the composting toilets, which are designed to compost the waste products within the units. Composting toilets are used in other parts of the world, but have limited distribution in the United States. The data from the pilot project will help determine whether the toilets are suitable for use in Occidental and in communities that have limited sewer capacity.

In addition to the composting toilet pilot project, the Sonoma County Water Agency (which operates the Occidental County Sanitation District) is offering a direct installation high-efficiency toilet program to sanitation district customers. Through this program, residents and businesses receive free installation of high-efficiency toilets, showerheads and faucet aerators.

For additional information about the composting toilet program, contact Doug Messenger, 707.547.1952 or e-mail: douglas.messenger@scwa.ca.gov.

For information about the direct installation program, call Brian Lee at 707.547.1918 or e-mail: brian.lee@scwa.ca.gov.

Below is some additional information on Composting Toilets - for the full document, please visit: http://oikos.com/library/compostingtoilet/

What is a Composting Toilet System and How Does it Compost?

Composting toilet systems (sometimes called biological toilets, dry toilets and waterless toilets) contain and control the composting of excrement, toilet paper, carbon additive, and, optionally, food wastes. Unlike a septic system a composting toilet system relies on unsaturated conditions (material cannot be fully immersed in water), where aerobic bacteria and fungi break down wastes, just as they do in a yard waste composter. Sized and operated properly, a composting toilet breaks down waste to 10 to 30 percent of its original volume. The resulting end-product is a stable soil-like material called "humus," which legally must be either buried or removed by a licensed seepage hauler in accordance with state and local regulations in the United States. In other countries, humus is used as a soil conditioner on edible crops.

The primary objective of the composting toilet system is to contain, immobilize or destroy organisms that cause human disease (pathogens), thereby reducing the risk of human infection to acceptable levels without contaminating the immediate or distant environment and harming its inhabitants.

This should be accomplished in a manner that
• is consistent with good sanitation (minimizing both human contact with unprocessed excrement and exposure to disease vectors, such as flies).
• produces an inoffensive and reasonably dry end-product that can be handled with minimum risk.
• minimizes odor.

A secondary objective is to transform the nutrients in human excrement into fully oxidized, stable plant-available forms that can be used as a soil conditioner for plants and trees.

The main components of a composting toilet are:
• a composting reactor connected to one or more dry or micro-flush toilets;
• a screened exhaust system (often fan-forced) to remove odors, carbon dioxide, water vapor, and the by-products of aerobic decomposition;
• a means of ventilation to provide oxygen (aeration) for the aerobic organisms in the composter;
• a means of draining and managing excess liquid and leachate;
• process controls, such as mixers, to optimize and manage the process; and
• an access door for removal of the end-product.

The composting reactor should be constructed to separate the solids from the liquids and produce a stable, humus material with less than 200 most probable number (MPN) per gram of fecal coliform.

General Types of Composting Toilet Systems
Composting toilet systems can be classified in several ways:


• Self-Contained versus Centralized
Composting toilet systems are either self-contained, whereby the toilet seat and a small composting reactor are one unit (typically small cottage models), or centralized or remote, where the toilet connects to a composting reactor that is somewhere else.

• Manufactured versus Site-Built
One can either purchase a manufactured composting toilet system or have a site-built composting toilet system constructed (however, the latter can be difficult to get permitted by local health agents).

• Batch (Multiple-Chamber) versus Continuous (Single-Chamber)
Most composting toilet systems use one of two approaches to manage the composting process: either single-chamber continuous composting or multi-chamber batch composting processes.

It is difficult to generalize about which process affords the greatest opportunity for complete processing and minimizes the potential for pathogen survival. In a batch system, a finite supply of nutrients is cycled and recycled through microbe populations until the nutrients, both the free ones and those bound in microbial protoplasm and cell walls, are ultimately converted to stable, fully oxidized forms, and the fungi have performed their work on the remaining lignin and cellulose compounds, releasing antibiotics in the process.

Definitive research is needed in this area.

Active versus Passive

As with solar systems, composting systems are usually either passive or active. Passive systems are usually simple moldering reactors in which ETPA (excrement, toilet paper and additive) is collected and allowed to decompose in cool environments without active process control (heat, mixing, aeration).

Active systems may feature automatic mixers, pile-leveling devices, tumbling drums, thermostat-controlled heaters, fans, and so forth. The trend in the composting of municipal solid waste (garbage and trash), sewage sludge and yard and agricultural residues is toward active systems. By making the process active, the size of the composter can be reduced, because composting efficiency is speeded up (and the volume of the material reduced faster).

Passive systems are designed to optimize the process by design, not mechanical action, allowing only time, gravity, ambient temperature and the shape of the container to control the process. Passive composters are often referred to as moldering toilets, as the process at work is natural uncontrolled decay at cool in-ground temperatures at or below 68° F. In this cool environment, molds (fungi and actinomycetes) are the primary biological decomposers, because it is a bit too cool for the faster-acting mesophilic and thermophilic bacteria.

For the full document this information was pulled from, please visit: http://oikos.com/library/compostingtoilet/