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The Composting Toilet: Turning Waste into a Resource

At Gingerhill Farm our community members have the luxury of using a composting toilet. The composting toilet is a valuable tool that is helping us move beyond sustainable agriculture toward regenerative agriculture. Using a flush toilet creates unnecessary waste. Clean water is used to carry away human waste, creating pollution every time we flush a conventional toilet. In using a compost toilet, we are creating a valuable resource - turning human biological waste, or ‘humanure,’ into compost, allowing us to generate fertility by delivering nutrients to the trees on the land.

A composting toilet is:

A system in which the continuous composting of humanure takes place, and in time creates humus: a nutrient dense, harmonious community of living microorganisms. A successful composting toilet is entirely self-contained and there is no risk of pathogens passing from the toilet into the ground or surrounding area; even in the event of heavy rain and storms. A composting toilet is a valuable tool in regenerative agriculture because it produces a yield by converting solid waste, toilet paper, and sawdust into compost.

Benefits of a composting toilet:

  • Saves clean water: When using a flush toilet an average of 6 liters of clean water is used in a single flush. About 50 liters or about 13 gallons of clean water per person is flushed away each day.

  • Creates no waste: Organic refuse becomes nutrient dense compost that supports the growth and resilience of plants.

  • Reduces reliance on non-renewable energy: Waste-disposal plants and systems rely on fossil fuels and toxic chemicals to transport, process and dispose of sewage. A composting toilet does not require transportation off site. Sawdust or another organic source of carbon is the only additional input necessary for decomposition to take place, and the final product is non-toxic.

  • Saves money: Using a composting toilet reduces water usage, thereby lowering water bills and waste-disposal costs. Once the structure for the composting toilet is built and paid for, it requires very little upkeep and can last decades if well cared for. At Gingerhill Farm, the composting toilet successfully serves a community of eight with daily use and requires zero water to operate. About every 12 months we are able to harvest a batch of compost to amend soil and support fertility of the land. This brings value to the farm by promoting abundance in fruit trees and hardwoods.

  • Prevents pollution: Reduces or eliminates sewage in septic tanks, cesspools, and municipal processing plants. Thermophilic composting masses, such as the composting toilet, can destroy human, plant and animal pathogens during the natural biological process of decomposition.

Four Phases of the Composting Toilet Process

A composting toilet is a continuous system where input is added, a little at a time, until the tank is full. There are four phases in the composting toilet process. First, the Mesophilic Phase occurs when a composting mass reaches temperatures ranging from 68℉-113℉. Organic refuse such as feces or food scraps combined with carbon such as sawdust or dry leaves in a contained area creates an environment in which biological decomposition can take place. Naturally occurring compost bacteria consume carbon and oxygen to produce carbon dioxide and energy. Some of this energy is used by the bacteria to grow and reproduce and the excess is released as heat. Under these conditions, the mesophilic bacteria begin to flourish and raise the temperature of the composting mass up to 111℉. Next, the Thermophilic Phase begins when a composting mass reaches temperatures of 113℉ or higher. The metabolic processes of the beneficial microbes release energy, creating a thermophilic environment where high temperatures destroy any dangerous bacteria as beneficial, heat-loving bacteria take over. Thermophilic bacteria thrive in temperatures above 113℉ and are some of the oldest organisms on the planet at 3.6 billion years old. When thermophilic bacteria such as those from the genus Bacillus take over, they greatly inhibit the growth of mesophilic bacteria such as E.Coli. The thermophilic phase takes place rather quickly and may last a few days to a few months. Some composting systems have a stacking function design where a secondary system is installed in addition to the composting system in order to capture resources, such as heat or methane, that are generated during the composting process. For example, a composting manure pile built around copper plumbing as part of a system that also serves as a radiant heater. The third stage in the composting process is the Cooling Phase. During the cooling phase the humanure may have been converted to compost but larger, coarser material such as toilet paper and wood chips will need to be digested by beneficial insects such as black soldier fly larvae or by fungi and mesophilic bacteria that return to the chamber as it cools. Once the toilet chamber is full it is closed and allowed to cool and complete the decomposition process for about 365 days. The closed toilet chamber then enters the final phase. The fourth and final step in the humanure composting process is the Curing Phase. The curing phase should be allowed at least 365 days to complete. Human pathogens and phytotoxins expire during this time as other beneficial microbes take over. Compost in it’s final stage is free of pathogens, plant seeds and is neutral in smell. While the first toilet chamber is completing the curing phase, the second toilet chamber is utilized. After compost has completed the curing phase, it can be mixed with dirt and applied to fruit trees and hardwood trees.

How the composting toilet works: At Gingerhill Farm the composting toilet is part of a stand-alone bathroom design that includes the composting toilet room, a separate wash-room with two sinks, a changing room and an open-air shower. The toilet room has a two-chamber composting system. There are two toilets, but only one is in use at a time. The toilet room is built atop a large chamber that is made of concrete and has three solid walls and a concrete floor. The back wall of the chamber has wooden planks that can be removed in order to access the cured compost at the end of a cycle.

The chamber for the active toilet is prepared by creating a thick base layer of organic, carbon-rich material such as wood chips before opening the toilet for use, which acts as a sponge for any moisture that drains to the bottom of the chamber. The active toilet is used by depositing only solid waste and toilet paper and then covering the waste with a layer of dry sawdust. It is essential that only solid waste goes into the toilet.

Microorganism that live in the compost pile, which include bacteria, fungi, and actinomycetes, need carbon as a source of energy and as a building block to live and reproduce. Nitrogen is also needed by the microorganism but only in small amounts to create cell structure, genetic material and proteins.

Beneficial microorganisms thrive in a compost pile that is about 30 parts carbon to 1 part nitrogen. Human urine is about 15% nitrogen with a carbon to nitrogen ratio of 0.8, and used in a composting toilet will result in the creation of smelly ammonia gas.

At Gingerhill Farm, people are encouraged to urinate outside under trees, helping deliver valuable nitrogen to the plants. Although urine is sterile when it leaves the body, it is important to keep away from vegetables because the high levels of nitrogen will damage the plant.

Objections to the Composting Toilet:

In western culture, waste management has long been a task that has been handled by municipalities or private industry so people naturally have some concerns about the safety of the composting toilet because most of us have not had to learn how to deal with our waste. Here are some common objections to the use of the composting toilet: Is human fecal waste dangerous? - In it’s raw form, feces has the potential to carry pathogens. However in a composting toilet human feces is the input but it is not the final product. During the Four Phases in the Composting Toilet Process a complex scientific process occurs where beneficial microbes digest feces in order to breed more beneficial and naturally occurring microbes out-compete the short-lived pathogens and in the process high heat is created where only thermophilic bacteria & fungi can live. Most pathogens do not survive the mesophilic phase and after 365 days in the curing phase all feces has been converted to humus. Isn’t a composting toilet foul-smelling? -A composting toilet should be neutral in smell if it is used correctly. A composting toilet is not a magic box that converts our waste into compost. It is a tool that requires proper methodology and science to work efficiently. Urinating excessively into the compost toilet will result in off-gassing of nitrogen and an unpleasant ammonia smell. A sufficient ratio of carbon to nitrogen is necessary for composting to occur - 30 parts carbon to 1 part nitrogen is a good rule to follow, so be sure to use enough sawdust after each deposit. This allows for the composting process to occur and also aerates the composting mass so that beneficial microorganism in the pile have access to the oxygen they need in order to convert carbon to carbon dioxide during an aerobic process. Foul-smelling methane is produced in an anaerobic environment so be sure to create proper layering in the composting chamber. Now, consider a farm that captures solar energy and stores the energy by growing vegetables. The vegetables leave the farm. Humans eat and digest the vegetables and eventually they defecate into a flush-toilet. In this story, where is the energy from the sun and the nutrients from the soil going? Some of the solar energy and nutrients become the human. The rest are passed as feces, flushed away and then becomes toxic waste for a waste-isolation plant to deal with by using incredible amounts of energy, water and chemicals. The composting toilet is a symbol of humble yet conscientious living. By caring for the land, growing fruits and vegetables, sharing nourishing meals, making a deposit into the composting toilet, and tending to the composting toilet processes, we are participating in a practice that sustains the fertility of the land and the health of the people. By encouraging others to consider moving away from wasteful methods and systems, we are making strides to being a regenerative community. We invite you to visit Gingerhill Farm for a tour where you can see (and use) the composting toilet design, and enjoy the vegetable gardens and the orchards.


The Humanure Handbook, Joseph Jenkins

I recommend this book if you want to learn more about composting toilet systems. Jenkins details the scientific processes of the composting toilet and extensively covers methods and resources for composting humanure. He also covers concerns such as, what happens to antibiotics and prescription medications that humans pass in their waste?

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