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Composting Toilet Header

A Guide to Composting Toilets

By Tobias Roberts Rise Writer
Mar 11, 2020

Indoor plumbing is a relatively new concept, with flush toilets only gaining widespread popularity in the mid-1800s. Our ancestors went to the bathroom in outhouses for thousands of years, usually separated from the main living area. Today, having water on demand for bathing, cleaning, washing clothes, and drinking certainly makes our lives easier. Composting toilets present us with an opportunity to dispose of human waste without relying on fresh, potable water.

Composting Toilet

Table of Contents

  1. How Does a Composting Toilet Work?
  2. Does a Composting Toilet Require a Septic Tank? 
  3. Can You Use Toilet Paper With Composting Toilets?
  4. Do Composting Toilets Smell Bad?
  5. Where Are Composting Toilets Legal?
  6. Composting Toilets and Blackwater
  7. How Often Does a Composting Toilet Need to Be Emptied?
  8. How Do You Clean Composting Toilets?
  9. Who Might Consider Using a Composting Toilet?
  10. What Are the Advantages of a Composting Toilet?
  11. Are Compost Toilets Good for the Environment?
  12. What Are the Disadvantages of Composting Toilets?
  13. The Best Composting Toilets on the Market Today
  14. A Firsthand Account of a Conscientious Decision to Use a Composting Toilet
  15. The Low Down on Composting Toilets

How Does a Composting Toilet Work?

Composting toilets encourage healthy, high-temperature, aerobic decomposition. Unlike anaerobic decomposition where oxygen is not present, the millions of microbes thrive in oxygen-rich atmospheres go to work. They break down human waste quickly, efficiently, and, most importantly, without foul smells.

Composting toilets avoid the accumulation of dangerous pathogenic waste. Municipal sewer systems regularly send sewage sludge to landfills. This results in harmful components such as pathogenic organisms, organic compounds, metals, phosphorus, and nitrogen can leach into the environment.

Does a Composting Toilet Require a Septic Tank? 

Americans flush the toilet an average of five times per day, using between 6 and 18 gallons of water each day. This amounts to about 24% of their daily water use. On a yearly scale, the billions of gallons of fresh, clean water flushed down the drain adds up to about $5 billion in water costs. Simultaneously, more than one-third of cities and towns worldwide might experience severe water shortages in the coming years. The impending water crisis should encourage homeowners to reconsider the intelligence of using water to dispose of our human waste.

On the other hand, composting toilets allow for a healthy, sanitary way to deal with human waste without a separate septic tank. An additional benefit, composting toilets can prevent contamination of groundwater and surface water sources that commonly occur with septic tanks and sewage systems.

Money in Toilet

Can You Use Toilet Paper With Composting Toilets?

Toilet paper is a source of carbon, breaks down, and can be used with composting toilets. Marine and RV toilet paper often breaks down the quickest and is recommended. Tampons, wipes, and diapers should not be disposed of in a composting toilet because they are usually chlorine-bleached and made from a mix of non-organic cotton and rayon.

Do Composting Toilets Smell Bad?

Composting toilets rely on high-carbon content to neutralize the smells of human waste. They create an ideal atmosphere where microbes, healthy bacteria, and other microorganisms can begin the decomposition process. The finished product of a composting toilet is humus, a rich, fertile soil that smells like a forest floor. The common practice is to add a few scoops of sawdust, leaf litter, or other dry, high-carbon material to the toilet after each use. The high carbon organic material immediately neutralizes the smell and encourages microbes to begin the natural decomposition process.

Where Are Composting Toilets Legal?

The ability to legally install a composting toilet differs by region and municipality, dependent on building and plumbing codes. Composting toilets that comply with the National Sanitation Foundation's NSF/ANSI Standard #41 or Electrical Testing Labs (ETL) often meet these local codes. Still, it's necessary to consult local codes before purchasing or installing to understand guidelines or restrictions.

Composting Toilets and Blackwater

Putting human waste in water also creates a considerable risk of contamination. Combining water and human waste that is high in nitrogen is a perfect recipe for putrid-smelling anaerobic decomposition where pathogens can quickly multiply. As a solution, blackwater is buried underground in septic tanks or sent to a municipal sewer system. Flushing the toilet, then, is an "out of sight, out of mind" solution where we rarely consider the downstream, long-term effects.  Recently, black water discharges near Niagara Falls caused a putrid smell that turned away tourists and visitors.

Converted Toilet

How Often Does a Composting Toilet Need to Be Emptied?

In our case, we used a raised cinder block tank. We retrofitted a ceramic toilet for the toilet seat. The tank, where water is usually located for flushing, is filled with sawdust that you scoop out and throw into the tank when finished using the toilet. When the tank fills up, usually every six months or so, we shovel the mostly decomposed material into a wheelbarrow through an outside access door, and take it to the compost pile. There, we add some more leaf litter or sawdust and let the compost age for 12-18 months. By this time, it has transformed into a pleasant smelling, rich, black compost teeming with earthworms and other healthy soil life. This compost is added yearly to our peach and macadamia nut orchard, undoubtedly contributing to our peaches' sweetness. This high temperature (thermophilic) composting process, added to the extra year of aging, ensures that any pathogens are eliminated before being sent to our fruit trees.

How Do You Clean Composting Toilets?

Unlike the "out of sight and out of mind" mentality characteristic of flush toilets (and many aspects of modern-day society), composting toilets require a dutiful sense of responsibility and accountability. The cyclical process of returning our waste to the soil from which it originally came creates a direct connection to the ecosystems we live in.

earthworms on a persons hand

Who Might Consider Using a Composting Toilet?

Composting toilets can be used in virtually every household, from rural homesteads without access to municipal water sources to inner-city homes in high population density areas. However, there are certain situations where composting toilets work best. 

While composting toilets can be used almost anywhere, the EPA states that the composting toilet is well suited for remote areas where water is:

  • Scarce
  • Low percolation
  • High water tables
  • Shallow soil
  • Rough terrain

In these conditions, there is a high probability of contaminating important water sources. Other environmentally sensitive areas where a septic system might cause harm would also benefit from composting toilet systems.

Composting toilets are an excellent alternative for tiny homes on wheels. Space is at a premium, and connection to sewer systems is not an option.

Plants in Toilet

What Are the Advantages of a Composting Toilet?

Composting toilets use little to no water to facilitate the composting of human waste. The process also provides a way for us to produce our own compost to promote healthier, more fertile soil for growing our own food.

Are Compost Toilets Good for the Environment?

Composting toilets can reduce the amount of phosphorous, potassium, and nitrogen entering wastewater by 50 percent, 60 percent, and 90 percent, respectively. This can lead to a reduction of nutrient pollution in waterways and groundwater. Composting toilets can also further reduce bathroom water usage by 25 percent and eliminate toilet water use.

What Are the Disadvantages of Composting Toilets?

The only disadvantage of composting toilets is that homeowners will need to put the decomposed humus once the decomposition process is complete. With commercial composting toilets, the final decomposing chamber usually only needs to be emptied every 2-3 months. During the decomposition process, the amount of waste is greatly reduced through evaporation. However, if you live on the 12th floor of a high rise apartment building, taking a bag of dirt (essentially) down the elevator might be a bit of an inconvenience. For homeowners, the humus from your composting toilet can also be mixed with regular potting soil for your household plants.

The Best Composting Toilets on the Market Today

While you could build your own DIY composting toilet system, several companies are producing commercial composting toilets. These toilets meet building codes around the country and offer a low-maintenance option for getting rid of black water flowing from your home.

Nature's Head Composting Toilet
Composting Toilet. Photo Credit: Nature's Head

Nature's Head Composting Toilet

Nature's Head composting toilets are self-contained systems that divert urine from the main composting chamber. A waterless operation is a great option for people who live in tiny homes or even in RVs and on houseboats. They have sold tens of thousands of units, and they are easily installed without the need of a professional plumber. Cost: about $925 USD.

Separett Villa Composting Toilet Lifewater Engineering
Separett Villa Composting Toilet. Photo Credit: Lifewater Engineering

Separett Villa

Separett offers another self-contained system. Their Villa 9200 system has a one-speed fan that expels odor and condensation from the toilet. The venting duct can be run out of the outer wall. This composting toilet is easily installed in warm and cold locations. Suppose you want to divert urine for use as an organic plant nutrient. In that case, you can also purchase a Separett Ejektortank for this use. Cost: about $1,000 USD.

Sun-Mar Excel Composting Toilet
Sun-Mar Excel Composting Toilet


Sun-Mar is a company that specializes in central composting toilet systems. They have several options that are well-rated, including Excel, Compact, and Centrex 2000. Centrex 2000 costs a bit more than self-contained compost toilets, but only needs to be emptied 2-3 times a year when used regularly by a family of four. The Centrex 2000 also contains a 370-watt thermostatically controlled heater with a 30-watt turbofan, and a 2" vent stack which removes evaporating liquid and fresh odors. Cost: range between $650 - $2,000 USD. 

A Firsthand Account of a Conscientious Decision to Use a Composting Toilet

When people visit our home, they are understandably attracted to the creative features that earthen building allows. Curved walls, wine bottles incorporated as unique-colored windows, and hand-sculpted bookcases are substantially different from "normal" home construction techniques. However, when giving our home tours, we never miss an opportunity to show off our bathroom. Not because it is architecturally impressive, but rather to see people's reactions when they notice that there is no way to flush the toilet with water. For us, the decision to use a composting toilet was born out of necessity but eventually grew into a practical and tangible way to live a sustainable lifestyle.

About four years ago, my wife, our seven-month-old daughter, and I moved to an abandoned farm in the mountains of El Salvador. For years we had dreamed about building our own home, but we knew that if we didn't take the plunge, that dream would always remain a distant possibility. Before moving, we spent a weekend on the farm building a simple, one room, 15 by the 10-foot wood cabin, just enough space to pack in a bed and a couple of suitcases of clothes. Once we unpacked our stuff and made the bed, the area felt comfortable, though slightly claustrophobic.

A small curtain partitioned a small corner of the hastily-built cabin to make space for a bathroom and shower. A simple garden hose coiled inside our compost pile gave a quick solution for warm showers. A raised cinder block tank and a sack full of sawdust would be our temporary toilet solution. 

Though we felt comfortable in the small cabin, we continually reminded ourselves that the tight quarters would only be temporary. At the same time, we worked long hours mixing mud for our cob home. Once our daughter started walking, however, the wood cabin seemingly shrunk in size. As she pulled books off shelves and suitcases of clothes were emptied daily, we had extra motivation to finish our permanent home.

When the move finally occurred, we found ourselves with loads of extra space. Our home is small at just over 800 square feet compared to the average home in the United States. Still, it felt extremely spacious with the creative storage ideas incorporated throughout the house. Having lived eight months in a 150 square foot cabin also helped add to the openness.

Nowhere did we feel that extra roominess than in the attached bathroom. Despite having enough space in the bathroom to even include a small, wood-fired sauna, we decided to forego the "common-sense" solution of installing a flush toilet. Instead, we decided to bring our composting toilet and sack of sawdust with us into the new home. 

Our decision to continue using a humble, composting toilet was mind-boggling for many of our friends and family. When we lived in a small cabin, it was seen as a temporary, "emergency" measure. It was assumed that we would eventually replace it with the customary solution - a ceramic toilet and plumbing connected to a septic system. However, after eight months of using our compost toilet, this solution seemed to be just as practical and hygienic as flush toilets. Sawdust and a compost pile became the new ordinary, and "doing our business" in the flush toilets of restaurants and businesses in town began to feel like the unconventional option.

The Low Down on Composting Toilets

Giving back to the Earth is a foundational element of most indigenous worldviews. Using a composting toilet, then, offers a tangible and physical way to participate in fertility cycles that allow natural abundance to flourish. Any homeowner with even a ¼ acre yard can virtually set up a simple compost toilet and composting system. In doing this, they can drastically increase the fertility and resilience of their yard ecosystem.

Our decision to use a composting toilet allows for a sense of proximity essential for making environmentally responsible decisions. Choosing a dual-flush toilet helps homeowners to reduce the amount of water that they use. However, most people have no idea what happens to that wastewater once it goes down the drain. Each year, about 1.2 trillion gallons of untreated wastewater, sewage, and industrial waste is dumped directly into water sources across the United States. That number will only increase in the future as aging infrastructure, floods, and water shortages put stress on municipal sewer systems.  

Cleaning our composting toilet is as simple as taking a shovel and scooping out dark, earthy smelling humus every 6-8 to months. For our family, the conscientious decision to use a composting toilet allowed us to take responsibility for our waste and use it as part of a holistic strategy to create a thriving, regenerative landscape.

Disclaimer: This article does not constitute a product endorsement however Rise does reserve the right to recommend relevant products based on the articles content to provide a more comprehensive experience for the reader.Last Modified: 2021-06-16T03:11:38+0000
Tobias Roberts

Article by:

Tobias Roberts

Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.