Humanure

Before building our house at the farm, it took Dev several months to nail down all the details involved in building a composting toilet for the Indian context. We have been using this composting toilet for over four years now. Here I share the history and details of this construction.

Developing An Understanding

A couple of decades ago, when we were living in California I remember reading somewhere “all of us are peeing and pooping in drinking water”. The blatant truth in this statement hit me really hard. I felt terrible about  what we were doing (or being forced to do). This understanding was weighing me down for sometime and slowly it receded into the background. Several years later I came across this quote by Joseph Jenkins:

“The world is divided into two categories of people: those who shit in their drinking water supplies and those who don’t.”

This was a wake-up call. Dev and I started reading “The Humanure Handbook” by Jenkins. (All the quotes in this article are from this book) Soon after reading this book we decided that we wouldn’t have a septic system in the house that we were planning to construct on the farm. Also, we had a self-imposed limit on the water (2000 liters per day for household and farm purposes) that we could pump from our bore well. We needed to conserve all the water we could and use it for growing trees. Thus a no-flush toilet idea appealed to us right away.

 “According to a composing toilet manufacturer, waterless composing toilets can reduce household water consumption by 150,000 liters per year. This is significant when one considers that only 3% of the Earth’s water is not salt water, and two-thirds of the fresh water is locked up in ice. That means less than one percent of the Earth’s water is available as drinking water. Why shit in it?”

Current Sewage System - A Nightmare

“Let’s assume the whole world adopted the sewage philosophy we have in the United States: defecate into water and then treat the polluted water. What would that scenario be like? Well, for one thing it wouldn’t work. It takes between 1000 and 2000 tons of water at various stages in the process to flush one ton of humanure. In a world of jut 6 billion people producing a conservative estimate of 1.2 million metric tons of human excrement daily, the amount of water required to flush it all would not be obtainable.”

"Our septic systems pollute groundwater; this is an undeniable fact ... Between 820 and 1460 billion gallons of this (water from the sewage systems) contaminated water were discharged per year into our shallowest aquifers. In the US, septic tanks are reported as a source of ground water contamination more than any other source.”

What about wastewater treatment plants or sewage plants?

These plants are basically huge septic tanks that collect excrement(floating in water) of a large population. Treatment plants use aerobic or anaerobic microbial digestion of the solids. Once the microbes do their job and the contents are allowed to settle down, we are left with solids (called sludge) and the waste water. Sludge is treated differently in different places -- benign to out-rightly harmful practices . “The water left behind is treated, usually with Chlorine, and discharged into a stream, river or other body of water.” Whatever happens to groundwater! In India, the fecal sludge is often emptied out into untreated water, agricultural fields or forests. This poses serious risk to the public and the environment.

The Human Nutrient Cycle

 

 

 

PC: The Humanure Handbook, by Joseph Jenkins

I found this excerpt on iharweb.org; it succinctly captures the mess we are in:

“humans are going through the elaborate process of mining and processing to manufacture fertilizers, applying them to crops, and then losing it all via wastewater. Lakes and streams, which receive an excess of nutrients from wastewater are suffering from serious ecological effects such as oxygen depletion and fish-kills. Also, synthetic fertilizer manufacturing is an energy-intensive industry and is expected to increase to feed an ever-growing population”.

Closing The Loop

 “Not all cultures think of human excrement in a negative way. For example, swear-words meaning excrement do not seem to exist in the Chinese language. Traditionally, there was nothing more valuable to a peasant than humanure.”

 "In China, the practice of composting humanure with crop residues has enabled the soil to support high population densities without loss of fertility for more than 4000 years. There certainly was no chemical fertilizer 4000 years ago. The practice of composting all waste (humanure, livestock manure, household organic residues, organic farm residues) yielded a rich manure". 

“Farmers of Forty Centuries” was a book written by Dr. F. H. King and published in 1910. Dr. King was interested in finding out how people could farm the same fields for millennia without destroying their fertility. He writes:

“One of the most remarkable agricultural practices adopted by any civilized people is the centuries long and well nigh universal conservation and utilization of all humanure in China, Korea and Japan, turning it to marvelous account in the maintenance of soil fertility ... mineral fertilizers so extensively employed in modern Western agriculture have been a physical impossibility to all people alike until within very recent years”.

Our Construction

One of our friends, Venetia Ansel, had built a composting toilet on their farm. She helped us understand the issues involved. After a series of discussions at home and some R&D, we arrived at a design that incorporates:

- a urine diverter

- a urinal (for men)

- a urine collecting tank, that receives urine from both the men's urinal and the urine diverter

- a granite-top bench that sits on top of a toilet chamber 

- a toilet chamber 

- an exhaust vent pipe from the chamber

Our Composting Toilet

Composting Toilet Bench

Technical Details:

• The granite-top bench has a "business" area and a wash bowl. The "business" area is basically an opening in the bench with a bucket underneath it. The opening is slightly bigger than a normal Western toilet seat. The height of this bench (38 cm) ensures that it can be used as a Western (sitting style) toilet or Indian (squatting style) toilet. We have a hand-crafted toilet seat, for Western use. 
• The urine diverter, installed in the front of the "business" area, separates urine from the solids. We got this fabricated. This is connected to a five liter can, that is placed outside the building. We dilute the collected urine and use it as a fertilizer. The urine diverter does its job irrespective of the user's position (sitting or squatting). It ensures that the bucket underneath doesn't get  much of the liquid. The user is oblivious of all these technical details. 
• The toilet chamber has an opening from outside the building. We have a metal gate here. We have used an old cycle tube to achieve an air-tight seal (to deter bugs). The floor of this chamber is sufficiently above the ground level, to prevent any water from getting in during heavy rain.
• The vent pipe, from the toilet chamber, is covered with mesh at the top and capped with a PVC 'T' joint
• A hand-crafted, inverted 'U' shaped, wooden platform sits on top of the wash bowl to enable easy washing
• A window with mesh keeps the place well ventilated

Usage

After every potty use, we gently scoot over to the wash bowl and use the health faucet (spray) situated on the wall behind us. To prevent any odour, the (solid) excrement needs to covered well. We use sawdust from the local saw mills as the cover material. We get our sawdust from timber-only mills (these mills don't process plywood). We have used crushed, dried leaves when we couldn't procure sawdust. 

This toilet wastes so little water -- hardly 5 liter, for a family of four for an entire day!

If a composting toilet is managed properly, it should be odour-free...these toilets should provide a suitable alternative to flush toilets for people who want to stop defecting in their drinking water".

Composting and  Pathogens

We do off-site composting. We have a 10 liter bucket, aligned to the center of the opening in the granite-top bench of our toilet. This bucket is placed on a wooden base, with castors. Once the bucket gets filled up, we use a long hook to drag it out of the chamber. We dump this on top of an (unfinished) compost pile. 

We add kitchen waste and farm's green waste to the same pile. We sometimes add the collected urine also, depending on the moisture level of the pile. The nitrogen in the urine balances the carbon in the sawdust. Before re-installing the bucket into the toilet chamber, we wash it and add sawdust to the bottom. This ensures that the contents of the bucket get cleanly dumped. This keeps the bucket fairly clean and uses very little water while washing.

Once the unfinished compost pile gets sufficiently big, we start the composting process. We let the pile cool down for a couple of months. We then use the end product -- dark, fluffy, earthy smelling humus -- to fertilize fruit trees. We have observed that the trees and bamboo close to the humanure compost pile absolutely thrive from the extra nutrition that they receive from this pile. We have not observed the same growth rate anywhere else in the farm.

"There are two primary factors leading to the death of pathogens in humanure. The first is temperature. A compost pile that is properly managed will destroy pathogens with the heat and biological activity it generates. The second factor is time ... Given enough time, the wide biodiversity of microorganisms in the compost will destroy pathogens by the antagonism, competition, consumption and antibiotic inhibitors provided by the beneficial microorganisms".

Feedback from our visitors

We have had visitors from all over India, the U.S. and London. The most common feedback that we have heard so far is "it is just like a normal toilet!" We are very happy to hear this. We have hosted many, many families and have had no problems. A friend who built his house recently remarked "how I wish I visited this place before building my house! I would have built a composting toilet too!" Surprised by the ease-of-use and odourless nature of the toilet, a friend from Bangalore said that she would recommend this design to anyone thinking about such a toilet.

Commercial Composting Toilets

There are many commercial composting toilets now. Eco-san toilets are used in many places in India. Clivus Multtrum USA has been in the market since 1964! BioLet toilets are being engineered and built in Sweden since 1972! "At least 21 different composting toilets were on the market in Norway alone in 1975".

Future

A no-flush movement is gaining momentum in Europe. People are waking up to the fact that the current way of flushing and polluting the environment is not a sustainable one. Just last week, the Sunday Times (UK) ran an article on how "Composting Loo" is becoming the new status symbol!

“we too will have to constructively deal with all of our organic byproducts eventually. We can put it off, but not forever”. 

”... human species must inevitably evolve ... flush toilets and bulging garbage cans represent well entrenched habits that must be rethought and reinvented”. 

-- Hema