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Human waste economy: humanure, diaper-derived concrete & more

When in 1837 Ignaz Semmelweis left his merchant family from Budapest to study Law in Vienna, he was already known for his stubbornly independent character. He again proved it one year after his arrival by switching to medicine.

Fate aligned with medical history when Semmelweis failed to get an appointment for internal medicine, which prompted him to reluctantly specialize in obstetrics, a field he was to transform a few years later, pioneering the use of antiseptics in medicine, even though the medical community of his time never recognized his work or its importance.

Laura Allen, an early advocate of greywater reuse and the feasibility of “humanure” even in urban environments

A pioneer of sorts, Ignaz Semmelweis, was soon criticized for his eccentricities and what other doctors considered mercurial outbursts. As the assistant of Johann Klein, head of the First Obstetrical Clinic at Vienna’s General Hospital, Ignaz Semmelweis was soon in charge of maternity care and so-called “difficult deliveries,” established to aid underprivileged women, including prostitutes.

The fever that medicine didn’t cure

The Hungarian doctor soon realized that obscenely high percentages of deliveries ended in tragedy in the First Clinic, averaging a maternal mortality rate of 10% (or ten deaths per 100 births; today, countries such as Greece or Australia have less than four maternal deaths per 100,000 births) due to puerperal fever, a disease attacking women after delivery.

Another maternity clinic in Vienna, known as the Second Clinic had a somehow lower mortality rate of 4%, and soon patients begged doctors not to go to the First Clinic.

Decades before the work of Louis Pasteur’s experiments on microbes, Semmelweis had to confront some of the most reputed doctors of his time to try to elucidate rationally what was causing puerperal fever and mortality in obstetrical clinics, especially the most concurred ones. There was one more difference between the First and Second Clinic: in the first establishment, medical students used their unclean scalpels to equally examine pregnant women, sick people, and corpses, whereas the Second Clinic was only served by midwives who weren’t in contact with cadaverous particles.

Emmanuel Pauwels relocated to the Catalan Pyrenees to renovate Cal Guerxo on his own (ecological) terms

The medical community in Central Europe had not yet accepted the germ theory of disease, and Semmelweis tried to instruct anybody in touch with patients to wash their hands and instruments, so in 1847 he instituted a new policy. All people had to wash their hands with a chlorinated solution after autopsy work and before examining patients. The mortality rate in the First Clinic declined by 90% right away and became lower than that of the Second Clinic.

Doctor Semmelweis’ chlorine handwash

However, doctor Semmelweis’ chlorine handwash procedure was mocked by the prevailing medical opinion of his time, which related most infectious diseases to imbalances in “body humors,” treated with bloodlettings. Semmelweis was soon dismissed from the Vienna hospital and discredited as a charlatan capable of relating hand washing to maternity mortality.

Decades after, once Pasteur’s experiments on microbes had revolutionized medicine, Ignaz Semmelweis’ pioneer work on antiseptic procedures to avoid a wide range of diseases, from puerperal fever pervasive until the late nineteenth century and microbial transmission of infection due to a general lack of hygiene and antiseptic procedures.

Laura Allen’s “greywater sink” sign (from our June 2008 visit)

Also in the late nineteenth century, as industrial cities cramped more people in unsanitary conditions, epidemics of cholera, hepatitis, or polio made living in certain quarters of London, Paris, or New York very dangerous as the transmission of the disease was pervasive before the arrival of modern sanitation as pathogens from untreated human and animal waste polluted food and water.

Medicine had finally accepted the microbial transmission of disease due to poor hygiene, though typhoid disease, diarrhea, and cholera were still pervasive. Only modern sanitation improved the health of millions, allowing people to access to wastewater disposal and to internalize common practices preventing the general transmission of infections through hands, water, and food.

Improving (not giving up) modern sanitation

Modern sanitation has been as crucial as antiseptics and antibiotics to increase life expectancy ever since, and one of the acknowledged development challenges that underdeveloped countries face is a generalized lack of sanitation capable of separating drinking water from human sewage. Unsafe sanitation is still a leading risk factor for death in poor countries, accounting for 775,000 deaths each year due to fecal-oral transmission (through water, food, and hands) of cholera, diarrhea, dysentery, hepatitis A, typhoid, and polio.

Emmanuel Pauwels, architect advocating for houses with a positive impact: “it’s not about being less bad, it’s about being good.”

To put it into context: people dying from lack of proper sanitation and hence developing cholera, diarrhea, dysentery, hepatitis A, typhoid, and polio, are double de number of people dying by homicide in the world, according to Our World in Data.

However, sanitation was designed with another mentality and never considered the consequences of using fresh water to flush toilets or of discarding grey water (water used domestically that lacks fecal contamination, like water coming from sinks).

At *faircompanies, we’ve tried to cover people finding other ways to keep the advantages of modern sanitation (effectively preventing disease transmission) with a circular approach of wastewater, which can be safely treated for reuse into greywater that gets reused in gardens, showers, and toilet cisterns. In contrast, even contaminated black water can be safely turned into nutrients and organic matter, minimizing fresh water use and landfill pollution (trickling down into aquifers and the food chain).

Laura Allen touches “odorless” humanure, once at the end of its curation process and ready to be used in the garden as humus

Sustainable sanitary systems promise to keep the advantages of modern sanitation with safe ways of converting greywater and excreta into opportunities for circular reuse in bathrooms for greywater and nutrients for gardens or fuel energy plants for black water. However, resource-oriented or “productive” sanitation faces several challenges, among them convincing regulators that ecological sanitation can be applied beyond its prototypical use in enclosed environments such as homes with eco-conscious residents.

Conscientious sanitation

When we visited Oakland teacher Laura Allen around fifteen years ago, she shared a San Francisco East Bay home with housemates up for the task of reducing their impact. They created what they called “greywater guerrillas” (later Greywater Action) as a way to educate friends and local representatives about the simplicity of safely watering plants with water coming from the kitchen sink (they used biodegradable soap exclusively) and the shower.

Composting toilet in Oakland from 15 years ago

What felt bolder was their use of a composting toilet feeding an enclosed “humanure” pile that was stored until completely treated by microorganisms, then used in their garden as a natural fertilizer with a high content of nitrogen, phosphorus, potassium, and other essential micro-nutrients.

In parallel, small companies were trying to create more sustainable composting toilets. In Europe, a small company called Urimat installed with success public urinals that didn’t use the constant flush of fresh water to stay clean.

Their water-free urinals soon turned to be popular in a few years. Then came the popularization of urine-diverting dry toilets (UDDTs), a type of dry toilet that prevents odor buildup and eases the process of pathogen reduction by separating liquid from solid waste.

A pioneering urban setup: Laura Allen’s Oakland house

In urine-diverting dry toilets, urine can be stored in containers to avoid the smell caused by ammonia after 24 hours; then it could be diluted with water as a source of nitrogen, phosphorous, and potassium in a garden; to ensure potential fecal-oral infection that modern sanitation prevents, UDDTs require pathogen reduction of feces by the effect of drying, with turns any pile of “humanure” into odorless compost after a slow process that takes from 6 to 12 months.

After our visit to the greywater guerrillas, Grist and The Guardian, among other media, began covering “humanure” and their urban waste experiment, still very controversial —and ‘alegal’ as long as it didn’t leave their property. Transporting human waste off a property would face legality issues virtually anywhere in North America or Europe, though there aren’t explicit laws, codes, or ordinances prohibiting the use of at-home composting toilets feeding enclosed piles of “humanure,” making the activity “alegal” more than “illegal” at a domestic scale.

Catalan Pyrenees, at the hamlet near Cal Guerxo

The pioneering efforts of the greywater guerrillas have come a long way, and we’ve visited several houses (and apartment building communities) reusing treated human waste: greywater (non-pathogenic water to reuse for flushing or irrigation) urine, and humanure treated through low-tech approaches of pathogen reduction such as drying for months, or through more advanced treatment facilities producing either fertilizer or energy.

House-scale: Cal Guerxo Living Building (Spain)

Spain-based Belgian architect and instructor of sustainable practices, Emmanuel Pauwels, decided to restore an abandoned hilltop ruin into a regenerative, zero-waste country home in the Catalan Pyrenees. According to Pauwels, the house (Cal Guerxo in honor of its traditional name among locals in the hamlet it belongs to) is a “Living Home.”

After spending a year observing the local wind, sun, and rain patterns, Pauwels opened the house via south-facing windows for passive heating, and wind funneled through the interior, allowing for passive cooling in summer.

The LEED Platinum certified house produces 112% of the energy it requires, harvests rain, and uses gravity-flow composting UDDT toilets: urine is used in the garden, whereas solid waste is ultimately dried. The house also includes an organic pool as a refuge for the local flora and fauna. According to Pauwels:

“It’s not about being less bad, it’s about being good.”

Apartment-scale: Kailash ecovillage in Portland

Unsatisfied with conventional living, Ole and Maitri Ersson decided to try a risky idea: in Portland, there was a rundown apartment complex surrounded by the concrete of a misused parking lot, an empty pool, and a dry garden.

They bought the apartment building and decided to de-pave the parking lot, turning the old pool and the surrounding grass into a food forest and garden.

Over the years, at Kailash ecovillage they’ve added solar panels for energy, extensive rainwater collection and storage, and an effective way of processing their own sewage, which complies with building codes. Their urine diversion system turns their urine and solid waste into (once treated) nitrogen and compost for their garden.

Their success is based on involving the residents, which collaborate in the garden in exchange for food, a little income, and a rent they can pay. According to Ole Ersson:

“If you look at it from an economic perspective, no business would want a complex landscape like this because it’s way too much maintenance, but what you have to do is turn the maintenance over to the residents, and then they do it: they get joy; it’s an antidepressant; it’s a way of creating food; it’s a way of creating community; so you have to do it in a certain way, but it’s definitely a lot more work than the typical grass and shrub landscape for sure.”

The city-wide perspective

Whereas greywater reuse expands in modern buildings designed to reduce their impact. However, using human waste diverted into urine and feces that can be safely treated at scale from the source is proving to be a challenging endeavor.

A San Francisco-based startup is trying to turn “humanure” into commercial-grade fertilizer by creating a self-enclosed treatment method that buildings or even towns could apply at scale.

Human waste can also make enough energy to power a gas stove, a hot water boiler, or a solid oxide fuel cell. Human waste isn’t an ideal source of methane to create biogas due to its high nitrogen content and elevated ammonia concentrations (which explain the strong smell of urine after 4 hours or so).

Laura Allen’s backyard edible garden in Oakland CA

Despite the shortcomings, some cities are using human waste to run their vehicles and power small maintenance facilities. Such is the case of Grand Junction, Colorado.

In the Netherlands, Rebecca Schedler from Desing Academy Eindhoven has designed Symbiopunk, an entirely mechanical prototype bioreactor that transforms feces into humus.


Human excreta ends up mixed with other substances, often non-biodegradable and potentially polluting, such as baby and adult diapers, as well as wipes (which clog sanitation and entire sewage systems, consolidated with other substances into “fatbergs“).

A team of housing engineers has come up with one imaginative way to confront the growing issue of diaper waste (which in several countries will grow more among the elderly population due to shrinking fertility rates): creating concrete and mortar made with shredded diapers.

This diaper reuse could address problems like plastic waste and sand shortages. Researchers at Japan’s University of Kitakyushu cleaned and shredded dirty diapers to build a modern-looking, minimalist tiny house that keeps 60 cubic feet of diapers out of landfills.

When the human waste of millions of people runs virtually untreated, there are few ways other than traditional, low-tech means to turn a potential disaster into an opportunity. Over generations, the East Kolkata Wetlands have turned the city’s human waste into a gigantic, highly-effective, circular digestive system that feeds fish ponds transforming the waste into food and fertilizer used in agriculture. Hence:

“This urban ecosytem filters wastewater, turning it into a productive fish habitat — and an engineer-turned-environmentalist is on a mission to save the unique, and free, system.”

“Maintained by farmers and fisher folk, these unique wetlands receive the city’s sewage, organically treat it with the help of sunshine, oxygen and microbial action and turn into a productive fish habitat – nothing short of ecological magic.”

With the right mentality and with no need to mess up with the conquests of human sanitation, human waste can turn into a bio-remediation project where edible algae and fish thrive.

When Mohandas Gandhi stated that “perfect sanitation makes an ‘ideal village,'” was he able to envision that modern systems have to learn to keep their antiseptic advantages while embracing ecosystems in a more sustainable way?