One day last autumn at the University of California, Berkeley, Ph.D. student Emily Woods rolled a small black globe between her fingers that left behind dark smudgy traces. She had fished it out of a bag of similar golf ball-sized black spheres, all made of the same charcoal-like substance, and stacked it with a few others in a cookstove to demonstrate how they can be used for preparing meals. These balls burn just like charcoal, she explained, but are not made of the traditional materials. They are made of human waste. That’s right—poop.

Woods, a student in Berkeley’s interdisciplinary Energy and Resources Group, thinks human poop is one of the best and most readily available charcoal “binders” on the market. When treated properly, it can be combined with agricultural waste and used instead of wood or traditional charcoal for heating. Woods and her partner Andrew Foote have staked their careers on the success of this concept with Sanivation, a social enterprise they founded in 2012.

Demand for household fuel alternatives is high in many parts of the world, especially in Naivasha, Kenya, where Sanivation is based. In Kenya, over 80 percent of urban households rely on charcoal for energy, and consumption and prices are soaring: since 2004, charcoal use has gone up by more than 50 percent while prices have almost tripled. This level of need has created a rampant illegal market, where more than 90 percent of the charcoal made in Kenya fails to comply with new sustainable harvesting laws.

“People are looking for more sustainable, cheaper and better ways to cook,” says Woods, who serves as Sanivation’s CTO. Having the ability to fill that need and being able to adapt their product for different uses are the most thrilling parts of Sanivation’s work for Woods. “We have never had a solid fuel that can be specifically designed to meet users needs,” she says. “Every day we are mixing up the recipe. Our setup allows for that kind of tinkering and that gets me excited.”

When Woods and Foote—Sanivation’s CEO—met, they were both focused on a different problem: sanitation. They met working in Cameroon through Engineers Without Borders, and later began bouncing around ideas for cost-effective sewage treatment technologies to help reduce diarrheal disease, which is a leading cause of death for children under five years old. They started with an idea for a solar toilet, which gradually evolved into something radically different: a subscription-based waste collection service for urban communities.

Human waste has the potential to create electricity for 138 million homes and become a US$9.8 billion charcoal market globally.

Seventy percent of sub-Saharan Africa’s nearly one billion people do not have access to hygienic sanitation facilities. Many (30 percent) still practice open defecation and the rest use communal pit latrines, which are unsanitary and often dangerous. Assaults on women and children are common around these stations, as they are often unlit and located away from where people live. Woods witnessed many of the problems firsthand while working on sanitation infrastructure projects in several countries, Kenya included.

“Many women and children stop drinking liquids after 5 p.m. so they don’t have to use the toilet after dark,” she says. “The number one reason people use our service is because they want access to a safe toilet in their home.”

It took years for Foote and Woods to arrive at the concept of turning human waste into fuel, but once they did, they discovered that their market is enormous. A recent United Nations report cited that human waste, if harnessed as an energy source on a global level, has the potential to generate energy for 138 million homes, and estimated that the market for human waste as charcoal could be worth US$9.8 billion. In Kenya, Foote says that feces-based charcoal has the potential to meet 50 percent of the country’s charcoal demand.

Charcoal production, consumption and costs in Kenya

“Even with an ambitious growth plan, Sanivation might be able to reach 0.5 percent of the market in the next five years. That’s about $5 million in annual revenue from what used to be a waste product,” he adds. Other ventures are also developing solutions in different segments of this space, like Nairobi-based Sanergy, a company that uses a franchise toilet model and transforms the end product into electricity and fertilizer.

The Business of Sanitation

Woods and Foote formally launched Sanivation in 2014 as comprehensive service, offering everything from in-home toilets to the production and sales of waste-based charcoal “briquettes.” The venture offers a subscription-based sanitation service, where customers pay a monthly fee of 600 Kenyan shillings (about US$6.50) for a Sanivation employee to install a toilet and then pick up the waste twice a week and transport it to Sanivation's work site.

At the site, the feces is transferred into repurposed metal paint drums, which are attached to large parabolic mirrors that act as solar energy concentrators. As the sun beams down, it heats the waste to a high enough temperature to deactivate pathogens. The exact amount of time Sanivation leaves the waste in the concentrator depends on how bright the sun is on any given day. If the temperature in the metal drums reaches 85 degrees Celcius, one hour is sufficient. If the drums only reach 65 degrees, the waste stays for six hours.

As human poop is heated, it transforms into a sticky substance because of its high lignin content, which is basically insoluble plant fiber. Heating lignin transforms its chemical bonds, turning it into what Woods and Foote found is a perfect binding agent for a non-wood-based charcoal briquette.

After the waste is treated, it is processed in a mixer to homogenize its composition, and then it is combined with rose waste from local flower farms. (Naivasha, which is in western Kenya, is a major supplier of roses throughout Europe, so rose waste is plentiful in the region.) Prior to mixing the rose waste with the poop, Sanivation carbonizes it in a carbonizer and then grinds it into a powder in a flower mill. The resulting powder is mixed with the heat-treated feces, and the mixture is put into a slowly turning agglomerator, where the briquettes naturally form as a result of centripetal force, like a snowball rolling down a hill. The briquettes are then put out to dry on tables made of chicken wire. It takes about three days for the briquettes to be fully dried and ready for the market, where they sell for roughly the same price as standard charcoal, which costs about $0.30 per kilo in Naivasha.

The endeavor might seem fairly straightforward, but Woods equates it to running 10 companies at the same time. “It is complicated and difficult, and the only reason we are handling all of the steps right now is that we have to prove all of this first,” she explains. Her vision is to eventually produce the binder only and sell it on to others “who are better at making briquettes.”

A Creative Fuel Recipe

Sanivation is not the first to use alternative materials to create charcoal. One organization that Woods encountered in Naivasha had some success combining molasses and charcoal dust. Others have used cassava, acacia gum or clay, among other materials. But the Sanivation briquette is possibly the most efficient one currently on the market, and its binding agent is certainly ubiquitous enough. It is also more sustainable than wood charcoal and releases fewer particulates and about 30 percent less carbon dioxide into the air when burned, Sanivation claims.

Fuel comparison

Paul Manda, who is Sanivation’s site manager, previously worked for organizations that made briquettes out of other binding agents, but this is his first experience working with human waste. Manda beams about what Sanivation has developed. “If I may say so, I think the product is super cool.” He acknowledges that there are ongoing issues to deal with, such as teaching people how to use the briquettes efficiently, but he genuinely feels that Sanivation is heading in the right direction. “This is a product I am very much proud of,” he says.

Foote says their briquette was the result of trying to figure out where they could offer the most value in the fuel sector, and how they could provide a lower-cost and higher performing fuel than what was available.

Sanivation charcoal is not a silver bullet however, as Manda’s “efficiency” comment suggests. One of its main drawbacks is that it is more difficult to ignite than wood charcoal. Also, its heating capacity is not as high, though it burns for longer. “The calorific value of wood charcoal is around 26 megajoules per kilogram. Our briquettes are anywhere from 19 to 22 megajoules per kilogram,” Woods says, which makes Sanivation briquettes better suited for cooking over a slow and steady temperature, rather than boiling water.

The team is currently experimenting with how to produce briquettes that can achieve a hotter and faster burn—not as a replacement to the current recipe, but as an alternative. “It is not the feces binder that affects the burn temperature but the density of the overall material,” explains Woods. “The higher the density, the less oxygen that can flow through the material, so the result is a lower burn. Standard charcoal is less dense so it achieves a higher airflow and burns off faster.”

She adds, “Because we now have the agglomerator, we can start playing with the particle size or turning the machine more slowly, so we’ll eventually come up with a briquette that is less dense or smaller in size.” They may have a hotter-burning briquette ready as early as 2017.

A more pressing issue is the pace at which they can produce their existing briquettes, for which the demand far exceeds what they can currently supply. “We have all of these contracts for two to three tons a month. People say as soon as we can make more, they will buy it,” Woods says.

Sanivation sells its charcoal to institutions that can buy in bulk—hospitals, restaurants and schools, for example—which means that its charcoal customers are different from its toilet service subscribers. The team initially tried selling their briquettes directly to households and quickly ran out of supply, but they turned to an institutional sales model because institutions are willing to pay the same price at a much lower distribution cost for Sanivation.

Sanivation's service model

An obvious question is why so many people are eagerly signing contracts to cook food with human waste. “We get asked about that a lot, but it’s been less of an issue than people might think. Fuel is a big need right now; people are looking for anything they can use. They like that our briquettes burn better and cleaner than local charcoal,” says Woods. “Plus they don't look like or smell like poop.”

The Less Obvious Stigma

In fact, Woods and Foote found that the word “toilet” was more of an obstacle when they were setting up Sanivation because “toilet” has negative connotations in many parts of Africa. They named their toilet the “Blue Box” to remove any association with public latrines.

For the Blue Box, Sanivation’s design is portable and easily made out of locally available materials. The box part is made out of locally sourced wood, while the toilet seat is a standard plastic toilet seat that Sanivation purchases at local hardware stores (and likely originates in China, says Foote.) Inside the box are two separate containers: one for feces and the other for urine. The containers are repurposed items, like buckets and oil jugs, that are readily available in Naivasha. A metal urine diverter—basically a funnel that is made by a local machinist—ensures that the liquid waste gets into the right container.

Each toilet costs about $60 to make, but Sanivation’s team says that it needs to eventually get this cost down to $35 per toilet.

The urine diverter proved the most difficult part of the design for the team to solve. Foote explains that for the sake of smell, the two types of waste have to be separated. When left by itself, solid waste dries out and does not smell—an important detail for in-home toilets that are cleaned only twice per week. After using the toilet, customers cover the feces in ash, which speeds up the drying process.

In addition to functionality, the other key part of the diverter’s design was its aesthetics. Sanivation wanted to minimize the need for behavior change to ensure people would actually use the toilets; Woods says research has proven that people are more willing to try and use nice looking products. In trying to build a diverter that could easily work for men and women, the team found that standard funnels were unattractive, but custom molded plastic diverters were too expensive. They eventually settled on a diverter made of sheet metal.

“When you paint the sheet metal it looks nice, but it costs about $8 to make one, so it’s expensive,” says Woods. “We have been working with design students and got some free consulting hours from Catapult Designs, so at some point, we might have an injection-molded design that looks nice and is cheap on a large scale.”

Continental Shift

In spite of grappling with certain design aspects of the Blue Box, the product is far simpler than their initial idea for a solar toilet. That concept originated back in 2011, when Woods and Foote first started experimenting with sanitation solutions—in Chile.

At the time, the Chilean government funded Start-Up Chile was accepting applications for early-stage entrepreneurs to bootstrap project ideas in Santiago. Woods, Foote and a few other engineers applied and were accepted to the program.

Their idea was for a dual-vault latrine that had a solar “oven” hitched to the back. But the cost of such a toilet was too high for most of their intended demographic to afford. Additionally, rapid urbanization was eating up land that might have otherwise been available for a large, all-in-one latrine. And, as many of their potential clients were renters, they did not get a lot of interest in what was effectively a home investment. Woods and Foote turned instead to a service-based model.

What the team then needed to figure out was how to neutralize pathogens in the waste they planned to collect. After many design iterations, the team built a solar concentrator that was both effective and affordable. However, Woods says the lack of scientific literature on deactivating fecal pathogens left them with a lot of questions about how to render the poop safe. They focused on certain parasites found in human feces called helminthes, and determined that if they could eliminate one in particular—Ascaris lumbricoides, an intestinal worm—then they would have a reliable system. A grant from the U.S. Centers for Disease Control and Prevention (CDC) allowed them to experiment with different time and temperature combinations, and they eventually settled on the 65-degree and 85-degree benchmarks that they currently use.

Having a weather-dependent system has limitations, however. Woods says she is currently working on a continual flow heat treatment that she expects to be ready for use sometime in 2016. For this process, they will use solar energy to warm a heating fluid, which will be kept at a steady temperature. They will then treat the feces over the fluid instead of directly in the sun. This process will allow Sanivation to treat a much higher volume of waste.

“Waste treatment is kind of the tragedy of the commons. In many countries, there is significant market failure when it comes to sanitation.”

What Woods and Foote realized through their work in Chile was that although they had put all the pieces together for a workable sanitation business, there was no market for it there: 92 percent of Chileans have access to adequate sanitation services.

“It was great to get to that place, but then it didn’t really get us anywhere, because we hadn't figured out how our model was going to fit into sanitation systems around the world,” Woods reflects. They also had not settled on what to do with the treated waste. Most of their initial ideas centered around composting for agricultural use.

After ten months in Chile, Woods and Foote opted to move to a place where they knew sanitation was a more substantial problem for a larger percentage of the population. They resettled in the urban center of Naivasha, not far from Kenya’s capital, Nairobi, where Woods had previously worked for a non-governmental organization digging pit latrines. A timely grant from the German development agency GIZ allowed them to perform more solar concentrator testing and kick off their first household subscription service pilot with six to 10 local homes. With success from these initial models, the CDC Innovation Fund awarded them additional funding to test a three-month pilot in the Kakuma refugee camp in northwest Kenya. They also purchased their briquette-making agglomerator through a crowd-fund campaign on Indiegogo.

As of December 2015, Sanivation had registered 300 people on its subscription service and had treated over two tons of human waste. By late-2016, the team expects to service 1,000 Kenyan homes and hopes to reach their business break-even point of 2,000 household subscribers and 150 tons of processed waste per month by early 2017. Thanks to a new waste treatment facility that opened last September, Sanivation has the equipment capacity to handle that volume of waste treatment and to produce 150 tons of briquettes per month.

Sanivation is also intent on continuing its work in refugee camps, where sanitation is an ongoing struggle for the international organizations that serve them.
“It sounds ambitious, but we held steady at about 50 households for a year to [position ourselves to] scale all of our processes and logistics. We would feel confident by the end of 2016 to replicate with investor capital in other cities,” Foote says.

The Future of Waste

Despite their deep-seated beliefs about the importance of their work, Woods and Foote readily admit that neither of them initially planned to be in the waste business.

“Waste treatment is kind of the tragedy of the commons. People on their own are not excited about paying for waste treatment, so in many countries, there is significant market failure when it comes to sanitation,” Foote says. This made it difficult for the Sanivation team to figure out whether they could build a viable business.

“What we did was think about the entire [sanitation] value-chain and try to come up with something that people actually wanted to pay for,” Foote adds. Foote, who studied cultural anthropology and environmental engineering in university, and Woods are both thoughtful about how laboratory solutions can work practically—and mindfully—in the field.

“We try to not look at only technical solutions to a problem, but also at how to implement solutions that people are willing to use,” Foote says. “We realized people might not want to pay for waste treatment, but they might be willing to pay for a nice, safe, clean toilet in their own home.”

So far, this approach appears to be working. Sanivation is hoping to replicate their model more rapidly by opening three more branches in 2017 and expanding to 15,000 households in urban communities of more than 100,000 people. By 2020, they aim to have nine waste-treatment sites and to license their model to over 10 refugee camps, reaching over a million people in the process.

They have their work cut out for them. But Woods and Foote are seeing signs of change in the field that dovetail with Sanivation’s approach. “We hear others talking about waste disposal becoming a thing of the past and looking at it as a potential energy source,” Foote says. “It’s exciting, and it seems that momentum is only continuing to build.”