A team of entrepreneurs and researchers in Kisumu, Kenya is converting human excrement into biochar and creating a low-cost, local fertilizer. Through their work they hope to keep excess nutrients out of Lake Victoria, address food insecurity, and improve quality of life. In this recording of our Spring 2026 webinar, Cornell University Professor Rebecca Nelson, an expert on the Circular Bionutrient Economy, describes the project.
The town of Kisumu, Kenya lies at the northeastern edge of Lake Victoria, the biggest lake in Africa and home of the earth’s largest freshwater fishing industry. The lake also provides water for agriculture, but high fertilizer costs and depleted soils prevent farmers from maximizing production. Meanwhile, excessive nutrients from informal settlements—communities without running water or sanitation—contribute to the harmful algal blooms in Lake Victoria that regularly kill thousands of fish.
To solve the three-pronged problem of runaway nutrients, food insecurity and poor quality of life, local enterprises are partnering with nonprofits and scientists to find solutions.
At the heart of the partnership is a farmers’ group called Kisumu Young Agripreneurs (KIYA) that has supported 500 farms and trained and mentored over 3500 youths. Roy Odawa, who heads up KIYA, works closely with an enterprise called Fresh Life, which provides and maintains 2,000 waterless, pee-and-poop-separating toilets in Nyalenda.
Professors Nelson and Charles Midega, executive director at Poverty and Health Integrated Solutions in Kenya, are central to the project. Nelson teaches and conducts research at Cornell University that dovetails with this partnership in Kenya. “This is a dream come true for me,” she says. “Nyalenda is the most favorable place to do this work; every day we’re making progress.”
To make the fertilizer, the team dries the feces on flat mats in a greenhouse. They mix these with wood chips and corn stalks or other crop waste, and heat the mixture to extremely high temperatures in a closed metal container to kill pathogens. The result is a porous, carbon-rich soil builder (similar to charcoal) that can absorb urine. Fresh Life has provided literally tons of human urine for the project and the team has figured out that adding magnesium to the urine will cause the phosphorus to precipitate. Now their partners can produce a beautiful granular fertilizer for crops that rivals commercial products.
“I think we’re onto something important, building on Fresh Life’s big network of source-separating toilets here,” says Nelson. “With the fertilizer crisis, we can really do something for farmers as well as for the unsewered majority. If we gather materials from the Fresh life toilets, instead of the company taking them to the wastewater treatment plant, we can make fertilizer, and thus it’s cheaper for the toilet company. They can expand the number of toilets, and it’s a positive feedback loop.”
On This Earth co-sponsored this webinar with Greywater Action and the Rich Earth Institute on May 11, 2026.
