Transforming waste into wealth

In Dakar, Senegal, a Stanford-led research project is creating a system poised to capitalize on a plentiful supply most wouldn’t consider a resource – fecal sludge. Many in the region rely on non-sewered sanitation, resulting in human waste, wastewater and debris, also called fecal sludge, accumulating in sanitation systems. Residents can remove it with a shovel and bucket, or hire a truck driver to pump and deliver the waste to a treatment center. The sludge poses health and environmental risks, as it can lead to algal blooms from excessive nutrients and water-borne illnesses, such as diarrheal disease when it reaches water sources.

While this problem is not unique to Dakar – over 2.4 billion people around the world lack sewered sanitation – converting this carbon, nitrogen and phosphorus rich sludge into usable products provides new economic, health and environmental benefits for resource constrained communities. Anna Kogler, a PhD student in Civil & Environmental Engineering at Stanford working in the Tarpeh Lab, leads a project in Dakar developing and implementing a technology turning fecal sludge into nitrogen-based fertilizer and disinfectants. Kogler, who was recently awarded a Stanford Interdisciplinary Graduate Fellowship, outlines the progress and implications of the project she spearheads with partner organization Delvic Sanitation Initiatives.

How does this work advance the goals of improving public health, access to clean water and global development? 

This opportunity gives a chance to improve our understanding of critical sanitation needs across sub-Saharan Africa. Working with an organization that can implement our technology provides valuable insight from a potential user, which can inform future technology development initiatives. Safe management, instead of discharging untreated fecal sludge into the environment, preserves the benefits of having a sanitation system in place. It prevents contamination of the environment with nutrients and pathogens, which is closely tied to protecting water supplies, and prevents human exposure to pathogens, which poses a major health burden in much of the world.

Local recovery of nitrogen for reuse as high-quality fertilizer could help reduce food shortages and as a disinfectant could protect human health. Additionally, it can reduce energy consumption, chemical use, greenhouse gas emissions and costs associated with waste management and chemical production. As we can see from Delvic’s experience, centering fecal sludge treatment around valorizing waste can be the foundation of a successful business. Generating revenue from fecal sludge processing and the products derived from fecal sludge can finance expansion of sanitation systems. By generating ammonia-based products locally our work also has implications for economic development and independence, as well as supply chain security. The additional profit, public health benefits and local sourcing of industrial chemicals can stimulate the broader economy and advance UN Sustainable Development Goals for clean both water and sanitation along with responsible consumption and production. 

Explain your collaboration with Delvic, and what you’ve learned working in the field. 

We traveled to Senegal to meet our partners, host a short-course on resource recovery for Delvic employees and students from Cheikh Anta Diop University and tour fecal sludge treatment plants to understand sanitation infrastructure and plan for field work. The interest and investment expressed by Delvic staff and potential collaborators at the university was really encouraging. Seeing the curiosity of Senegalese students studying environmental engineering and interested in sanitation as we ran a demonstration of our electrochemical stripping technology was great. Challenges of science communication, particularly across an English-French language barrier, have also arisen, so this project offers a chance to expand my language skills and ability to make science accessible to people of different cultural and educational backgrounds. Working in the field will improve my understanding of critical sanitation needs across sub-Saharan Africa to guide my future work toward maximizing the value of human excreta.

A four-chamber electrochemical stripping reactor and lab-scale setup for recovery of nitrogen-based fertilizer and disinfectant from fecal sludge. photo credit: Anna Kogler

What are the most exciting findings thus far in the project?

One of the most exciting findings was successfully generating an ammonia-based disinfectant using a novel four-chamber reactor (a series of four unique chemical environments separated by membranes and connected by electrical circuits to drive the recovery of desired chemical products). We had tried to use our three-chamber reactor – which has been demonstrated to recover ammonium sulfate fertilizer from various wastewaters – to produce disinfectant but were unsuccessful. It was really rewarding to see a relatively simple modification to the reactor result in a system that can produce both fertilizer and disinfectant. This proof-of-concept demonstration opened the doors to optimizing the process by maximizing recovery efficiency while reducing energy consumption, which I am excited to pursue as a crucial step toward making the technology more viable for implementation.

How does this fit into the bigger picture of your research interests and work? 

I see my work in Senegal as a way of grounding my PhD research in practice. I think it’s easy to be swept up in an academic bubble and forget to consider how one’s work ties in and can influence the wastewater industry. Working with an industry partner pushes me to conduct work that is academically rigorous, and could also directly impact Delvic’s operations. I’ve also had a long-standing interest in working on water, sanitation and hygiene in the developing world, and this project has been a great opportunity to lead my lab’s growing work in that space.