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Bite-Size Climate Tech · Season 5 · E10
The Fertilizer We Flush Away | Roca Water
Can we recover valuable nitrogen from wastewater instead of spending energy removing it?
Recorded 6 August 2026.
About this episode
We use enormous amounts of energy to manufacture ammonia for fertilizer. That fertilizer helps grow our food, but some of the nitrogen eventually ends up in wastewater, where treatment plants must remove it to protect the environment.
What if we could recover that useful nitrogen instead of losing its value?
In this episode of Bite-Size Climate Tech, Lydia Chen speaks with Margaret Lumley, Founder & CEO of Roca Water, about the company’s battery-inspired electrochemical approach to recovering ammonium from wastewater.
Together, they follow the journey of nitrogen from the atmosphere to fertilizer, food and wastewater, before exploring how Roca aims to close the loop.
There’s also a playful eight-year-old challenge. After experimenting with several analogies during the recording, Lydia and Margaret settle on an unexpected one: a pot of soup, a grain of rice, and the challenge of recovering something valuable from a complicated mixture.
The conversation moves beyond the science to explore why wastewater treatment plants might adopt resource-recovery technology, the potential value of recovered fertilizer, and Roca’s journey from laboratory validation toward field pilots.
Margaret also shares how experiencing drought in California and flooding in Wisconsin shaped her relationship with water and climate change.
Key takeaways
- Why nitrogen fertilizer production is energy-intensive and how valuable nitrogen ends up in wastewater.
- How Roca uses battery-inspired electrochemical separation to selectively recover ammonium.
- Why the soup-and-rice analogy helps make resource recovery understandable to an eight-year-old.
- How nitrogen removal and fertilizer recovery could create commercial value for wastewater utilities.
- What Roca is working to prove as it moves from laboratory testing toward field deployment.
- Why water is central to how people experience climate change, from drought to flooding.
Guest
Margaret Lumley
Founder & CEO, Roca Water
Listen and watch
Selected explanations use AI-assisted CLI animations and conceptual illustrations. These help explain the scientific ideas and are not engineering schematics or literal representations of Roca Water’s operating equipment. The episode documents Roca’s research, commercial approach and planned milestones as discussed at the time of recording. Bite-Size Climate Tech is an independent editorial series, not sponsored promotional coverage.