Welcome back. After examining the life-support loops for air and water, we now arrive at the system that fuels the crew: food. Growing food in a closed environment is a monumental task, moving beyond basic survival to the challenge of creating a truly sustainable and nourishing habitat. Our two case studies, the ISS and Biosphere 2, approached this problem from opposite ends of the spectrum, providing us with invaluable insights.

Welcome back to our series where we ground our vision for a closed-loop city in the lessons from real-world experiments. Having secured a breathable atmosphere, we now address the solvent of life itself: water. In any sealed environment, recycling water isn't just a good idea—it's the only path to long-term survival.

Welcome back. In our last article, we introduced our two guiding stars for grounding our closed-loop city in reality: the ISS, our pragmatic engineer, and Biosphere 2, our ambitious gardener. Today, we put them to the test on the most critical and immediate challenge of any sealed habitat: creating and maintaining a stable, breathable atmosphere.