The Engineering Book: From the Catapult to the Curiosity Rover: 250 Milestones in the History of Engineering

1991

Biosphere 2

John P. Allen (b. 1929)

Imagine what would happen if we decided to put a long-term, self-sustaining colony on the moon or Mars. Or if we wanted to create a spaceship, using current technology, that would fly to another star over the course of many years. To accomplish these goals, we would need to engineer an enclosed, self-sustaining biosphere—a sealed terrarium of sorts big enough to hold human beings. It would contain the food, water, and oxygen the people need, and also recycle all of the waste products. And the system would need to be able to run this cycle reliably for many years without significant problems—otherwise, the people inside would die.

Is a self-contained biosphere like this even possible? In one of the most fascinating experiments ever performed, engineer John P. Allen actually created a complete biosphere and ran it for two years. This large-scale science project, conducted by the University of Arizona and Space Biosphere Ventures, is called Biosphere 2, and the two-year run started in 1991.

First, a huge sealed container with a floorplan 3.15 acres in size and a glass enclosure high enough to hold a small rainforest was created. The structure is essentially a big ship, with the steel hull buried in the ground and the massive glass superstructure visible. Specialized systems were then designed to handle water and air.

Many things learned from the experiment have applicability in a real-life scenario. For example, CO2 levels fluctuated wildly depending on time of day and season. In daylight the plants would suck up the CO₂ and then at night levels would rise. Levels got so high at one point that the crew grew and stored plant material to sequester carbon.

The crew of eight had trouble growing enough food to eat in year one. Everyone lost weight, but became healthier in the process.

Oxygen levels presented the biggest problem because O₂ was mysteriously disappearing from the air. This turned out to be caused by a reaction between concrete and CO2, taking oxygen out of circulation. Eventually fresh oxygen supplies had to be injected for the crew’s safety.

Biosphere 2 library and living quarters in Arizona, USA.