Obviously, Biosphere II was not self-sustaining if outside oxygen had to be added in order for the crew to survive. The reasons behind this flaw in the project were not fully understood until some time later. As it turned out, the problem had more to do with carbon dioxide than with oxygen. Biosphere IIís soil, especially in the rain forest and savanna areas, is unusually rich in organic material. Microbes were metabolizing this material at an abnormally high rate, in the process of which they used up a lot of oxygen and produced a lot of carbon dioxide. The plants in Biosphere II should have been able to use this excess carbon dioxide to replace the oxygen through photosynthesis, except that another chemical reaction was also taking place.
A vast majority of Biosphere II was built out of concrete, which contains calcium hydroxide. Instead of being consumed by the plants to produce more oxygen, the excess carbon dioxide was reacting with calcium hydroxide in the concrete walls to form calcium carbonate and water.
Ca(OH)2 + CO2 --> CaCO3 + H2O
was confirmed when scientists tested the walls and found that they contained
about ten times the amount of calcium carbonate on the inner surfaces as
they did on the outer surfaces. All of the walls in Biosphere II are now
coated with a protective layer, but oxygen levels continue to be somewhat
At the same time, some species absolutely thrived in this man-made environment. Crazy ants, cockroaches, and katydids ran rampant, while certain vines (like morning glories) threatened to choke out every other kind of plant. The crew members were forced to put vast amounts of energy into simply maintaining their food crops. Biosphere II could not sustain a balanced ecosystem, and therefore failed to fulfill its goals.
Also, as a symptom of further atmospheric imbalances, the level of dinitrogen oxide became dangerously high. At these levels, there was a risk of brain damage due to a reduction in the synthesis of vitamin B12.
And of course,
there were inevitable disputes among the crew, as well as among those running
the project from the outside.
[Earth: Biosphere I][Why
Biosphere II?] [Biosphere Plans]
[Grand Experiment] [What
Went Wrong?][Lessons for the Future]
Erin Walker and Diana Carroll