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Chemical Reaction Sucked Oxygen Out of Biosphere 2 Air

November 14, 1996 GMT

WASHINGTON (AP) _ Biosphere 2, the costly experiment in creating a closed, self-sustaining ecosystem in Arizona, failed because the concrete walls ate up oxygen and left humans inside with barely enough to breathe.

What was supposed to be a glass-enclosed copy of a pristine and smoothly functioning Earth evolved into a place choked with carbon dioxide and nitrogen, replete with uncontrollable weedy vines. Cockroaches, ants and katydids thrived.

``It was the boldest attempt ever″ to create a closed ecosystem, said David Tilman, a University of Minnesota scientist, but it failed miserably. ``This suggests that there are areas of nature that are sufficiently great mysteries that we don’t know how to manage them or make them better.″

``This is very humbling,″ he said.

Tilman and Joel E. Cohen of Rockefeller University and Columbia University in New York, wrote an analysis of the Biosphere 2 experiment for the journal Science, to be published Friday.

Biosphere 2, built in Oracle, Ariz., at a cost of $200 million, was designed to contain all of the soil, water, air, animals and plants. It was to be a self-contained living system capable of supporting eight humans without help from the outside.

The 139,935-square-foot facility had miniature forests, lakes, streams and an ocean that imitated the natural systems sustaining the Earth.

Eight people were sealed into the Biosphere in September, 1991, expecting to be isolated for two years and to raise their own food, breathe air recirculated by plants living with them and drink water cleaned by natural processes.

But in less than 18 months, it was clear the system was terribly out of balance, said Tilman. Oxygen concentration dropped from 21 percent to 14 percent, about the same level present at 17,500 feet and barely enough to keep the crew functioning.

It was learned later, said Tilman, that the humans were being suffocated by the Biosphere’s cement walls.

``To grow food, they put in very rich soils, which contained a great amount of organic material that bacteria consumed,″ said Tilman. ``The bacteria used a lot of oxygen, dropping the oxygen levels. The bacteria released carbon dioxide, which became chemically bound up in the cement. That broke the cycle.″

With the carbon dioxide molecules trapped, the Biosphere’s plants were unable to remove the molecules’ carbon atoms and release their oxygen atoms for the projects’ humans and other animals to breathe. This led eventually to the oxygen shortage.

To enable the eight crew members to complete their stay, the Biosphere was opened and oxygen pumped in. The crew remained for the project’s full two years and emerged relatively healthy despite the problems that continued to the end. The project also was marred by disputes among the crew and with sponsors over pay and other matters.

Of the Biosphere’s 25 small-animal species, 19 became extinct.

All the insects that pollinate plants also died, so plants that counted on the pollinators could not reproduce.

``The plants in there are sort of a living dead,″ said Tilman. ``As soon as they die, they will not be naturally replaced.″

Nitrous oxide levels in the air rose to 79 parts per million, a level that disrupts the synthesis of B12, a vitamin essential to brain function.

Trees and most food plants struggled, but weedy vines, particularly morning glories, flourished in the carbon dioxide-rich atmosphere.

``The vines turned into a major problem,″ said Tilman. The vines overgrew other plants, choking out food crops. Since the Biosphere had no herbicides, the humans had to do weeding by hand.

``They spent hours and hours just pulling the vines, trying to control them,″ said Tilman.

Nutrients leached from soil polluted the water systems. The water had to be cleaned by running it over mats of algae. The mats then had to be removed, dried and stored.

The eight people living in the Biosphere, said the authors, ``had to make enormous, often heroic, personal efforts to maintain ecosystem services that most people take for granted.″

But even this was not enough.

``The majority of the introduced insects went extinct, leaving crazy ants running everywhere, together with scattered cockroaches and katydids,″ the authors wrote.

``There are lessons from this that are important for society,″ said Tilman. The Biosphere experience, he said, showed that if humans continue to destroy the natural systems that sustain the Earth, there will be no way to engineer solutions because ``we don’t know how.″

Since the initial failure, Biosphere’s use has changed. The structure has been cleaned and modified, Tilman said, and Columbia University will use it as an environmental laboratory.