Recycling CO2 (was Could life in solar system complicate space settlement?)

--- In spacesettlers@yahoogroups.com, Al Globus wrote:
> It is really quite easy to run out of O2 or get too much CO2 -- meaning too much for humans to survive. Space settlers will either be environmentalists or dead.

Or they'll use machines that recycle CO2 into oxygen:
http://chview.nova.org/station/life-sup.htm

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Currently, carbon dioxide is removed from the air by a machine using a material called "zeolite" as a molecular sieve, while hydrogen that is generated from this process is vented into space. Eventually, however, a machine will be used to combines the hydrogen with excess carbon dioxide from the air in a chemical reaction to produce water and methane. The water produced would partially replace the water used to make oxygen, while the methane would be vented to space.
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