
How many plants would you need to generate oxygen for yourself in an airlock? - cpeterso
http://io9.com/5955071/how-many-plants-would-you-need-to-generate-oxygen-for-yourself-in-an-airlock
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dbuxton
I am not a biologist but my recollection of high school biology is that
photosynthesis is basically carbon dioxide + water + light energy = oxygen +
glucose. So saying, "About 300 to 500 plants would produce the right amount of
oxygen, but it's much harder to estimate the amount of carbon dioxide the
plants absorb" is wrong - the quantity of oxygen produced will be exactly
proportionate to the amount of carbon dioxide consumed. (There is also an
issue of how much oxygen the plants' respiration would consume but let's not
get into that).

 _And finally, some plants only "breathe," at night in order to save water_ \-
I also remember this (many if not most plants control water loss through
transpiration by shutting down their stomata during , but I'm pretty much sure
that no plants are able to photosynthesise at night! That _would_ be an
interesting species...

Overall, seems like some relatively serious misunderstandings of the basic
science if even I (not a great GCSE mark in biology...) find myself wringing
my hands...

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ars
> but I'm pretty much sure that no plants are able to photosynthesise at
> night! That would be an interesting species...

There are three types of plants, and instead of explaining them, let me just
provide links.

The type of plant that breathes at night are the CAM ones.

* <http://en.wikipedia.org/wiki/C3_carbon_fixation> \- most common, almost all plants are like this

* <http://en.wikipedia.org/wiki/C4_carbon_fixation> \- very efficient, corn is the most common example

* <http://en.wikipedia.org/wiki/CAM_photosynthesis> \- night breathing, pineapple is the example

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dbuxton
Very interesting! Although as the other reply points out only some of the
photosynthetic reactions take place at night. However I assume (but it's not
exactly clear from scanning the article linked) that the actual emission of
oxygen is likely also happening at night as this would require stomata to be
open, although the actual production of oxygen is one of the light-dependent
reactions in the photosynthetic chain. Is this correct?

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ari_elle
_"[...] but it's much harder to estimate the amount of carbon dioxide the
plants absorb, especially if every time a person breathes out, they inhibit
oxygen production."_

Not having scrolled down far enough to see the end, this is the moment where i
hoped this article would burst into a wild jungle of different scenarios and
scientific data analysis. But it ended... :(

Still nice thing to ponder about though...

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imchillyb
Algae, would prove a much better oxygen producer than plants.

There are many studies being done, and done previously, on the viability of
algae oxygenating artificial atmospheres.

<http://www.ecology.com/2011/09/12/important-organism/>

~~~
ghshephard
I read through the article a couple times, but couldn't find any pointers
regarding the efficiency of algae as an oxygen producer - only that there is a
lot of it out in the ocean. Do you have any citations that would suggest algae
would be better in an airlock than a potted plant? (starts off on his 90
minute google/wikipedia distraction of the day)

[15 minutes later - this is the best link I've been able to find - from a Navy
research paper in 1963, no less:
[http://torpedo.nrl.navy.mil/tu/ps/doc.html?dsn=7590785&h...](http://torpedo.nrl.navy.mil/tu/ps/doc.html?dsn=7590785&hi=1&p=1)

\-- snip --

The results obtained with a small pilot plant containing 6200 ml of algal
suspension have been evalu- ated; the effects of light intensity, rate of
stirring, rate of carbon dioxide supply, and other variables were part of this
study. Light energy was supplied by six 1500-watt incandescent lamps which
extended through the suspension and were encased in 50-mm O.D. cooling
jackets. When the light intensity at the surface of these jackets was 34,000
foot-candles (the limit with the equipment at hand), the oxygen production was
4500 cc per hour. Oxygen production increases with light intensity, but the
oxygen produced per watt of electrical en- ergy expended is constant over a
wide range of light intensities. The amount of electrical energy re- quired to
provide enough oxygen for one man is between 30 and 50 kw, depending on the
design of the gas exchanger. This high requirement makes the process
prohibitive at present; but the development of more efficient high-intensity
light sources could change the outlook. The dependability of the algal system
in providing a constant supply of oxygen has been assured by this study; also,
the volume requirements of the algal system are competitive with existing
systems for carbon dioxide removal and oxygen production.

\-- snip --

~~~
mturmon
That's nice, because it pays some attention to alternative means to use energy
to sink CO2, which is one way to look at the plant example.

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derekp7
One simple rule of thumb -- get enough plants to produce 100% of the food you
consume. Your body converts food into co2, and plants convert co2 into food
(yeah, a bunch of details are left out, but that is the simple version).

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ghshephard
Photosynthesis really seems to be this weeks "what if" scenario: <http://what-
if.xkcd.com/17/>

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mochizuki
I wonder if you can scale this down to be scientifically accurate for Sandy
from Spongebob, one tree per squirrel seems like it would be alright.

