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| Hey, I was recently talking with a friend about
alternative fuel sources (maily for automobiles)
and primarily nitrogen. I am not 100% sure how
the nitrogen that is used for nitrogen powered
cars is obtained, but my friend thought that it
is usually just taken from the atmosphere and
purified. This is what brought about my
question, as we then got into a discussion as to
what would happen to the atmosphere if nitrogen
powered cars became very popular, and the
nitrogen was just taken from the atmosphere. My
friend pointed out that if this became the case,
that since nitrogen makes up a considerable
amount of our atmosphere, something would have to
replace it's void if we were to take a percent of
it out of the air. He then presented his two
opinions on what would happen: 1. Oxygen, or some
other gas, would make up a larger percent of our
atmosphere to replace the void of the
disappearing nitrogen, and in the case of oxygen,
we could suffer from oxygen intoxication if the
percent of it in our atmosphere became to great.
His other opinion was that, if nothing was able
to replace the nitrogen, our atmosphere would
more or less implode. So my question is: what
would happen? Because after we discussed it a
little further, we realized that the second
opinion might not be right, given the fact that
space is void of all matter, and therefore could
not make the earth's atmosphere implode. Thanks.
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| Question Date: 2004-09-10 | | Answer 1:
Hmm -- it is a bit difficult to make a fuel
out of nitrogen, despite the enormous binding
energy of the molecule. Nitrogen really sticks to
itself.
Unfortunately, if you made monatomic nitrogen,
you would have the problem of storing it until you
wanted to use it. It doesn't need any media to
re-bind -- releasing all that energy. This is not
to say that it cannot be done, just that I don't
know how.
On the related question, Nitrogen
makes up 78% of the atmosphere, and there is a lot
of it: most of the earth is at sea level, where
the mass of the atmosphere is 14.7 lbs/sq inch. So
the mass of the Nitrogen
is:
0.78*14.7*4*pi*(12*5280*3980miles)2 =
9.2x1018 lbs or 4.6x1015
tons. Assume that each
person can drive and uses 20 lbs of nitrogen a
week (which is somehow lost). Everyone could then
drive for 4.6x1017/5x109 =
9.2x107 weeks or 1.77
million years.
In practice, it would be impossible to lose
the nitrogen -- and very likely it would be
released back to the atmosphere. If you did use up
the nitrogen by making a solid or liquid waste,
you would very slowly decrease the
partial pressure of nitrogen which would lower the
total air pressure, but not directly change the
partial pressure of oxygen. If you have a
reference or more information on how to make a
nitrogen based power cycle, I'd like to see it.
There are ways to use nitrogen compounds to
release energy and produce nitrogen as a
by-product. NASA uses such compounds in rocket
fuels for thrusters. Unfortunately, most of these
compounds cyanide, azide, etc., are very
poisonous. | | Answer 2:
Actually, this does not present a problem at
all. To use nitrogen to power a car, I believe you
would use pressurized nitrogen to mechanically
move something while expanding the nitrogen back
to atmospheric pressure. So any nitrogen removed
from the atmosphere would eventually be returned.
There would be some amount of nitrogen that would
be removed from the atmosphere at any given time
and stored in cars and other places waiting to be
used but I suspect this is a relatively small
amount. | | Answer 3:
Two things:
1. Nitrogen is not a viable fuel
source. Nitrogen in its gaseous form is
largely inert - energy must be used to combine it
with other compounds to do so. The alternative
fuel source that you probably heard about is
hydrogen. Go to the US Department of Energy
website if you want to learn more about this
technology at:
energy
2.If you removed gas from the atmosphere,
the atmospheric pressure would drop. However,
if you somehow managed to take only nitrogen from
the atmosphere, the oxygen concentration would
remain the same. It would take up a larger
fraction of the atmosphere, but would be no more
abundant (there being less atmosphere to begin
with). Thus, you would not notice anything trying
to breathe, but several physical effects would be
felt, these being (1) water would evaporate
more readily and boil at a lower
temperature, and (2) the entire atmosphere
would become cooler for exactly the same
reason that it gets scold when you go up into the
mountains. However, since you are not reducing the
amount of oxygen, you would not get altitude
sickness.
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