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Methane
Hydrates
Clathrates
A clathrate is a cage or lattice like structure of
molecules enclosing another type of molecule.
There are a variety of molecules that can be enclosed this way by water
molecules, but water is not the only molecule that can do this.
Methane
Hydrate
The clathrate formed by Methane molecules (CH4)
being enclosed by a cage of water molecules (H2O) in a lattice like structure is referred to as
Methane Hydrate. This is a much more
specific name than Methane Clathrate and is therefore to be preferred.
Unstable
Under the conditions that most of us normally live,
Methane Hydrate decomposes to water and Methane. This does not happen instantly.
High pressure and/or low temperatures are necessary
for Methane Hydrates to be stable. These
conditions apply deep in the oceans, and under the permafrost of the Arctic
Tundra.
How Much?
We do not know how much Methane Hydrate there is in
the world. Even a conservative
estimate suggests that the amount of Carbon tied up in Methane Hydrates
is twice as much as is in all other fossil fuels combined.
Estimates as high as 400 quadrillion cubic feet of
methane gas tied up in the form of Methane Hydrates have been made.
Certainly there is a colossal amount of this mineral.
Methane
Hydrates as Fuel
This mineral looks like ice, but will burn if a
lighted match is applied. However, it is
more likely to be used as a source of Methane gas rather than a solid fuel.
Some methane is already being taken from Hydrates, but
large scale exploitation is not yet being done.
As with all fossil fuels, some deposits are easier to get at than
others. In using Methane Hydrates, it is
necessary to get the Methane out of the lattice of water molecules. This can be done by lowering the pressure or
by warming it up, or by displacing the Methane molecules with some other
molecule. Research is being done to find
practical ways of getting the Methane.
Methane
Hydrate as a Food
Although Humans and most animals we are familiar with
cannot use Methane Hydrate, more and more organisms that can use it as their
primary source of energy are being found, but we really have little idea how
important these organisms are.
Dangers of
Methane Hydrates
Undersea deposits of Methane Hydrates can suddenly
break down, releasing large volumes of Methane gas. In theory, a ship above this release could be
sunk. In practice this is not a major
danger to ships.
Quite often, the Methane would not even reach the
surface, but would dissolve in the water.
Methane dissolved in the sea gets oxidised to carbon dioxide. This removes Oxygen from the water and could
make thing difficult for fish and other water creatures depending on dissolved
Oxygen for their respiration.
The carbon dioxide makes the sea more acidic which can
be a problem.
Methane is a
greenhouse gas, much more potent than
carbon dioxide. Methane does not stay in
the atmosphere as long as carbon dioxide because it gets oxidised to carbon
dioxide.
A vast scale
release of Methane could cause the temperature of the Earth to heat up very
quickly.
Sources
Gas (Methane) Hydrates -- A New
Frontier.
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Methane Hydrate Burning
Methane Hydrate looks like Ice, but it will burn.
In the top left hands corner of the picture is a representation of the molecular structure of this mineral, showing the Methane surounded by a cage of water molecules.
The picture came from the United States Geological Survey.
Some bacteria can live on Methane Hydrates, getting their energy from the Methane, or by eating organisms that live on this source of energy. In 1997 a polychaete worm was discovered in the Gulf of Mexico about 150 miles from New Orleans. Picture from NASA.
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