Methane (CH4)
M
ethane is the main component of
natural gas, a valuable fossil fuel. It
is such a good fuel because the combustion of methane with oxygen
CH4(g) 2O2(g) n CO2(g) 2H2O(g)
produces 55 kJ of energy per gram of methane.
Natural gas, which is associated with petroleum
deposits and contains as much as 97%
methane, originated from the decomposition of plants in ancient forests that became
buried in natural geological processes.
Although the methane in natural gas represents
a tremendous source of energy for our civilization,
an even more abundant source of methane lies in
the depths of the ocean. The U.S. Geological Survey estimates that 320,000 trillion cubic feet of
methane is trapped in the deep ocean near the
United States. This amount is 200 times the amount
of methane contained in the natural gas deposits in
the United States. In the ocean, the methane is
trapped in cavities formed by water molecules that
are arranged very much like the water molecules in
ice. These structures are called methane hydrates.
Although extraction of methane from the ocean
floor offers tremendous potential benefits, it also
carries risks. Methane is a “greenhouse gas”—its
presence in the atmosphere helps to trap the heat
from the sun. As a result, any accidental release of
the methane from the ocean could produce serious
warming of the earth’s climate. As usual, environmental trade-offs accompany human activities.
Flaming pieces of methane hydrate.