Methane hydrates

    A gas hydrate is an example of a clathrate, a crystalline solid comprising a host (a three-dimensional assembly of H₂O molecules which form cage-like arrays) and guest molecules (small molecules such as CH₄ which occupy the cavities in the host lattice). Gas hydrates occur naturally in the Arctic and in deep-sea continental margins, and their importance lies in their ability to trap gases within crystalline masses, thereby acting rather like natural gas ‘storage tanks’. It is possible that such deposits could be tapped for fuel sources, but on the other hand, any uncontrolled release of the huge amounts of CH₄ that is presently trapped inside these clathrates could add to the ‘greenhouse’ effect. The total amount of naturally occurring organic compound-based carbon on Earth is estimated to be about 19 000 ≈ 1015 t. In addition to this, carbon occurs widely in inorganic minerals such as carbonates. The chart opposite shows the relative importance of methane hydrates as a potential source of carbon from organic-based carbon materials.