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240 Managing Global Warming

Methane
gas

Crystal of ice

Methane gas trapped inside cage-
like crystal structures made up of
water molecules

Fig. 7.1 Crystal structure of methane hydrate.

Fig. 7.2 Methane hydrate-bearing sediment [3].

amount of MH exists stably undersea. The natural methane hydrate may not be purely
a white agglomeration like artificial methane hydrate. Since methane hydrate exists in
between the sand particles of sandy sediments as shown in Fig. 7.2, the methane
hydrate-bearing sediments do not appear white but rather look similar to soil.

7.1.2 Where is the reserve and how much?

MH exploitation has attracted great attentions since the total carbon content in MH is
twice as large as that in petroleum or coal [4]. One cubic meter of MH dissociates to
3
approximately 160–170 m (at 0°C and 1 atm) of methane gas. MH is distributed
almost all over the world (Figs. 7.3 and 7.4). The total worldwide estimated reserve
15 3
is around (1 5) 10 m [7]. It is considered as a type of promising and hugely