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FROZEN HEAT
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Carbon mass in gas-hydrate-bound
methane compared to other
sources of organic carbon
0
1 000
2 000
3 000
4 000
5 000
6 000
10 000
Gigatonnes of Carbon
Gas hydrates Energy resources
Other major pools
Peat
Vegetation
Detrital organic matter
Frozen soils
Non-frozen soils
Dissolved in water
Natural gas
Coal
Oil
Estimates of the global methane content in gas hydrates
fell as researchers began linking gas hydrate occurrence to
the supply of organic material from which methane could
be generated. Since the early 1980s, global estimates have
varied widely (blue region in Fig. 1.6), reflecting continued
uncertainties regarding the amount of methane delivered to,
and subsequently stored in, the hydrate stability zone (Buf-
fett and Archer 2004; Wood and Jung 2008).
Significant reduction of the uncertainty associated with
global estimates will require additional mapping and coring
to define local and regional patterns of gas hydrate distribu-
tion (Archer 2007) and to improve our basis for estimating
porosity and gas hydrate saturation in unexplored regions.
Such assessments are now underway, resulting in more
rigorously constrained estimates for some of the world’s
promising production regions (see Volume 2 Chapter 2), as
well as for regions that are sensitive to climate change (see
Volume 1 Chapter 3).
As shown in Figure 1.7, even a median estimate of 5 000
Gt of methane carbon in methane hydrate represents a sig-
nificant fraction of the world’s organic carbon, and is of
similar magnitude to the combined estimates of carbon in
traditional global fossil fuel resources, such as oil, coal, and
natural gas. Not only is the gas hydrate estimate uncertain,
however, but not all gas hydrates are equally accessible as
an energy resource (see Volume 2 Chapter 2) (Boswell and
Collett 2011). Nonetheless, with annual global consump-
tion estimated at 1.8 Gt of methane carbon in 2011 and
2.15 Gt in 2020 (U.S. Energy Information Administration
2010), recovering even a small fraction of the methane in
gas hydrates could significantly affect the global energy
mix (see Volume 2).
Figure 1.7:
Carbon mass in gas-hydrate-bound methane compared
to other sources of organic carbon. A 2008 workshop estimated
the global methane content in gas hydrates to range from 1 000
to 10 000 gigatonnes of carbon (GtC) (Krey
et al.
2009). Taking a
midrange value of 5 000 GtC as an example, gas hydrates would
account for ~33 per cent of Earth’s organic carbon (excluding
dispersed carbon such as bitumen and kerogen). Other major
carbon pools and their mass estimates in GtC are presented
here in top-to-bottom order as they are displayed in the figure.
Values for vegetation and non-frozen soil are taken from Sabine
et al.
(2004), frozen soils from Tarnocai
et al.
(2009), peat from
Limpens
et al.
(2008b, a), detrital matter from Matthews (1997),
and atmospheric values from Blasing (2013). All other values are
from Sundquist and Visser (2003).