Energiforsyning i Arktis – hvilken vej vælger Grønland? - Artek ...

GEOMAR Centre is intensely involved in
investigations on the possibility to explore
and produce methane from gas hydrate
bearing sediments in combination with the
return of carbon dioxide into the clathrate
structure (ongoing projects SUGAR and
CLATHRAT). In the near future, it is
expected that the depletion of fossil fuels
will further increase the global interest in
gas hydrate exploration.
3. Environmental Impact
As mentioned before, gas hydrates are
stable only under specific pressuretemperature
conditions. Changes in pressure
and temperature, for example due to
climate change or drilling, can result in
dissociation of gas hydrates and methane
might be released into the atmosphere.
Methane is a greenhouse gas 20 times
stronger than carbon dioxide and thus may
accelerate the process of global warming
(Chapellaz et al., 1993, Blunier et al., 1995,
Brook et al., 1996). With reference to
marine gas hydrate deposits, it is unclear
how much methane can actually reach the
atmosphere. In seawater released methane
will oxidize to carbon dioxide by microbial
and chemical processes (Cicerrone &
Oremland, 1998), which will be stored in the
ocean. In contrast, when gas hydrates are
dissociated in continental permafrost
regions, methane will be directly released
into the atmosphere and perpetuate global
warming. Kvenvolden (1988) suggest that
gas hydrate deposits of the polar continental
shelves are presently most vulnerable to
climate change.
The dissociation of gas hydrates in
submarine environments can result in
landslides and thus, can cause geohazards
like tsunamis (Dillon et al., 1998). The
continental slope and rise of West Africa
(Summerhayes et al., 1979), the Norwegian
continental margin (Jansen et al., 1987,
Bugge et al., 1987), and the Alaskan
Beaufort Sea continental margin (Kayen &
Lee, 1991) might have been subject to such
submarine geohazards in the past. This
geohazard issue of gas hydrates should
seriously be taken into account when
exploring and producing methane from gas
57
hydrate bearing sediments (Yakushev &
Collett, 1992).
4. Conclusion
Natural gas hydrates can be widely found in
marine sediments and continental
permafrost regions. Due to the large amount
of methane stored in gas hydrates, they
have recently gained international attention
as potential energy source. The total
amount of methane available is estimated
between 10 x 10 15 m 3 to 40 x 10 15 m 3 . No
profitable and safe method for exploration
and production of methane from gas
hydrates has been established so far.
However, the ongoing depletion of
conventional fossil fuel sources will further
increase the interest in gas hydrates as a
new energy source and thus, will stimulate
research and the development of innovative
technologies. Besides the utilization as an
energy source, the impact of gas hydrates
on climate change and submarine geohazard
is critical and needs to be further
investigated. The risk of methane being
released into the atmosphere, and thereby
accelerating global warming, has to be
considered in the exploration process.
References
Blunier, T., Chapellaz, J., Schwander, J.,
Stauffer, B. & Raynaud, D. (1995):
Variations in methane concentration during
the Holocene epoch. Nature, Vol. 374, pp.
46-49.
Bohrmann, G. & E. Suess (2004):
Gashydrate der Meeresböden: Ein
dynamischer Methanspeicher im Ozean. In:
Keilhacker, M. (Eds.): Vorträge der
Münchener Tagung, Deutsche Physikalische
Gesellschaft, pp. 133-152.
Brook, E.J., Sowers, T. & Orchardo, J.
(1996): Rapid variations in atmospheric
methane concentrations during the past
110,000 years, Science, Vol. 273, pp. 1087-
1091.
Bugge, T., Befring, S., Belderson, R. H.,
Eidvin, T., Jansen, E., Kenyon, H., Hotedahl,
H. & Sejrup, H. P. (1987): A giant three-