Transcript No Slide Title

Qu ickT ime™ an d a
GI F dec omp ress or
are nee ded t o se e this pic ture.
Methane hydrates (Clathrates):
New Fuel or Major Threat for
Increased Global Warming, Huge
Slumps and Disastrous
Tsunamis?
Clathrates
(methane hydrates)
• What are clathrates?
• What is the origin of the methane in
clathrates?
• Beasties living off decaying clathrates
• Where do clathrates occur naturally?
• How much clathrates are there?
• Clathrates as possible fuel source
• Clathrates as a cause of tsunamis/ climate
change
What are Methane
Hydrates?
• Methane Hydrates are one
example of ‘clathrates’
• Clathrates are compounds which
consist of a ‘cage structure’, in
which a gas molecule is trapped
inside a cage of water molecules
• Methane (CH4) is trapped in
Water (H2O) forming an “ICE”
Grey=carbon
Green=hydrogen
in CH4
Red = oxygen
White= hydrogen
in H2O
1 m3 of hydrate -> ~170 m3 methane gas (STP)
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Pentagonal dodecahedron
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Cage made of water molecules - may contain CH4 or CO2
(a bit like a bucky ball made of Carbon)
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IFu icFnke(LTeim
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p reis sps ico rtu re .
Origin of natural methane
• Bacterial degradation of organic matter
in low-oxygen environments within
sediments
• Thermal degradation of organic matter,
dominantly in petroleum (e.g., Gulf of
Mexico)
Where do clathrates occur?
How much clathrate is there?
• Methane and water must be
available (organic matter:
produced by biota; in oceans:
close to continents)
• Clathrate must be stable (ice):
cold and/or high pressure
High latitudes (permafrost)
In medium deep sea sediments (300-2000 m)
Hydrate
Stability
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Hydrate
Stability
Gas Hydrate on the
Sea floor
Beasties!
Organisms living on cold gas seeps
‘The lair of the ice
worm’
Beasties!
Tube
worms
and crab
MODEL OF SEEP CLAM BED
(VAN DOVER, 2000)
SEA WATER
Host
S
Organic material
endosymbiotic che moautotrophic Archaea
H2S
CO2
sulfate reducing Bacteria
SO 42-
CH4
?
coarse,
porous
sediment
How does
the
foodchain in
these ‘seep’
communities
function?
How much hydrate is there?
• Estimates vary widely: globally 600,000
to 2,000,000 Tcf (trillion cubic feet)
• 1 Tcf ~ 1 quadrillion Btu (quad)
• World energy use (2000): about 375-400
Quad = 500 Tcf hydrate gas per year
• US gas hydrates: estimated at about
100,000 to 600,000 Tcf
• Gas hydrates abundant in oil-poor
countries (Japan, India)
•Clathrates as fuel:
• Problems: how to collect the gas in a controlled way?
• Small % recoverable?
• Need to be treated as ‘synfuels’ to
get ‘oil-equivalent’
Climate change/Tsunamis
• Methane is a strong greenhouse gas
• If clathrates are destabilized, huge
amounts of methane are added to the
atmosphere (55 106 years ago??)
• Sediments loose strength==>slip
downslope==> slumps==> tsunamis
• Methane is rapidly oxidized to CO2,
also a greenhouse gas
Have clathrates ever been
destabilized in the past?
• Increase in temperature, decrease in
pressure (drop sea level)
• At the end of the last ice age, megaslumps occurred in regions with gas
hydrates
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Methane hydrates:
• Possibly LARGE fuel source
(natural gas): more than twice all
other fossil fuels
• Unknown difficulties in recovery
• Production may cause major
slumps, tsunamis, and
exacerbated greenhouse effect