Methane hydrates Clathrates New Fuel or Major Threat

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 (CH 4) is trapped in Water (H 2 O) forming an “ICE”

Grey=carbon Green=hydrogen in CH 4 Red = oxygen White= hydrogen in H 2 O 1 m 3 of hydrate -> ~170 m 3 methane gas (STP)

Pentagonal dodecahedron Cage made of water molecules - may contain CH 4 or CO 2 (a bit like a bucky ball made of Carbon)

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

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

How does the foodchain in these ‘seep’ communities function?

How much hydrate is there? • Estimates vary widely: globally 600, 000 to 2, 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 CO 2, 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

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