Gas Hydrates: Our Energy (and Climate) Future? Lecture Outline: What are gas hydrates anyway? Gas hydrates as an energy source – pros and cons Gas hydrates and climate change: adding fuel to the flames?

Hydrates - What are they? Gas Hydrates are solids formed from hydrocarbon gas and liquid water They resemble wet snow and can exist at temperatures above the freezing point of water They belong to a form of complexes known as clathrates

Clathrates - What are they? Clathrates are substances having a lattice-like structure or appearance in which molecules of one substance are completely enclosed within the crystal structure of another Hydrates consist of host molecules (water) forming a lattice structure acting like a cage, to entrap guest molecules (gas) CH4 (most common), CO2, H2S form hydrates

98% in ocean 2% on land white dot = gas samples recovered black dot = hydrate inferred from seismic imaging dotted lines = hydrate-containing permafrost http://walrus.wr.usgs.gov/globalhydrate/images/browse.jpg

using seismic-reflection profiles Bottom Simulating Reflection (BSRs) BSR – (bottom simulating reflection) Interface between the free methane and the gas hydrates cause the BSR phenomena This phenomena allows a quantification of the amount of hydrates present Blanking – The cementation effect of the hydrate causes a lower signal to be sent back to the ship. Allows quantification of the hydrate zone. Hydrate acoustical velocity 3.3 km/s. Which produce a strong signal. (http://www.pgc.nrcan.gc.ca/marine/hydra.htm#ref ) http://woodshole.er.usgs.gov/project-pages/hydrates/hydrate.htm

Methane Hydrate stability diagram methane hydrates can occur at water temperatures up to 30°C, if the pressure is high enough -stable over most of ocean floor! a methane hydrate lattice redrawn after Kvenvolden (1993)

“The Burning Snowball” Methane hydrate supporting its own combustion

Methane Hydrates as an energy source BENEFITS: - 1 cubic meter of gas hydrate (90% site occupied) = 163 m3 of gas there is A LOT of it, and it’s everywhere clean-burning natural gas

USA has gas hydrate reserves estimated between 112000 tcf and 676,000 trillion cubic feet (tcf) USA has 1400 tcf of natural gas reserves USA uses 25-30 tcf/yr of natural gas India and Japan are leading the charge to hydrate recovery

Methane Hydrates as an energy source PROBLEMS: hydrate dissociation upon recovery; engineering challenge expense of long pipelines across continental slope, subject to blockage with solid hydrate -methane release into atmosphere problem for climate change fragile ecosystems surround sediment surface hydrates & seeps ice worm that lives in hydrate photo by Ian Mc Donald

1 cubic meter of gas hydrate (90% site occupied) = 163 m3 of gas + 1 cubic meter of gas hydrate (90% site occupied) = 163 m3 of gas + .87 m3 Undersea slides (slope failures) may be caused by methane hydrate dissociation; implications for pipeline?

Large, expensive pilot programs focus on drilling in frozen permafrost areas Ex: Mallik, Canada http://energy.usgs.gov/other/gashydrates/mallik.html

New ocean sediment drilling technologies invented for hydrate recovery and storage an Ocean Drilling Program core locker with lone hydrate core in pressurized chamber

dissociating methane hydrate at sediment/water interface

Westbrook et al., 2009

lots of CH4 escaping from melting gas hydrates -powerful positive feedback on global warming because CH4 is a powerful greenhouse gas -most likely oxidizes to CO2 before it enters the atmosphere… but still! see Archer et al., 2007 for detailed investigation of methane hydrate dissociation during global warming Westbrook et al., 2009

- replace CH4 with CO2 in the hydrate lattice An interesting twist: - replace CH4 with CO2 in the hydrate lattice - have your energy cake and eat it too? Park et al., PNAS, 2006

Take-home point Methane hydrates represent the largest fossil fuel reservoir, but problems ranging from yet-to-be-developed technologies and climate change feedbacks remain to be resolved.