Clathrate Hydrate

But First…

http://i.treehugger.com/images/2007/10/24/methane%20clathrate-jj-001.jpg

Papers

• Double spaced• 12 point font• 1” margins• Your own words (I

already read the reading assignment and I am familiar with the internet, so I don’t want you to make me read it again)

• I REALLY want to read what YOU think

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Clathrate Hydrate

And Global Warming

http://i.treehugger.com/images/2007/10/24/methane%20clathrate-jj-001.jpg

What is a clathrate?

• A chemical substance consisting of a lattice of one type of molecule trapping and containing a second type of molecule

• clathrate is derived from the Latin clatratus meaning with bars or a lattice

http://focus.aps.org/files/focus/v4/st31/pic-v4-st31-1.gif

What is a clathrate?

• Consist of a host molecule (forming the basic frame) and

• A guest molecule (set in the host molecule by interaction)

http://en.wikipedia.org/wiki/Clathrate_hydrate

What is a clathrate hydrate?

• Crystalline water based solids physically resembling ice– "cages" of hydrogen

bonded water molecules

• Small non polar molecules (typically gases) trapped inside – low molecular weight

gases (including O2, H2, N2, CO2, CH4, H2S, Ar, Kr, and Xe), as well as some higher hydrocarbons and freons

http://chem.ps.uci.edu/~kcjanda/Group/images/4cages.jpg

Chemical or Physical?

• Without the support of the trapped molecules, the lattice structure of hydrate clathrates would collapse into conventional ice crystal structure or liquid water

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Methane

• Carbon’s molecular number is 6

• “Wants” 4 electrons in the valence shell

• Methane molecule is formed by one carbon atom and 4 hydrogen atoms – CH4

http://www.energy.gov.ab.ca/NaturalGas/graphics/NGC_Molecule.jpghttp://www.hk-phy.org/articles/laser/c-atom_e.gif

Greenhouse Gases (GHG)

• Greenhouse gases are in an atmosphere that absorb and emit radiation within the thermal infrared range

• Greenhouse gases are molecules of a compound

http://searchwarp.com/UserImages/102016/about-infrared-image.jpg

Global Warming Potential

• Measure of how much a given mass of greenhouse gas is estimated to contribute to global warming – Compares the gas in

question to that of the same mass of carbon dioxide (whose GWP is by definition 1)

– calculated over a specific time interval

http://www.nysforum.org/documents/html/2007/execcommittee/may/enterprisepowerconsumptionreduction_files/images/image6.png

Methane

• Properties of methane– 2CH4 + 3O2

2CO2 + 2H2O

– high global warming potential

• of 72 (averaged over 20 years) or

• 25 (averaged over 100 years)

– atmospheric half life of 7 years

spark

http://scienceguy288.files.wordpress.com/2008/01/cow.gifhttp://www.school-for-champions.com/chemistry/images/hydrocarbon-methane.gif

Methane

• Properties of methane (cont.)– Methane is the

major component of natural gas, about 87% by volume

– At room temperature and standard pressure, methane is a colorless, odorless gas

C CCH

H

http://en.wikipedia.org/wiki/Methane

Methane

• Properties of methane (cont.)– Methane has a boiling

point of −161 °C at a pressure of one atmosphere

– As a gas it is flammable only over a narrow range of concentrations (5–15%) in air. Liquid methane does not burn unless subjected to high pressure (normally 4–5 atmospheres)

http://www.pnl.gov/science/images/highlights/cmsd/oil_welllg.jpghttp://www.citycollegiate.com/methane2.gif

Methane

• The abundance of methane in the Earth's atmosphere in 1998 was 1745 parts per billion, up from 700 ppb in 1750

• Still increasing

http://climateprogress.org/wp-content/uploads/2008/04/methane2.jpghttp://www.windows.ucar.edu/earth/Atmosphere/images/methane_atmosph_concentr_1984_2004_big.gif

Methane as a GHG

• Methane traps over 21 times more heat per molecule than carbon dioxide

• Expected to cause between 15 and 17% of the global warming over the next 50 years

http://www.eia.doe.gov/oiaf/1605/archive/gg97rpt/gifs/fig07.gif

Sources of Methane

• Of the total estimated methane present, little less than half is naturally occurring

• Rice agriculture attributes from 8 to 29% of the total emissions

Wetlands (incl. Rice agriculture) 37Termites 3Ocean 3Hydrates 2Natural Total 45

Energy 18Landfills 7Ruminents (livestock) 19Waste Treatment 4Biomass Burning 7Anthropogenic Total 55

Origin

Natural Emissions

Anthropogenic Emissions

% CH4 Emission

Sources of Methane

• Cows are the number one source of methane (guess how!)– Eat low energy diet

that is impossible to break down

– Rely on “gut flora” to break down grass

– Bacteria live without oxygen

http://www.moonbattery.com/archives/farting-cow.jpg

Methanogenic Bacteria

• Anaerobic (oxygen is poison to them so they live in atmospheres without it – like guts)

• Belong to Archaea• About 50 different

species described • Methane is waste

product when breaking down molecules to harvest energy

http://www.preciseenergy.com/lookandfeel/images/bacteria/fig5.jpghttp://www.soi.wide.ad.jp/class/20070046/slides/02/img/46.png

We Have Them Too!

• They are responsible for the methane content of flatulence

• So the next time you toot, you can say, “Oh, please excuse my gut flora!”

http://microimm.queensu.ca/people/faculty/Jarrell%20Lab/methanogens_files/image005.jpghttp://www.dailyhaha.com/_pics/girl_farting_water.jpg

Methane Hydrate

• Methane Clathrate (or methane hydrate) is cage of ice trapping methane gas inside

• Found in deep oceans around the world

• Found frozen in permafrost tundra in Northern Hemisphere

• May be found in deep lakes (e.g. Lake Baikal)

• Antarctica?• Flammable Ice

http://www.randform.org/blog/wp-content/2007/01/Burning_hydrate_inlay_US_Office_Naval_Research.jpg

Methane Hydrate

• Naturally occurring

• Represent ~2% of world’s total methane

• Estimated 7.055 trillion tons (14 quadrillion lbs) of methane clathrates

http://upload.wikimedia.org/wikipedia/commons/f/f8/Methane_Clathrate_Location_Map_USGS.gif

Clathrate Gun Hypothesis

• Rise in sea temperature can trigger the sudden release of methane from methane clathrate

• Because methane is a powerful greenhouse gas, it will cause further temperature rise and further methane clathrate destabilization

• Initiating a runaway process

• Irreversible once started as the firing of a gun

http://aphriza.files.wordpress.com/2006/07/methane_seep.jpg

Runaway Greenhouse Effect

• Venus– Atmosphere is over

96% CO2

– Clouds predominantly sulfur dioxide (SO2) another GHG

– Pressure at surface is 92 times that of Earth, or 6.5 times that of water!

– Add heat to gas and pressure goes up

– Hottest planet 860°F

http://zuserver2.star.ucl.ac.uk/~idh/apod/image/0405/venus2_gal_big.gif

Runaway Greenhouse Effect

• Evidence that Venus’ atmosphere more like Earth’s several billion years ago with oceans

• Runaway greenhouse effect evaporated water, pumping more GHG’s into atmosphere

• Positive feedback

http://zuserver2.star.ucl.ac.uk/~idh/apod/image/0405/venus2_gal_big.gif

One more piece to go…

• How has the Earth changed in the past

• Then, we can start putting all the pieces together to build a better understanding of the complexity and predict the future

• Questions?

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