Clathrate Hydrate But First…

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Clathrate Hydrate And Global Warming

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

What is a clathrate? Consist of a host molecule (forming the basic frame) and A guest molecule (set in the host molecule by interaction)

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 O 2, H 2, N 2, CO 2, CH 4, H 2 S, Ar, Kr, and Xe), as well as some higher hydrocarbons and freons

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

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 – CH 4

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

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

Methane Properties of methane –2CH 4 + 3O 2 2CO 2 + 2H 2 O –high global warming potential of 72 (averaged over 20 years) or 25 (averaged over 100 years) –atmospheric half life of 7 years spark

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 C C H H

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)

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

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

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

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

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

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!”

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

Methane Hydrate Naturally occurring Represent ~2% of world’s total methane Estimated trillion tons (14 quadrillion lbs) of methane clathrates

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

Runaway Greenhouse Effect Venus –Atmosphere is over 96% CO 2 –Clouds predominantly sulfur dioxide (SO 2 ) 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

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

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?