Wednesday, February 24, 2010

Methane Venting from the Seabed can be used

One of the fascinating episodes in Iain Stewart's film (see yesterday's blog) was to see him diving on a seabed release of methane. Huge amounts of methane were bubbling up around him.

Geological methane (natural gas) often combines with water at high pressures and low temperatures to form clathrates, a white solid.  There are 1-5 million cubic kilometers of this within the earth, equivalent to 500-2500 GigaTonnes of carbon, which is more than the ~230 GigaTonnes of natural gas reserves.

Global warming increases the release of methane from clathrates, and one potential tipping point (the "Clathrate Gun Hypothesis") leading to catastrophic runaway climate change, would result from ever increasing release of this methane.

Methane has 25x the global warming potential of CO2, so it is better to collect it and extract its energy, saving on the use of more carbon dense fuels like coal and oil.

I could not find the amounts of methane which are bubbling up from the seabed in the situations of Iain's film, but it makes perfect sense to collect and use it.

Collection is not rocket science. I knocked up this little design for a Methane Capure Tent last night.

Vents (1) on the seabed outgas methane (2) which is captured in a conical fabric structure (3) which is fastened by cables (4) to anchor blocks (5).  The methane collects at (6) and is pumped away for use at the pipe (7). In the physical embodiment the pump and pipe could preferably be below the sea surface, to isolate the whole structure from surface waves.

Simple, no?  This design is offered free of charge to anyone who wishes to realise it.

While we are at it, it is totally mad to flare off gas at drilling rigs and refineries. Apart from the waste of energy, it is bad for birds and local humans. Pumped, purified and compressed, it becomes CNG, which can be used as transport fuel. Years ago, I asked an oil company why they flare, and they said "It is only 2% of the total production". 2%! You only need 50 2% savings, and you've saved the whole lot. Words fail me.


Anonymous said...

A most interesting topic but too lightly handled.
Will methane vent so neatly to be captured under little hats in such stormy Arctic waters?
If we then use it as fuel we may reduce the damage caused from a grand disaster to a slightly delayed disaster.
Capture and storage on any scale appears impossible.
We just have to avoid this tipping point.

DocRichard said...

The surface is affected by storms. If the capture technlogogy, pumps &c are arranged in submersibles, anchored to the seabed, it can be done. Using it as fuel (a) saves other forms of fuel, and (b) reduces the atmospheric load as CH4 is 30x worse than CO2.

Even if we magically stopped all CO2 emissions today, we would still probably hit a tipping point.

I always say this stuff is like a parachute on a hang glider - it may or may not save your life, but at least it gives you something to do on your way down.

Thanks for commenting.