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.
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.