Basically I was horrified when I found out that hydro-electric dams are about as bad for the environment as a petroleum based powerplant due to the the methane that they release. So why not build a tent to sequester the methane. It's lighter than air and will naturally want to settle at the top of the tent. Dams are generally tall which gives you a tall superstructure to build off of. What would probably be needed, and I'm really going out on a limb on this one, is a pool to catch the water that has just been used to turn the turbines so that it can settle and release even more methane.

Phase 2 has a few potentially beneficial schemes for the methane. a) find a way to remove impurities from it use the gas for natural gas for local homes. b) build a long cylinder at the top of the tent which would reduce the presence of other gases and then fix a fuel cell so that the methane can be converted into less polluting CO2 and a bit of energy that could be added to the energy production of the dam. c) burn the methane and distill dam water to make locally available potable water.
-- wuss, Aug 30 2007

Yeah I saw that one too from the BBC, but they just want use energy from the dam to extract it so they can just burn it. Seems like a waste to me.
-- wuss, Aug 30 2007


But that begs the question of all the methane released by river beds away from dams. I remember punting on the Cam: on occasion, the pole would release quantities of methane from the muck on the river bed, that would then bubble to the surface. (That's when the pole didin't get stuck in said muck.)
-- DrCurry, Aug 31 2007


I, too, have punted on the Cam and seen the methane. Other rivers that I've poled along have more concentrations of muck in their quiet spots, and the methane released isn't being captured in any way.

I'm guessing that dams only concentrate the decaying vegetation in a different place than it would naturally accumulate.
-- baconbrain, Aug 31 2007


There are off the shelf technologies for capturing biogas. Many landfills have them. It is not clear to me if something about passing thru the turbine releases dissolved methane, but this seems plausible. A biogas catcher could be installed in the turbine room. I suspect that increased water oxygenation would get rid of a lot of dissolved methane as well, releasing it as CO2.
-- bungston, Aug 31 2007


Bungston- I guess what I was trying to say about the methane produced by still water in a dam was that it's not necessarily a bad thing. In fact free methane production is a good thing. People spend a lot of money to heat digesters so that they can produce methane. What is bad though is that this gas is being released into the atmosphere where it isn't doing anyone any good. Secondly, if you read the BBC link, it says something to the effect that dams release a lot of methane, because the water inlets are at the bottom of the dam where methane concentrations are highest. So rather than stick another device in the turbine room, just let the natural inclination for methane to rise in air do all the work. Just think of the dam as a large digester that collects organic material and converts it into methane, and all that's being proposed is a collection method that requires little upkeep and little energy.
-- wuss, Sep 01 2007



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