I am a Dragon. I emerge from my Egg. The "dams produce lots of methane" arguement has come up again, in Nature (subs req): In the specific case of Balbina, there is now a rough consensus: in terms of avoiding greenhouse-gas emissions, a fossil-fuel plant
would have been better. Balbina is a dam in Brazil. Opinions seem to vary on just how much methane it emits from decay of vegetable matter, with (oh dear) people partly funded by the hydro industry getting somewhat lower numbers. But the data appear to be sparse... a clear case for more monitoring.
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Comments
There are many negatives associated with large dams, hydro-electric or otherwise, but I cannot see where release of GHG's esp. methane can be a problem. I assume that the methane is supposed to come from the many hundreds of thousands or millions of trees submerged by the rising water. There may be a significant amount produced immediately after the soil and trees have been submerged from more easily degraded biomass in the soil.
However, whole trees are very resistant to bacterial decay. There are numerous examples of people harvesting trees from underwater in many locations, both fresh and salt water, trees which have been submerged for over one hundred years. Those trees are now more valuable than freshly cut trees since the many years under water have given them unique staining patterns.
A company in the interior of British Columbia in Canada has developed an underwater saw which they use to cut down submerged trees which are still standing after many years of being submerged by the flooding of hydro dams in BC and NW USA. Most of these dams were flooded 30 to 40 years ago.
I think this is a case of theoretical considerations not behaving according to theory in the real world.
[I think you're probably wrong; methane emissions from dams are contested as to the exact amount, but that they are significant isn't in dispute - W]
Posted by: Ian Forrester | December 1, 2006 1:25 PM
And let's not forget that a cow emits 500 liters of methane every day, together with 6000 liters of carbon dioxide per day.
http://rucus.ru.ac.za/~wolfman/Essays/Cow.html
A law to fight against these gases that are vital even beyond farting is an anti-cow holocaust law at the same moment.
Posted by: Lubos Motl | December 2, 2006 12:53 AM
Eructing Lubos, most of the gas comes out the front end of cows....hmmm.
Posted by: Eli Rabett | December 2, 2006 9:11 PM
Hardly a surprise that Lubos can't tell his hot air from his bullshit.
Posted by: James Annan | December 3, 2006 5:01 AM
I think that all of you are confused about all these things. Methane is always a component of farts. Read e.g.
http://exn.ca/Stories/2000/04/12/56.asp
Global warming: why we can't afford to be sheepish about farts. ;-)
Even if the farts went from the front, I still call them farts if they smell like all other farts. What matters to identify a fart is the composition, not the origin.
Posted by: Lubos Motl | December 3, 2006 11:08 AM
[this commen edited for politeness -W]
Posted by: Carl Christensen | December 3, 2006 11:20 AM
I always appreciate your Gentlemanly protection, William. ;-)
Posted by: Lubos Motl | December 3, 2006 12:57 PM
Half an hour ago, two old French guys found germs in a French lake that will eat the methane from cows and sheep. ;-)
http://www.nzherald.co.nz/section/story.cfm?c_id=5&ObjectID=10413619
Posted by: Lubos Motl | December 3, 2006 1:04 PM
Actually not Lubos dear, cows have four stomachs, which is why they are such efficient large lawnmowers. In the first, the rumen, grass is softened by anaerobic bacteria, which, among other things generate methane, so it am cow burps (eruction), not farts that pollute the atmosphere with methane. Mercaptains are something else. By thinking about this it has been demonstrated that the amount of methane can be reduced by changing the diet of the cows. They can also be fed various cow additives to do same. You can google it. Now rice paddies, those are REALLY dirty.
Posted by: Eli Rabett | December 3, 2006 5:54 PM
Dear Eli, thanks for your comments. I don't really want to teach you how to deal with your native language. Nevertheless, the right word for your "eruction" is actually "eructation". Otherwise, I have already agreed with you that the gases are emitted by the mouth. Still, the smell is like farts.
Posted by: Lubos Motl | December 3, 2006 10:21 PM
Ah yes, the spelling flame, but never having kissed a cow I will take your word on the smell.
Posted by: Eli Rabett | December 4, 2006 6:25 PM