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Michael that's exactly correct what you say. However...it's not always 'the same'. The CO2 'footpritn' of any large concrete structure (actually concrete and steel) is usually a 'one off' shot of lots of energy. They don't 'discharge' CO2 as a matter of course, even when the concrete is 'curing'. It's all tied up in the manufacting of the concrete (which uses a lot of natural gas) and the steel. The methane issue is one that Louis P. brought to this list years ago and I believe he still has some really good links on this. There is some controversy over the issue. Largly these are geographic issues. Places where they build dams in tropical areas tend to have very high methane effluent problems. But in China many of these dams are in areas that have a relatively sparser vegetation that gets flooded, thus reducing their methane out put a lot. The other issue this raises...if methane is a problem (it's 30 times worse a greenhouse gas than CO2, for example) then the Amazon basin is the largest single emitter of methane in the world given the amount of rotting vegeitation. The carbon might get reabsored because of the plant growth, but methane? I don't think so. So I've always doubted, meaning I've questioned, how big a problem this really is, given how little difference a big ass lake that is formed by a dam and a 'natural' lake that is formed over time...especially over decades when they begin to exist more and more alike. David ________________________________________________ Send list submissions to: [email protected] Set your options at: http://lists.econ.utah.edu/mailman/options/marxism/archive%40mail-archive.com
