Quote:
Originally Posted by PeteMoss
The story I've read is that they've said that Quebec hydro power isn't very green because it results in flooding that kills trees. And those trees release their carbon when they die.
It sounds like nonsense to me, but that's part of the opposition story behind getting people to reject the transmission lines.
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Biomass by tree is not exactly carbon neutral, and the carbon being captured is still in the biosphere. It's a temporary hold at best. Canada's boreal forests have been net emitters for about 17 years because of forest fires and invasive pests. The pests knock the trees down and they rot, emitting methane which is a more potent GHG.
Hydro can be an emitter in operation through a similar process of methane production, but it isn't just the trees that get flooded out. You get upstream methane forming from algae and other plant material that grows, dies and rots, but you also get methane off-gassing downstream after the water flows through the turbines because some of that methane produced upstream will be dissolved in the water and released once it is agitated. One paper I read a while back estimated that downstream hydro sites in Brazil accounted for 3% of all the methane released in the Amazon Basin which was a significant figure.
I seem to recall that a significant portion of this methane could be captured and combusted to produce power and reduce the potency of methane as a GHG, but I don't think it is a common practice.