Brazilian scientists have estimated that methane emissions from dams worldwide could be equivalent to 800 to 900 million tonnes of CO2 annually. They have devised a means of capturing the methane from dams and using it to fuel extra power generators to supplement the output from the dam. The amount of methane from any given dam varies but some dams in the Amazon region of Brazil could increase their power output by up to fifty percent.
While burning the methane would produce C02, because the original source is decaying plant material, the net carbon effect would be neutral. The CO2 would also be replacing methane which has about twenty times the greenhouse effect of CO2, so the net benefit would be huge.
[Source: BBC via TreeHugger]