Damming rivers to produce hydropower sounds like the perfectsolution the problem of relying on fossil fuels?EXCEPT thatit also produces large amounts of methane, which is one ofthe worst greenhouse gases. Methane’s effect on globalwarming is over 20 times more than carbon dioxide?andhydroelectric dams also give off CO2. This will be anespecially big problem for China, which is relying on itsdams to produce the high volume of electricity it will needin the future. In 1990, the greenhouse emissions from a hugenew dam in Brazil were more than 3? times more than wouldhave been produced by creating the same amount ofelectricity from fossil fuels.

New Scientist Magazine explains how this works: largeamounts of carbon are tied up in trees and other plants,which is released as CO2 when the reservoir is initiallyflooded and the plants on the bottom of the reservoir rot.After this initial burst of CO2, plant matter regularlysettles to the bottom, where it decomposes without oxygen,resulting in a build-up of methane. The methane is releasedinto the atmosphere when water passes through the dam’sturbines. Regular seasonal changes in water depth guaranteea continuous supply of decaying material, since in the dryseason plants grow on the banks of the reservoir and drown when the water level rises during the rainy season.

Why does our government keep so manysecrets?

Art credit: http://www.freeimages.co.uk

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