Not-so-Clean Energy?
May 05 - Environment
Hydroelectric power's clean image has come under scrutiny, as some experts claim that greenhouse-gas production at hydroelectric power plants can exceed that of power plants running on fossil fuels. According to Philip Fearnside, a research professor at Brazil's National Institute for Research in the Amazon, emissions of two greenhouse gases, carbon dioxide and methane, vary from dam to dam. However, he says, "We do know that there are enough emissions to worry about." Fearnside uses the case of the Curu-Una dam in Par, Brazil, to illustrate: When the reservoir there was initially flooded in 1990, large stores of carbon were released from the subsequent rotting of trees and plants. Fearnside estimates that this process released more than three times the emissions that would have been produced by a fossil-fuel plant generating the same amount of electricity. In addition, the dam continues to release greenhouse gases: As plant matter that has settled at the bottom of the reservoir decomposes without oxygen, it creates stores of methane that are released when water passes through the dam's turbines. "Everyone thinks hydro is very clean, but this is not the case," says Eric Duchemin, a consultant for the Intergovernmental Panel on Climate Change. The issue is gaining recognition at international levels, and emissions produced by hydropower are slated for inclusion into National Gas Inventory Programme calculations, which tally countries' carbon budgets. In warmer countries like Brazil, where conditions lend themselves more to greenhouse-gas production at dams than in colder countries, the new calculations could mean significantly higher inventories-by as much as 7 percent. "I think it is important that these emissions are counted," says Fearnside.
Copyright HELDREF PUBLICATIONS May 2005