Greenhouse Gases from Hydropower: Turning a Liability into an Asset

June 13, 2007 – Vol.12 No.12

GREENHOUSE GASES FROM HYDROPOWER:
TURNING A LIABILITY INTO AN ASSET.

From many people’s perspective the biggest problems of hydroelectric power are the loss of land, property, livelihoods and wildlife habitats as backed up rivers behind dams flood the landscape.

But there’s another concern. Under certain circumstances hydroelectric dams can emit greenhouse gases in large quantities.

It makes perfect sense. When hydroelectric dams are built, land flooded behind them may have been previously covered with vegetation and bio-rich soil, little of which (if any) is removed before the land is inundated. Further, as rain water run-off flows from the flooded river’s watershed it carries with it more bio-matter.

Over time accumulated bio-matter decomposes in the depths of the reservoir, releasing methane and carbon dioxide. Depending on the depth of the water some of these gases stay trapped under water by the pressure of the water itself. But, when water containing bubbles of greenhouse gases passes through turbines and spillways the gas bubbles are released like the fizz from a carbonated soft drink.

The warmer the climate and the water, the more bio-matter in the reservoir, the more greenhouse gases are released. Hydroelectric facilities in the tropics may be more of a problem than those in cooler climates or projects built where there was little, if any, plant life on the land before the project was built.

At first glance this problem may spell trouble for countries dependent on, and building new, hydroelectric power while trying to cut greenhouse gas emissions. However, according to news stories from the BBC and Inter Press Service News, research is already underway in Brazil to capture the carbon dioxide and use methane from hydroelectric facilities to generate power.

The bonus, the liability turned into an asset, is more renewable power, and more revenues, from existing grid-connected hydroelectric plants. Enough power could be generated from captured methane that new hydroelectric facilities might not need to be built. According to Brazil's National Institute of Space Research (INPE) a $100 million investment at TucuruÌ, Brazil's second largest hydroelectric dam, could capture one million tons of methane a year and produce 1,760 megawatts of power.

One method of methane capture would be to use a tubing system, similar to a swimming pool cleaner, that would troll the reservoir seeking the highest concentrations of gas. Methane would be stored, then pumped to a combustion generator.

Another idea developed by a researcher for the Large-Scale Biosphere-Atmosphere Experiment in the Amazon (LBA) would be to capture the gases from water as it passes through the turbines and onto the spillways. This method would be able to capture methane and carbon dioxide, which could be sequestered.

Whatever greenhouse gas capture method is chosen, the technology could find an almost immediate export potential: China. China’s recently released plan to cut greenhouse gases includes building more hydroelectric powerplants. Depending on where the plants are built they may end up increasing China’s growing greenhouse gas problem, rather than controlling it.

Visit Inter Press Service News at http://www.ipsnews.net/ , National Institute of Space Research (INPE) http://www.inpe.br/

Articles:

"Brazil: Tapping Hydroelectric Dams for Methane Gas" by Mario Osava http://www.ipsnews.net/news.asp?idnews=38070

"Project Aims to Extract Dam Methane" http://news.bbc.co.uk/2/hi/science/nature/6638705.stm