The hydroelectric dams in the Brazilian Amazon could generate 30 to 50 percent more energy by making use of the methane gas found in the waters, says a study by the National Institute of Space Research. Brazil's hydroelectric plants release an estimated 21.8 million tons of methane, one-fifth of the country's emissions of so-called greenhouse gases.

That capacity is greatly increased with the gas that accumulates deep in the reservoirs.

In addition to being profitable, projects that “do not require big structures or investments” would earn carbon credits (as created in the Kyoto Protocol on climate change) and would prevent the need to build more dams that would flood farmland and forests, Fernando Ramos, one of the authors of the study based on three dams in the Amazon, told Tierramérica.

Worldwide, 31,000 large dams contribute four percent of all climate-changing gases.