For many years new hydropower dams were assumed to be zero greenhouse gas emitters. Now with 847 large (more than 100 MW) and 2,853 smaller (more than 1 MW) hydropower projects currently planned or under construction around the world, a new global study has shown that dam reservoirs are major greenhouse gas emitters.
The study looked at the carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emitted from 267 reservoirs across six continents. Globally, the researchers estimate that reservoirs contribute 1.3 percent of human-made greenhouse gas emissions, comparable to those from rice paddy cultivation or biomass burning.
Reservoir emissions are not currently counted within the UN Intergovernmental Panel on Climate Change (UN IPCC) emissions assessments, but they should be, argue the researchers. In fact, countries are currently eligible under the UN’s Clean Development Mechanism (CDM) to receive carbon credits for newly built dams.
The study raises the question as to whether hydropower should continue to be counted as green power or be eligible for UN CDM carbon credits.
— source news.mongabay.com