Methane emissions from hydroelectric dams

Climatic Change, 2004

This article is an attempt to relook at the hydropower energy based on the new findings and argues that popular understanding of hydropower as environment-friendly with no emission should be questioned against the backdrop of allegations of methane emissions from the submerged reservoir. As climate change is taking place due to increased presence of greenhouse gases in the atmosphere, the scientists and climatologists are putting emphasis on promotion of renewable energy, like hydropower energy. The article questions validity of the statement and unearths the issue of methane emission both upstream and downstream of the reservoir-a fact based on recent scientific findings. The paper suggests that promotion of hydropower by Clean Development Mechanism (CDM) under Kyoto Protocol 1997 and subsequently by Intergovernmental Panel on Climate Change (IPCC) as an alternative to non-renewable energy should be immediately halted and further investigations needed to be carried out on the probable adverse impacts of hydropower energy on the environment.

Climatic Change, 2006

In the September 2004 edition of Climatic Change (N • 66), an editorial comment was published by Philip Fearnside, jointly with an article written by ourselves reporting on a broad-ranging project through which we measured CO 2 and CH 4 emissions at eleven Brazilian hydroelectric dams, from Itaipu, with the largest installed capacity in Southern Brazil, northwards to Tucuruí in Amazonia.

This paper discusses emissions by power-dams in the tropics. Greenhouse gas emissions from tropical power-dams are produced underwater through biomass decomposition by bacteria. The gases produced in these dams are mainly nitrogen, carbon dioxide and methane. A methodology was established for measuring greenhouse gases emitted by various power-dams in Brazil. Experimental measurements of gas emissions by dams were made to determine accurately their emissions of methane (CH 4 ) and carbon dioxide (CO 2 ) gases through bubbles formed on the lake bottom by decomposing organic matter, as well as rising up the lake gradient by molecular diffusion. The main source of gas in power-dams reservoirs is the bacterial decomposition (aerobic and anaerobic) of autochthonous and allochthonous organic matter that basically produces CO 2 and CH 4 . The types and modes of gas production and release in the tropics are reviewed.

Geophysical Research Letters, 2007

This paper gives an overview on the greenhouse gas production of hydroelectric reservoirs. The goals are to point out the main factors for the CO 2 and CH 4 production, to show the most important emission pathways and to give a hint how big the greenhouse gas emissions from hydroelectric reservoirs are compared to thermo-power plants. The main factor which drives the CO 2 and CH 4 production in a hydroelectric reservoir is the decomposition of organic matter on the bottom. The organic matter originates from the flooded area, the primary production in the reservoir and from the river upstream. The different pathways the gases reach the atmosphere are by diffusing and bubbling in the reservoir itself and in the river downstream. A huge amount of gases is also released when the water is passing the turbine and the spillway. Methanotrophy can be an important sink for CH 4 reduction. A comparison with thermo-power plants shows that in some cases greenhouse gas emissions from hydroelectric reservoirs are even higher than the ones from thermo-power plants. Hydroelectric reservoirs and especially the ones in the tropics represent an important anthropogenic greenhouse gas source.

Mitigation and adaptation …, 2008

By means of a theoretical model, bootstrap resampling and data provided by the International Commission On Large Dams (ICOLD (2003) World register of dams. http://www.icold-cigb.org) we found that global large dams might annually release about 104 ± 7.2 Tg CH 4 to the atmosphere through reservoir surfaces, turbines and spillways. Engineering technologies can be implemented to avoid these emissions, and to recover the non-emitted CH 4 for power generation. The immediate benefit of recovering non-emitted CH 4 from large dams for renewable energy production is the mitigation of anthropogenic impacts like the construction of new large dams, the actual CH 4 emissions from large dams, and the use of unsustainable fossil fuels and natural gas reserves. Under the Clean Development Mechanism of the Kyoto Protocol, such technologies can be recognized as promising alternatives for human adaptations to climate change concerning sustainable power generation, particularly in developing nations owning a considerable number of large dams. In view of novel technologies to extract CH 4 from large dams, we estimate that roughly 23 ± 2.6, 2.6 ± 0.2 and 32 ± 5.1 Tg CH 4 could be used as an environmentally sound option for power generation in Brazil, China and India, respectively. For the whole world this number may increase to around 100 ± 6.9 Tg CH 4 .