Methane From Dams

Methane From Dams



May 2007 - Scientists from Brazil's 
National Institute for Space Research, INPE, have published a new study 
showing that large dams contribute to global warming by releasing the 
greenhouse gas methane into the atmosphere. The authors propose capturing 
the methane and using it to generate electricity. 
Dr. Ivan Lima and his colleagues used a theoretical model, bootstrap 
resampling and data provided by the International Commission On Large Dams 
World register of dams to demonstrate that global large dams annually 
release about 104 million metric tons of methane to the atmosphere through 
reservoir surfaces, turbines and spillways. 
Methane is the principal component of natural gas. The INPE scientists say 
engineering technologies now in existence can be implemented to avoid 
these emissions, and to recover the non-emitted methane for power 
generation. 

Dr. Ivan Lima of Brazil's National Institute for Space Research (Photo 
courtesy Scitizen)
Under the Clean Development Mechanism of the Kyoto Protocol, they write, 
such technologies can be recognized as promising alternatives for human 
adaptations to climate change, particularly in developing nations owning a 
considerable number of large dams. 
Methane is about 21 times more powerful at warming the atmosphere than the 
most abundant greenhouse gas, carbon dioxide. Methane's relatively short 
atmospheric lifetime of 12 years, coupled with its potency as a greenhouse 
gas, makes methane a candidate for mitigating global warming in the short 
term. 
Dr. Lima and his co-authors propose capturing methane in reservoirs and 
using it to fuel power plants in Brazil, China and India. 
"If we can generate electricity from the huge amounts of methane produced 
by existing tropical dams we can avoid the need to build new dams with 
their associated human and environmental costs," Lima said. 
The immediate benefits of recovering methane from large dams for renewable 
energy production is the mitigation of human impacts like the construction 
of new large dams, avoidance of the actual methane emissions from large 
dams, and the use of unsustainable fossil fuels and natural gas reserves, 
the authors explain in their study, published by Springer Netherlands. 
Large hydroelectric dams release methane into the atmosphere because trees 
and other plants settle to the bottom when the reservoir is first flooded. 
This plant material decomposes without oxygen and dissolved methane builds 
up. When water passes through the dam's turbines, this methane is 
released. 

The Itaipu hydroelectric power plant is the largest development of its 
kind in the world. It was built by Brazil and Paraguay from 1975 to 1991 
on the Parana River. 
Executive Director of International Rivers Network Patrick McCully said 
today, "Climate policy makers must address this issue." 
From his office in Berkeley, California, McCully said Lima's calculations 
imply that the world's 52,000 large dams contribute more than four percent 
of the total warming impact of human activities. 
They also imply that dam reservoirs are the largest single source of 
human-caused methane emissions, contributing around a quarter of these 
emissions, McCully said. 
The massive amounts of methane produced by hydropower reservoirs in the 
tropics mean that these dams can have a much higher warming impact than 
even the dirtiest fossil fuel plants generating similar quantities of 
electricity, he said. 
"It is unfortunate that Lima's study has come too late to be included in 
the recent reports from the Intergovernmental Panel on Climate Change, 
IPCC," McCully said. "Partly because of the influence of the hydro 
industry and its government backers, climate policymakers have largely 
overlooked the importance of dam-generated methane." 
Another Brazilian scientist has also made the connection. Philip Fearnside 
from Brazil's National Institute for Research in the Amazon in Manaus 
published a study in 2002 showing that the greenhouse effect of emissions 
from the Curuá-Una dam in Pará, Brazil in 1990, was more than 3.5 times 
what would have been produced by generating the same amount of electricity 
from oil. 
The International Hydropower Association, IHA, says considering only total 
greenhouse gases measured at the surface of reservoirs can be misleading; 
these measurements should be considered as "gross" emissions. "Net" 
emissions for which dams are responsible must consider the emissions from 
ecosystems before the creation of a reservoir when the land was in its 
natural state. 


       
      

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