[DEBATE] : (Fwd) Eskom's dams to emit more greenhouse gases
pbond at mail.ngo.za
Sat May 12 08:31:49 BST 2007
(Mpanda Nkuwe on the Zambezi - the largest hydropower addition to
Eskom's production - will be a major addition, for "dam reservoirs are
the largest single source of human-caused methane emissions,
contributing around a quarter of these emissions."
International Rivers Network
May 9, 2007
ï Patrick McCully, Executive Director, IRN, Berkeley, California:
+1 510 213 1441 (mobile) +1 510 848 1155 (office), patrick at irn.org
ï Ivan Lima, National Institute for Space Research, Brazil:
+ 55 67 3233-2430 ext. 241 (office) ivan at dsr.inpe.br
ï Tim Kingston, Communications Manager, IRN, Berkeley, California:
+1 510 290 7170 (mobile) +1 510 848 1155 (office), tim at irn.org
Four Percent of Global Warming Due to Dams, Says New Research
Large dams may be one of the single most important contributors to global
warming, releasing 104 million metric tonnes of methane each year. This
estimate was recently published in a peer-reviewed journal by Ivan Lima and
colleagues from Brazil's National Institute for Space Research (INPE).
"There is now more than enough evidence to show that large dams are a major
source of climate-changing pollution," says Patrick McCully, Executive
of International Rivers Network. "Climate policy makers must address this
Lima's calculations imply that the world's 52,000 large dams contribute more
than 4% of the total warming impact of human activities. They also imply
dam reservoirs are the largest single source of human-caused methane
contributing around a quarter of these emissions.
Methane is a more potent heat-trapping gas than carbon dioxide, although it
does not last as long in the atmosphere. One year's large dam methane
emissions, as estimated by Lima, have a global warming impact over 20 years
equivalent to that of 7.5 billion tonnes of carbon dioxide ñ higher than
carbon dioxide emissions from fossil fuel burning in the US.
Lima and his co-authors propose capturing methane in reservoirs and
using it to
fuel power plants. Lima says, "If we can generate electricity from the huge
amounts of methane produced by existing tropical dams we can avoid the
build new dams with their associated human and environmental costs."
"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," says
Patrick McCully. "Partly because of the influence of the hydro industry
government backers, climate policy-makers have largely overlooked the
importance of dam-generated methane. The IPCC urgently needs to address this
Methane is produced by the rotting of organic material in reservoirs. 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.
This is only the second estimate published in the scientific literature of
global greenhouse gas emissions from dams. The previous estimate,
2000, which included only emissions from reservoir surfaces, estimated
releases at 70 million tonnes of methane and a billion tonnes of carbon
Lima's calculations take account of emissions from turbines and
the rivers immediately downstream of dams, in addition to reservoir
Lima's paper does not address dam emissions of carbon dioxide or another
greenhouse gas, nitrous oxide.
Lima has also produced the first published estimates of methane
dams at the national level in Brazil, China and India. These estimates show
dams in Brazil and India are responsible for a fifth of these countries'
global warming impact. Dams in China are estimated to produce 1% of the
country's climate pollution, although for methodological reasons this is
ï Ivan B.T. Lima et al. (2007) "Methane Emissions from Large Dams as
Renewable Energy Resources: A Developing Nation Perspective," Mitigation and
Adaptation Strategies for Global Change, published on-line March 2007.
ï "FAQ: Greenhouse Gas Emissions from Dams."
ï IRN web pages on reservoir emissions.
More information about the Debate-list