Date published: 2007/05/13
The BBC says:
Scientists in Brazil have claimed that a major source of greenhouse gas emissions could be curbed by capturing and burning methane given off by large hydro-electric dams.
The team at the country's National Space Research Institute (INPE) is developing prototype equipment designed to stop the greenhouse gas from entering the atmosphere.
The technology will extract the methane from the water to supplement the energy produced by the dam turbines.
The scientists estimate that worldwide the technique could prevent emissions equivalent to more than the total annual burning of fossil fuels in the UK - and reduce the pressure to build new dams in sensitive areas such as the Amazon.
The project follows a long-running controversy over how clean hydro-electric power really is.
Critics of the industry have claimed that in tropical areas of Brazil - which supplies more than 90% of its electricity from large dams - some reservoirs emit so much methane that their contribution to climate change is greater than an equivalent power station burning fossil fuels like coal or gas.
Methane is produced mainly by bacteria that break down organic matter where there is little or no oxygen, for example at the bottom of lakes and reservoirs.
Since intake pipes for hydroelectric turbines tend to be placed quite deep, methane-rich water is suddenly transferred from conditions of high-pressure to the open air.
The lead scientist of the INPE project, Fernando Ramos, told the BBC's Science In Action programme: "It's like opening a bottle of soda. A large part of the methane is dissolved in the water bubbles, and it's released to the atmosphere.
"That's the reason big hydro-electric dams built in tropical areas are harmful to the environment."
There is still great uncertainty about the precise amount of methane added to the atmosphere in this way, as each dam behaves in very different ways depending on the amount of vegetation in the water, the temperature, the shape of the reservoir and many other factors.
However, a statistical analysis carried out by the INPE scientists has estimated that large dams could be responsible for worldwide annual emissions equivalent to some 800 million tonnes of carbon dioxide.
To put that in perspective, last year's total greenhouse gas emissions from the UK were around 660 million tonnes.
...
INPE hopes to develop prototype equipment to demonstrate the process later this year.
It's good that someone is looking at this, although the proposed process (illustrated in the BBC article) does not look that trivial to implement nor necessarily that efficient, so INPE will indeed need to have a pretty convincing demonstration that their claims add up.
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