Hydroelectric dams produce 6% of the planet’s methane emissions and continue to pollute more than 20 years after their construction, a team of Quebec researchers has concluded.
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“Methane is a devastating type of greenhouse gas. We hope to measure the specific quantity released by the reservoirs. [des barrages hydroélectriques]But we were surprised by the significance of these emissions”, submits Ku Log Biologist Yves Prairie from UQAM published this week Nature Geosciences This is the result of a study that measures the methane released by large dams for the first time.
The publication of the study coincided with a statement on Tuesday by Francois Legault, the leader of the Quebec premier and Alliance Avenir Quebec, who said if he were to return, he would “like to build new dams to have additional clean energy in Quebec.” Elected.
Hydropower is not environmentally benign. Professor Prairie, who has been studying greenhouse gases for 15 years, says that in addition to the carbon footprint left behind by the construction of dams, dams and roads, we have to deal with greenhouse gas emissions from flooded areas.
A decaying substance
It is the decaying organic matter in the soil which, under the action of bacteria, releases gases into the atmosphere when reservoirs fill up and flood vast tracts of land to turn turbines.
The first 20 years are the most productive, and therefore destructive; Later, decomposition is slower and emissions are reduced.
Fortunately, underwater bacteria don’t like the cold.
“In northern regions like ours, the effects are less potent. Bacteria activity is reduced as it is kept in the refrigerator,” explains Professor Prairie.
The researchers’ data came from studies conducted since 1900 around the world. They studied 9,000 dams on five continents and created a model that measures methane. According to their conclusions, the maximum level of emissions of this gas from dams was reached in 1987.
“The worst is behind us, but in recent years we have seen a new boom in projects, especially in Asia and South America. »
Wind power is green
President of the Rivers Foundation, Alain Salatzius, was surprised by Prime Minister Legault’s announcement to restart dam projects.
“We oppose hydropower development, especially for large dams,” he said.
According to him, the additional energy needs of 10 terawatt hours can be met by wind power with less impact on the environment.
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