The world is doing its best to try and work together to reduce its carbon footprint, and a rise in the use of renewable energy generation is certainly one way in which to achieve this. In what is a nothing less than a profoundly irritating revelation, a new study in the journal BioScience has confirmed that one of these supposedly clean sources of renewable energy – hydroelectric dams – actually unleashes a vast amount of greenhouse gases every single year.
Specifically, they release methane from their enormous reservoirs over time. This foul gas is a powerful heat-trapping compound that, although shorter lived that carbon dioxide, is 28 to 36 times more potent in terms of global warming. Aggravatingly, this team's calculations suggest that the world’s hydroelectric dams release the equivalent of 907 million tonnes (1 billion tons) of carbon dioxide on annual basis.
This is 1.3 percent of the world’s man-made greenhouse gas emissions, which may not sound like a lot on its own, but it’s extremely disappointing that an otherwise clean energy source turns out to be an underappreciated source of climate-changing gases. When comparing this value to the output of entire nations, however, it really stands out as something quite shocking.
Hydroelectric dams emit more greenhouse gases than Germany, Indonesia or Canada. They emit over twice as much as the UK, and three times as much as France. China, the world’s largest carbon emitter, releases 9.7 billion tonnes (10.7 billion tons) of carbon dioxide per year. This means that hydroelectric dams emit about a tenth of this.
“We had a sense that methane might be pretty important but we were surprised that it was as important as it was,” lead author Bridget Deemer, a research associate at Washington State University, said in a statement. “It’s contributing right around 80 percent of the total global warming impact of all those gasses from reservoirs. It’s a pretty important piece of the budget.”
The top 12 carbon emitters in the world, as of 2014, measured in megatonnes (million tonnes) of carbon dioxide per year. Hydroelectric dams alone would in sixth place if they were a separate nation. Global Carbon Atlas