Dams like Muskrat Falls produce more greenhouse gas than expected: study
Methane another pollutant with big environmental impact, scientist says
Some scientists are questioning whether energy produced by man-made dams is as green as previously believed.
A study published recently in the monthly journal BioScience says carbon pollution from reservoirs — like the one soon to be flooded at Muskrat Falls — deserves more consideration.
Methane is biggest contributor
The research looked at a hundred pre-existing studies, that covered greenhouse emissions from different types of reservoirs.
"The rate of methane emission from these reservoirs was about 25% higher than what was previously thought," Bridget Deemer, the first author on the study, told CBC's Labrador Morning.
"That means acre-for-acre … these systems are having a bigger impact on the global greenhouse gas budget than we previously thought."
The report found 79% of a dam's greenhouse effect was a result of methane. Carbon dioxide, at 17 per cent, and nitrous oxide at 4 per cent make up remaining emissions.
Methane, which is formed primarily by rotting organic matter, has a short life in the atmosphere but has the stronger short-term warming effect of the three gasses.
'Working hypothesis' around clearing
While Muskrat Falls in particular wasn't studied, Deemer said she had a "working hypothesis" about how clearing vegetation prior to flooding would impact the amount of greenhouse gases emitted from the project.
We can't think of these systems as greenhouse neutral.- Bridget Deemer, study author
"I would think that [clearing] might reduce methane emissions," the aquatic biogeochemist and reservoir limnologist said.
"But it remains to be tested."
Emissions need to be calculated
Although hydroelectric projects generally have a better reputation than the oil and gas energy production industry, Deemer says emissions from all reservoirs should be calculated into the global carbon budget.
"We can't think of these systems as greenhouse neutral," she said.
"We need to be considering their emission when we're making management decisions either about building new reservoirs or how we're managing existing systems."