The hydropower paradox_ is this energy as clean as it seems_ _ guardian sustainable business _ the guardian

In July, UN Secretary Ban Ki-Moon highlighted the role of hydropower in boosting the use of renewable energy globally, when he visited a nonprofit institute in China that helps emerging nations develop and build hydropower plants. Gas x strips after gastric sleeve Many countries consider hydroelectricity a clean source of power because it doesn’t involve burning dirty fossil fuels. Gas mask drawing But that’s far from true. Electricity projects for class 12 Hydropower is a significant source of greenhouse gas emissions: a new study shows that the world’s hydroelectric dams are responsible for as much methane emissions as Canada.

The study from Washington State University finds that methane, which is at least 34 times more potent than another greenhouse gas, carbon dioxide, makes up 80% of the emissions from water storage reservoirs created by dams. Gas laws worksheet with answers What’s more, none of these emissions are currently included in global greenhouse gas inventories. Gas pain in shoulder These are already revealing a worrisome future in which rising global temperatures will likely cause environmental changes such as rising sea levels and stronger hurricanes, which could uproot communities and intensify competition for food and other resources.

“I think this study shows that dams as a source of energy aren’t without their greenhouse gas costs,” says Bridget Deemer, a research ecologist at the US Geologic Survey, who led the study during her prior position as a research associate at Washington State. Electricity production “Even though it’s a renewable source of energy, people should keep the greenhouse gas side of the picture in mind when making planning and policy decisions regarding dams.”

The research, which examines 100 recent studies on greenhouse gas emissions from 267 large reservoirs around the world, also calls into question the wisdom of building more hydroelectric dams as countries try to nix their dependence on coal, natural gas and oil. Gas vs diesel towing An estimated 3,700 new dams are proposed or under construction around the globe, the study reports. Gas city indiana police department It suggests the hydropower industry will need to control its emissions.

As recently as a decade ago, little was known about emissions from water storage reservoirs. Gas 37 weeks pregnant But understanding has evolved rapidly. D cypha electricity futures For instance, researchers initially thought shallow reservoirs in tropical regions were the largest emitters because their stored water was more prone to heating up, which could fuel greenhouse gas production.

But analysis by Deemer and her colleagues shows that the latitude and depth of water are not leading factors. Gasset y ortega biografia Instead, “biological activities” in a reservoir – such as decaying vegetation and nutrient runoff from watersheds upstream – are more important indicators of greenhouse gas emissions. Electricity and magnetism pdf The nutrient runoff can be from natural processes or from farming, logging and land development.

Using data from the 267 reservoirs, the authors estimate total emissions from all reservoirs worldwide and conclude that those water storage facilities account for 1.3% of all manmade greenhouse gas emissions.

Another new study published by the journal PLOS One reaches similar conclusions, although it finds carbon dioxide to be a bigger share of emissions than methane. Natural gas jokes After examining data from more than 1,400 dams worldwide, it identifies the rate of soil erosion into a reservoir as a leading predictor of carbon dioxide emissions.

Led by Laura Scherer, a research associate at the Swiss university ETH Zurich, that study concludes the “carbon footprint of hydropower is far higher than previously assumed”.

“These are massive emissions, and we can’t ignore that,” says Kate Horner, executive director of the environmental group International Rivers, based in Berkeley, California. Gas 02 “There are a massive number of dams that are currently proposed to be built. Gas number It would be a grave mistake to continue to finance those with the impression that they were part of the solution to the climate crisis.”

It is challenging to measure reservoir emissions because so many factors can play a role, Deemer acknowledges. Gas and supply shreveport The scientific community also doesn’t follow a standard practice for counting emissions, even though the International Hydropower Association and the United Nations Educational, Scientific and Cultural Organisation (Unesco) published a set of guidelines in 2010.

Emissions vary according to a wide variety of factors, including water and air temperatures, season and time of day, vegetation and soil types in both the reservoir and the upstream watershed, and watershed management practices.

Hydropower dams constantly manipulate water levels to make electricity, a process that also affects the amount of emissions that make their way into the atmosphere from the reservoir. Gas pain relief As water levels decline, the hydrostatic pressure on submerged soils also lowers and allows gas bubbles to escape. Electricity song youtube Sometimes the methane in these bubbles is absorbed by the water column and never reaches the surface. Gas density and molar mass Other times it makes the great escape into the air.

Deemer and her colleagues note that many studies don’t sample emissions thoroughly enough both across reservoir surface area and over time. Gas definition state of matter As a result, she says, the emissions estimates in her study are probably low.

The challenge in measuring emissions also makes it difficult to figure out how to reduce them. Power generation definition Researchers speculate it may be possible to reduce emissions by managing water levels in a reservoir differently. Physics c electricity and magnetism formula sheet This, however, could affect electricity generation, fishery and flood protection, and other operations.

Protecting watersheds to reduce erosion into reservoirs could also reduce emissions as well as improve water quality, forest health and aquatic habitat.

At an October meeting in Bangkok, a committee of the Intergovernmental Panel on Climate Change took a first step by agreeing to include reservoirs, which it categorizes as “flooded lands”, in an updated guidance document that instructs nations on accounting for their greenhouse gas emissions. Types of electricity generation But it may be several more years until that document is formally approved.

The US government does not account for reservoir emissions in its own greenhouse gas inventory. Ideal gas definition chemistry The country is dotted with roughly 79,000 dams, including more than 2,200 private and public hydropower plants. 1 electricity unit in kwh The US Bureau of Reclamation, for example, manages 337 reservoirs, and a science advisor to the agency, Dave Raff, says the bureau is taking on the emissions accounting task.

“We’re engaged in trying to understand what the different mechanisms are for reservoirs as they generate these greenhouse gases,” Raff says. Power kinetic energy “And ultimately, what are the management levers we have to pull that could mitigate those. Electricity for refrigeration heating and air conditioning 9th edition answers I do think we feel a sense of urgency to be on that path.”

• The article was amended on 6 November 2016 to show that the cost of building and operating a hydropower plant is about $68 per megawtt-hour, not kilowatt-hour.