From the Cary Institute of Ecosystem Studies
Greenhouse gas impact of hydroelectric reservoirs downgraded
Site design and location can minimize carbon dioxide, methane emissions
An international team of scientists has amassed the largest data set to date on greenhouse gas emissions from hydroelectric reservoirs. Their analysis, published today in the online version of Nature Geoscience, posits that these human-made systems emit about 1/6 of the carbon dioxide and methane previously attributed to them.
Prior studies based on more limited data cautioned that hydroelectric reservoirs could be a significant and large source of both carbon dioxide and methane to the atmosphere.
Through an analysis of 85 globally-distributed hydroelectric reservoirs, the authors revealed that these systems emit 48 million metric tons of carbon annually, a downgrade from earlier estimates of 321 million metric tons. Further putting things in perspective, hydroelectric reservoirs are responsible for less than 16% of the total carbon dioxide and methane emissions from all types of human-made reservoirs combined.
“Our analysis indicates that hydroelectric reservoirs are not major contributors to the greenhouse gas problem,” comments Dr. Jonathan Cole, a limnologist at the Cary Institute of Ecosystem Studies and one of the paper’s authors. “But there are some caveats. To date, only 17% of potential hydroelectric reservoir sites have been exploited, and impacts vary based on reservoir age, size, and location.”
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  IMAGE: Located in the State of Mato Grosso, the APM Manso Dam impounds the Manso River and has a capacity of 5,600,000,000 m3 and a surface area of 357 km2….
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Carbon dioxide and methane are two of the main greenhouse gases created by human activities. Carbon dioxide is produced during the combustion of nearly any organic material; methane has a variety of industrial sources. Both gases are also produced naturally, particularly in wetlands and lakes.
When rivers are dammed to make the reservoirs needed for hydroelectricity, flooding creates lake-like conditions that generate carbon dioxide and methane. Emissions are the highest following reservoir construction, due to decomposing vegetation and soil organic matter. As reservoirs age, emissions decline, with cold-water systems stabilizing more rapidly than their warm-water counterparts.
Lead author MSc. Nathan Barros, of the Federal University of Juiz de Fora further explains, “The bottom line is that per unit of energy, hydroelectric generation produces much less carbon dioxide and methane emissions than previously thought, but impacts are not equal across all landscapes.”
The amount of greenhouse gases generated by hydroelectric reservoirs depends on where they are built, with the team’s analysis indicating that emissions are correlated with latitude and the amount of biomass in the watershed. With Barros adding, “Reservoirs in tropical locations, such as the Amazon, emit more methane and carbon throughout their lifecycles.”
Hydroelectricity supplies an estimated 20% of the world’s electricity and accounts for more than 85% of electricity from renewable sources. Future development is expected globally.
The paper’s authors urge careful consideration of site location and design. “During the environmental impact phase, it should be a goal to minimize the amount of carbon dioxide and methane emitted per unit of energy generated,” Cole notes.
To truly tease apart the emissions generated by hydroelectricity, the authors also call for a study that assesses a site’s carbon budget before and after reservoir construction. Pre- and post flooding analysis would clarify the net carbon impact of hydroelectric reservoirs.
Other contributors to the paper included Drs. Lars J. Tranvik, Yves T. Prairie, David Bastviken, Vera L. M. Huszar, Paul del Giorgio, and Fábio Roland.
The work was supported by grants from FURNAS Centrais Elétricas and from the Swedish Foundation for International Cooperation in Research and Higher Education (STINT).
The Cary Institute of Ecosystem Studies is a private, not-for-profit environmental research and education organization in Millbrook, N.Y. For more than twenty-five years, Cary Institute scientists have been investigating the complex interactions that govern the natural world. Their objective findings lead to more effective policy decisions and increased environmental literacy. Focal areas include air and water pollution, climate change, invasive species, and the ecological dimensions of infectious disease. Learn more at www.caryinstitute.org
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Bystander says:
August 2, 2011 at 6:03 am
Waiting for the anti-hydro power crew to show up here based on the anti-wind and anti-solar responses to those updates….
You misunderstand (as usual). What rational people object to is being forced to pay for more expensive, and less reliable energy sources (such as wind and solar), based on the idiotic notion that “carbon” is bad. As long as hydro can stand on its own, and doesn’t require subsidizing, then it is usually fine as an energy source.
I say usually, because, here in New Hampshire there is an issue with Hydro Quebec and PSNH trying to railroad through a gigantic transmission line project, called “Northern Pass”, which has a number of issues, among them being destruction of wilderness in the northern part, and some land-taking through emminent domain, as well as destroying some of the beauty of the state. The power isn’t even for NH, but rather for Massachusetts and Connecticut.
Well now, article not only states the impact is less then thought but also says hydro is green, renewable power. Now that it’s official I wonder if Oregon legislature can relabel our hydro power as green.
As dp has already noted, water vapor is an even bigger GHG produced by human activities, such as irrigation, tree planting, exhalation, showering, hydrocarbon combustion, and even dam building.
If CO2 is a global enemy, then H2O is Global Enemy No. 1. Why is the EPA not cracking down on H2O emissions? The biggest source of this “pollutant” is evaporation from the oceans. Fortunately, Exxon and BP now have the combined technology to reduce oceanic air pollution, by ramming tankers into oil rigs so as to cover the water with a film of oil. If you want to save the world, you have to be willing to make a few sacrifices! \sarc
What am I missing here? It was my belief that trees, and thus wood, submerged in water does not break down. Kariba Dam on the Zambezi was flooded around 1957 creating Lake Kariba. There were hundreds upon hundreds of acres of trees submerged and semi-submerged. They are dead of course, but the trees themselves are still there some fifty or so years later. Couldn’t have been a lot of CO2 generated from that source. Great for the bream and tiger fish that inhabit the lake and great for those of us who have been privileged to fish there.
Since the total estimated carbon from dams (48 million tonnes annually) is only six-tenths of one percent (0.6%) of the total emissions of carbon from fossil fuels (about 7 billion with a “b” tonnes annually), even if it were an issue it wouldn’t be an issue.
w.
eyesonu says:
August 2, 2011 at 11:15 am
In my home town there is a hydro power plant that uses wood from an African tree for the bearings on the shafts. The wood gets harder submerged over time. The plant was originally built by Union Carbide to make acetylene, but when UC left became a commerical enterprise. Wood better than steel for bearings who’d a thunk it.
So now the latitude-based carbon emissions-reduction rankings are:
Tropics and near-tropics: Solar, perhaps wind.
Mid-latitudes: Nuclear, solar and wind where practical, hydroelectric.
Polar and near-polar: Nuclear, possibly wind (equipment issues), possibly hydroelectric.
Wait, do the residents of the tropics and near-tropics want reliable continuous electricity as well? If “warm water” reservoirs are “the worst” for carbon emissions, then there can’t be open-air reservoirs for hydroelectric-based pumped storage. There is no other practical form of pumped storage, other storage methods still aren’t practical.
So the tropics and near-tropics get nuclear as well. Also, since nuclear is base load, for the peaks as needed there are fast-reacting gas turbine plants using methane generated from “inevitable” sources like landfills and sewage, suitable for all latitudes (provided they’re protected from too-cold temperatures).
Problem solved (assuming there is a problem).
http://www.theglobeandmail.com/report-on-business/small-business/start/company-logs-wood-from-panama-canal/article1817698/singlepage/#articlecontent
http://www.theglobeandmail.com/report-on-business/small-business/business-categories/sustainability/african-treasure-bc-firm-harvests-submerged-forest/article2101132/
Underwater logging…
http://www.theglobeandmail.com/report-on-business/small-business/start/company-logs-wood-from-panama-canal/article1817698/singlepage/#articlecontent
http://www.theglobeandmail.com/report-on-business/small-business/business-categories/sustainability/african-treasure-bc-firm-harvests-submerged-forest/article2101132/
Bob Kutz asked some good questions above. I don’t see that anyone’s answered yet so I’ll take a crack at it. In reverse order:
> Can anybody explain why a reservoir would produce substantially more CO2 than a non-dammed river?
Damming the river floods much of the surrounding hillside, killing all the grasses, trees and bushes that lived there as the reservoir fills. While those plants are replaced by water-plants (algae, etc), the total biomass is much smaller, at least according to these researchers. The net loss of biomass becomes a net gain of gas when the it rots. Assuming steady-state, this is a one-time hit, I think.
> Can anybody explain the logic why hydroelectric dams produce substantially more CO2 than non-hydro?
Hydroelectric dams are designed to keep more of the water moving than non-hydro dams. While both will kill the plants on the surrounding hillsides as the reservoir fills up, the non-hydro dams have a good chance of becoming anerobic at the bottom fairly quickly. If it happens fast enough, the dead trees, etc may never rot at all. Hydroelectric dams will tend to keep the bottom water moving more, keeping the water aerobic and allowing decomposition to progress.
The movement of water also affects the temperature distribution, keeping the bottom water from getting as cold as in a more still reservoir. (See above about the reason temperature affects decomposition.)
Hope that helps.
CO2 is NOT the complete story about dams. Believe me I’ve been underground at the Upper Churchill hydro Project in Labrador and I’ve seen the effect of said dam downstream. What used to be CHURCHILL FALLS with a much larger and higher falls than Niagara Falls (only talking about the Canadian Niagara Falls) is NOW reduced to a mere trickle you can almost catch in a bucket. Which changed the entire course of the Churchill River all the way down to Happy Valley-Goose Bay. Salmon used to run in that river but no longer – resulting in a much lower river now full of sand bars in essence changing the landscape. I drove back there four years ago to see the once might falls reduced to this is heart breaking scene. It makes me sick every time I see that image in my mind all over again.
The worst part – we only wanted jobs at the time and could never imagine the after effects – we only saw jobs. I was one of them that just wanted a job. I never knew what the true cost of damning a river such as the Churchill meant and I probable didn’t want to know either. I don’t think any of us understood. The sad part after construction none of us had jobs anymore and Quebec got all the benefits signed away for 100 years. Today they’re going to build another dam on the Churchill River about thirty miles from Happy Valley Goose Bay. The same thinking I had back then is being said all over again. I understand people need the jobs modern society brings but I’m not so sure folks understand the consequence of another dam on that once vibrant river system.
What almost everyone forgets regarding alternative energies, including hydro, is how much carbon dioxide was poduced and btus were burned to manufacture and erect these monuments to energy stupidity.
Hydro in particular uses an enormous amount of concrete. Concrete is about 1/3 cement. Cement making accounts for about 4% of all the CO2 put into the atmosphere by man. (Man only accounts for 3.27% of all CO2 put into atmosphere.)
Does anyone know what the Energy Returned On Energy Invested (EROIE) is for hydro?
Chilli @ur momisugly 6.56 am sums it up well. I cannot believe they have sunk the level of lunacy so far in their efforts to find topics to research on this thoery.
From mkelly on August 2, 2011 at 1:10 pm:
http://www.plantservices.com/articles/2005/469.html
There’s a pdf on the construction and use of wood bearings. The originating source:
http://practicalaction.org/docs/technical_information_service/oil_soaked_wood_bearings.pdf
Problem is it’s not downloading well for me, and what came through was reported as damaged, unreadable. I found it at this alternate site, use download link:
http://sheltercentre.org/library/oil-soaked-wood-bearings-how-make-them-and-how-they-perform
M$ Word in pdf, opened just fine.
Important warning! As found out by knifemakers using “exotic woods” for handle materials, these naturally-oily woods can be very dangerous. Search for “exotic wood dust danger” for more official info, here’s a blog thread with precautionary advice and anecdotal reports. Severe allergic reactions can be triggered by dust or even mere skin contact with the wood. IIRC people have died from exposure, come to think of it since a person can die from a single peanut I would be surprised if no one had died.
Oh, and as a “The state of California has determined” warning, the dust is carcinogenic. Apparently technically all wood dust is carcinogenic as well.
The very best way to season timber before use is to submerge it in water for a decade or three, they do not rot they season naturally without warping or splitting. Look up records of ship building from centuries past. This rotting log stuff in lakes is BS.
Charles S. Opalek, PE says:
August 2, 2011 at 2:34 pm
Does anyone know what the Energy Returned On Energy Invested (EROIE) is for hydro?
======================================================
Charles I don’t have it with me at the moment, but I can probably get it at work. But my thoughts are that as time passes, it surpasses any other source of electricity. The pricing certainly beats anything else. Coal and Nuke included. While it does take a great bit of energy to place a generating dam, once in place, its relatively done as far as energy invested. Sure, there’s maintenance and monitoring, but the fuel is free and is delivered to the generator with no further investment. The life expectancy of a turbine in out of this world! There’s some over 50 y/o still in use! (If we updated them, we’d prob get more generation…….)
An international team of scientists has amassed the largest amount of gravy from the Carbon Scaremongering Gravy Train. They have determined yet another useless speculative number concerning a minuscule amount of a harmless gas and managed to leech off of the tax payer for another couple years. A spokesman from the The Journal of Speculative BS propaganda, aka Nature, stated that we need more taxes and less public access to data and journal articles through the implementation of a complex pay-wall system based on a points wise analysis of the readers belief in AGW.
Sport Now. Go to sleep.
To all the “logs don’t rot in lakes” commentors,
1) Some logs, some lakes – it depends on the type of wood and the temperature, aeration, acidity and other factors of the water.
2) Logs don’t actually matter anyway. The majority of the biomass of a tree is in its leaves, not in the trunk. (This, of course, depends on the type of tree.) And thats even before factoring in the biomass of the grass, shrub and other sunken vegetation. No matter how many unrotted logs you’ve found, it’s exceptionally rare to find a deposit of unrotted leaves or grass unless the water is very cold, still and anaerobic.
Precious little. You may be imagining the water to be “seltzer-like”, where the liquid phase is supersaturated with CO2. When you drop the pressure, out comes the fizz. Lake or impoundment water has a very low bulk flow rate and is in equilibrium with the CO2 content of the air. Only temperature changes will affect the net flux of CO2 in the water that flows through the turbines.
Wil says:
August 2, 2011 at 2:23 pm
Dams do not decrease the flow rate of a river once the water is held in reserve. You see, once the water is there, its a question of the people manning the dam to speak who are not doing their jobs. You can not blame a dam for low flow after the river is back to its flow-rate.
In the case of the river always “flowing at a certain rate..” Well its probably just as likely that it happens like that too at times that it is in drought and the flow-rate is reduced. Dams do not stop water from flowing, people do. When people take water out of the system as in Colorado this is something to be concerned about. When people do not take flow rate and environmental concerns such as fish into consideration, this is a concern. You can solve these problems easilly and flow-rate is never reduced by dams. Its all depended on water flowing into the system.
So as you can see…. its more about the management of the dam after the fact then anything else. But by saying dams ruin the country-side is really not looking at the big picture. They add to the country-side by creating a lake that is permanent instead of flood-plains that flood periodically and can not really be used for anything of value.
Further putting things in perspective, most of Earth’s methane is emitted by the oceans, and most of it is probably of abiotic origin. I was taught to regurgitate the phrase “fossil fuel” without consideration, as if the explanation not only had some scientific merit, but was established fact. I was also taught that methane is a biological molecule and a sign of life. Recent discoveries undermine and contradict these myths.
1) “The [Martian] methane could be a byproduct of volcanic gassing. Or it could be the chemical reaction between water and rocks in the soil and crust.”
http://news.nationalgeographic.com/news/2004/10/1007_041007_mars_methane.html
2) “…a hydro-geological process between water and rocks deep inside the moon could be producing [Titan’s] methane.”
http://esse.engin.umich.edu/PSL/PRESS/Titan_Cassini_Huygens/AP_Wire_012705.pdf
3) It is also argued that atmospheric methane can come from volcanoes or other fissures in the planet’s crust and that without an Isotopic signature it is difficult to say what exactly was the origin.
http://en.wikipedia.org/wiki/Methanogenesis
4) But that does not solve the larger question of why methane in the atmosphere seems to have reached a plateau. “The scientific community agrees that the pause is source-driven rather than sink-driven, that is, caused by decreasing emissions of methane,” Simpson says:
http://www.scientificamerican.com/article.cfm?id=mysterious-stabilization
No special pleadings for Earth!
In the hydo reservoirs down the road there are entire forests of trees underwater from when they built the dams, one in 1905, one in 1930. When they lowered the water to fix the dams people were shocked that they were water skiing above a forest of trees only 3-5′ below the surface. Many had to be knocked down for safety reasons.
As far as AGW, I would theorize that the dam would be a net positive. The waterfalls used to put up a tremendous water vapor. Now the river slowly boils out water at the base of the dam. Likewise while there isn’t a forest or grasslands under the water any more, there is a whole biosphere of plant life that probably represents far more flora than the earlier forests did. It also provides clean energy.
The biggest CO2 producer for the dams probably be tourism as people boat, fish, swim, and catch a sunset. Next would be the licensing process that took 8 years and a 40,000 page document plus supporting studies.
The hydo projects don’t leave the rivers dry as happens some places, they are ‘Run of River’, what goes in goes out and water levels in the reservoir are maintained within inches, unless they fall below minimum flow to support the river downstream.
Bloke down the pub says:
If there’s loads of methane being outgassed as the water passes through the turbines, couldn’t it be collected and used to drive a gas turbine
Or add a little butanethiol and sell it.
Methane also works as fuel for a four stroke spark ignition engine.
Viv Evans says:
“the authors revealed that these systems emit 48 million metric tons of carbon annually“ (my bold)
Blimey – what is happening to all that carbon? Are we harvesting it? Is it being burned in coal power stations?
It dosn’t help that these kind of people frequently say “carbon” when they actually mean “carbon dixoide” so they may actually mean 12Tg.
Pure unadulterated wool gathering. I’m gobsmacked.