6 ms·

Reservoirs are contributing 1.5% of global greenhouse gas emissions

70 points by Osiris30 10y ago

ckastner 10y ago
According to the report, they supposedly underestimated methane production by 25%. What surprised me more though was that even going be the previous value (which I'll simply assume to be 1.5%/1.25=1.2%), that sounds like a _lot_ of greenhouse gas contribution for a resource which in 2014 "only" contributed 3.8% to global energy consumption, according to [1]. [1] https://en.m.wikipedia.org/wiki/World_energy_consumption https://en.m.wikipedia.org/wiki/World_energy_consumption
- Shivetya 10y ago
  but energy isn't their main benefit. flood control and proving water to cities and even farms is the main benefit. throw in the recreational opportunities, increased tax base because all that lake front is worth something, and it seems they are more than worth it. to be honest I walked into that article expecting another dam killer tirade with an all new reason to take down more and was pleasantly surprised they defend the use of them in the end
heisenbit 10y ago
I found this article confusing: >There are three main differences between man-made reservoirs and lakes: >1. Man-made reservoirs require flooding terrestrial land, supplying a large pulse of dead organic matter from trees and grasslands. The timescale of how this happens to natural lakes is much longer. >2. Man-made reservoirs experience greater fluctuations than natural lakes. As reservoirs reduce in volume, the weight of the water over the sediments drop freeing even more methane molecules from the confines of their origin. >3. Man-made reservoirs are often closer to human activities, such as agricultural run-off containing fertilizers that can promote the growth of organic matter in the water. Here one-off effects are mixed with ongoing effects which makes limited sense. Also agricultural run-off is mixed in. But if that is not producing methane in the reservoir then in will be producing methane elsewhere - cause and effect is mixed up. Then later on the alternative: > Groundwater recharge basins are regularly maintained to have less organic matter at the bottom, since it can clog the percolation of water into groundwater aquifers beneath. In addition, recharge basins are shallower than man-made reservoirs and periodically become empty during dry periods when less water is available to recharge groundwater. I'm confused about a shallower basin being less problematic as the methane is produced by the wet sediment. A shallower basin for the same amount of hydro power would be much larger. What is miss is putting the generated methane in relationship with the generated energy.
- ckastner 10y ago
  > But if that is not producing methane in the reservoir then in will be producing methane elsewhere Not necessarily. The article explains methane production as so: [...] bacteria eating this dead organic matter to depend on other molecules containing oxygen. These include nitrate, phosphate, sulfate, and carbon dioxide. The least appealing molecule to breathe for these microbes is carbon dioxide because it requires the greatest energy to break the molecule apart to access the oxygen. When these microbes have no choice than to breathe carbon dioxide, a process called “methanogenesis” occurs.
- Brakenshire 10y ago
  Methane is produced by anaerobic digestion, which I would think is much more likely to happen when a whole area is flooded at once. The same biomass bring broken down in atmospheric oxygen would have a significantly lower effect. Agree the mix of ongoing and one-off effects is confusing.
- schiffern 10y ago
  To borrow a phrase from Sheldon Brown, "As always, Bill Mollison has the answer." :) (for those unfamiliar with what I affectionately call the "Perma-cult": https://en.wikipedia.org/wiki/Bill_Mollison https://en.wikipedia.org/wiki/Bill_Mollison) >So, it seems as though hydropower is not as clean as we once thought. But that’s isn’t a good reason to be ripping out dams. Hydropower generation often replaces much dirtier sources of energy, such as coal and even natural gas. In addition, dams provide us a wide range of public benefits such as flood control, recreation, and water management. It sounds like the Permaculture strategy of disfavoring singular large dams (huge concrete construction projects) and favoring smaller "farm dams" (cheap earthen construction) is the way to go. The smaller scale means more surface area:volume, increasing the equilibrium oxygen level in the water and reducing methanogenesis. Also, the typical Permaculture dam construction practice is to scrape off and conserve all the topsoil from the inside of the dam. This should further reduce methane production (which also represents squandered biomass, ie stored carbon). This technique is practical on the scale of a farm dam, but totally impractical for a huge reservoir. Farm dams have cost advantages in flood control and water management over monolithic dam projects, since they're near to the big consumers of water (farms). So the largest diversion canals and tunnels never need to be built. Simple gravity-fed water run through plastic pipes serves for irrigation purposes, so it improves on-farm water security. >groundwater storage may be a ‘cleaner’ alternative. Groundwater recharge basins are regularly maintained to have less organic matter at the bottom, since it can clog the percolation of water into groundwater aquifers beneath. In addition, recharge basins are shallower than man-made reservoirs and periodically become empty during dry periods when less water is available to recharge groundwater. This periodic drying out helps keep soils aerated, whereas man-made reservoirs can stay inundated with water for longer periods of time. I wonder how "groundwater recharge basins" differ from swales (long on-contour ditches)? They also intercept large quantities of runoff and divert it to recharging groundwater. They also require minimal earth movement, since it's a small surface feature compared to farm dams. Swales can also feed into dams, dramatically increasing their total catchment and infiltration capacity (since before the dam overflows, it floods and soaks the length of the swale). https://www.youtube.com/watch?v=E79C9tdcgEA https://www.youtube.com/watch?v=E79C9tdcgEA http://permaculturenews.org/category/earthworks-earth-resources/dams/ http://permaculturenews.org/category/earthworks-earth-resour...
Tharkun 10y ago
Why does this article talk about cow burps in connection with methane? Surely that's cow farts? Or do cows somehow produce methane while cud chewing?
- lambertsimnel 10y ago
  I think ruminants including cows do significantly contribute to methane emissions by burping. "Cows don't emit 400 quarts of daily flatulence, as the term is usually understood. According to Professor Johnson, they emit 400 quarts' worth of burps,known in polite circles as eructation." http://www.straightdope.com/columns/read/832/do-cow-and-termite-flatulence-threaten-the-earths-atmosphere http://www.straightdope.com/columns/read/832/do-cow-and-term...
  - ptaipale 10y ago
    And it is fairly self-evident when you think of it: cows are ruminants, and the process of rumination means fermentation before digestion. Methane is released in this fermentation, so it naturally comes as burping, not flatulence.
Hondor 10y ago
Methane isn't the most potent greenhouse gas as stated in the article. Water vapor is both the most potent and the most abundant. It also has a positive feedback loop so the hotter the Earth gets, the more water vapor goes into the atmosphere!
- botexpert 10y ago
  Methane is about 25-100 times more potent than CO2. Nitrous oxide about 300 times than CO2. Although, the biggest worry is the stored methane. [1] The amounts stored are equivalent (in CO2) to about 20-35 years of human activity (2014 CO2 output). If that gets quickly released, who knows what will happen. [1]: https://en.wikipedia.org/wiki/Arctic_methane_emissions https://en.wikipedia.org/wiki/Arctic_methane_emissions
- hannob 10y ago
  The most potent greenhouse gas is actually SF6 (Sulfur hexafluoride), a chemical used in some industry processes. Water vapor is however the most common one.
  - snowwindwaves 10y ago
    SF6 is used as an insulator in high voltage breakers and switchgear. It is heavier than air so it sinks. There is a YouTube video where they float a paper boat on a basin of sf6 gas and also breathe it and it makes your voice low, opposite of helium http://youtu.be/u19QfJWI1oQ http://youtu.be/u19QfJWI1oQ
- lambertsimnel 10y ago
  Good point. I would add that presumably water vapour, methane and carbon dioxide have been in the atmosphere influencing temperatures since before anthropogenic climate change. I imagine rising concentrations of atmospheric water vapour are partly a consequence of emissions of carbon dioxide and methane emissions. (I believe that methane breaks down into chemicals including water.) I imagine that humans are more responsible for levels of atmospheric water vapour indirectly (through carbon dioxide and methane emissions) than directly. I imagine temperature and concentrations of atmospheric water vapour are in equilibrium in the absence of changes in the concentrations of other greenhouse gases.
teh_klev 10y ago
Direct link to the study: http://bioscience.oxfordjournals.org/content/early/2016/10/02/biosci.biw117.full.pdf http://bioscience.oxfordjournals.org/content/early/2016/10/0... If you see "Failed to load PDF document", clicking "Reload" will load the PDF.
Angostura 10y ago
This can be seen as good news, I suspect. Now we have identified a substantial source of the gasses it gives us an opportunity to look at how we can fix it. Oygenation? Stirring?
- giarc 10y ago
  Perhaps these shade balls could work. It does mention that they inhibit microbial growth and slow evaporation. http://news.nationalgeographic.com/2015/08/150812-shade-balls-los-angeles-California-drought-water-environment/ http://news.nationalgeographic.com/2015/08/150812-shade-ball...
brownbat 10y ago
A lot of rice production involves standing water (and the burning of rice straw between seasons), and so rice farming is a major contributor to GHG emissions: http://www.southasia.ox.ac.uk/sites/sias/files/documents/GHG%20emissions%20from%20rice%20-%20%20working%20paper.pdf http://www.southasia.ox.ac.uk/sites/sias/files/documents/GHG... It also happens to be a staple for over 60% of the world's population. And unlike transportation and energy, obvious substitutes are much harder to identify. The more I read about novel sources of GHG the more intractable this problem appears absent geoengineering.
- Fej 10y ago
  Global warming is going to require a massive, species-wide effort to counteract. The problem gets worse every day. When do we decide to stop? We're already pretty far gone. Now it's a matter of controlling how Earth-shattering the damage is.
egberts1 10y ago
I hotly disagree. Reservoir who empty at drought season typically have immeasurable methane output during good season. -- Lake bed dries up and bakes in the sun. For that, we can rule out Lake Folsom, California.

70 points by Osiris30 10y ago

According to the report, they supposedly underestimated methane production by 25%. What surprised me more though was that even going be the previous value (which I'll simply assume to be 1.5%/1.25=1.2%), that sounds like a _lot_ of greenhouse gas contribution for a resource which in 2014 "only" contributed 3.8% to global energy consumption, according to [1]. [1] https://en.m.wikipedia.org/wiki/World_energy_consumption https://en.m.wikipedia.org/wiki/World_energy_consumption

Shivetya 10y ago
but energy isn't their main benefit. flood control and proving water to cities and even farms is the main benefit. throw in the recreational opportunities, increased tax base because all that lake front is worth something, and it seems they are more than worth it. to be honest I walked into that article expecting another dam killer tirade with an all new reason to take down more and was pleasantly surprised they defend the use of them in the end

heisenbit 10y ago

I found this article confusing: >There are three main differences between man-made reservoirs and lakes: >1. Man-made reservoirs require flooding terrestrial land, supplying a large pulse of dead organic matter from trees and grasslands. The timescale of how this happens to natural lakes is much longer. >2. Man-made reservoirs experience greater fluctuations than natural lakes. As reservoirs reduce in volume, the weight of the water over the sediments drop freeing even more methane molecules from the confines of their origin. >3. Man-made reservoirs are often closer to human activities, such as agricultural run-off containing fertilizers that can promote the growth of organic matter in the water. Here one-off effects are mixed with ongoing effects which makes limited sense. Also agricultural run-off is mixed in. But if that is not producing methane in the reservoir then in will be producing methane elsewhere - cause and effect is mixed up. Then later on the alternative: > Groundwater recharge basins are regularly maintained to have less organic matter at the bottom, since it can clog the percolation of water into groundwater aquifers beneath. In addition, recharge basins are shallower than man-made reservoirs and periodically become empty during dry periods when less water is available to recharge groundwater. I'm confused about a shallower basin being less problematic as the methane is produced by the wet sediment. A shallower basin for the same amount of hydro power would be much larger. What is miss is putting the generated methane in relationship with the generated energy.

ckastner 10y ago
> But if that is not producing methane in the reservoir then in will be producing methane elsewhere Not necessarily. The article explains methane production as so: [...] bacteria eating this dead organic matter to depend on other molecules containing oxygen. These include nitrate, phosphate, sulfate, and carbon dioxide. The least appealing molecule to breathe for these microbes is carbon dioxide because it requires the greatest energy to break the molecule apart to access the oxygen. When these microbes have no choice than to breathe carbon dioxide, a process called “methanogenesis” occurs.
Brakenshire 10y ago
Methane is produced by anaerobic digestion, which I would think is much more likely to happen when a whole area is flooded at once. The same biomass bring broken down in atmospheric oxygen would have a significantly lower effect. Agree the mix of ongoing and one-off effects is confusing.
schiffern 10y ago
To borrow a phrase from Sheldon Brown, "As always, Bill Mollison has the answer." :) (for those unfamiliar with what I affectionately call the "Perma-cult": https://en.wikipedia.org/wiki/Bill_Mollison https://en.wikipedia.org/wiki/Bill_Mollison) >So, it seems as though hydropower is not as clean as we once thought. But that’s isn’t a good reason to be ripping out dams. Hydropower generation often replaces much dirtier sources of energy, such as coal and even natural gas. In addition, dams provide us a wide range of public benefits such as flood control, recreation, and water management. It sounds like the Permaculture strategy of disfavoring singular large dams (huge concrete construction projects) and favoring smaller "farm dams" (cheap earthen construction) is the way to go. The smaller scale means more surface area:volume, increasing the equilibrium oxygen level in the water and reducing methanogenesis. Also, the typical Permaculture dam construction practice is to scrape off and conserve all the topsoil from the inside of the dam. This should further reduce methane production (which also represents squandered biomass, ie stored carbon). This technique is practical on the scale of a farm dam, but totally impractical for a huge reservoir. Farm dams have cost advantages in flood control and water management over monolithic dam projects, since they're near to the big consumers of water (farms). So the largest diversion canals and tunnels never need to be built. Simple gravity-fed water run through plastic pipes serves for irrigation purposes, so it improves on-farm water security. >groundwater storage may be a ‘cleaner’ alternative. Groundwater recharge basins are regularly maintained to have less organic matter at the bottom, since it can clog the percolation of water into groundwater aquifers beneath. In addition, recharge basins are shallower than man-made reservoirs and periodically become empty during dry periods when less water is available to recharge groundwater. This periodic drying out helps keep soils aerated, whereas man-made reservoirs can stay inundated with water for longer periods of time. I wonder how "groundwater recharge basins" differ from swales (long on-contour ditches)? They also intercept large quantities of runoff and divert it to recharging groundwater. They also require minimal earth movement, since it's a small surface feature compared to farm dams. Swales can also feed into dams, dramatically increasing their total catchment and infiltration capacity (since before the dam overflows, it floods and soaks the length of the swale). https://www.youtube.com/watch?v=E79C9tdcgEA https://www.youtube.com/watch?v=E79C9tdcgEA http://permaculturenews.org/category/earthworks-earth-resources/dams/ http://permaculturenews.org/category/earthworks-earth-resour...

Tharkun 10y ago

Why does this article talk about cow burps in connection with methane? Surely that's cow farts? Or do cows somehow produce methane while cud chewing?

lambertsimnel 10y ago
I think ruminants including cows do significantly contribute to methane emissions by burping. "Cows don't emit 400 quarts of daily flatulence, as the term is usually understood. According to Professor Johnson, they emit 400 quarts' worth of burps,known in polite circles as eructation." http://www.straightdope.com/columns/read/832/do-cow-and-termite-flatulence-threaten-the-earths-atmosphere http://www.straightdope.com/columns/read/832/do-cow-and-term...
- ptaipale 10y ago
  And it is fairly self-evident when you think of it: cows are ruminants, and the process of rumination means fermentation before digestion. Methane is released in this fermentation, so it naturally comes as burping, not flatulence.

Hondor 10y ago

Methane isn't the most potent greenhouse gas as stated in the article. Water vapor is both the most potent and the most abundant. It also has a positive feedback loop so the hotter the Earth gets, the more water vapor goes into the atmosphere!

botexpert 10y ago
Methane is about 25-100 times more potent than CO2. Nitrous oxide about 300 times than CO2. Although, the biggest worry is the stored methane. [1] The amounts stored are equivalent (in CO2) to about 20-35 years of human activity (2014 CO2 output). If that gets quickly released, who knows what will happen. [1]: https://en.wikipedia.org/wiki/Arctic_methane_emissions https://en.wikipedia.org/wiki/Arctic_methane_emissions
hannob 10y ago
The most potent greenhouse gas is actually SF6 (Sulfur hexafluoride), a chemical used in some industry processes. Water vapor is however the most common one.
- snowwindwaves 10y ago
  SF6 is used as an insulator in high voltage breakers and switchgear. It is heavier than air so it sinks. There is a YouTube video where they float a paper boat on a basin of sf6 gas and also breathe it and it makes your voice low, opposite of helium http://youtu.be/u19QfJWI1oQ http://youtu.be/u19QfJWI1oQ
lambertsimnel 10y ago
Good point. I would add that presumably water vapour, methane and carbon dioxide have been in the atmosphere influencing temperatures since before anthropogenic climate change. I imagine rising concentrations of atmospheric water vapour are partly a consequence of emissions of carbon dioxide and methane emissions. (I believe that methane breaks down into chemicals including water.) I imagine that humans are more responsible for levels of atmospheric water vapour indirectly (through carbon dioxide and methane emissions) than directly. I imagine temperature and concentrations of atmospheric water vapour are in equilibrium in the absence of changes in the concentrations of other greenhouse gases.

teh_klev 10y ago

Direct link to the study: http://bioscience.oxfordjournals.org/content/early/2016/10/02/biosci.biw117.full.pdf http://bioscience.oxfordjournals.org/content/early/2016/10/0... If you see "Failed to load PDF document", clicking "Reload" will load the PDF.

Angostura 10y ago

This can be seen as good news, I suspect. Now we have identified a substantial source of the gasses it gives us an opportunity to look at how we can fix it. Oygenation? Stirring?

giarc 10y ago
Perhaps these shade balls could work. It does mention that they inhibit microbial growth and slow evaporation. http://news.nationalgeographic.com/2015/08/150812-shade-balls-los-angeles-California-drought-water-environment/ http://news.nationalgeographic.com/2015/08/150812-shade-ball...

brownbat 10y ago

A lot of rice production involves standing water (and the burning of rice straw between seasons), and so rice farming is a major contributor to GHG emissions: http://www.southasia.ox.ac.uk/sites/sias/files/documents/GHG%20emissions%20from%20rice%20-%20%20working%20paper.pdf http://www.southasia.ox.ac.uk/sites/sias/files/documents/GHG... It also happens to be a staple for over 60% of the world's population. And unlike transportation and energy, obvious substitutes are much harder to identify. The more I read about novel sources of GHG the more intractable this problem appears absent geoengineering.

Fej 10y ago
Global warming is going to require a massive, species-wide effort to counteract. The problem gets worse every day. When do we decide to stop? We're already pretty far gone. Now it's a matter of controlling how Earth-shattering the damage is.

egberts1 10y ago

I hotly disagree. Reservoir who empty at drought season typically have immeasurable methane output during good season. -- Lake bed dries up and bakes in the sun. For that, we can rule out Lake Folsom, California.