Liming Lake Kivu

[ScienceNostalgia101]

 

So basically, this lake has a lot of dissolved CO2, and people are concerned that seismic activity is all it'll take to make life-threatening concentrations of it come out of solution and suffocate nearby villagers.

 

Doesn't limewater react with CO2 to form calcium carbonate? Why not just pour enough quicklime into this lake to convert all the CO2 to chalk?

[Strange]

4 minutes ago, ScienceNostalgia101 said:

Why not just pour enough quicklime into this lake to convert all the CO2 to chalk?

Have you calculated how much it will take? How much that will cost? How to deliver it? What the effect on the environment will be?

[ScienceNostalgia101]

They said there are 256 cubic km of CO2... that'd be 256 trillion litres, or 11.4 trillion moles of CO2.

 

CaO + CO2 -> CaCO3

 

To neutralize that much CO2 you'd need 11.4 trillion moles of CaO. Its molar mass is 56g/mol, so we're talking 640 trillion grams.

 

That's 640 billion kilograms, or 640 million metric tons.

 

This source says worldwide production of CaO is at hundreds of millions of metric tons per year. It's only a few years' worth of the stuff. You could put it on a boat (or a fleet of 'em) and let the currents take it to the east coast of Africa, then some trucks can take it the rest of the way. You mean to say people won't crowdfund to save lives?

 

Methane might still be released, but it could be ignited.

[studiot]

Thank you for introducing an interesting topic.

 

I found this reference dated 2015

https://psmag.com/environment/what-happens-if-lake-kivu-explodesObviously it hasn't happened yet.

Does anyone know any more about it?

 

[Sensei]

1 hour ago, ScienceNostalgia101 said:

This source says worldwide production of CaO is at hundreds of millions of metric tons per year. It's only a few years' worth of the stuff. You could put it on a boat (or a fleet of 'em) and let the currents take it to the east coast of Africa, then some trucks can take it the rest of the way.

Do you know how CaO is produced? Mostly from CaCO₃... CaCO₃ + heat -> CaO + CO₂..

 

Edited August 20, 2018 by Sensei

[studiot]

7 minutes ago, Sensei said:

Do you know how CaO is produced? Mostly from CaCO₃... CaCO₃ + heat -> CaO + CO₂..

 

+1

[Strange]

1 hour ago, ScienceNostalgia101 said:

That's 640 billion kilograms, or 640 million metric tons.

I would be rather concerned that dumping all that in the lake would destabilise it and cause the very problem you are trying to solve.

Also, what is the rate of CO₂ production? Presumably this would need to be an ongoing process, not just a one-off fix.

[ScienceNostalgia101]

2 hours ago, Strange said:

I would be rather concerned that dumping all that in the lake would destabilise it and cause the very problem you are trying to solve.

Also, what is the rate of CO₂ production? Presumably this would need to be an ongoing process, not just a one-off fix.

Yeah, I was thinking add it gradually, and find some way to store the CO2 (and/or use the forces resulting from a pressure change as an energy source if possible) while generating it.

 

Also, if it releases heat energy, you could force the steam through a turbine and generate power while you're at it.

[studiot]

9 minutes ago, ScienceNostalgia101 said:

Yeah, I was thinking add it gradually, and find some way to store the CO2 (and/or use the forces resulting from a pressure change as an energy source if possible) while generating it.

 

Have you not appreciated Sensei's excellent point that for every mole of carbon dioxide you remove from the lake via lime, you release one to the atmosphere in the making of that lime?

[ScienceNostalgia101]

That's why I was suggesting finding some way to store it. I'm not sure how best to go about it, though.

[John Cuthber]

50 minutes ago, studiot said:

Have you not appreciated Sensei's excellent point that for every mole of carbon dioxide you remove from the lake via lime, you release one to the atmosphere in the making of that lime?

The carbon dioxide in the atmosphere isn't the problem.
Massive sudden releases of concentrated dense gas that displace oxygen are the problem.

3 hours ago, Strange said:

I would be rather concerned that dumping all that in the lake would destabilise it and cause the very problem you are trying to solve.

I agree- you have pointed out that it's the equivalent to the world's biggest "mentos in coke" stunt.

[Sensei]

12 hours ago, ScienceNostalgia101 said:

Yeah, I was thinking add it gradually, and find some way to store the CO2

The easiest thing would be to let microorganisms consume it and build their cells and sugar, which eventually could be fermented to produce ethanol, and release more CO₂ (which will be reused by microorganisms in 1st stage).. Ethanol would have organic origin, so it could be consumed, or used as a cheap fuel, or used to produce acetylene C₂H₂, which could be used in e.g. chemistry industry as precursor to e.g. plastic.

[Silvestru]

Sensei is on fire in this thread. I am aware that this a more complicated subject and more research has to go into this but you are bringing up some very good points.

[ScienceNostalgia101]

6 hours ago, Sensei said:

The easiest thing would be to let microorganisms consume it and build their cells and sugar, which eventually could be fermented to produce ethanol, and release more CO₂ (which will be reused by microorganisms in 1st stage).. Ethanol would have organic origin, so it could be consumed, or used as a cheap fuel, or used to produce acetylene C₂H₂, which could be used in e.g. chemistry industry as precursor to e.g. plastic.

That actually sounds like a pretty damn good idea.

 

Would any of us be entitled to a slice (however small) of the profits if they ever used it?

[John Cuthber]

The easiest (and by far the safest) thing to do is move anything you care about away from the lake. However that's expensive.

It is absurd to imagine that the lake water does not contain microorganisms which are using the CO2- but they can only do so at a rate governed by the energy provided by the Sun.
And they are probably fairly near to either that limit, or to some other limiting  factor.

Good luck extracting  alcohol from a lake.
You may find this interesting

https://en.wikipedia.org/wiki/Vinegar#Production

It's not a simple problem
https://en.wikipedia.org/wiki/Lake_Kivu

Edited August 21, 2018 by John Cuthber

[StringJunky]

Quote

Degassing

Efforts are under way to develop a solution for removing the gas from these lakes and to prevent a build-up which could lead to another catastrophe. A team led by French scientist Michel Halbwachs began experimenting at Lake Monoun and Lake Nyos in 1990 using siphons to degas the waters of these lakes in a controlled manner.[7] The team positions a pipe vertically in the lake with its upper end above the water surface. Water saturated with CO2 enters the bottom of the pipe and rises to the top. The lower pressure at the surface allows the gas to come out of solution. Only a small amount of water must be mechanically pumped initially through the pipe to start the flow. As saturated water rises, the CO2 comes out of solution and forms bubbles. The natural buoyancy of the bubbles draws the water up the pipe at high velocity resulting in a fountain at the surface. The degassifying water acts like a pump, drawing more water into the bottom of the pipe, and creating a self-sustaining flow. This is the same process which leads to a natural eruption, but in this case it is controlled by the size of the pipe.

Each pipe has a limited pumping capacity and several would be required for both Lake Monoun and Lake Nyos to degas a significant fraction of the deep lake water and render the lakes safe. The deep lake waters are slightly acidic due to the dissolved CO2 which causes corrosion to the pipes and electronics, necessitating ongoing maintenance. There is some concern CO2 from the pipes could settle on the surface of the lake forming a thin layer of unbreathable air and thus potentially causing problems for wildlife.

In January 2001, a single pipe was installed by the French-Cameroun team on Lake Nyos, and two more pipes were installed in 2011 with funding support from the United Nations Development Programme.[8][9] A pipe was installed at Lake Monoun in 2003 and two more were added in 2006.[8][9] These three pipes are thought to be sufficient to prevent an increase in CO2 levels, removing approximately the same amount of gas that naturally enters at the lake bedcitation needed. In January 2003, an 18-month project was approved to fully degas Lake Monoun,[10] and the lake has since been rendered safe.[8]

https://en.wikipedia.org/wiki/Limnic_eruption

All I can say is"wow". I've never heard of this phenomenon before. The lake is 450m deep and lake bed pressure is about 45 atmospheres at around 24C; a can of Coke  holds just over 2 atmospheres of pressure at 20C, for comparison.

Edited August 21, 2018 by StringJunky