BIENT: CO2 Sequestration: Is Burying CO2 Safe?

[Andrew Mason]

There is a big move in the fossil fuel industry, particularly coal, to solve the problem of green-house gas emissions by sequestering CO₂ in the Earth in geological formations that are believed to be stable. This gives rise to a number of questions to which I would like to see comments, particularly from regular posters to this board.

1. Is burying CO₂ really a reliable way to prevent it from entering the atmosphere? Since a concentration of 5% CO₂ will kill a human being, and since CO₂ is heavier than air, a release of CO₂ from one of these storage seams could be an environmental and human disaster.

2. Since we would be burying an O₂ with each C, we would be permanently depleting the atmosphere of Oxygen as well. In the normal carbon cycle, this O₂ would make its way back into the atmosphere eventually. Not so if it is buried. What are the environmental implications of this? I have not seen any mention of this anywhere.

AM

 

[Andre]

What can I say.

First of all, there are a number of people, who still think that also greenhouse gasses should follow physical laws and due to saturation effects an increase of global temperature due to a higher concentration of CO₂ is very small. Therefore the current warming should have another cause, be it anthropogenic or natural. Possible candidats are:

- decadal scale changes in cloud cover (albedo) which are actually measured.

- decadal to century scale solar activity governing cloud forming, (phytoplankton seems to do the same: http://www.physorg.com/news82115682.html )

- High troposphere water vapor due to aviation

- Albedo land change.

Next, CO2 of course is the most basic building block of life, the fuel for photo synthesis. As the element carbon is cycling in the biosphere, large amounts are semi permanently tied to calcium oxide forming limestone rocks. Therefore the amount of available carbon tends to decrease until some catastrophe (Vulcano or so) recycles the limestone back to CO₂ and calcium. So carbon dissapears naturally and in doing so reduces the available biomass. Therefore, speeding up that process by sequestering CO₂ will once be known as the singlemost stupid action ever.

But it's happening already for years on a smaller scale. It's used to re-pressurize oil and natural gas fields, and increase the production of thouse fossil fuels. Oil industries will probably have nice dreams of doing that for their own production process and being paid for it as well.

I don't think that the dangers are bigger than natural releases of CO₂ that happen every once and a while.

 

[Bystander]

(snip)1. Is burying CO₂ really a reliable way to prevent it from entering the atmosphere?

No.

Since a concentration of 5% CO₂ will kill a human being, and since CO₂ is heavier than air, a release of CO₂ from one of these storage seams could be an environmental and human disaster.

No.

2. Since we would be burying an O₂ with each C, we would be permanently depleting the atmosphere of Oxygen as well.

No.

In the normal carbon cycle, this O₂ would make its way back into the atmosphere eventually. Not so if it is buried.

No.

What are the environmental implications of this?

None.

 

[Andrew Mason]

No. No. No. No. No.
None.

So are you saying that oxygen is not removed from the atmosphere or that it is not a problem because there is so much of it?

And why would not a release of CO₂ be a concern to human safety? Is it because it would not escape quickly or because it would not result in unsafe concentrations?

AM

 

[Bystander]

So are you saying that oxygen is not removed from the atmosphere or that it is not a problem because there is so much of it?

I'm saying that it's unwise to marry the "all atmospheric oxygen is derived from photosynthesis" model that has become a cornerstone of grade school Earth science.

And why would not a release of CO₂ be a concern to human safety? Is it because it would not escape quickly or because it would not result in unsafe concentrations?

Both. There are no gas tight formations that are permeable enough to be used for storage; they'll be leaking like sieves, carbonating ground water, blowing sand in the air ten miles away, cracking foundations, and being enough a general nuisance to keep the ABA fully employed for centuries.

 

[Andrew Mason]

I'm saying that it's unwise to marry the "all atmospheric oxygen is derived from photosynthesis" model that has become a cornerstone of grade school Earth science.

So what is wrong with the theory that the carbon in the ground came from higher levels of CO₂ in the atmosphere? What other explanation is there?

Both. There are no gas tight formations that are permeable enough to be used for storage; they'll be leaking like sieves, carbonating ground water, blowing sand in the air ten miles away, cracking foundations, and being enough a general nuisance to keep the ABA fully employed for centuries.

This is an interesting comment. Data from injecting CO₂ into the oil reservoirs in southern Saskatchewan shows that the CO₂ increases the concentration of bicarbonate and this causes a dramatic increase in concentration of CO₂ in the ground- apparently a 10 fold increase. I am not sure what this means. But if by injecting CO₂ into the ground we are actually increasing by 10 fold the amount of CO₂ that could leak out of the ground, I am thinking this may not be a good idea.

AM

 

[LURCH]

I think that most of the CO₂ slated for sequestration is the same gas being released by mining and drilling, so I don't think there's much reason to fear depletion. We're not talking about taking the naturally-occurring carbon out of the air, only reducing the rate at which we are artificially adding carbon to the air.

 

[Andrew Mason]

I think that most of the CO₂ slated for sequestration is the same gas being released by mining and drilling, so I don't think there's much reason to fear depletion. We're not talking about taking the naturally-occurring carbon out of the air, only reducing the rate at which we are artificially adding carbon to the air.

Well the idea is to use the CO₂ produced by burning coal or other fossil fuels and put it into the ground rather than the atmosphere.

AM

 

[LURCH]

Ah yes. So the CO₂ being put into the ground is the same that is being taken out of the ground and released into the air by man. So the same principle applies, the CO₂ being put into the ground will not create a change in the atmosphere, it will only minimize the change that is being caused by mining the carbon and burning it for fuel.

 

[Andrew Mason]

Ah yes. So the CO₂ being put into the ground is the same that is being taken out of the ground and released into the air by man. So the same principle applies, the CO₂ being put into the ground will not create a change in the atmosphere, it will only minimize the change that is being caused by mining the carbon and burning it for fuel.

Except that the CO₂ being put in the ground includes the O₂ that was taken from the atmosphere. So not only is the C being removed from the biosphere in being reinterred, oxygen is being removed.

It appears that no one has been looking at the long term effect of removing O₂ from the atmosphere.

If the primordial atmosphere was rich in CO₂, as the current scientific consensus seems to be (I don't know how else one could explain the enormous amount of fossil carbon in the earth), our current abundance of O₂ comes from the capture (and subsequent interrment) of the C and the release of the O₂ from the CO₂into the atmosphere (by photosynthesis).

If we were to burn all of the fossil carbon and introduce the CO₂ back into the atmosphere we would recreate the primordial atmosphere. But if, instead of releasing it into the atmosphere, we were to sequester the CO₂ in the earth, we would be reducing the total quantity of gases (ie oxygen) in the atmosphere. I don't see how this can be a sustainable solution.

AM

 

[Bystander]

Two tons of atmospheric oxygen per square meter of Earth's surface implies how much reduced carbon (methane, elemental carbon, cellulose) per square meter? The biological origin of oxygen in the atmosphere gets a little tough to defend once you do the mass balance. Explains the amount of work being done on atmospheric evolution. There are no conclusions from which to go leaping to conclusions.

 

[Andrew Mason]

Two tons of atmospheric oxygen per square meter of Earth's surface implies how much reduced carbon (methane, elemental carbon, cellulose) per square meter? The biological origin of oxygen in the atmosphere gets a little tough to defend once you do the mass balance. Explains the amount of work being done on atmospheric evolution. There are no conclusions from which to go leaping to conclusions.

Two tons of O₂ per m² implies that there could have been a little less than 3 tons of CO₂ per m². Is that not plausible?

AM

 

[Bystander]

Where's the carbon?

 

[Andrew Mason]

Where's the carbon?

Now? It is in the Earth and oceans.

AM

 

[Bystander]

Where's the reduced carbon?

 

[Andrew Mason]

Where's the reduced carbon?

If by reduced carbon you mean chemically reduced carbon, it is in the hydrocarbons buried in the Earth and seabeds.

AM

 

[Bystander]

Half ton of methane, 2/3 ton of elemental C, to 2 tons cellulose per square meter? I say again, "Where is it?"

 

[Ivan Seeking]

There is, however, one additional reservoir of methane about which very little is known: the methane clathrate reservoir in the oceans — the 600-pound gorilla of methane variability!

http://www.giss.nasa.gov/research/features/methane/

 

[Bystander]

"Current best guesses suggest that maybe 500 to 2000 gigatonnes of carbon may be stored as methane clathrates (5-20% of total estimated reserves). Some estimates are as high as 10,000 gigatonnes." That takes care of 4% --- now, where's the rest?

 

[Darryl]

my chemistry might be rusty, but when you mix CO2 and water, you get acid, (sulfuric i think), (or soda water).

acid melts, or dissolves lime stone, (alkline).

so you geosequestrate your co2, a bit of water seeps in, turns to acid, melts the rock, and releases the CO2 !. Soon or later.. !

im from a region, and country that's makes HUGE $$$ mining and exporting coal, and natual gas.
but i believe that if fossel fuels were outlawed tomorrow, or general consumption and power generation, within 6 months, we would have electric cars, and alternative power systems, and reusable fuels to meet our requirements.

there is little incentive to use science and technology, when its just SO CHEAP to dig up and burn coal at 31% efficiency.
releasing CO2 that's been stored in the ground 100% safely for millions of years.

its 2006 now, surly we can do better than dig up rotten plants and animals, liquify it or crush it up and burn it as our primary sources of energy !. future generations will look back at our generation and ask "what were we thinking".

or do we just keep going until we run out, or we have runaway global warning. ? we can't re-run the experiment if it fails.
so you want to make sure your right, for us all !

 

[Bystander]

my chemistry might be rusty, but when you mix CO2 and water, you get acid, (sulfuric i think)

Transmutation of elements? Nope.

, (or soda water).

That's a much better guess.

acid melts, or dissolves lime stone, (alkline).

CaCO₃ + H₂O + CO₂ = Ca(HCO₃)₂

so you geosequestrate your co2, a bit of water seeps in, turns to acid, melts the rock, and releases the CO2 !. (snip)

Nope. You dissolve limestone without release of CO₂. It can be reprecipitated with loss of the CO₂ originally used to dissolve it (sinkholes, karst, caves, stalactites, stalagmites, whitings), and the net changes in atmospheric CO₂ and limestone mass are zero.

 

[Ivan Seeking]

"Current best guesses suggest that maybe 500 to 2000 gigatonnes of carbon may be stored as methane clathrates (5-20% of total estimated reserves). Some estimates are as high as 10,000 gigatonnes." That takes care of 4% --- now, where's the rest?

Could you provide references for all of the specific data cited? You often provide a lot of information without links or any context. And what do other scientists say about this? What is the other side of the debate?

 

[Bystander]

Could you provide references for all of the specific data cited? You often provide a lot of information without links or any context. And what do other scientists say about this? What is the other side of the debate?

The 10¹³ tons? That's your link. You want references for the area of earth? For oxygen content of the atmosphere? Atmospheric pressure? "g" ? Mass of atmosphere? 10¹³ tons/5x10¹⁴m² = 2x10^-2 ton/m²? 2x10^-2/.5 x 100 = 4% ? 2 tons O + x tons C = CO₂, solve for "x" ? General Sci. from middle school/jr. hi..

AM's worried about burying all the oxygen we breathe if the CO₂ sequestration idea gets off the ground. I'm trying to get him to do the mass balance. He hasn't.

 

[Gokul43201]

Going by the 10,000GT from Ivan's link and assuming that resources for all other forms of C put together are cumulatively 3-4 times more plentiful, and then throwing in a little safety factor gets us to about 5-10% of total atmospheric oxygen. Should this be a concern? Will it be a respiratory hazard (1. if this happened overnight; 2. if it happened over decades/centuries) if there's only say 19% oxygen (instead of 21%, or whatever the real number is) ?

Or else, is the 10,000GT for methane likely to be the dominant resource (I don't imagine a one percent change will be noticeably problematic) of all carbon?

EDIT: http://www.biologie.uni-hamburg.de/b-online/e54/54d.htm says there's only 0.25 tons of O2 per sq. meter. That number looks low by an order of magnitude. Someone confirm?

EDIT2: The above link must be wrong. Other places give me numbers closer to 2T/m^2.

 

[Andrew Mason]

There is an article in this month's http://www.dufourlaw.com/physics/co2.pdf" about a huge CO₂ lake at the bottom of the East China Sea, 4600 feet below sea level. The CO₂ is liquid due to the pressure at that depth and appears to be stable.

Perhaps deep ocean burial of CO₂ will work better than sequestering it in the ground.

AM