Ocean outgassing of CO2 slows emissions reductions

[eclipse]

So how bad is it? Would the ocean's need to reach chemical equilibrium as we reduce CO2 emissions undo our good work? Is there a chemical law that says the ocean has to outgas the same amount of carbon that we reduce, so that the ocean reaches equilibrium with the atmosphere? Does it have to outgas the same amount, or only some portion, because the ocean is a liquid and our atmosphere full of gases? Does it happen quickly?

Anyone know?

[grlcowan]

Jul 11, 2013 21:59:51 GMT 9.5 eclipse said:

So how bad is it? Would the ocean's need to reach chemical equilibrium as we reduce CO2 emissions undo our good work? Is there a chemical law that says the ocean has to outgas the same amount of carbon that we reduce, so that the ocean reaches equilibrium with the atmosphere? Does it have to outgas the same amount, or only some portion, because the ocean is a liquid and our atmosphere full of gases? Does it happen quickly?

Anyone know?

CO2 has been accumulating in the atmosphere at about half the rate fossil fuel burners have been adding it. That suggests to me that reductions in net emissions will be about half offset by reductions in the ocean's rate of taking.

The simple way to look at it: we can and should remove from the atmosphere as many CO2 molecules as fossil fuel combustion has added since 1859. Charring plants and deeply burying or sinking the char may be a helpful way to do this, although there can be the temptation to burn the char. Magnesite doesn't burn.

[David B. Benson]

eclipse --- Yes, the oceans will ingas or outgas enough carbon dioxide so as to maintain partial pressure balance with the atmosphere at the ocean surface. The details are complex do to the carbonate reactions in the water. However, actually reducing CO2 in the atmosphere will help to undue the acidification currently taking place in seawater and tend to restore the natural pH; that would be a good thing.

[Roger Clifton]

Eclipse said: "Would the ocean's [outgassing] as we reduce CO2 emissions undo our good work?"

The phrasing of the question conflates reducing greenhouse gas concentrations with reducing the rate at which we emit greenhouse gases.

No one has been able to propose a method of reducing greenhouse gas levels faster than we are adding to them. Not even the oceans are deep enough to trap that growing mass of CO2 for the thousands of years required.

On the other hand, claims that someone gains virtue by reducing their emissions are scientifically fraudulent. While we continue to emit anything at all, no matter how ostentatiously "reduced", we hasten the end of the climate that gave rise to industrial man.

Let's leave the doublespeak to politicians. They make it their job to deceive children into thinking that we are fixing the problem and everything is going to be all right. After all it is they who will one day appear at our bedsides, asking why we let it happen.

[eclipse]

Jul 13, 2013 12:38:35 GMT 9.5 Roger Clifton said:

Eclipse said: "Would the ocean's [outgassing] as we reduce CO2 emissions undo our good work?"

The phrasing of the question conflates reducing greenhouse gas concentrations with reducing the rate at which we emit greenhouse gases.

1. We've got to reduce greenhouse gases which hopefully, one day, will lead to...
2. Creating an industrial ecosystem that is not only carbon neutral, but significantly carbon negative,
3. which leads to the question I'm asking.

There was nothing sneaky or subversive in my question... just maybe a few steps in my thinking not spelled out for you.

[grlcowan]

I can see my posting but apparently no-one else can.

[anonposter]

Jul 13, 2013 23:22:19 GMT 9.5 grlcowan said:

I can see my posting but apparently no-one else can.

I can see it.

[Roger Clifton]

The title of the thread "Ocean outgassing of CO2 slows emissions reductions" embeds a wilful confusion beloved of denialists. It is so misleading and so commonly reasserted that we should call it out as a lie, intended or not. Reducing rates of emission does not reduce GHG levels. The former is the rate at which we worsen the latter, they are not equivalent.

Any notion of somehow reducing greenhouse gas levels in our time is so hopelessly naive we should dismiss it as impossible, lest it become an excuse for continuing to emit. BNC site has examined and reduced to nonsense the many GHG-reducing schemes that have been proposed on it.

For anyone who came in late: almost all of the CO2 that we have emitted is still in the atmosphere and the surface layer of the oceans. The half that is in the atmosphere comprises most of the excess greenhouse gas (GHG) and is the cause of our runaway global warming. There are disasters ahead, inevitable precisely because the greenhouse gases are effectively up there for good. It would take thousands of years for the weathering of rock to reduce those levels, even if we all dropped dead today. But we haven't dropped dead, our industrial society just continues to emit and fiddles with delusions while Rome burns.

[eclipse]

I wonder if anyone else has Roger's problem with the way I tried to cram the issue into a short sentence to start this thread? I certainly never dreamt I would be accused of a denialist tactic! Wow. All I can say is... Roger, have a warm milk and get to bed early. It might not seem so bad in the morning.

[edireland]

The ocean can effectively be used as a giant carbon dioxide scrubber.
One way to trap carbon dioxide is to make cement like materials from calcium carbonate using electric heat (tapping off the pure stream of carbon dioxide made by the process) and then dump it in the sea.

The alkali component will absorb carbon dioxide and fall to the sea bottom as calcium carbonate.
Its probably cheaper in the long run than traditional direct trapping methods, assuming we can get low enough cost energy to do the job.

[eclipse]

Hi edireland, was it you that showed me the desert irrigation paper? I like geo-engineering schemes that have enormous win win win benefits. If we're going to geo-engineer, shouldn't we also look for schemes that produce food, fibre, and some fuel?
eclipsenow.wordpress.com/green-deserts/

[anonposter]

Jul 15, 2013 21:49:12 GMT 9.5 eclipse said:

Hi edireland, was it you that showed me the desert irrigation paper?

That was David B. Benson.

Also I took the liberty of splitting that topic off here.

Jul 15, 2013 21:49:12 GMT 9.5 eclipse said:

I like geo-engineering schemes that have enormous win win win benefits. If we're going to geo-engineer, shouldn't we also look for schemes that produce food, fibre, and some fuel?

Getting something else out of it isn't such a bad idea, though of course if that causes it to cost more you've got to also account for what the benefits would cost another way to determine if it's worth doing that instead of another scheme that may only provide the climate change we desire without any side benefits.

[Roger Clifton]

edireland said: "The ocean can effectively be used as a giant carbon dioxide scrubber. ... make cement .. tapping off ... CO2… then dump it in the sea."

Nope, we can't hide it there either. The cycle time for "intermediate oceanic water" is about 300 years, and as John O'Neill pointed out, the hotter it gets in the future, the faster the ocean will outgas. Far from being a solution, dumping CO2 deep into the oceans would create a timebomb.

One way to reduce CO2 emissions from the making of new cement, is to use the fine material produced when recycling concrete. If ordinary concrete made with Portland cement is heated, it weakens and may be crushed to recover its aggregate. Because the fines have already lost their CO2 during the manufacture of the cement, the reconstituted Portland cement could be clinkered with much lower emissions.

Ironically, high-alumina cement (which is fused) can be made fresh in an electric furnace unlike Portland (which is clinkered), but is stronger after heating than Portland cement, so its concrete is harder to recycle.

[edireland]

Jul 16, 2013 9:07:44 GMT 9.5 Roger Clifton said:

Nope, we can't hide it there either. The cycle time for "intermediate oceanic water" is about 300 years, and as John O'Neill pointed out, the hotter it gets in the future, the faster the ocean will outgas. Far from being a solution, dumping CO2 deep into the oceans would create a timebomb.

You misunderstand, the introduction of the calcium silicate will increase the pH of the ocean, causing the less soluble ions to precipitate out as insoluble salts.
The least soluble common cations in seawater are calcium and magnesium and the least soluble common anion is carbonate.
Therefore the bulk of the precipitated material is either calcium or magnesium carbonate.

The net effect is carbon dioxide moves out of the atmosphere and into the storage tanks downstream of the cement kilns.
Limestone also moves to the bottom of the sea but thats not really important.

Jul 16, 2013 9:07:44 GMT 9.5 Roger Clifton said:

One way to reduce CO2 emissions from the making of new cement, is to use the fine material produced when recycling concrete. If ordinary concrete made with Portland cement is heated, it weakens and may be crushed to recover its aggregate. Because the fines have already lost their CO2 during the manufacture of the cement, the reconstituted Portland cement could be clinkered with much lower emissions.

Ironically, high-alumina cement (which is fused) can be made fresh in an electric furnace unlike Portland (which is clinkered), but is stronger after heating than Portland cement, so its concrete is harder to recycle.

Problem is that that cement has already cured once and thus cannot cure again without being refired, so you don't really gain anything. (Concrete actually slowly absorbs carbon dioxide over the years after it cures, becoming closer and closer in composition to a mix of calcium carbonate and silica)

Using it as aggregate on the hand is useful but not going to save that much energy.

The carbon dioxide trapped from the kilns can be used as a concentrated feedstock for various things including plastics, synthetic fuels or even food (via Pruteen and livestock).

It sets a hard upper limit on the cost of carbon dioxide capture.
(Since to start with you can sell the cement and allow it to soak up carbon over decades while its part of a building).

[Roger Clifton]

Edireland spoke of concrete as a sink for CO2: Concrete hardens by hydration rather than carbonation.

Carbon dioxide does get laid down as carbonates in shallow inland seas, where they may be buried and even subducted. In the open ocean, carbonates such as marine shells re-dissolve as they sink, depositing their carbon dioxide in the so called intermediate water between the mixing layer and the cold bottom water. Any carbonates that reach the abyssal plain tend to redissolve as they descend into the trenches.

Outgassing by parts of the oceans is quite real, but it is caused by warming of tropic-bound currents rather than reduction in GHG partial pressure.

[edireland]

Well since I would assume the calcium silicate would be introduced in coastal waters (since that is where we have access too) it would seem reasonable that most of the resulting carbonates would be laid down in shallow water.

While carbonates that reach the abyssal plain tend to redissolve we have to consider the entire system as a whole, and it appears that adding calcium salts to the ocean will cause calcium salts to exit the oceanic system somewhere, and since the least soluble salts tend to be carbonates this is probably the form which they will be laid down in.
Additionally this process can be encouraged by the deployment of biorock style equipment provided that sufficient low cost energy is available - you could probably even cause the biorock to form ready made polders if you wanted to.

While concrete does initially harden by hydration old concrete will very gradually carbonate, while it is true that if you ground up new concrete you would not find many carbonates, most ground up concrete tends to be decades old and has undergone significant carbonation, drastically reducing your carbon dioxide emissions saving.

Additionally the amount of concrete being ripped up in any one year is a rather small fraction of the amount being manufactured, so it probably won't make any significant difference.

[David B. Benson]

Ocean surface tipping point could accelerate climate change
2023 Mar 02
Phys.org
phys.org/news/2023-03-ocean-surface-climate.html

Stratification with fresher water on the surface slows ocean CO2 uptake.