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Old 06-24-2019, 08:48 AM
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Could we suck out CO2 from atmosphere?


If we had cheap, unlimited source of energy would it be viable to actively remove CO2 from atmosphere on a large scale?
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Old 06-24-2019, 08:53 AM
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I read a book a month ago or so (wish I could recall the title) that pointed out that while this is certain technically possible as a way of dealing with climate change, it is prohibitively expensive using today's technology. It would cost $30 trillion or more, or some figure like that.
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Old 06-24-2019, 09:13 AM
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If we had some magical cheap, unlimited source of energy we wouldn't be producing much CO2 in the first place. We would use that magical cheap and unlimited source of energy in place of most of our fossil fuels. That would drastically reduce the amount of CO2 you'd need to scrub from the atmosphere.
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Old 06-24-2019, 09:14 AM
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If we had cheap, unlimited source of energy would it be viable to actively remove CO2 from atmosphere on a large scale?
This is exactly what plants do: they take cheap, unlimited solar energy and pull CO2 from the atmosphere to make biomass. I'm not presenting that fact to be a smartass: biosequestration is being promoted as a real tool for deliberately reducing atmospheric CO2 levels.
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Old 06-24-2019, 09:16 AM
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There are companies working right now trying to develop cost-effective direct carbon capture. (Sucking CO2 out of the atmosphere.) Probably the most promising one right now is Carbon Engineering which has Bill Gates (and several oil companies) among its investors. They use big giant fans and a proprietary chemical process to remove CO2 from the air and turn it into calcium carbonate. Then the carbonate is heated to release the CO2 into a controlled collection mechanism.

It does take a lot of energy. And there's still the matter of what you do with the CO2 once you have it.

Their prototype plant does appear to work, though, and they are working on scaling it up to a full-size demonstration plant.
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Old 06-24-2019, 09:37 AM
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If we had some magical cheap, unlimited source of energy we wouldn't be producing much CO2 in the first place. We would use that magical cheap and unlimited source of energy in place of most of our fossil fuels. That would drastically reduce the amount of CO2 you'd need to scrub from the atmosphere.
This.

Also, if course it's possible to remove CO2 from the atmosphere, but even with cheap unlimited energy, it will still be expensive, and there is no financial incentive for anyone to make that investment.
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Old 06-24-2019, 09:41 AM
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There are a huge number of technologies which could be used to solve the climate change problem--the question is which are the most cost effective. Sucking CO2 out of the atmosphere is certainly one of the technologies being researched. At currently cost levels it is not cost effective. Currently wind, solar and energy efficiency measures are the most cost effective and are where massive amounts of money should now be spent--however they will only partially solve the problem--so sucking CO2 out of the atmosphere could turn out to be one of the later solutions.

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If we had some magical cheap, unlimited source of energy we wouldn't be producing much CO2 in the first place. We would use that magical cheap and unlimited source of energy in place of most of our fossil fuels.
If those energy sources are solar and wind then those won't work when the sun isn't shining and the wind isn't blowing. And using excess solar and wind power to suck out CO2 might be more cost effective than massive electricity storage systems--batteries...

Last edited by PastTense; 06-24-2019 at 09:46 AM.
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Old 06-24-2019, 09:41 AM
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This is exactly what plants do: they take cheap, unlimited solar energy and pull CO2 from the atmosphere to make biomass. I'm not presenting that fact to be a smartass: biosequestration is being promoted as a real tool for deliberately reducing atmospheric CO2 levels.
The problem is, any CO2 removed by plants will come right back into the atmosphere as soon as the plant decomposes or burns. So we need to take the plant mass and put them where they don't decompose.

Ironically, if we stop recycling paper and put them in landfills instead, that would help. Though the amount would be negligible.
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Old 06-24-2019, 10:10 AM
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Is there a downside to biosequestration? Assuming that it's done conscientiously, without bringing in invasive species, would it still be possible to, say, drive out desert-dwelling critters out of their habitats? Or suck too much CO2 out of the atmosphere and created a different climate problem?
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Old 06-24-2019, 10:23 AM
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The problem is, any CO2 removed by plants will come right back into the atmosphere as soon as the plant decomposes or burns. So we need to take the plant mass and put them where they don't decompose.
Much of the surface biomass decomposes relatively quickly. But not all of it. And it depends on the plant and local environment. Root systems are more persistent. Soil and its associated organic carbon can accumulate.
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Old 06-24-2019, 10:26 AM
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The OP asks if this method is "viable", which is a word I usually mentally add a "financially" in front of. Right now it is not. With some carbon credit/tax/something, it could be. But that depends on the details. Air is ~400 ppm CO2. More concentrated streams are cheaper to concentrate.
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Old 06-24-2019, 10:30 AM
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The better question is what couldn't be done if we had a cheap, unlimited source of energy. That would be a very short list.
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Old 06-24-2019, 10:33 AM
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I read a book a month ago or so (wish I could recall the title) that pointed out that while this is certain technically possible as a way of dealing with climate change, it is prohibitively expensive using today's technology. It would cost $30 trillion or more, or some figure like that.
It would be nice to know more about this. We find money like this to fund other objectives. Climate change would seem to be much more important.
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Old 06-24-2019, 10:33 AM
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The problem is, any CO2 removed by plants will come right back into the atmosphere as soon as the plant decomposes or burns. So we need to take the plant mass and put them where they don't decompose.
However, converting atmospheric CO2 into long-lived trees (that are not harvested) at least stores it for some centuries, as does using wood to build houses, furniture, and other long-term uses. Also, although burning new biomass for energy won't reduce CO2 in the atmosphere, it at least can replace fossil fuels to some extent and reduce the amount of new CO2 entering the atmosphere.

At this point, the problem of excess CO2 in the atmosphere is so massive that all technologies for reducing it or at least slowing its increase need to be explored. Direct atmospheric capture is a new technology and at present generally too expensive as an option. However, further research may bring costs down.
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Old 06-24-2019, 10:52 AM
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DAC is hardly new. It's just not attractive to most people building a carbon capture system today because there are plenty of easier sources to concentrate than air.
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Old 06-24-2019, 11:05 AM
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The problem is, any CO2 removed by plants will come right back into the atmosphere as soon as the plant decomposes or burns. So we need to take the plant mass and put them where they don't decompose.
Yep. There is talk of reforestation, burying plant biomass in peat bogs, or sinking it in the ocean. These are all situations where the dead biomass would persist, resulting in some measure of enduring sequestration.
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Old 06-24-2019, 11:05 AM
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The better question is what couldn't be done if we had a cheap, unlimited source of energy. That would be a very short list.
Heat would be an issue. Using energy produces heat as a waste product. It's not a serious issue now because we only have access to a limited amount of energy. But if we had cheap unlimited energy and used it, we'd be producing unlimited heat.
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Old 06-24-2019, 11:13 AM
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You could say that the fossil fuels we're burning now are the result of plant sequestration, but that the sequestration was only temporary, since it's now being re-released as the dead plant matter is being burned.

But "temporary" can still be a very long time, and if we had the energy to do it, we could convert it into forms and put it in places that would last just as long as fossil fuels did.

I don't think that active sequestration is really worth looking at right now, though. Right now, we're burning fossil fuels and releasing CO2 to power lightbulbs etc. If we had a clean energy source that we could use to sequester carbon, it would be better to use that clean energy source to light the lightbulbs instead of using fossil fuels for that. Only once we've scaled up clean energy to the point where we can provide all of our lightbulb needs would it make sense to use it to sequester carbon.
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Old 06-24-2019, 11:22 AM
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If we're digging sequestered carbon in the form of coal and burning it for energy, it makes absolutely zero sense to use energy to pull carbon out of the air and bury it in the ground. We'd be massively better off if we just skipped both steps.

The only form of carbon sequestration that makes sense is to allow forests to grow, and then prevent the burning of the wood in the forests so it doesn't become carbon dioxide again. Active carbon sequestration is a foolish task in a world where we're still digging up and burning millions of tons of coal every year.
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Old 06-24-2019, 11:56 AM
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Is there a downside to biosequestration? Assuming that it's done conscientiously, without bringing in invasive species, would it still be possible to, say, drive out desert-dwelling critters out of their habitats? Or suck too much CO2 out of the atmosphere and created a different climate problem?
So much land has been deforested and converted to other uses that you could reforest previously forested land without needing to plant trees in habitats where they formerly didn't occur. (This said, human afforestation through irrigation or other provision of water can be detrimental to species that are adapted to non-forest conditions.)

There's a lot of land, especially in the tropics, that has been deforested but is not currently in productive use. One option is to allow natural regeneration of secondary forests to occur, although such forests won't have the diversity of the original primary forest.

Sucking "too much" carbon out of the air could cause global cooling, but we are so far from that level that we really don't need to worry about it right now.
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Old 06-24-2019, 12:04 PM
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Heat would be an issue. Using energy produces heat as a waste product. It's not a serious issue now because we only have access to a limited amount of energy. But if we had cheap unlimited energy and used it, we'd be producing unlimited heat.
But just because we had cheap unlimited energy doesn't mean that we'd have to do everything and all at once. Though it would be exactly like humans to try.
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Old 06-24-2019, 12:55 PM
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If we had some magical cheap, unlimited source of energy we wouldn't be producing much CO2 in the first place. We would use that magical cheap and unlimited source of energy in place of most of our fossil fuels. That would drastically reduce the amount of CO2 you'd need to scrub from the atmosphere.
Not necessarily. For example, the problem of intermittent wind and solar, which creates real difficulties when trying to use it as grid power, is absolutely irrelevant to a project to sequester CO2. All you need care about is annual averages. Just build a system that can ramp up and down as available power fluctuates.

You could also put such a facility in a place like the Sahara desert, which gets huge amounts of sun energy but is a long way from consumers. So bring the consumer to the Sahara.

This could also be a good way to skip the NIMBY problem with nuclear, as you could build a sequestering facility far, far away from people, and power it with as many nuclear plants as you need. Somewhere up on the Canadian Shield in the sparsely settled areas, for example.

The problem is really one of scale. The amount of CO2 we are talking about is massive. If we want to freeze CO2 rise, we would need to scrub about 2.3ppm of CO2 out of the atmosphere per year. A rough back of the envelope estimate is that would require sequestering roughly 20 billion tonnes of Co2 every year. The cost of sequestration is right now around $100 per ton. Let's say that we can figure out how to cut that in half with a massive project. That's a trillion dollars per year.

Then there's the problem of where to store it all. Socking away 20 billion tons of material per year sounds pretty difficult. And anything we do to process or convert it or bind it with something will raise costs and energy requirements.

Still, we should be open to this option if we can make it work. The price of carbon is currently around $20/tonne. If we could get carbon capture anywhere near that cost, we might be able to make it work, and it would be a lot less disruptive to the economy and the political order than the other options, which will ultimately require extensive taxes on carbon, global tariffs and other coercive means.

But as of today, I don't think it's feasible to just sequester the stuff..
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Old 06-24-2019, 01:12 PM
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Well, yeah, of course you can suck carbon out of the air - that's where all that coal and oil originally came from, after all. Plants split CO2 into carbon (which they used to make their bodies) and oxygen (which aerobic animals and other things used to breathe). This reduced the total carbon dioxide in the atmosphere.

Then we went and dug up a lot of that coal and oil and recombined it with oxygen in a process called "burning" which re-created carbon dioxide, pumping up the level of it in the atmosphere to a degree not seen for hundreds of millions of years.

Eventually plants will do the same thing again if we leave them alone... for millions of years. Which is unlikely.

Then there are chemical and mechanical processes for pulling CO2 out of the air, which only cost money and energy.

It's definitely possible. The real question is whether or not the process(es) are affordable and if we can scale them up to work in a time frame smaller than "geological".
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Old 06-24-2019, 01:14 PM
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Heat would be an issue. Using energy produces heat as a waste product. It's not a serious issue now because we only have access to a limited amount of energy. But if we had cheap unlimited energy and used it, we'd be producing unlimited heat.
Compared to the amount of solar energy the Earth takes in each year, the waste heat we could produce is trivial. Total global annual energy production is around 22,000 TWh. It takes the sun a little more than an hour to provide Earth with that much energy. And of that energy we produce, most of it goes into doing other work than producing heat. Making concrete, for example. Or moving people and goods around. All work produces waste heat, but not 100%.

Also, if you heat the surface artificially, most of that heat will eventually escape into space. Earth's overall energy balance is totally dominated by the sun and the atmosphere's heat trapping ability. Human heat output is a rounding error, unless it changes the atmosphere, cloud cover, etc.

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Old 06-24-2019, 01:25 PM
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CleanTechnica has a few articles on this topic:

Chevron’s Fig Leaf Part 1: Carbon Engineering Burns Natural Gas To Capture Carbon From The Air

Best Carbon Capture Facility In World Emits 25 Times More CO2 Than Sequestered

They have more articles and links to them are in those two.
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Old 06-24-2019, 01:32 PM
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But just because we had cheap unlimited energy doesn't mean that we'd have to do everything and all at once. Though it would be exactly like humans to try.
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Compared to the amount of solar energy the Earth takes in each year, the waste heat we could produce is trivial.
I was pointing out there is an upper limit even if we assume unlimited energy is available. The amount of CO2 in the atmosphere is huge. Clearing it out by some mechanical means would be the biggest engineering project in history. At that kind of scale, waste heat would become significant. Effects you can ignore in a prototype can become a problem when you expand a billionfold.
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Old 06-24-2019, 01:45 PM
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I was pointing out there is an upper limit even if we assume unlimited energy is available. The amount of CO2 in the atmosphere is huge. Clearing it out by some mechanical means would be the biggest engineering project in history. At that kind of scale, waste heat would become significant. Effects you can ignore in a prototype can become a problem when you expand a billionfold.
We're not talking about a billion-fold increase in energy, though. As I pointed out above, Global energy production is equivalent to about one hour's worth of solar irradiance. And power plants are 30-60% efficient thermally, so maybe half that produced power goes to doing useful work and not waste heat.

Sequestering all the co2 we produce would not double our power production, so it's still a rounding error. It may not be feasible, but not because of the heat it would generate.

You are of course correct that even if energy were free there would be an upper limit. But that limit is so far away that we can't fathom reaching it with any known technology of thr near or medium future.

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Old 06-24-2019, 02:54 PM
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I think when bio-sequestration is talked about earlier in the thread, it is assumed that it has to be land based.

Well avoid 71% of earth is covered with water and much of the oceans are deserts.

So there is this controversial idea going around where they want to use the oceans for bio-sequestration. https://www.scientificamerican.com/a...s-controversy/

It seems the guy behind this did an experimental ocean revival in Canada with some success.
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Old 06-24-2019, 04:03 PM
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Quoth Sam Stone:

All work produces waste heat, but not 100%.
I'm having a difficult time thinking of any sort of useful work that doesn't result in 100% waste heat. Like, you mention moving people and goods around: OK, so you turn chemical energy into kinetic energy. But then what happens to that kinetic energy? If you're not keeping the vehicle moving forever, then all of that kinetic energy will end up getting turned into some other form. Which is almost guaranteed to be waste heat.
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Old 06-24-2019, 04:24 PM
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Then there's the problem of where to store it all. Socking away 20 billion tons of material per year sounds pretty difficult. ....
Old mines, especially old coal mines. Storing it isnt a issue, actually. Getting it out of the air is the tough part.

I saw some plans for little devices, solar powered, that sucked carbon out and it was just dumped on the ground as fine dust that blows away. We'd need thousands and thousands of them.

However, this may be the way to go, even if we can cut back Carbon emissions. We need to work on it.
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Old 06-24-2019, 04:42 PM
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I'm having a difficult time thinking of any sort of useful work that doesn't result in 100% waste heat. Like, you mention moving people and goods around: OK, so you turn chemical energy into kinetic energy. But then what happens to that kinetic energy? If you're not keeping the vehicle moving forever, then all of that kinetic energy will end up getting turned into some other form. Which is almost guaranteed to be waste heat.
In the case of a car, pretty much. You could claim that some energy goes into things like tire wear, but yeah.

BUt other things are not like that. You can burn energy to convert a material into something else through an endothermic reaction. Making concrete takes a lot of energy, some of which is left in the form of the concrete.

Or as another example, it takes energy to charge a battery. Or to make a chemical or product that could burn and release the energy that went into making it. And some heat is always lost in the process of creation - a battery has internal resistance, and will warm up as you heat it, and again when you discharge it. But some goods may hold onto to their energy for a very long time.

In the end, in the very long term, you can't escape entropy. So yes, eventually all energy devolves down to heat.

The point remains that the amount of energy we create is trivial compared to the amount the sun bathes on the Earth, and if the Earth's equilibrium temperature is set by the atmosphere, adding heat will just cause the radiation of heat from Earth to increase, unless the added heat changes the atmosphere (say, by changing cloud cover). How much and how fast, I don't know.
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Old 06-24-2019, 04:45 PM
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Old mines, especially old coal mines. Storing it isnt a issue, actually. Getting it out of the air is the tough part.

I saw some plans for little devices, solar powered, that sucked carbon out and it was just dumped on the ground as fine dust that blows away. We'd need thousands and thousands of them.

However, this may be the way to go, even if we can cut back Carbon emissions. We need to work on it.
Do you have any idea HOW MUCH CO2 we're talking about?

Imagine the infrastructure we have today for moving fossil fuels around. All the pipelines, the tanker ships, tank farms, yada yada. Now imagine having to get rid of a waste product THREE TIMES that size. Because a gallon of gas (about 6.3 lbs) produces about 20 lbs of CO2. And depending on the form, the CO2 may be much more bulky per unit weight. And we have to find space for all that every year, year in and year out.

And, you'll probably have to bind it with something to make something stable you can deal with. Because if we pumped Co2 directly into huge underground caverns and empty oil formations and such, we would have to worry about catastrophic releases.

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Old 06-24-2019, 04:51 PM
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Do you have any idea HOW MUCH CO2 we're talking about?

Imagine the infrastructure we have today for moving fossil fuels around. All the pipelines, the tanker ships, tank farms, yada yada. Now imagine having to get rid of a waste product THREE TIMES that size. Because a gallon of gas (about 6.3 lbs) produces about 20 lbs of CO2. And depending on the form, the CO2 may be much more bulky per unit weight. And we have to find space for all that every year, year in and year out.

And, you'll probably have to bind it with something to make something stable you can deal with. Because if we pumped Co2 directly into huge underground caverns and empty oil formations and such, we would have to worry about catastrophic releases.
We're not moving CO2, we're moving just the carbon. leaving the 0xygen back in the atmosphere.
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Old 06-24-2019, 05:00 PM
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We're not moving CO2, we're moving just the carbon. leaving the 0xygen back in the atmosphere.
Are the proposed processes doing that? Or do we have to account for the energy of cracking the Co2 and binding the carbon with something else?

I guess I better do some reading. I was under the impression that the CCS programs I've seen were actually dealing with CO2. I saw one proposal that suggested deep ocean burial, which would turn the CO2 in a clathrate or something.
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Old 06-24-2019, 05:32 PM
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Are the proposed processes doing that? Or do we have to account for the energy of cracking the Co2 and binding the carbon with something else?

I guess I better do some reading. I was under the impression that the CCS programs I've seen were actually dealing with CO2. I saw one proposal that suggested deep ocean burial, which would turn the CO2 in a clathrate or something.

There are different proposals. Just sequestering the CO@ is the easiest, but taking Carbon out of the atmosphere is more elegant.
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Old 06-24-2019, 06:09 PM
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Do you have any idea HOW MUCH CO2 we're talking about?

Imagine the infrastructure we have today for moving fossil fuels around. All the pipelines, the tanker ships, tank farms, yada yada. Now imagine having to get rid of a waste product THREE TIMES that size. Because a gallon of gas (about 6.3 lbs) produces about 20 lbs of CO2. And depending on the form, the CO2 may be much more bulky per unit weight. And we have to find space for all that every year, year in and year out.

And, you'll probably have to bind it with something to make something stable you can deal with. Because if we pumped Co2 directly into huge underground caverns and empty oil formations and such, we would have to worry about catastrophic releases.
I am kinda boggled a bit on this. How does burning 6.3 pounds of gas make 20 pounds of co2? Is it taking more than three times the weight in oxygen from the air? My understanding is that burning a hydrocarbon cleanly and efficiently gives you water and co2. How many pounds of water do you get from 6.3 gallons of gasoline?

Sorry, I'm a little lost on this.
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Old 06-24-2019, 06:24 PM
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And, you'll probably have to bind it with something to make something stable you can deal with. Because if we pumped Co2 directly into huge underground caverns and empty oil formations and such, we would have to worry about catastrophic releases.
Several of the proposals involve reacting the CO2 with underground rock formations to produce carbonates, or using unmineable coal seams to absorb it. Such formations are extensive enough to absorb CO2 in the kind of volumes envisaged.
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Old 06-24-2019, 06:31 PM
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OK, let's work this out. For the sake of calculation, let's say that the gasoline is pure octane, C8H18. The balanced combustion equation would be

2 C8H18 + 25 O2 -> 16 CO2 + 18 H2O .

Each carbon atom has a mass of 12u, each oxygen atom 16u, and each hydrogen atom 1u. So the left side of that equation has 228u of octane and 800u of oxygen, and the right side has 704u of carbon dioxide and 324u of water (total of 1028u either way). 704/228 = 3.09, so each kilogram (or pound or whatever) of octane produces 3.09 kilograms (or pounds or whatever) of carbon dioxide. If I multiply that by 6.3 pounds of octane, I get 19.5 pounds of carbon dioxide, close enough to Sam Stone's figure of 20 (there might be some rounding there, or his numbers might be based on the real-world composition of gasoline instead of pure octane).
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Old 06-24-2019, 06:37 PM
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Quote:
Originally Posted by Translucent Daydream View Post
I am kinda boggled a bit on this. How does burning 6.3 pounds of gas make 20 pounds of co2? Is it taking more than three times the weight in oxygen from the air? My understanding is that burning a hydrocarbon cleanly and efficiently gives you water and co2. How many pounds of water do you get from 6.3 gallons of gasoline?

Sorry, I'm a little lost on this.
Yes, it's because oxygen from the air is combined with the carbon during combustion to create the CO2. You get about 7 lbs of water from a gallon of gas when it's burned. It comes out the tailpipe mostly as water vapor, as the hot exhaust can hold a lot of water in saturation. On cool days you'll see it condense in the air. You can also often see residual water dripping from the tailpipe of a car.

The inability to pull oxygen out of the air is one of the reasons why batteries have such low energy density - they have to carry their own oxidizer. Internal combustion engines just pull in the oxygen they need from the atmosphere - or have it forced in with turbochargers/superchargers. The more power you want, the more air you have to consume.

There are batteries that can pull their oxygen from the environment - zinc/air batteries, for example. But they have a lot of engineering problems we haven't solved at large scales.
  #40  
Old 06-24-2019, 06:38 PM
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Originally Posted by Chronos View Post
OK, let's work this out. For the sake of calculation, let's say that the gasoline is pure octane, C8H18. The balanced combustion equation would be

2 C8H18 + 25 O2 -> 16 CO2 + 18 H2O .

Each carbon atom has a mass of 12u, each oxygen atom 16u, and each hydrogen atom 1u. So the left side of that equation has 228u of octane and 800u of oxygen, and the right side has 704u of carbon dioxide and 324u of water (total of 1028u either way). 704/228 = 3.09, so each kilogram (or pound or whatever) of octane produces 3.09 kilograms (or pounds or whatever) of carbon dioxide. If I multiply that by 6.3 pounds of octane, I get 19.5 pounds of carbon dioxide, close enough to Sam Stone's figure of 20 (there might be some rounding there, or his numbers might be based on the real-world composition of gasoline instead of pure octane).
I was approximating 20 lbs because in the real world there are many gasoline compounds, plus diesel, avgas, Jet fuel, etc. Some are higher than others. But 20 lbs is close enough.

Last edited by Sam Stone; 06-24-2019 at 06:40 PM.
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Old 06-24-2019, 06:43 PM
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That helps me see whats up. Thanks Sam and Chronos.
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Old 06-24-2019, 06:49 PM
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Roughly, hydrocarbons (gasoline) weigh a bit more than the carbon in them, the hydrogen not so much. Carbon has molecular weight around 12: oxygen around 16, CO2 around 44, which is 3.7 times as much as carbon: 6 pounds of carbon gives around 22.

Allowing for the hydrogen, 6 pounds of gasoline gives 20 pounds of CO2, so that sounds about right.

(Edit: damn, what are you all doing here at this time of day. Hang on, what am I doing here at this time of day?)

Last edited by Melbourne; 06-24-2019 at 06:50 PM.
  #43  
Old 06-24-2019, 07:02 PM
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...would it be viable to actively remove CO2 from atmosphere on a large scale?
This article (Hanson, 2013) discusses this. It would apparently cost from $50 trillion to $200 trillion to capture and reduce atmospheric CO2 by 50 ppm: https://journals.plos.org/plosone/ar...l.pone.0081648

The referenced 2012 article by the American Physical Society was "Direct Air Capture of CO2 with Chemicals: A Technology Assessment for the APS Panel on Public Affairs"

https://www.aps.org/policy/reports/a...ad/dac2011.pdf
  #44  
Old 06-24-2019, 07:19 PM
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NETL estimates we have domestic geological capacity for 3 to 22 trillion metric tons -- far more than we've released since the start of the industrial revolution. And that's just in the US.
I'm LOLing at the idea of converting any of this to oxygen and carbon black. Then we'll have a "where do we put it" problem. We were joking at work about stuffing it back into old mined coal seams.
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Old 06-24-2019, 07:26 PM
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Several of the proposals involve reacting the CO2 with underground rock formations to produce carbonates, or using unmineable coal seams to absorb it. Such formations are extensive enough to absorb CO2 in the kind of volumes envisaged.
That sounds a like a great idea.
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Old 06-24-2019, 08:54 PM
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Chemical plants have been capturing CO2 and sequestering it for decades now. Every time you make Urea, CO2 + 2NH3 ó> CO(NH2)2 + H2O, you are capturing CO2.

The Dakota gasification plant converted low rank coal to synthetic natural gas and pumped CO2 to Canadian oil fields for enhanced oil recovery.

A big economic and engineering factor, missing in the discussion is the purification of CO2 removed either from flue gas or from the atmosphere. For example, CO2 needs to be bone dry to flow through pipes otherwise it will eat the pipes up. Cleaning up CO2 needs energy which seems to be missing from a lot of papers cited above.
  #47  
Old 06-25-2019, 01:32 PM
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Probably the most promising one right now is Carbon Engineering which has Bill Gates (and several oil companies) among its investors.
Here is a video about that project that was released a few days ago.
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  #48  
Old 06-25-2019, 03:31 PM
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Quote:
Originally Posted by Velocity
while this is certain technically possible as a way of dealing with climate change, it is prohibitively expensive using today's technology. It would cost $30 trillion or more, or some figure like that.
It would be nice to know more about this. We find money like this to fund other objectives.
We don't, really. The entire cost of the Iraq/Afghanistan war so far, for example, is estimated at around 6 trillion dollars, and that's over fifteen years. The combined annual GDP for the entire world is something like 80 trillion dollars.

Which three-eighths of the total yearly economic activity of the whole world do you suggest we could do without to get the $30T for this endeavor? Even a six-billion-dollar Mars mission is just couch-cushions change compared to this kind of money. (And don't forget that unless we massively reduce our greenhouse-gas emissions, we'd have to keep doing this expensive atmospheric CO2 removal indefinitely if we want to control climate change.)
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Old 06-25-2019, 05:52 PM
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The problem is, any CO2 removed by plants will come right back into the atmosphere as soon as the plant decomposes or burns. So we need to take the plant mass and put them where they don't decompose.

Ironically, if we stop recycling paper and put them in landfills instead, that would help. Though the amount would be negligible.
Total mass of carbon dioxide in the atmosphere is roughly 3,200 billion metric tonnes. Total world paper production is about 400 million metric tonnes.

If we bury all the world's paper production for the next 4,000 years we'd halve the carbon dioxide in the atmosphere! (Assuming of course that the paper production and burial is a carbon zero process...)
  #50  
Old 06-25-2019, 06:20 PM
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That's almost exactly the same amount of plastic that's created each year. And plastic sequesters carbon, but again the amount is trivial compared to how much CO2 we emit.
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