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.
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…
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”.
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.
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.
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.
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/article/iron-dumping-ocean-experiment-sparks-controversy/
It seems the guy behind this did an experimental ocean revival in Canada with some success.
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.
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.
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.
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.
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.
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.
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.
OK, let’s work this out. For the sake of calculation, let’s say that the gasoline is pure octane, C[sub]8[/sub]H[sub]18[/sub]. The balanced combustion equation would be
2 C[sub]8[/sub]H[sub]18[/sub] + 25 O[sub]2[/sub] -> 16 CO[sub]2[/sub] + 18 H[sub]2[/sub]O .
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).
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.
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.