8 ms·

How much energy does it take to remove CO2? We’re still burning record amounts of coal for energy. https://www.forbes.com/sites/rrapier/2023/09/04/global-coal

How much energy does it take to remove CO2? We’re still burning record amounts of coal for energy. https://www.forbes.com/sites/rrapier/2023/09/04/global-coal-consumption-returns-to-record-levels/amp/ https://www.forbes.com/sites/rrapier/2023/09/04/global-coal-... Will these processes need to wait until we can get the proper amount of renewable energy?

jandrese 3y ago
If you want to turn it back into an oil like substance you will need to expend more energy than you originally got out of it thanks to thermodynamics. In practice it is even worse than that since separating the CO2 from the N2, O2, and everything else in the atmosphere is also energy intensive. The general idea is that you grossly overbuild your renewable energy production (solar and wind mostly) and during the middle of the day when the grid is fully saturated and all of the storage systems are filled up you dump the excess energy into carbon sequestration. This is why people are so angry at NEM 3.0, it's cutting the excess energy production we need as a prerequisite for saving the environment off at the knees.
- panzi 3y ago
  And then you need to pump these giant amounts of CO2 sludge (or whatever form it will have) back where you drilled oil out of, hoping it will stay down. That will cost a lot of energy too.
- tzs 3y ago
  > The general idea is that you grossly overbuild your renewable energy production (solar and wind mostly) and during the middle of the day when the grid is fully saturated and all of the storage systems are filled up you dump the excess energy into carbon sequestration Or you build solar and wind plants specifically for carbon sequestration. Then you don't have to worry about coordinating with the needs of the grid. You don't even need the plants to be on the grid. That frees you up to put them places where there is plenty of wind or solar but no infrastructure transporting electricity which would otherwise by useless for solar and wind currently.
  - AnthonyMouse 3y ago
    California currently gets much of its electricity from a 500 mile long intertie to the Pacific Northwest. There are plenty of plausible places to put a big solar farm which are less than that distance from civilization, e.g. Arizona or Nevada. At which point you want any of its output during peak consumption hours to go to decarbonizing the grid, regardless of what you do with the off-peak.
- elil17 3y ago
  No, this is incorrect. You can absolutely burn hydrocarbons, use the energy to do carbon capture, and end up with less CO2 in the air than when you started. Compressed CO2 is still a lower energy state than the hydrocarbons, so you can get net energy out. You couldn't end up with the same hydrocarbon that you started with, of course - that would violate the laws of thermodynamics.
  - blkhawk 3y ago
    There is no place to store all that - and don't say depleted gas and oil wells since those are ruined as long term storage by whats been done to them to get the oil or gas out. So you need to build the structures to keep 20km³ of liquefied CO2 each year (liquefying also takes energy).
api 3y ago
It must take at least what coal releases when burned, but there are two catches… The first is that it could use intermittent renewable energy. Solar PV during the day is already cheaper than coal. Just run CO2 removal when renewables generate surplus. The second is that coal plants are heat engines. Most of the energy released burning coal is rejected as heat. CO2 removal might in theory be made more efficient than this. So it might not be quite as bad as it appears at first glance. That being said I still doubt this technology could make a dent in the problem without massively cheap energy. It would require either solar panels that are as cheap as vinyl siding or something like practical high yield fusion.
- ianburrell 3y ago
  We will need more wind and solar than required for load to cover cloudy and calm days. I have seen 3x to 5x overcapacity. This should be cheaper than long-term storage, at least with current storage prices, and better to have more power than storage. The result is there will be extra capacity for running intermittent stuff like capture. I haven't seen anyone address how we will pay for carbon capture. By the time we start doing real capture, the CO2 produced should be low so carbon tax will be low.
  - AnthonyMouse 3y ago
    > We will need more wind and solar than required for load to cover cloudy and calm days. I have seen 3x to 5x overcapacity. The theory being that power would be essentially free most of the time because there would be a surplus. But then wouldn't people just use more? It's only "free" until people come up with other uses for inconsistently available large amounts of power, at which point you have to outbid them.
    - staunton 3y ago
      This assumes that what people pay for power is determined by how much it costs to produce. That's already not the case in most countries. Energy prices are determined by taxes and subsidies.
gmuslera 3y ago
It costs orders more than extracting it in the first place. Unless you take into account the long term cost of keep extracting oil, then is infinite vs a finite cost, no matter how high is it.
tzs 3y ago
I did some calculations on this a while back, using the energy requirements of direct air capture (DAC) CO2 removal that we currently know how to produce and deploy. The results I got where that if we built a very large solar farm (500 000 km^2) operating at the efficiency of current commercial solar farms and used all its output to power DAC CO2 removal, that would be enough to remove about half as much CO2 as we currently emit each year. In effect it would be as if we had cut emissions back to 1970 levels. Note that since the solar farm would just be used to power DAC, it would not need electrical infrastructure outside the farm itself. We just need a place where we can put in 500 000 km^2 of solar panels and a bunch of DAC facilities. The atmosphere does a good job of distributing CO2 so the solar/DAC facility doesn't need to be near any heavy CO2 emitters either. BTW, the output of a 500 000 km^2 solar farm per year is about equal to the total yearly energy use of humanity, which shows just how insane the amount of solar energy available is. Let's call this one Human Energy Unit (HEU). Build two HEU's worth of solar/DAC and we are effectively carbon neutral. Of course you wouldn't have to build these as 500 000 km^2 facilities. 500 facilities of 1000 km^2 would do, or any other combination that gives us 1 HEU total of energy that is all used for DAC. How far could we take this? The 5 largest subtropical deserts in the world have enough room to hold 30 HEUs worth of solar farms. If we built all those and turned them all on at once it would take one year to remove enough CO2 to get us down to 320 ppm, which is around the levels we had in 1960. Two years would take us back to levels last seen around 1800. 6 years would get us down to pre-industrial levels. That was all using technology that we have today. It would be a huge project, but it does not require any new science or new engineering. Just a lot of money, politics, manufacturing, and construction.
- bwestergard 3y ago
  I'm curious, did you try to calculate the mass of ores that would need to be mined?
  - tzs 3y ago
    No, I just wanted to know if we covered some large deserts with solar panels could that power enough DAC to make a difference. A quick Googling to find current worldwide solar panel production suggests that it would take about 90 years of current production for the panels for a 500 000 km^2 solar farm, so to build enough to just cancel out current emissions would need about 180 times the resources that currently go annually into solar panel production. So we'd probably need to increase mining (and several other things) by about 20x if we wanted to use this approach to get enough DAC to bring emissions to net zero. I think that's about as far as I can go. I don't know enough about the availability of various resources to figure out if the various things needed are abundant enough and accessible enough that we could increase production by 20x.
elil17 3y ago
You actually end up with net negative carbon if you burn natural gas and use the energy to do CO2 capture (albeit just barely). This is because the carbon-carbon and carbon-hydrogen bonds of a hydrocarbon have more energy in them than the carbon-oxygen bonds in the CO2 that is released from combustion.
- sanderjd 3y ago
  This is an interesting factoid!
  - Turskarama 3y ago
    I'm not sure if you meant to do this on purpose but... Factoid actually means something that sounds true but isn't, which is exactly the case with the post you're referring to because they didn't account for the extra losses on top of the base thermodynamics.
    - bmacho 3y ago
      The word 'factoid' means what the communicating parties agree it means. As per my observation, on HN it currently means something like "a small probably unimportant but interesting fact" (wiki definition for factlet[0]). I don't like it, but HN is not the place to cultivate our own language, dang will shadowban and eventually ban us :\ Best we can do is using the word factlet, and hope people will switch to it. [0] : https://en.wikipedia.org/wiki/Factoid#Versus_factlet https://en.wikipedia.org/wiki/Factoid#Versus_factlet
- alexey-salmin 3y ago
  No, because capturing the CO2 from the atmosphere at 0.04% concentration takes much more energy.
- appplication 3y ago
  What you’re describing is the reason combustion is exothermic, but doesn’t really have much bearing on the efficiency of carbon capture as a process.
rayiner 3y ago
No, because energy isn’t fungible and the world isn’t a single country. Using nuclear to do CO2 extraction in the developed world will still help even as China and India continue to use coal.
- ant6n 3y ago
  This isn’t the first comment in this thread that implies that we need carbon capture to „help out“ those developing countries become carbon neutral.but developing countries are contributing less to the problem than developed ones, have used up only a fraction of the carbon budget of the industrial countries and are also more likely to emit less in the future. China will likely become carbon neutral before the US, current coal plants notwithstanding.
  - rayiner 3y ago
    China is the world’s largest CO2 emitter. India and Africa will join them as they develop in terms of standard of living. It’s irrelevant to climate change who contributed more to the problem in the past.
cactusfrog 3y ago
This is all from memory: Diethyl-ammonia works but is energy intensive to regenerate. Zeolites require less energy to regenerate but also absorb water. Some zeolite crystal structures might exist that are less hydroscopic, but have yet to be discovered. MOFs are like zeolites, but easier to fine tune and some good CO2 absorbers that are also not too hydroscopic have been identified. MOFs have some serious stability issues.

jandrese 3y ago

If you want to turn it back into an oil like substance you will need to expend more energy than you originally got out of it thanks to thermodynamics. In practice it is even worse than that since separating the CO2 from the N2, O2, and everything else in the atmosphere is also energy intensive. The general idea is that you grossly overbuild your renewable energy production (solar and wind mostly) and during the middle of the day when the grid is fully saturated and all of the storage systems are filled up you dump the excess energy into carbon sequestration. This is why people are so angry at NEM 3.0, it's cutting the excess energy production we need as a prerequisite for saving the environment off at the knees.

panzi 3y ago
And then you need to pump these giant amounts of CO2 sludge (or whatever form it will have) back where you drilled oil out of, hoping it will stay down. That will cost a lot of energy too.
tzs 3y ago
> The general idea is that you grossly overbuild your renewable energy production (solar and wind mostly) and during the middle of the day when the grid is fully saturated and all of the storage systems are filled up you dump the excess energy into carbon sequestration Or you build solar and wind plants specifically for carbon sequestration. Then you don't have to worry about coordinating with the needs of the grid. You don't even need the plants to be on the grid. That frees you up to put them places where there is plenty of wind or solar but no infrastructure transporting electricity which would otherwise by useless for solar and wind currently.
- AnthonyMouse 3y ago
  California currently gets much of its electricity from a 500 mile long intertie to the Pacific Northwest. There are plenty of plausible places to put a big solar farm which are less than that distance from civilization, e.g. Arizona or Nevada. At which point you want any of its output during peak consumption hours to go to decarbonizing the grid, regardless of what you do with the off-peak.
elil17 3y ago
No, this is incorrect. You can absolutely burn hydrocarbons, use the energy to do carbon capture, and end up with less CO2 in the air than when you started. Compressed CO2 is still a lower energy state than the hydrocarbons, so you can get net energy out. You couldn't end up with the same hydrocarbon that you started with, of course - that would violate the laws of thermodynamics.
- blkhawk 3y ago
  There is no place to store all that - and don't say depleted gas and oil wells since those are ruined as long term storage by whats been done to them to get the oil or gas out. So you need to build the structures to keep 20km³ of liquefied CO2 each year (liquefying also takes energy).

api 3y ago

It must take at least what coal releases when burned, but there are two catches… The first is that it could use intermittent renewable energy. Solar PV during the day is already cheaper than coal. Just run CO2 removal when renewables generate surplus. The second is that coal plants are heat engines. Most of the energy released burning coal is rejected as heat. CO2 removal might in theory be made more efficient than this. So it might not be quite as bad as it appears at first glance. That being said I still doubt this technology could make a dent in the problem without massively cheap energy. It would require either solar panels that are as cheap as vinyl siding or something like practical high yield fusion.

ianburrell 3y ago
We will need more wind and solar than required for load to cover cloudy and calm days. I have seen 3x to 5x overcapacity. This should be cheaper than long-term storage, at least with current storage prices, and better to have more power than storage. The result is there will be extra capacity for running intermittent stuff like capture. I haven't seen anyone address how we will pay for carbon capture. By the time we start doing real capture, the CO2 produced should be low so carbon tax will be low.
- AnthonyMouse 3y ago
  > We will need more wind and solar than required for load to cover cloudy and calm days. I have seen 3x to 5x overcapacity. The theory being that power would be essentially free most of the time because there would be a surplus. But then wouldn't people just use more? It's only "free" until people come up with other uses for inconsistently available large amounts of power, at which point you have to outbid them.
  - staunton 3y ago
    This assumes that what people pay for power is determined by how much it costs to produce. That's already not the case in most countries. Energy prices are determined by taxes and subsidies.

gmuslera 3y ago

It costs orders more than extracting it in the first place. Unless you take into account the long term cost of keep extracting oil, then is infinite vs a finite cost, no matter how high is it.

tzs 3y ago

I did some calculations on this a while back, using the energy requirements of direct air capture (DAC) CO2 removal that we currently know how to produce and deploy. The results I got where that if we built a very large solar farm (500 000 km^2) operating at the efficiency of current commercial solar farms and used all its output to power DAC CO2 removal, that would be enough to remove about half as much CO2 as we currently emit each year. In effect it would be as if we had cut emissions back to 1970 levels. Note that since the solar farm would just be used to power DAC, it would not need electrical infrastructure outside the farm itself. We just need a place where we can put in 500 000 km^2 of solar panels and a bunch of DAC facilities. The atmosphere does a good job of distributing CO2 so the solar/DAC facility doesn't need to be near any heavy CO2 emitters either. BTW, the output of a 500 000 km^2 solar farm per year is about equal to the total yearly energy use of humanity, which shows just how insane the amount of solar energy available is. Let's call this one Human Energy Unit (HEU). Build two HEU's worth of solar/DAC and we are effectively carbon neutral. Of course you wouldn't have to build these as 500 000 km^2 facilities. 500 facilities of 1000 km^2 would do, or any other combination that gives us 1 HEU total of energy that is all used for DAC. How far could we take this? The 5 largest subtropical deserts in the world have enough room to hold 30 HEUs worth of solar farms. If we built all those and turned them all on at once it would take one year to remove enough CO2 to get us down to 320 ppm, which is around the levels we had in 1960. Two years would take us back to levels last seen around 1800. 6 years would get us down to pre-industrial levels. That was all using technology that we have today. It would be a huge project, but it does not require any new science or new engineering. Just a lot of money, politics, manufacturing, and construction.

bwestergard 3y ago
I'm curious, did you try to calculate the mass of ores that would need to be mined?
- tzs 3y ago
  No, I just wanted to know if we covered some large deserts with solar panels could that power enough DAC to make a difference. A quick Googling to find current worldwide solar panel production suggests that it would take about 90 years of current production for the panels for a 500 000 km^2 solar farm, so to build enough to just cancel out current emissions would need about 180 times the resources that currently go annually into solar panel production. So we'd probably need to increase mining (and several other things) by about 20x if we wanted to use this approach to get enough DAC to bring emissions to net zero. I think that's about as far as I can go. I don't know enough about the availability of various resources to figure out if the various things needed are abundant enough and accessible enough that we could increase production by 20x.

elil17 3y ago

You actually end up with net negative carbon if you burn natural gas and use the energy to do CO2 capture (albeit just barely). This is because the carbon-carbon and carbon-hydrogen bonds of a hydrocarbon have more energy in them than the carbon-oxygen bonds in the CO2 that is released from combustion.

sanderjd 3y ago
This is an interesting factoid!
- Turskarama 3y ago
  I'm not sure if you meant to do this on purpose but... Factoid actually means something that sounds true but isn't, which is exactly the case with the post you're referring to because they didn't account for the extra losses on top of the base thermodynamics.
  - bmacho 3y ago
    The word 'factoid' means what the communicating parties agree it means. As per my observation, on HN it currently means something like "a small probably unimportant but interesting fact" (wiki definition for factlet[0]). I don't like it, but HN is not the place to cultivate our own language, dang will shadowban and eventually ban us :\ Best we can do is using the word factlet, and hope people will switch to it. [0] : https://en.wikipedia.org/wiki/Factoid#Versus_factlet https://en.wikipedia.org/wiki/Factoid#Versus_factlet
alexey-salmin 3y ago
No, because capturing the CO2 from the atmosphere at 0.04% concentration takes much more energy.
appplication 3y ago
What you’re describing is the reason combustion is exothermic, but doesn’t really have much bearing on the efficiency of carbon capture as a process.

rayiner 3y ago

No, because energy isn’t fungible and the world isn’t a single country. Using nuclear to do CO2 extraction in the developed world will still help even as China and India continue to use coal.

ant6n 3y ago
This isn’t the first comment in this thread that implies that we need carbon capture to „help out“ those developing countries become carbon neutral.but developing countries are contributing less to the problem than developed ones, have used up only a fraction of the carbon budget of the industrial countries and are also more likely to emit less in the future. China will likely become carbon neutral before the US, current coal plants notwithstanding.
- rayiner 3y ago
  China is the world’s largest CO2 emitter. India and Africa will join them as they develop in terms of standard of living. It’s irrelevant to climate change who contributed more to the problem in the past.

cactusfrog 3y ago

This is all from memory: Diethyl-ammonia works but is energy intensive to regenerate. Zeolites require less energy to regenerate but also absorb water. Some zeolite crystal structures might exist that are less hydroscopic, but have yet to be discovered. MOFs are like zeolites, but easier to fine tune and some good CO2 absorbers that are also not too hydroscopic have been identified. MOFs have some serious stability issues.