4 ms·

> They are a very strong argument to immediately commence CO2 removal You do realize that removing CO2 will require massively more energy than what went into a

> They are a very strong argument to immediately commence CO2 removal You do realize that removing CO2 will require massively more energy than what went into adding it to the atmosphere, right? In other words, unless you know of a way to violate the laws of physics without consequence, the concept of viable CO2 removal is a bad joke of tragic proportions. Anyone proposing this should be instantly laughed off the stage. This is a fantasy. Which is why every single proposal for CO2 removal has failed as the scams they actually are.

hgomersall 2y ago
That's not true. You've got a requirement to reduce entropy but none to pack it back into energy dense fuel.
- robomartin 2y ago
  > You've got a requirement to reduce entropy but none to pack it back into energy dense fuel. C'mon, this is laughable. What are we going to do with it? Fill-up massive balloons? Also, I have never suggested that the objective should be to pack it back into energy dense fuel. You are trying to talk your way around violating the laws of physics. Look, it's OK if you want to believe this. However, this does not change reality. This is why every single so-called solution has failed and ultimately is discredited. As I suggested to someone else. If you don't see the point, do this: Go to the store and buy a 10 Kg bag of finely ground flour. Walk around your office or home and start throwing flour everywhere. Coat every single surface and crevice with it. Make sure it goes into your TV, computer, air conditioning system, setup a few fans to blow it around. Now go back and retrieve every single particle. The time, energy and resources required is astronomical when compared to the damage you can cause in 30 to 60 minutes. Anyone with minimal critical thinking capacity can understand that it will take weeks, if not months, of a very serious effort and lots more energy to remove every grain of flour. Note that there is no requirement to put it back into the bag. You can eat it, cook with it. I don't care. Yet, you must repair the damage you caused down to the last particle. Are you suggesting you can clean the room/office using less time, resources and energy than that required to create the disaster? I hope not. That's the problem. You need to understand that small-scale hypothetical first. Now expand it to a planetary scale, where you have CO2 floating around the atmosphere at all levels, over every continent and ocean. The mere suggestion that we can actually claw this back should be ridiculous to anyone who stops to really apply some thinking to this problem. It's a fantasy.
  - kragen 2y ago
    I am disappointed to see that you are relying on vague reasoning by analogy instead of thermodynamic calculations or empirical performance figures from currently existing carbon dioxide scrubber systems in this conversation. Generally you are more intellectually rigorous than this. There are significant and relevant differences between carbon dioxide and flour for this purpose; for example, carbon dioxide is a gas and therefore diffuses continuously through the atmosphere, so a scrubber in a fixed location can eventually remove all of it, which is common practice in submarines and space stations. Also, the amount of energy obtained by burning carbon is orders of magnitude larger than, and actually the opposite sign from, the amount of energy obtained by scattering a similar mass of solid particles around, and this is relevant because you are specifically and explicitly comparing the energy consumed by the emission and capture processes.
    - robomartin 2y ago
      > I am disappointed to see that you are relying on vague reasoning by analogy instead of thermodynamic calculations or empirical performance figures from currently existing carbon dioxide scrubber systems in this conversation. Generally you are more intellectually rigorous than this. I have presented detailed calculations in the past only to be met with the same mindless brutalization via downvotes, comments and flagging. The HN masses are just as intellectually lazy as masses can be in any other context. This is no different from recent events in the political spectrum, such as nearly the entire political and media machinery telling the world that Biden was just fine (and a bunch of other lies). Only those of us who managed to think outside the indoctrination seemed to have understood --years ago-- the sad reality that the poor man was being used and abused by the political machinery. Only when reality became inescapable did they start speaking the truth. In fact, it was worse than that, they actively attacked the man and popped him out of the system like a painful puss-filled pimple. The end result? They gave the leadership position to a candidate so flawed that billions of dollars and massive amounts of support from luminaries could not get her elected. The point is: The truth always has a way to come out, sooner or later. Sometimes with undesirable consequences. Climate change became a religion a long time ago. The domain is supported by the indoctrinated masses who love to regurgitate what they are told to think. Researchers fear going against the grain because their funding and careers depend on it. The powerful and those making money with this madness actively promote it and make sure they have support for insane projects. Frankly, it would be far easier to join them, regurgitate the nonsense and make millions of dollars per year by being a member of this dishonest club. Not my style. Sorry. Regarding the flour analogy. You are reading too much into it. This was not a model of the planet and our atmospheric system. I only use these kinds of analogies to show how it takes far more effort, resources and energy to reverse damage that can be done in mere minutes. That's all. Lot's of commenters on HN do not seem able to (or willing to) exercise critical thinking. Some might not have the requisite scientific background or real-world experience to understand what are otherwise simple arguments rooted in physics. One of the common comments goes something like: If we polluted it in X years we can clean it up in X years or less. Of course, this is ridiculous. The example of flour spread all over the office is simple enough to illustrate just how silly this idea actually is. And, if someone cares enough to think it through a bit deeper, it also illustrates just how much more energy and resources is required than a sack of flour. That's it. It isn't a model of a planet and its atmosphere. It's there to say: You cannot fix a problem with less energy, resources or time than what went into creating it in the first place. Nothing else. > a scrubber in a fixed location can eventually remove all of it That would be nice if it were possible. Sorry, this is another fantasy. Once again, things fail in a violent manner once considered at a global scale. You cannot filter air at a planetary scale, this is simply preposterous starting with the reality of building these kinds of systems every 10, 20, 50 or 100 miles throughout the planet, the scale, energy, resources and realities of air processing all work against you. These systems are far more likely to "filter" the same air over and over again than to actually "remove all of it". In a prior life I was involved in large systems installations requiring the construction of clean rooms of varying scales, from small 20 x 20 foot labs to massive aerospace-level clean rooms (think Home Depot scale). What works well in a smallish environment (a room, submarine, space station) quickly fails at larger scales. In the end, you cannot create a clean room by filtering the enclosed volume. That's not how it is done except for very specific applications (spacecraft, submarine, space station and that's it). The only way is to inject clean air and create positive pressure such that nothing is able to come in from the outside. Scrubber systems in the corner-case applications where this isn't an option are incredibly expensive and complex. They do not scale well at all. Of course this isn't to suggest that we can bring in clean air into our atmosphere. My point is that the idea of filtering our entire atmosphere (or a substantial enough portion of it) only works on paper, research grant applications and proposals for funding by politicians eager to continue the narrative that drives unthinking masses to vote for them. Who wants to vote for someone who says "The emperor has no clothes"? Nobody. Far easier for the machinery to convince everyone that the naked man in front of them is wearing the finest garments every conceived. Sadly, that book [0] covers climate change with great accuracy. Look, the scenario today is no different from what it has been for the last, 50 years or more. This articles [1] is an interesting compilation of predictions over time. All crazy nonsense. Yet, at the time, taken seriously and used to set policy and more. Who would dare go against the likes of Nobel Prize winners, Ted Turner, Al Gore and other merchants of FUD? From a career standpoint, as academics, media or politicians, it would have been suicidal. Anyone can understand this. And yet, all of these and many others were selling pure unrefined bullshit. I mean, crap like this, quoting: "A senior UN environmental official (Noel Brown) says entire nations could be wiped off the face of the Earth by rising sea levels if the global warming trend is not reversed by the year 2000." (1970) "Air pollution may obliterate the sun and cause a new ice age in the first third of the next century if population continues to grow and earth’s resources are consumed at the present rate…" "Harvard biologist and Nobel Prize winner George Wald, speaking at the University of Rhode Island in November 1970: “Civilization will end within 15 or 30 years unless immediate action is taken against problems facing mankind.”" "In April 2008, media mogul Ted Turner provided far more detail than either Gore or Pachauri, emphasizing the consequences of climate inaction. “Not doing it will be catastrophic. We’ll be eight degrees hotter in ten, not 10 but 30 or 40 years and basically none of the crops will grow. Most of the people will have died and the rest of us will be cannibals. Civilization will have broken down. The few people left will be living in a failed state like Somalia or Sudan, and living conditions will be intolerable. The droughts will be so bad there’ll be no more corn growing.” (2019, AOC) "The world is gonna end in 12 years if we don’t address climate change" When I say that this domain has become a sad joke, a religion, an incredible farce supported by those seeking political and financial gain, rather than real science, well, there's ample evidence to support this statement going back over 50 years. In other words, it is far more likely that this is all a big smelly pile of bullshit than otherwise. [0] https://en.wikipedia.org/wiki/The_Emperor%27s_New_Clothes https://en.wikipedia.org/wiki/The_Emperor%27s_New_Clothes [1] https://www.agweb.com/opinion/doomsday-addiction-celebrating-50-years-failed-climate-predictions https://www.agweb.com/opinion/doomsday-addiction-celebrating...
toss1 2y ago
Not true at all (or only in limited circumstances that do not apply First, it was not the original energy expenditure that is the problem. The problem is that the CO2 CHANGES the solar energy exchange equation, by allowing ~the same amount of solar energy to the earth's surface, but REDUCING the earth's ability radiate that energy back to space. That newly captured energy VASTLY EXCEEDS the original energy that went into adding the CO2 to the atmosphere. That original energy spent has almost zero impact on climate change. Next, capture requires none of the things you say. — Carbon capture can be done by 'farming' high-uptake organisms, which has extreme leverage for energy expended. Examples include iron-seeding of water to make algae blooms, planting high uptake trees, etc. — Carbon capture can be done by accelerating natural chemical processes, e.g., exposing rocks that react with water and CO@, or crushing those rocks and spreading them on fields (iirc, Google just contracted with a company doing exactly that) — Carbon capture can be done by enzyme-driven processes that make the desired reactions happen with minimal artificial energy input — Even if you want to use a chemistry that requires direct energy input, there is zero requirement to recover the original highly complex and energy-dense molecules previously used for fuel, it only needs to make a compound that can be captured. Still requires less energy than original used. — Even if you insist on producing new molecules as energy-dense as the originals, there is vastly more energy available via non-CO2-outputting sources, such as solar, wind, etc. which often produce surpluses. Again, the energy of the process has almost zero to do with promoting climate change. So, NO, it neither a bad joke, a process that requires breaking laws of physics, at fantasy, or a scam.
pfdietz 2y ago
> You do realize that removing CO2 will require massively more energy than what went into adding it to the atmosphere, right? The reaction of CO2 with silicate rocks that pulls CO2 out of the atmosphere naturally (and is why the Earth is not like Venus with 90 bar of CO2 in the atmosphere) is exothermic. So, the energy needed is not just not large, it could even be negative.
kragen 2y ago
I used to think that too, but then I found out it wasn't true. It turns out that by instantly laughing at people who disagree with you, you lose the opportunity to learn the things they know that you don't. Specifically, in this case, the standard enthalpy of formation of carbon dioxide is -393.5 kilojoules per mole (that's the energy you get when you burn coal). If you burn coal in a sealed 1-bar chamber to drive a heat engine (such as a steam turbine), and pump the exhaust gases through a passively-air-cooled 1-bar heat exchanger to cool them back down to room temperature, you have obtained those 394kJ/mol thermal, about 138kJ/mol electric, for only the cost of blowing the gas around, without releasing any carbon dioxide into the atmosphere. Blowing the gas around with blowers takes typically about three orders of magnitude less energy than the heat energy the gas carries, though this depends on things like gas temperature and duct length, diameter, and smoothness. So physics is no bar (heh!) to getting from the coal-and-atmospheric-oxygen state into the electricity-and-captured-carbon-dioxide state. There is some necessary energy cost involved in atmospheric carbon dioxide capture, because the air is only 400 ppm carbon dioxide and 99.96% other things, so there is an entropic cost to unmixing it. That entropic cost is not where you get the energy from burning it; the mixing happens above your smokestack where you can't extract any energy released and, as demonstrated above, can be avoided entirely. I don't understand thermodynamics well enough to calculate the thermodynamically necessary energy to reverse that entropy, but my understanding is that even at 400ppm it is orders of magnitude lower than the fuel's heating value. Recompressing the carbon dioxide to liquid form requires about as much energy as you got in mechanical form out of the turbine; carbon dioxide liquefies at room temperature at 60 bar, liberating its enthalpy of vaporization of 16.7 kilojoules per mole, 4.2% of the enthalpy of formation. 59 bar is 5.9 kJ/l, and at room temperature and 1 bar an ideal gas occupies 24.4 l/mol, so you need to put about 140kJ/mol into compression. But as I understand it (and correct me if I'm wrong) almost all of that energy comes back out as heat. In practice, atmospheric carbon capture systems use absorbents or adsorbents such as calcium oxide, zeolites, or ethanolamine solutions to avoid this complicated and inefficient compression step. They use a substantial amount of energy to regenerate the sorbents, but, as I understand it, much less than burning the fuel generates. For example, https://cobblab.eas.gatech.edu/energy/Readings/rochelle2009.pdf https://cobblab.eas.gatech.edu/energy/Readings/rochelle2009.... (DOI: 10.1126/science.1176731) says that a monoethanolamine scrubber used for flue-gas treatment at a 450-megawatt power plant in the year 02006 used 0.37 megawatt hours per ton of CO₂ removed. Assuming they mean metric tonnes, that's 1.332 gigajoules per 22700 moles of CO₂, which works out to 59kJ/mol, which is 43% of the energy obtained from burning the carbon. (Although amine scrubbers have been used for capturing CO₂ from flue gas at a number of power plants since the 01980s, I'm unclear on whether this 59kJ/mol number represents measurements from an actually deployed system or the projected performance of a proposed design.) You could argue that it's easier to remove CO₂ from power-plant flue gas where it's fairly concentrated (12% rather than 0.04%), but in fact sorbents like monoethanolamine and triethanolamine are also quite effective at removing CO₂ from breathable air in environments such as submarines and space stations. At room temperature, their vapor pressure of CO₂ is quite low indeed, so it's mostly just a question of needing to expose the sorbent solution to air over a longer period of time. It doesn't result in requiring a proportional increase in the energy consumption of the process. A recent open-access survey of the direct-air-capture problem is https://pubs.rsc.org/en/content/articlepdf/2022/ee/d1ee03523a https://pubs.rsc.org/en/content/articlepdf/2022/ee/d1ee03523... (doi 10.1039/d1ee03523a). (However, note that that's still from November 02021, at which point photovoltaic panels still cost three times as much as they do now, so its calculations of energy costs are inflated by at least a factor of three.) So, no, the laws of physics don't require that removing CO₂ will require even as much energy as what went into adding it to the atmosphere, much less "massively more energy", as you claim. Even if they did, though, that wouldn't make atmospheric carbon capture impractical or a scam. Burning methane (natural gas) yields 55.6 MJ/kg (https://en.wikipedia.org/wiki/Energy_density#Chemical_reactions_(oxidation) https://en.wikipedia.org/wiki/Energy_density#Chemical_reacti...) which works out to 892kJ/mol, but each mole of methane only produces one mole of carbon. The other 892 - 394 = 498kJ/mol (HHV) comes from burning the hydrogen (water's enthalpy of formation is -285.83kJ/mol, and methane's is -74.6kJ/mol, so we get 497.1 kJ/mol extra after the rounding errors). So even if we had to pay back all of that 286kJ/mol from the carbon to stuff it back into a bottle, we'd still have 56% of the energy we got from burning the natural gas left over. And, of course, photovoltaics and wind provide abundant energy we can use for atmospheric carbon capture without releasing any more carbon dioxide, and nowadays they do it far more cheaply than fossil-fuel power plants ever did. There are also schemes for atmospheric carbon dioxide capture with biological photosynthesis, which I think are probably not feasible at the required scale due to the required area, and with enhanced weathering by pulverizing olivines, which are probably feasible but strike me as risky. In the olivine case, the energy required to extract the gas from the atmosphere was provided billions of years ago by the heat of the earth driving carbon dioxide and other volatiles out of the mantle, so we don't have to care how big it is. The reason "every single proposal for CO2 removal has failed" is (1) most of them are pretty energy-intensive, and until five years ago, energy was expensive (and cheap energy still hasn't reached most places); and (2) there's no clear way to make money at CO2 removal at current carbon credit prices, which are in part because the carbon credit market is pretty corrupt but also because at this point there's still a lot of low-hanging fruit in the emissions-reduction sector.

hgomersall 2y ago

That's not true. You've got a requirement to reduce entropy but none to pack it back into energy dense fuel.

robomartin 2y ago
> You've got a requirement to reduce entropy but none to pack it back into energy dense fuel. C'mon, this is laughable. What are we going to do with it? Fill-up massive balloons? Also, I have never suggested that the objective should be to pack it back into energy dense fuel. You are trying to talk your way around violating the laws of physics. Look, it's OK if you want to believe this. However, this does not change reality. This is why every single so-called solution has failed and ultimately is discredited. As I suggested to someone else. If you don't see the point, do this: Go to the store and buy a 10 Kg bag of finely ground flour. Walk around your office or home and start throwing flour everywhere. Coat every single surface and crevice with it. Make sure it goes into your TV, computer, air conditioning system, setup a few fans to blow it around. Now go back and retrieve every single particle. The time, energy and resources required is astronomical when compared to the damage you can cause in 30 to 60 minutes. Anyone with minimal critical thinking capacity can understand that it will take weeks, if not months, of a very serious effort and lots more energy to remove every grain of flour. Note that there is no requirement to put it back into the bag. You can eat it, cook with it. I don't care. Yet, you must repair the damage you caused down to the last particle. Are you suggesting you can clean the room/office using less time, resources and energy than that required to create the disaster? I hope not. That's the problem. You need to understand that small-scale hypothetical first. Now expand it to a planetary scale, where you have CO2 floating around the atmosphere at all levels, over every continent and ocean. The mere suggestion that we can actually claw this back should be ridiculous to anyone who stops to really apply some thinking to this problem. It's a fantasy.
- kragen 2y ago
  I am disappointed to see that you are relying on vague reasoning by analogy instead of thermodynamic calculations or empirical performance figures from currently existing carbon dioxide scrubber systems in this conversation. Generally you are more intellectually rigorous than this. There are significant and relevant differences between carbon dioxide and flour for this purpose; for example, carbon dioxide is a gas and therefore diffuses continuously through the atmosphere, so a scrubber in a fixed location can eventually remove all of it, which is common practice in submarines and space stations. Also, the amount of energy obtained by burning carbon is orders of magnitude larger than, and actually the opposite sign from, the amount of energy obtained by scattering a similar mass of solid particles around, and this is relevant because you are specifically and explicitly comparing the energy consumed by the emission and capture processes.
  - robomartin 2y ago
    > I am disappointed to see that you are relying on vague reasoning by analogy instead of thermodynamic calculations or empirical performance figures from currently existing carbon dioxide scrubber systems in this conversation. Generally you are more intellectually rigorous than this. I have presented detailed calculations in the past only to be met with the same mindless brutalization via downvotes, comments and flagging. The HN masses are just as intellectually lazy as masses can be in any other context. This is no different from recent events in the political spectrum, such as nearly the entire political and media machinery telling the world that Biden was just fine (and a bunch of other lies). Only those of us who managed to think outside the indoctrination seemed to have understood --years ago-- the sad reality that the poor man was being used and abused by the political machinery. Only when reality became inescapable did they start speaking the truth. In fact, it was worse than that, they actively attacked the man and popped him out of the system like a painful puss-filled pimple. The end result? They gave the leadership position to a candidate so flawed that billions of dollars and massive amounts of support from luminaries could not get her elected. The point is: The truth always has a way to come out, sooner or later. Sometimes with undesirable consequences. Climate change became a religion a long time ago. The domain is supported by the indoctrinated masses who love to regurgitate what they are told to think. Researchers fear going against the grain because their funding and careers depend on it. The powerful and those making money with this madness actively promote it and make sure they have support for insane projects. Frankly, it would be far easier to join them, regurgitate the nonsense and make millions of dollars per year by being a member of this dishonest club. Not my style. Sorry. Regarding the flour analogy. You are reading too much into it. This was not a model of the planet and our atmospheric system. I only use these kinds of analogies to show how it takes far more effort, resources and energy to reverse damage that can be done in mere minutes. That's all. Lot's of commenters on HN do not seem able to (or willing to) exercise critical thinking. Some might not have the requisite scientific background or real-world experience to understand what are otherwise simple arguments rooted in physics. One of the common comments goes something like: If we polluted it in X years we can clean it up in X years or less. Of course, this is ridiculous. The example of flour spread all over the office is simple enough to illustrate just how silly this idea actually is. And, if someone cares enough to think it through a bit deeper, it also illustrates just how much more energy and resources is required than a sack of flour. That's it. It isn't a model of a planet and its atmosphere. It's there to say: You cannot fix a problem with less energy, resources or time than what went into creating it in the first place. Nothing else. > a scrubber in a fixed location can eventually remove all of it That would be nice if it were possible. Sorry, this is another fantasy. Once again, things fail in a violent manner once considered at a global scale. You cannot filter air at a planetary scale, this is simply preposterous starting with the reality of building these kinds of systems every 10, 20, 50 or 100 miles throughout the planet, the scale, energy, resources and realities of air processing all work against you. These systems are far more likely to "filter" the same air over and over again than to actually "remove all of it". In a prior life I was involved in large systems installations requiring the construction of clean rooms of varying scales, from small 20 x 20 foot labs to massive aerospace-level clean rooms (think Home Depot scale). What works well in a smallish environment (a room, submarine, space station) quickly fails at larger scales. In the end, you cannot create a clean room by filtering the enclosed volume. That's not how it is done except for very specific applications (spacecraft, submarine, space station and that's it). The only way is to inject clean air and create positive pressure such that nothing is able to come in from the outside. Scrubber systems in the corner-case applications where this isn't an option are incredibly expensive and complex. They do not scale well at all. Of course this isn't to suggest that we can bring in clean air into our atmosphere. My point is that the idea of filtering our entire atmosphere (or a substantial enough portion of it) only works on paper, research grant applications and proposals for funding by politicians eager to continue the narrative that drives unthinking masses to vote for them. Who wants to vote for someone who says "The emperor has no clothes"? Nobody. Far easier for the machinery to convince everyone that the naked man in front of them is wearing the finest garments every conceived. Sadly, that book [0] covers climate change with great accuracy. Look, the scenario today is no different from what it has been for the last, 50 years or more. This articles [1] is an interesting compilation of predictions over time. All crazy nonsense. Yet, at the time, taken seriously and used to set policy and more. Who would dare go against the likes of Nobel Prize winners, Ted Turner, Al Gore and other merchants of FUD? From a career standpoint, as academics, media or politicians, it would have been suicidal. Anyone can understand this. And yet, all of these and many others were selling pure unrefined bullshit. I mean, crap like this, quoting: "A senior UN environmental official (Noel Brown) says entire nations could be wiped off the face of the Earth by rising sea levels if the global warming trend is not reversed by the year 2000." (1970) "Air pollution may obliterate the sun and cause a new ice age in the first third of the next century if population continues to grow and earth’s resources are consumed at the present rate…" "Harvard biologist and Nobel Prize winner George Wald, speaking at the University of Rhode Island in November 1970: “Civilization will end within 15 or 30 years unless immediate action is taken against problems facing mankind.”" "In April 2008, media mogul Ted Turner provided far more detail than either Gore or Pachauri, emphasizing the consequences of climate inaction. “Not doing it will be catastrophic. We’ll be eight degrees hotter in ten, not 10 but 30 or 40 years and basically none of the crops will grow. Most of the people will have died and the rest of us will be cannibals. Civilization will have broken down. The few people left will be living in a failed state like Somalia or Sudan, and living conditions will be intolerable. The droughts will be so bad there’ll be no more corn growing.” (2019, AOC) "The world is gonna end in 12 years if we don’t address climate change" When I say that this domain has become a sad joke, a religion, an incredible farce supported by those seeking political and financial gain, rather than real science, well, there's ample evidence to support this statement going back over 50 years. In other words, it is far more likely that this is all a big smelly pile of bullshit than otherwise. [0] https://en.wikipedia.org/wiki/The_Emperor%27s_New_Clothes https://en.wikipedia.org/wiki/The_Emperor%27s_New_Clothes [1] https://www.agweb.com/opinion/doomsday-addiction-celebrating-50-years-failed-climate-predictions https://www.agweb.com/opinion/doomsday-addiction-celebrating...

toss1 2y ago

Not true at all (or only in limited circumstances that do not apply First, it was not the original energy expenditure that is the problem. The problem is that the CO2 CHANGES the solar energy exchange equation, by allowing ~the same amount of solar energy to the earth's surface, but REDUCING the earth's ability radiate that energy back to space. That newly captured energy VASTLY EXCEEDS the original energy that went into adding the CO2 to the atmosphere. That original energy spent has almost zero impact on climate change. Next, capture requires none of the things you say. — Carbon capture can be done by 'farming' high-uptake organisms, which has extreme leverage for energy expended. Examples include iron-seeding of water to make algae blooms, planting high uptake trees, etc. — Carbon capture can be done by accelerating natural chemical processes, e.g., exposing rocks that react with water and CO@, or crushing those rocks and spreading them on fields (iirc, Google just contracted with a company doing exactly that) — Carbon capture can be done by enzyme-driven processes that make the desired reactions happen with minimal artificial energy input — Even if you want to use a chemistry that requires direct energy input, there is zero requirement to recover the original highly complex and energy-dense molecules previously used for fuel, it only needs to make a compound that can be captured. Still requires less energy than original used. — Even if you insist on producing new molecules as energy-dense as the originals, there is vastly more energy available via non-CO2-outputting sources, such as solar, wind, etc. which often produce surpluses. Again, the energy of the process has almost zero to do with promoting climate change. So, NO, it neither a bad joke, a process that requires breaking laws of physics, at fantasy, or a scam.

pfdietz 2y ago

> You do realize that removing CO2 will require massively more energy than what went into adding it to the atmosphere, right? The reaction of CO2 with silicate rocks that pulls CO2 out of the atmosphere naturally (and is why the Earth is not like Venus with 90 bar of CO2 in the atmosphere) is exothermic. So, the energy needed is not just not large, it could even be negative.

kragen 2y ago

I used to think that too, but then I found out it wasn't true. It turns out that by instantly laughing at people who disagree with you, you lose the opportunity to learn the things they know that you don't. Specifically, in this case, the standard enthalpy of formation of carbon dioxide is -393.5 kilojoules per mole (that's the energy you get when you burn coal). If you burn coal in a sealed 1-bar chamber to drive a heat engine (such as a steam turbine), and pump the exhaust gases through a passively-air-cooled 1-bar heat exchanger to cool them back down to room temperature, you have obtained those 394kJ/mol thermal, about 138kJ/mol electric, for only the cost of blowing the gas around, without releasing any carbon dioxide into the atmosphere. Blowing the gas around with blowers takes typically about three orders of magnitude less energy than the heat energy the gas carries, though this depends on things like gas temperature and duct length, diameter, and smoothness. So physics is no bar (heh!) to getting from the coal-and-atmospheric-oxygen state into the electricity-and-captured-carbon-dioxide state. There is some necessary energy cost involved in atmospheric carbon dioxide capture, because the air is only 400 ppm carbon dioxide and 99.96% other things, so there is an entropic cost to unmixing it. That entropic cost is not where you get the energy from burning it; the mixing happens above your smokestack where you can't extract any energy released and, as demonstrated above, can be avoided entirely. I don't understand thermodynamics well enough to calculate the thermodynamically necessary energy to reverse that entropy, but my understanding is that even at 400ppm it is orders of magnitude lower than the fuel's heating value. Recompressing the carbon dioxide to liquid form requires about as much energy as you got in mechanical form out of the turbine; carbon dioxide liquefies at room temperature at 60 bar, liberating its enthalpy of vaporization of 16.7 kilojoules per mole, 4.2% of the enthalpy of formation. 59 bar is 5.9 kJ/l, and at room temperature and 1 bar an ideal gas occupies 24.4 l/mol, so you need to put about 140kJ/mol into compression. But as I understand it (and correct me if I'm wrong) almost all of that energy comes back out as heat. In practice, atmospheric carbon capture systems use absorbents or adsorbents such as calcium oxide, zeolites, or ethanolamine solutions to avoid this complicated and inefficient compression step. They use a substantial amount of energy to regenerate the sorbents, but, as I understand it, much less than burning the fuel generates. For example, https://cobblab.eas.gatech.edu/energy/Readings/rochelle2009.pdf https://cobblab.eas.gatech.edu/energy/Readings/rochelle2009.... (DOI: 10.1126/science.1176731) says that a monoethanolamine scrubber used for flue-gas treatment at a 450-megawatt power plant in the year 02006 used 0.37 megawatt hours per ton of CO₂ removed. Assuming they mean metric tonnes, that's 1.332 gigajoules per 22700 moles of CO₂, which works out to 59kJ/mol, which is 43% of the energy obtained from burning the carbon. (Although amine scrubbers have been used for capturing CO₂ from flue gas at a number of power plants since the 01980s, I'm unclear on whether this 59kJ/mol number represents measurements from an actually deployed system or the projected performance of a proposed design.) You could argue that it's easier to remove CO₂ from power-plant flue gas where it's fairly concentrated (12% rather than 0.04%), but in fact sorbents like monoethanolamine and triethanolamine are also quite effective at removing CO₂ from breathable air in environments such as submarines and space stations. At room temperature, their vapor pressure of CO₂ is quite low indeed, so it's mostly just a question of needing to expose the sorbent solution to air over a longer period of time. It doesn't result in requiring a proportional increase in the energy consumption of the process. A recent open-access survey of the direct-air-capture problem is https://pubs.rsc.org/en/content/articlepdf/2022/ee/d1ee03523a https://pubs.rsc.org/en/content/articlepdf/2022/ee/d1ee03523... (doi 10.1039/d1ee03523a). (However, note that that's still from November 02021, at which point photovoltaic panels still cost three times as much as they do now, so its calculations of energy costs are inflated by at least a factor of three.) So, no, the laws of physics don't require that removing CO₂ will require even as much energy as what went into adding it to the atmosphere, much less "massively more energy", as you claim. Even if they did, though, that wouldn't make atmospheric carbon capture impractical or a scam. Burning methane (natural gas) yields 55.6 MJ/kg (https://en.wikipedia.org/wiki/Energy_density#Chemical_reactions_(oxidation) https://en.wikipedia.org/wiki/Energy_density#Chemical_reacti...) which works out to 892kJ/mol, but each mole of methane only produces one mole of carbon. The other 892 - 394 = 498kJ/mol (HHV) comes from burning the hydrogen (water's enthalpy of formation is -285.83kJ/mol, and methane's is -74.6kJ/mol, so we get 497.1 kJ/mol extra after the rounding errors). So even if we had to pay back all of that 286kJ/mol from the carbon to stuff it back into a bottle, we'd still have 56% of the energy we got from burning the natural gas left over. And, of course, photovoltaics and wind provide abundant energy we can use for atmospheric carbon capture without releasing any more carbon dioxide, and nowadays they do it far more cheaply than fossil-fuel power plants ever did. There are also schemes for atmospheric carbon dioxide capture with biological photosynthesis, which I think are probably not feasible at the required scale due to the required area, and with enhanced weathering by pulverizing olivines, which are probably feasible but strike me as risky. In the olivine case, the energy required to extract the gas from the atmosphere was provided billions of years ago by the heat of the earth driving carbon dioxide and other volatiles out of the mantle, so we don't have to care how big it is. The reason "every single proposal for CO2 removal has failed" is (1) most of them are pretty energy-intensive, and until five years ago, energy was expensive (and cheap energy still hasn't reached most places); and (2) there's no clear way to make money at CO2 removal at current carbon credit prices, which are in part because the carbon credit market is pretty corrupt but also because at this point there's still a lot of low-hanging fruit in the emissions-reduction sector.