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Binding carbon from CO2 does not necessarily cost energy. The reactions CaO -> CaCO3 is exothermic, and the same is true for the equivalent reaction for magnesi

Binding carbon from CO2 does not necessarily cost energy. The reactions CaO -> CaCO3 is exothermic, and the same is true for the equivalent reaction for magnesium, and the reactions forming carbonates from the silicates of those metals. Eroding volcanic rock naturally pulls CO2 out of the atmosphere, as erosion slowly reveals metals that were reduced by the volcanic heat. This process is naturally quite slow, but it can be sped up, for example, by fracking basaltic rocks and feeding carbonated water in them. The pilot project for was ran in Iceland and was successful enough to lead to both constructing a full-scale plant and scaling the process out to multiple different locations in Europe. The current main open problem is substituting seawater for fresh water for the process (Using a lot of fresh water is not exactly a problem in Iceland, but presents challenges for scaling the process out).

leoedin 7y ago
This relies on the right sort of rock. Is it ubiquitous enough that we can account for meaningful amounts of carbon sequestration?
- Tuna-Fish 7y ago
  Yes, by many orders of magnitude, to capture not just all existing emissions but the emissions that results from burning of all the fossil fuels on the planet.
  - bamboozled 7y ago
    Have you read about this! Curious about what others think!
  - darkmighty 7y ago
    By available, do you mean 'It exists on the planet crust', or 'It can be accessed at a significantly lower cost than the forward (breakdown, e.g. the cost of equivalent oil) energy cost?'[1], and if so, do you have sources to back that up? [1] If it costs more, or even not significantly (an order of magnitude at least) less than the cost of oil for equivalent emissions, than the economic proposition is dire. Solutions so far have those economic difficulties afaik, and we're still at a stage where we have easily available capture resources (i.e. we haven't depleted or saturated a number of them) -- we're talking about a planetary scale solution here
    - Tuna-Fish 7y ago
      The first definitely, the second remains to be proven. You can find most of the relevant scientific articles by searching for 'carbfix' on sciencedirect. The current results are promising, but there are still challenges to overcome. Notably, the system they run in Iceland absolutely guzzled fresh water, and while this is not a problem in Iceland, it would prevent the scaling up of this project to a true planetary-scale solution. Work is ongoing for figuring out if saltwater would clog up the wells too badly, and how this can be mitigated. Also, as the carbfix project took in CO2 and H2S as highly concentrated gases, as the direct problem was to get rid of the emissions of a geothermal plant. To scale up to carbon capture from the atmosphere, they'd have to either set up their system to use less concentrated input gases, or figure out a cost-effective method of separating and concentrating CO2 from the atmosphere. Not saying this is necessarily a silver bullet for all our emissions, just saying that the original concern of the poster I replied to about where the energy to split CO2 it going to come from is not actually as big of a deal as it seems.
rightbyte 7y ago
Planting trees is a possibility too.
H8crilA 7y ago
CaO is created by frying CaCO3, typically heated with coal. You can then mix it with water to get cement. At least that's what I learned in school. How would you like to create CaO without providing energy if the reverse reaction is exothermic? Or am I missing the fact that there's a lot of unbound CaO in rocks? Also, production of cement is one of the major sources of CO2 emissions.
- Tuna-Fish 7y ago
  The volcano did the frying, and the result was trapped into bubbles of rock where it could not come into contact with CO2 from the air. Although most of it is not directly as oxides but some form of silicates. (This forces the use of lots of water in the process -- you can go from CaO -> CaCO3 without much water, but to dissolve silicates you need the CO2 dissolved in water.)
- pfdietz 7y ago
  The exothermic reactions involved in mineral carbonation are silicates + CO2 => carbonates + SiO2. These reactions mimic those that naturally extract CO2 from the atmosphere over geologic time, but greatly accelerated.

leoedin 7y ago

This relies on the right sort of rock. Is it ubiquitous enough that we can account for meaningful amounts of carbon sequestration?

Tuna-Fish 7y ago
Yes, by many orders of magnitude, to capture not just all existing emissions but the emissions that results from burning of all the fossil fuels on the planet.
- bamboozled 7y ago
  Have you read about this! Curious about what others think!
- darkmighty 7y ago
  By available, do you mean 'It exists on the planet crust', or 'It can be accessed at a significantly lower cost than the forward (breakdown, e.g. the cost of equivalent oil) energy cost?'[1], and if so, do you have sources to back that up? [1] If it costs more, or even not significantly (an order of magnitude at least) less than the cost of oil for equivalent emissions, than the economic proposition is dire. Solutions so far have those economic difficulties afaik, and we're still at a stage where we have easily available capture resources (i.e. we haven't depleted or saturated a number of them) -- we're talking about a planetary scale solution here
  - Tuna-Fish 7y ago
    The first definitely, the second remains to be proven. You can find most of the relevant scientific articles by searching for 'carbfix' on sciencedirect. The current results are promising, but there are still challenges to overcome. Notably, the system they run in Iceland absolutely guzzled fresh water, and while this is not a problem in Iceland, it would prevent the scaling up of this project to a true planetary-scale solution. Work is ongoing for figuring out if saltwater would clog up the wells too badly, and how this can be mitigated. Also, as the carbfix project took in CO2 and H2S as highly concentrated gases, as the direct problem was to get rid of the emissions of a geothermal plant. To scale up to carbon capture from the atmosphere, they'd have to either set up their system to use less concentrated input gases, or figure out a cost-effective method of separating and concentrating CO2 from the atmosphere. Not saying this is necessarily a silver bullet for all our emissions, just saying that the original concern of the poster I replied to about where the energy to split CO2 it going to come from is not actually as big of a deal as it seems.

rightbyte 7y ago

Planting trees is a possibility too.

H8crilA 7y ago

CaO is created by frying CaCO3, typically heated with coal. You can then mix it with water to get cement. At least that's what I learned in school. How would you like to create CaO without providing energy if the reverse reaction is exothermic? Or am I missing the fact that there's a lot of unbound CaO in rocks? Also, production of cement is one of the major sources of CO2 emissions.

Tuna-Fish 7y ago
The volcano did the frying, and the result was trapped into bubbles of rock where it could not come into contact with CO2 from the air. Although most of it is not directly as oxides but some form of silicates. (This forces the use of lots of water in the process -- you can go from CaO -> CaCO3 without much water, but to dissolve silicates you need the CO2 dissolved in water.)
pfdietz 7y ago
The exothermic reactions involved in mineral carbonation are silicates + CO2 => carbonates + SiO2. These reactions mimic those that naturally extract CO2 from the atmosphere over geologic time, but greatly accelerated.