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Can you elaborate on the optimistic assumptions in robotics that may enable accelerated silicate weathering? Or could you point me to some readings on the matte

Can you elaborate on the optimistic assumptions in robotics that may enable accelerated silicate weathering? Or could you point me to some readings on the matter?

philipkglass 9y ago
A search on Google Scholar for "accelerated silicate weathering" will be more informative than my comment. But here's the shortish version... Naturally occurring silicates of magnesium, calcium, sodium, and potassium are thermodynamically prone to weather to carbonates in ambient conditions, when water absorbs CO2 and passes over rocks. In the case of magnesium and calcium in particular, the weathering leads to stable solids that will not spontaneously release CO2 again. A schematic example with calcium silicate: CO2 + CaSiO3 -> SiO2 + CaCO3 Gaseous carbon dioxide and solid calcium silicate become solid silicon dioxide and calcium carbonate. Silicate weathering has multiple advantages over other carbon dioxide removal/sequestration schemes: • The end state is naturally stable. You don't have to worry about the leakiness of underground containment. • It restores the pH balance of the oceans as well as reducing radiative forcing (warming) effects. • It deals equally well with point and distributed sources of CO2 (coal plants, automobile tailpipes). • It can be located anywhere on Earth. It does not need to be adjacent to CO2 sources. • It does not require concentrated CO2 streams, but works with ambient atmospheric concentrations. Natural silicate weathering reactions dominate Earth's CO2 balance in the very long term. But they are strongly kinetically hindered in nature. After a freshly exposed rock surface has weathered to a depth of a few microns, the cation-depleted "rind" drastically slows the weathering of the remaining interior. Without human intervention, it'll take about 100,000 years for natural silicate weathering to restore the pre-industrial baseline of atmospheric CO2 concentrations. There are different ways to improve the kinetics: • Crush bulk rock to a fine sand texture, so full interior weathering finishes much faster (still takes years-to-decades, but no longer takes geological time scales). • Place crushed rock in near-shore ocean environments where mechanical wave erosion keeps removing rinds. • Place crushed rock in acidic tropical agricultural soils where it weathers faster due to low pH and elevated temperature. This also improves soil quality for growing crops. It's not explicitly included in the scholarly literature, but I say that advanced robotics are necessary because the required scale of intervention is staggering, bigger than any engineering endeavor in history. For example, the Columbia Plateau in the United States contains basalt whose alkali and alkaline earth content could bind about 20% of its own mass in CO2, after complete weathering: https://crustal.usgs.gov/geochemical_reference_standards/basaltbcr2.html https://crustal.usgs.gov/geochemical_reference_standards/bas... To neutralize the CO2 that humans emitted in 2015, about 36 billion tons (https://en.wikipedia.org/wiki/List_of_countries_by_carbon_dioxide_emissions https://en.wikipedia.org/wiki/List_of_countries_by_carbon_di...), would require mining and pulverizing about 180 billion tons of Columbia Plateau basalt. That's about 60 cubic kilometers. We're in no danger of running out of plateau -- it contains more than 170,000 km^3. As for energy estimates, the Bond Work Index for crushing basalt such that 80% of particles pass a 100 micron screen is in the neighborhood of 17-20 kWh per ton: https://www.911metallurgist.com/blog/table-of-bond-work-index-by-minerals https://www.911metallurgist.com/blog/table-of-bond-work-inde... I'll add a factor of 2 for overhead to estimate the whole process energy expenditure. That would mean that using Columbia Plateau basalt, you'd expend 40 kWh per ton of basalt, about 200 kWh per ton of CO2 removed from the atmosphere. That is, energetically speaking, really good compared to schemes that try to run "combustion-in-reverse" to regenerate hydrocarbons from CO2. It's efficient enough that you could actually use coal fired power to drive the whole process and it would still be a net CO2 sink. But at 200 kWh per ton-CO2-scrubbed, it would take 7.2 billion megawatt hours to neutralize humanity's 2015 CO2 emissions. That's an annualized power of 821 gigawatts -- nearly twice the average electrical power generated in the United States. The scale is so vast that I can only imagine advanced robotic manufacturing, mining, and energy generation being up to the task. However you want to modify my baseline scenario -- smaller projects scattered around the Earth instead of one mega-project, being pickier about processing only the best rocks -- I think that the scale is still daunting. But I think it may still be possible because I see automation advancing a lot in the 21st century if we don't precipitate a civilization-ending crisis first.
- anon1253 9y ago
  It's not the only option either. Combine that solution on a massive scale with re-forestation and (even though eventually it's CO2 neutral) it might actually make a dent. My go-to model was always: - Plant heliostat molten salt reactors in desert coastal areas [1] - Use generated heat to desalinate water - Use desalinated water to provide irrigation - Plant (potentially GMO'ed) bootstrapping organisms to create a soil (greening) - Plant trees - Rinse repeat. However, your idea makes more sense if the only goal is CO2 scrubbing. But adding the heliostat molten salt reactors in a desert might be quite feasible, they generate tons of heat, which can be translated into energy or simply mechanical force (water pressure)…and there is no shortage of silicates in the desert. [1] http://www.solarreserve.com/en/technology/molten-salt-energy-storage http://www.solarreserve.com/en/technology/molten-salt-energy...
  - philipkglass 9y ago
    Yes, re-forestation or afforestation is another scheme worth considering. It can't scale up to the extent of accelerated silicate weathering but it could reach a scale of gigatons of CO2 per year. And it could produce food, wood products, and desirable living space for humans where once there were deserts with little biomass of any kind. You need to harvest-and-bury wood (as biochar, preferably) pretty regularly if the primary goal is CO2 sequestration; otherwise the steady state is approximately equal to current mature forested areas (which store plenty of carbon in soils but aren't great at continuing to remove more from the air). Accelerated silicate weathering and "greening the deserts" are concepts that work well together, too. Mature fertile soil contains weathered minerals and organic matter. Crushing basalt can speed up the weathering part of producing soil, and provide micronutrients for plants plus a couple of important macros (phosphorus and potassium).
    - SwetDrems 9y ago
      Only tangentially related, but here[0] is a video of the great reforestation program that South Korea undertook after the Korean War. They effectively transformed vast arid landscapes into healthy forests. Shows the power of a nation/people coming together with careful planning, forethought, unity, and grit can literally shape the earth. [0] https://www.youtube.com/watch?v=_3KkN8hvUCI https://www.youtube.com/watch?v=_3KkN8hvUCI

Can you elaborate on the optimistic assumptions in robotics that may enable accelerated silicate weathering? Or could you point me to some readings on the matter?

philipkglass 9y ago

A search on Google Scholar for "accelerated silicate weathering" will be more informative than my comment. But here's the shortish version... Naturally occurring silicates of magnesium, calcium, sodium, and potassium are thermodynamically prone to weather to carbonates in ambient conditions, when water absorbs CO2 and passes over rocks. In the case of magnesium and calcium in particular, the weathering leads to stable solids that will not spontaneously release CO2 again. A schematic example with calcium silicate: CO2 + CaSiO3 -> SiO2 + CaCO3 Gaseous carbon dioxide and solid calcium silicate become solid silicon dioxide and calcium carbonate. Silicate weathering has multiple advantages over other carbon dioxide removal/sequestration schemes: • The end state is naturally stable. You don't have to worry about the leakiness of underground containment. • It restores the pH balance of the oceans as well as reducing radiative forcing (warming) effects. • It deals equally well with point and distributed sources of CO2 (coal plants, automobile tailpipes). • It can be located anywhere on Earth. It does not need to be adjacent to CO2 sources. • It does not require concentrated CO2 streams, but works with ambient atmospheric concentrations. Natural silicate weathering reactions dominate Earth's CO2 balance in the very long term. But they are strongly kinetically hindered in nature. After a freshly exposed rock surface has weathered to a depth of a few microns, the cation-depleted "rind" drastically slows the weathering of the remaining interior. Without human intervention, it'll take about 100,000 years for natural silicate weathering to restore the pre-industrial baseline of atmospheric CO2 concentrations. There are different ways to improve the kinetics: • Crush bulk rock to a fine sand texture, so full interior weathering finishes much faster (still takes years-to-decades, but no longer takes geological time scales). • Place crushed rock in near-shore ocean environments where mechanical wave erosion keeps removing rinds. • Place crushed rock in acidic tropical agricultural soils where it weathers faster due to low pH and elevated temperature. This also improves soil quality for growing crops. It's not explicitly included in the scholarly literature, but I say that advanced robotics are necessary because the required scale of intervention is staggering, bigger than any engineering endeavor in history. For example, the Columbia Plateau in the United States contains basalt whose alkali and alkaline earth content could bind about 20% of its own mass in CO2, after complete weathering: https://crustal.usgs.gov/geochemical_reference_standards/basaltbcr2.html https://crustal.usgs.gov/geochemical_reference_standards/bas... To neutralize the CO2 that humans emitted in 2015, about 36 billion tons (https://en.wikipedia.org/wiki/List_of_countries_by_carbon_dioxide_emissions https://en.wikipedia.org/wiki/List_of_countries_by_carbon_di...), would require mining and pulverizing about 180 billion tons of Columbia Plateau basalt. That's about 60 cubic kilometers. We're in no danger of running out of plateau -- it contains more than 170,000 km^3. As for energy estimates, the Bond Work Index for crushing basalt such that 80% of particles pass a 100 micron screen is in the neighborhood of 17-20 kWh per ton: https://www.911metallurgist.com/blog/table-of-bond-work-index-by-minerals https://www.911metallurgist.com/blog/table-of-bond-work-inde... I'll add a factor of 2 for overhead to estimate the whole process energy expenditure. That would mean that using Columbia Plateau basalt, you'd expend 40 kWh per ton of basalt, about 200 kWh per ton of CO2 removed from the atmosphere. That is, energetically speaking, really good compared to schemes that try to run "combustion-in-reverse" to regenerate hydrocarbons from CO2. It's efficient enough that you could actually use coal fired power to drive the whole process and it would still be a net CO2 sink. But at 200 kWh per ton-CO2-scrubbed, it would take 7.2 billion megawatt hours to neutralize humanity's 2015 CO2 emissions. That's an annualized power of 821 gigawatts -- nearly twice the average electrical power generated in the United States. The scale is so vast that I can only imagine advanced robotic manufacturing, mining, and energy generation being up to the task. However you want to modify my baseline scenario -- smaller projects scattered around the Earth instead of one mega-project, being pickier about processing only the best rocks -- I think that the scale is still daunting. But I think it may still be possible because I see automation advancing a lot in the 21st century if we don't precipitate a civilization-ending crisis first.

anon1253 9y ago
It's not the only option either. Combine that solution on a massive scale with re-forestation and (even though eventually it's CO2 neutral) it might actually make a dent. My go-to model was always: - Plant heliostat molten salt reactors in desert coastal areas [1] - Use generated heat to desalinate water - Use desalinated water to provide irrigation - Plant (potentially GMO'ed) bootstrapping organisms to create a soil (greening) - Plant trees - Rinse repeat. However, your idea makes more sense if the only goal is CO2 scrubbing. But adding the heliostat molten salt reactors in a desert might be quite feasible, they generate tons of heat, which can be translated into energy or simply mechanical force (water pressure)…and there is no shortage of silicates in the desert. [1] http://www.solarreserve.com/en/technology/molten-salt-energy-storage http://www.solarreserve.com/en/technology/molten-salt-energy...
- philipkglass 9y ago
  Yes, re-forestation or afforestation is another scheme worth considering. It can't scale up to the extent of accelerated silicate weathering but it could reach a scale of gigatons of CO2 per year. And it could produce food, wood products, and desirable living space for humans where once there were deserts with little biomass of any kind. You need to harvest-and-bury wood (as biochar, preferably) pretty regularly if the primary goal is CO2 sequestration; otherwise the steady state is approximately equal to current mature forested areas (which store plenty of carbon in soils but aren't great at continuing to remove more from the air). Accelerated silicate weathering and "greening the deserts" are concepts that work well together, too. Mature fertile soil contains weathered minerals and organic matter. Crushing basalt can speed up the weathering part of producing soil, and provide micronutrients for plants plus a couple of important macros (phosphorus and potassium).
  - SwetDrems 9y ago
    Only tangentially related, but here[0] is a video of the great reforestation program that South Korea undertook after the Korean War. They effectively transformed vast arid landscapes into healthy forests. Shows the power of a nation/people coming together with careful planning, forethought, unity, and grit can literally shape the earth. [0] https://www.youtube.com/watch?v=_3KkN8hvUCI https://www.youtube.com/watch?v=_3KkN8hvUCI