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That would only be true if you were trying to change carbon back into energy dense hydrocarbons. Accelerated weathering exposes rock that reacts with CO2 withou

by jjk166 3y ago

That would only be true if you were trying to change carbon back into energy dense hydrocarbons. Accelerated weathering exposes rock that reacts with CO2 without any external energy input. The reaction actually produces energy, though not enough to be used as a practical power source. You need to do work to expose the rock, but this can be orders of magnitude less than the energy released when the CO2 was produced.

vlovich123 3y ago
OK point taken, but that’s actually a very small point when you run the numbers. Industrial scale direct air capture technology right is ~1200KWh per ton of CO2. And this energy cost is non linear - as we scale up, the lower CO2 concentration in the air will result in higher energy costs being needed to extract the remaining. I don’t think exposing the rock will be cheaper or can even scale as a process but harder to say. But that energy used is largely waste - sure we’ll maybe find a use for some of the co2 but then that’s also not sequestration and will release some of the captured co2 back into the air. Using those numbers means we’d need to be spending 48TWh to capture the carbon we emit each year, which is almost half of our current global energy production. Those are massive numbers. Of course you could overbuild less and slowly extract the co2, but then climate change gets even more baked in.
- lumost 3y ago
  The technology being discussed is not direct air capture. However even in the context of 1200 KWh/ ton, that works out to .04*1200 = $48 per ton. Wind generally runs 4 cents per kwh rate, and there is limited need to distribute electricity to high intensity areas. In total, that means we could sequester all global CO2 emissions for ~1.68 Trillion dollars per year - or 1.9% of global GDP. This is a small fraction of the estimated costs of economic disruption of climate change, why wouldn't we spend money on this?
  - vlovich123 3y ago
    So first it’s 1.68 trillions of dollars per year every year with political battles over who should be paying for this. And that’s just to get to net 0 for 1 year with a technology we don’t know how to actually scale to do 40Gton a year. That 1.68T number (insanely optimistic btw because 4c/kwh is quite cheap and it’s probably closer to 3-5x more expensive in practice), is just electricity. People to build these factories need salaries. There are significant construction costs. And then there’s the 40GTon of captured co2 we’d need to sequester - figuring out where to store it is a huge problem. And remember we need to repeat this process each year ongoing to keep up - forget about all the co2 already in the air. Oh and these tend to be chemical reactions so you’re also going to have to be shipping large scale of consumables around to perform the sequestration process. Sequestration is a long long long way off from being practical if it ever even gets there and you’ve wildly underestimated the cost and complexity I think.
    - lumost 3y ago
      Sequestration via pulverized stone will yield various precipitates into the soil, in many cases - the byproducts should be tunable to enrich the soil. I’m less concerned about total cost, olivine weathering proposals generally sit at $50 per ton delivered and applied where it’s needed. Which is 1/3rd the price of the electricity I estimated. That gets us into the realm of 500 billion per year. Less than the US’s defense budget. If more economic efforts materialize - perhaps we’d get to 100-300 billion per year at which point joint funding becomes obvious. Still great to do the other things, but let’s not ignore a technology which is promising and cheap.

by jjk166 3y ago

vlovich123 3y ago

OK point taken, but that’s actually a very small point when you run the numbers. Industrial scale direct air capture technology right is ~1200KWh per ton of CO2. And this energy cost is non linear - as we scale up, the lower CO2 concentration in the air will result in higher energy costs being needed to extract the remaining. I don’t think exposing the rock will be cheaper or can even scale as a process but harder to say. But that energy used is largely waste - sure we’ll maybe find a use for some of the co2 but then that’s also not sequestration and will release some of the captured co2 back into the air. Using those numbers means we’d need to be spending 48TWh to capture the carbon we emit each year, which is almost half of our current global energy production. Those are massive numbers. Of course you could overbuild less and slowly extract the co2, but then climate change gets even more baked in.

lumost 3y ago
The technology being discussed is not direct air capture. However even in the context of 1200 KWh/ ton, that works out to .04*1200 = $48 per ton. Wind generally runs 4 cents per kwh rate, and there is limited need to distribute electricity to high intensity areas. In total, that means we could sequester all global CO2 emissions for ~1.68 Trillion dollars per year - or 1.9% of global GDP. This is a small fraction of the estimated costs of economic disruption of climate change, why wouldn't we spend money on this?
- vlovich123 3y ago
  So first it’s 1.68 trillions of dollars per year every year with political battles over who should be paying for this. And that’s just to get to net 0 for 1 year with a technology we don’t know how to actually scale to do 40Gton a year. That 1.68T number (insanely optimistic btw because 4c/kwh is quite cheap and it’s probably closer to 3-5x more expensive in practice), is just electricity. People to build these factories need salaries. There are significant construction costs. And then there’s the 40GTon of captured co2 we’d need to sequester - figuring out where to store it is a huge problem. And remember we need to repeat this process each year ongoing to keep up - forget about all the co2 already in the air. Oh and these tend to be chemical reactions so you’re also going to have to be shipping large scale of consumables around to perform the sequestration process. Sequestration is a long long long way off from being practical if it ever even gets there and you’ve wildly underestimated the cost and complexity I think.
  - lumost 3y ago
    Sequestration via pulverized stone will yield various precipitates into the soil, in many cases - the byproducts should be tunable to enrich the soil. I’m less concerned about total cost, olivine weathering proposals generally sit at $50 per ton delivered and applied where it’s needed. Which is 1/3rd the price of the electricity I estimated. That gets us into the realm of 500 billion per year. Less than the US’s defense budget. If more economic efforts materialize - perhaps we’d get to 100-300 billion per year at which point joint funding becomes obvious. Still great to do the other things, but let’s not ignore a technology which is promising and cheap.