Carbon capture from the smokestack will create significant exhaust backpressure, which will reduce generation efficiency by up to 25%. There's also the other major component of hydrocarbon combustion: water vapor. In the worst case, methane combustion, water vapor makes up 2/3 of the volume of the exhaust (the best case, naphthas, have about 3/4 CO2
by volume). I'm wondering whether CO2
O is favored by olivine, and I don't know enough chemistry to answer that question.
Coal doesn't have much hydrogen, so water vapor isn't a problem. But coal has a bunch of impurities (many of them heavy metals) that, when they're not crapping up our air, get trapped in expensive fly-ash scrubbers. If carbon capture tech is placed after scrubbers, coal plants will be more expensive than they currently are, which utilities and consumers won't like (coal's currently the cheapest power source in the US and many other parts of the first world). If carbon capture is used before or instead of scrubbers, the minerals used may be coated and rendered useless by those impurities, like lead used to do to automotive exhaust catalysts.
Carbon capture at the source also does nothing about fossil fuels used for transportation. It'll be impractical to implement on automobiles. It may be implementable on ships, rail, and possibly trucks, but the effect on efficiency will raise operating costs that will be passed on to the rest of the economy in the form of higher prices on pretty much every physical product.
So capturing it at the source is problematic or impossible. What about capturing it from the atmosphere? The concentration of CO2
in the atmosphere is a couple hundred ppm. Water vapor has a higher concentration than that in hot, humid areas (which also tend to be heavily populated). That brings us back to the open question from the first paragraph. We could sidestep the problem by dehumidifying the air before running it over our carbon capture rocks, but industrial-scale dehumidifying is expensive, bringing us back to raised costs, this time with much lower CO2
And then there's the difficulty, expense, and energy required to dig all this olivine up from 3 miles down. There's a reason miners prefer to take the top off a mountain rather than dig into it.
Carbon capture may well have a place in the future energy ecosystem, but it seems to me that it's a band-aid over a sucking chest wound, not a real solution.