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Comment by hn_throwaway_99 | Hacker News Reader

The thing I'd like to understand about carbon capture is that, I would assume that once the process is scaled and costs come down that most of the cost would come from the energy to run the process.

But then, of course, the energy to run that process needs to come from a renewable, non-carbon emitting source, or else the whole thing is moot. So my question is that if we had all this renewable energy to run carbon capture systems, wouldn't it just make more sense to have this renewable energy put to use to offset fossil fuels in the first place?

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I don't see scaling direct air capture of CO2 beyond demo facilities until we are near zero CO2 emissions. But fixed concentrated CO2 streams should have had CO2 capture decades ago.

The problem of course is that no matter how cheap CO2 capture gets, it's not likely to beat dumping it to the atmosphere for free.

The best carbon capture technology is to plant trees. As in, billions of trees per year, which is carbon negative only if the net number of trees is growing. Maybe even get creative on the biology side of things to make them easier to plant in harsh environments.

Genetically engineered ultratrees in the Sahara! Of course this would have impacts on rainfall patterns in Europe and South America and might backfire (the large amounts of Saharan dust apparently helps form raindrops and new soil in both places)

> As in, billions of trees per year, which is carbon negative only if the net number of trees is growing.

Or if you chop the trees down and use them as building materials. Your hardwood floors and wood wall paneling are also sequestering carbon!

For many uses, renewable energy needs to be stored and/or transmitted. If you use wind energy to heat your house, you need a way to transmit that energy from where it is windy to your house, and you need a back up plan for when it isn't windy. Many times that back up plan is energy that produces CO2.

Carbon capture could be done where the renewable energy is, and it doesn't need to be done on a set schedule. If you are using wind to power carbon capture and it isn't windy, you say OK I'm not capturing any carbon today and you wait until the wind picks up. You can do it anytime and anywhere land and energy is cheap.

Another thing is the cost of converting existing infrastructure. You're not going to scrap every internal combustion engine overnight, and you're not going to remake the food chain overnight, you're not going to stop people from clearing forests overnight, and you're not going to stop producing cement overnight. Or in the next quarter of a century.

I'll do you one step better: you could use that energy source to produce closed-loop hydrocarbon fuels (e.g. methane via the Sabatier process).

It seems to me that virtually all of these problems reduce to the problem of finding a plentiful, climate-neutral energy source. (If only we had already invented such a thing in the 1940's....)

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