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Comment by 08-15 | Hacker News Reader

But why is anyone cheerleading for this pointless technology? Why bother with capturing a trace gas from the atmosphere?

It seems to me that stranded clean energy would be better spent making ammonia. We've been making ammonia from air and natural gas for a hundred years, we know how to make it from air, water and electricity. It is easy to transport, the market for it is huge, and making ammonia "captures" CO2 by replacing a different plant that would have emitted it.

If we really wanted to take CO2 back out of the atmosphere (and we don't need to even think about that as long as there a coal, oil and gas burning power plants everywhere), we should simply grind up silicate rocks. Doing so makes reasonably good soil that may not even need fertilizer (other than ammonia), and once plants grow in it, it with weather rather quickly, thereby permanently sequestering CO2.

Seriously, why bother with CO2 capture from air? Looks like a fool's errand to me.

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If you can beat the HB and Ostwald processes, I say go for it. I think the idea behind carbon capture from serious people is: 1. That it should be solar powered / low energy 2. Catalyst cheap as dirt, so that 3. CO2 in the air is free, so you'd basically have the plant start up costs and then the rest is free money. Also envy of the plants for making it look easy.

Anybody saying it would make a dent on the global CO2 consumption is just spouting grant proposal talk, for the entropic reasons everyone else is talking about on this thread, or else is a crazy geoengineering nut.

That being said, if you dig into it, most groups that publish papers on the subject do it as an interesting sideline / something to grab some low hanging attention. It's really just checked out as a side effect of other things, like being able to functionalize hard to move chemical groups.

One of my Fe compounds could capture CO2 gas and convert it into oxalic acid ( H2O + 2CO2 =cat=> H2(CO2)2 + 1/2O2 ) ... almost a whole 50 cycles before it got poisoned by its own O2 production (the compound burst into flames in air, btw). But it could also functionalize one of the lowest energy N bonds known, and in a selective fashion. It was floated as a means for a two step synthesis of some kidney drug, but ... the bursting into flame thing.

If you can beat the HB and Ostwald processes, I say go for it.

You wouldn't try to beat those processes. You'd run them as usual but with hydrogen from water electrolysis instead of from steam-reformed fossil resources. Of course both levelized cost of renewable electricity and cost of running electrolyzers at low duty cycle need to decline significantly more before that could compete with the current status quo of cheap natural gas and no CO2 emission taxes.

Renewable ammonia made this way still seems more plausible for near-future commercialization than making liquid hydrocarbon fuels from renewable electricity and atmospheric CO2. Which is admittedly faint praise. The advantage that might eventually be significant is that it's easier to ship ammonia or simple derivatives of it from some remote but renewable-energy-resource-rich place, like windy islands, than to build electricity transmission lines.

This reminds of the idea of a true urea/diesel hybrid (instead of just using urea as DEF). Of course, the diesel would have to be used first.

> the bursting into flame thing

I've always believed this is why people start a career in chemistry but alas as you point out, it's not why people pay anyone (except DARPA) to carry on.

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