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Comment by abhv | Hacker News Reader

Quick math:

Density of air at sea level: 1225 g/m^3

C02: 0.0383% by volume (383 ppmv) corresponds to 0.0582% by weight.

Ergo, 1m^3 of air has 0.713 g of C02 in it.

Ergo pulling 1 metric ton (10^6 grams) of C02 per day requires processing AT LEAST : 10^6/ .713 = 1.4m m^3 of air per day or 16 m^3 of air per second!

(That would assume 100% capture)

I was skeptical that 1 cooling tower generates this much flow, but the example in [1] suggests 17*10^6 ft^3/minute, or roughly 8000 m^3/sec.

Thus, as long as your capture chemical has 2% efficiency, it seems reasonable.

[1] https://www.power-eng.com/emissions/cooling-tower-heat-trans...

[EDITED after I detected an error in my math]

The amazing observation for me is that evaporative cooling towers process A LOT OF AIR per second.

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> Ergo pulling 1 metric ton (10^6 grams) of C02 per day

The CO2 footprint per capita in the United States is 15 metric tons [1], so at 300M population, that's 4.5e9 metric tons of CO2 per year.

At 1 metric ton CO2 removed per day per tower, we would need 4.5e9/365 = 12.3M such cooling towers. Even if the efficiency increased 2 orders of magnitude it is still not enough, and I doubt there is a need for even 123,000 cooling towers.

None of this is to say that it shouldn't be pursued as a business opportunity to sell CO2 to commercial customers.

But realistically, given the scale of the CO2 problem, we still need to dramatically reduce the amount of CO2 we are emitting per capita as a primary measure, with any carbon capture as secondary.

1. https://data.worldbank.org/indicator/EN.ATM.CO2E.PC?location...

Couldn't agree with you more - the less we emit, the less critical the need for carbon removal technologies becomes.

We have two levers for reversing climate change: the first is reducing emissions, and the second is remove carbon from the atmosphere. Most of the pathways in the most recent UN climate report incorporate some amount of carbon removal to maintain global temperature rise below 1.5°C [1].

Humans have been hard at work for a while on our first lever, and we need many shots on goal with the second lever to give ourselves a chance at success.

[1]: https://www.ipcc.ch/sr15/chapter/chapter-4/

> Humans have been hard at work for a while on our first lever, and we need many shots on goal with the second lever to give ourselves a chance at success.

Agreed, and best of luck with your efforts!

Most of your yearly 15 tons is emitted via specific exhaust pipes, where capture part is quite easy problem, even without these cooling towers. The big problem is what to do with all of it: there is no commercial use/market, especially if you want that to be climate friendly, ie not dumped to atmosphere quite soon anyway. We'd need to think of it as toxic waste, similar to nuclear one, to be stored forever underground, but can we (as civilization) afford it?

for every 'can we afford it?' question you can also ask 'can we afford not to do it?' and in this case the answer is at the very least not simply 'no.'

> The big problem is what to do with all of it

Which is why the primary way to deal with the CO2 problem isn't capture, but by reducing the amount emitted in the first place, via renewables + storage, more and better mass transit, EVs replacing ICEVs, heat pumps replacing furnaces, etc.

Compared to the CO2 reduction potential o

We had a similar observation and related feelings — cooling towers move, quite literally, tons of air every day.

One suggestion I'd make to the math above: the concentration of CO2 in the air is a bit higher, at 415ppm per Scripps UCSD: https://www.co2.earth/

Yeah, I was going to say, it hasn't been 385 since about 2008.

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