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We need to take CO2 out of the sky – an overview of climate tech

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Re: We need to take CO2 out of the sky – an overview of climate tech

#31

Post by millstone »

beachy wrote: post #11
symplee wrote: post #4

I empathize with people who are trying to help by reducing their footprint. Though I fear it'll all be in vain when a machine is invented that can suck a lifetime's worth of frugality out of the air in a fraction of a second.

Fear instead what will happen if such a machine is ever developed. Which country(s) will own the machine? Who will decide what we dial the CO2 back to? You'd think it would be back to pre-industrial times but who knows? Will regions that have benefited from climate change and can now grow crops be on board? Or will they prefer to keep things as they are?

We should be so lucky as to have these problems.

Re: We need to take CO2 out of the sky – an overview of climate tech

#32

Post by scythe »

symplee wrote: post #4

I empathize with people who are trying to help by reducing their footprint. Though I fear it'll all be in vain when a machine is invented that can suck a lifetime's worth of frugality out of the air in a fraction of a second.

There is a non-negotiable entropy cost associated with removing CO2 from the atmosphere: you need to either pump it, so P0 = 0.0004 atm; if P1 = 5 atm (liquid CO2) then E = M R T ln(5 / 0.0004) / 44 => E/M = about 500 J/kg, or you need to absorb it chemically, which requires a chemical with a vapor pressure of CO2 I expect that we will eventually develop technology for CO2 extraction, but it's not going to be easy or convenient. 500 joules per kilogram is a lot and I doubt chemical methods will beat it. Currently there are about 3.5 trillion tonnes of CO2 in the atmosphere, or about 3.5 * 10^15 kg. To decrease the concentration by 1/3, returning us to preindustrial CO2 levels, you'd need about 600 petajoules or 170 terawatt-hours of input energy assuming thermodynamically perfect isothermal compression (which is impossible to actually achieve). Global world electricity consumption per year is about 21000 TWh.

No current method of CO2 extraction comes close to this limit and it's very unlikely that any ever will. Nonetheless, we have several orders of magnitude of wiggle room to let real-life methods work out okay. But the energy cost is not small and the negative effects of present-day CO2 emissions should not be considered easily curable.

And just for the fun of it, a human being releases about 4 * 10^5 kg of CO2 during their lifetime, requiring about 2 * 10^8 J. So the most efficient CO2 pump possible would require at least 200 million watts of power (about a thousand Tesla Roadsters at maximum output) to confine this CO2 within a second.

Re: We need to take CO2 out of the sky – an overview of climate tech

#33

Post by ttul »

ComputerGuru wrote: post #28

What the article leaves to the conclusion is what needs to be stated up front and center: it's virtually impossible to do this efficiently, cheaply, or effectively because there's so little CO2 in the air, meaning a) adding even a little bit more greatly affects the CO2 levels b) with a global ppm of ~400, it basically means that you need to filter 2500 molecules of air to get a single molecule of CO2, and that's ass…

If you can capture the CO2 using transient power from wind or solar and use it to make a synthetic fuel, then you have a potentially viable option. Carbon Engineering in Squamish BC is doing this for $100 a tonne. Their synthetic fuel costs about $2/L to make - still too expensive, but not if the carbon price rises to about $100/T.

Re: We need to take CO2 out of the sky – an overview of climate tech

#34

Post by avmich »

ComputerGuru wrote: post #28

What the article leaves to the conclusion is what needs to be stated up front and center: it's virtually impossible to do this efficiently, cheaply, or effectively because there's so little CO2 in the air, meaning a) adding even a little bit more greatly affects the CO2 levels b) with a global ppm of ~400, it basically means that you need to filter 2500 molecules of air to get a single molecule of CO2, and that's ass…

> There is no magic powder we can mix that'll cause CO2 to precipitate out of the atmosphere and fall to the ground like snow; it's a grueling energy intensive process to filter that out of the air around us.

Why not to cool down air so that CO2 would fall off? Cooled air can be used for pre-cooling incoming "dirty" air stream?

Re: We need to take CO2 out of the sky – an overview of climate tech

#35

Post by ElKrist »

roel_v wrote: post #14
symplee wrote: post #4

I empathize with people who are trying to help by reducing their footprint. Though I fear it'll all be in vain when a machine is invented that can suck a lifetime's worth of frugality out of the air in a fraction of a second.

The article links to a website where you can calculate your footprint, and buy offsets in various programs to negate that footprint (projectwren.com). It would cost me USD 17 / month to offset my (larger than average for my country) footprint. Why do I even bother with my reusable coffee cup and paper straws for that kind of money? I just don't understand. If an extra charge of $10 / month for everyone in Europe woul…

Basically the programs to "offset your footprint" don't scale.

They do not address the fundamental causes of emissions which are steadily growing.

They have some merits for mitigation of the problem but not as a long-term solution

Re: We need to take CO2 out of the sky – an overview of climate tech

#36

Post by millstone »

maerF0x0 wrote: post #6

Why do we always phrase it as changing the climate instead of facing that it's an energy balance issue? Too much energy is entering the earth and getting trapped. We can solve it by letting less enter, or otherwise sinking some of it. Consider if we stored the excess energy as chemical energy? or reflected some fraction of the energy back out away from us? reducing consumption is a failing project and the greener tec…

"Energy balance" isn't the right diagnosis because the energy balance has not changed significantly: the sun is and has forever been the dominant energy source in climate terms.

Broad-spectrum sunlight hits the earth, and is later emitted as infrared. CO2 is transparent to UV, but absorbs infrared. So global warming is a consequence of the fact that the major fossil fuel emission is opaque to a wavelength of light emitted by the sunlit earth.

"Letting less enter", "stored the excess energy", and "reflected some fraction" are all huge engineering solutions to the global warming crisis. And I support them all! But space mirrors and geo-scale energy sinks are sci-fi, they will not save us any time soon.

Reducing consumption buys time. Switching to renewables buys time too. Maybe you use renewable biofuels and capture the CO2 emissions: now your car is carbon negative, without launching a space mirror!

Re: We need to take CO2 out of the sky – an overview of climate tech

#37

Post by privateSFacct »

ComputerGuru wrote: post #28

What the article leaves to the conclusion is what needs to be stated up front and center: it's virtually impossible to do this efficiently, cheaply, or effectively because there's so little CO2 in the air, meaning a) adding even a little bit more greatly affects the CO2 levels b) with a global ppm of ~400, it basically means that you need to filter 2500 molecules of air to get a single molecule of CO2, and that's ass…

It only has to do it cheaply now because there is NO COST to putting CO2 into the air.

Why are people surprised that if something is free (pumping CO2 into air) demand for it is high?

You are telling me that doing a charge of let's say $10 - $100/ton of CO2 wouldn't have a DRAMATIC impact on emissions? Is $10 - $100/ton too little for a supposed climate emergency?

There is so much funding and lawmaking and finger pointing and shaming - but still - dumping CO2 into the atmosphere if free and dumping remains high and people pretend to be surprised.

On energy: CA curtails (turns off) solar (and wind) power because there is not enough demand. In 2019 CA had 921,000 MWhs of curtailment.

Let's start by charging something for CO2 emissions.

Re: We need to take CO2 out of the sky – an overview of climate tech

#39

Post by beefield »

TL;DR: We need dirt cheap energy.

It would have a couple of benefits: First CCS would be feasible. Second if (non-fossil) energy is dirt cheap, nobody bothers digging fossil energy sources from ground. Third, there are always more fun things available when energy is cheap vs when energy is expensive) So, keep on pushing solar and try to make nuclear competitive with something like small modular reactors, they are pretty much only ones with massive enough potential to properly disrupt energy markets.

Re: We need to take CO2 out of the sky – an overview of climate tech

#40

Post by mdorazio »

avmich wrote: post #34
ComputerGuru wrote: post #28

What the article leaves to the conclusion is what needs to be stated up front and center: it's virtually impossible to do this efficiently, cheaply, or effectively because there's so little CO2 in the air, meaning a) adding even a little bit more greatly affects the CO2 levels b) with a global ppm of ~400, it basically means that you need to filter 2500 molecules of air to get a single molecule of CO2, and that's ass…

> There is no magic powder we can mix that'll cause CO2 to precipitate out of the atmosphere and fall to the ground like snow; it's a grueling energy intensive process to filter that out of the air around us. Why not to cool down air so that CO2 would fall off? Cooled air can be used for pre-cooling incoming "dirty" air stream?

I had the same thought as well. It's an option, but the energy required to cool air to the precipitation point of CO2 (-79C) is pretty large, and the cooling process itself will produce greenhouse gas, so you end up with a pretty small return.
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