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The impact of direct air carbon capture on climate change

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Re: The impact of direct air carbon capture on climate change

#11

Post by _rpd »

jarvist wrote: post #6

I'm not sure if this article hammers home the key point: extracting carbon from the air always takes more energy that was gained by burning the fossil fuel to make that carbon. This is inevitable due to the entropy cost of de-mixing CO2 from the air, and from the limited efficiencies of thermal power generation (~33-40% for a coal power plant, perhaps 20% in an internal combustion engine), and limited efficiency of t…

> it only makes sense to spend energy on sucking CO2 out of the atmosphere, once you've already de-carbonised everything which you possibly can.

Except possibly when energy prices are negative due to wind and solar intermittency - although that is also a signal that you need more storage in the grid, additional storage may not be economic for some reason.

Re: The impact of direct air carbon capture on climate change

#12

Post by basicplus2 »

jarvist wrote: post #6

I'm not sure if this article hammers home the key point: extracting carbon from the air always takes more energy that was gained by burning the fossil fuel to make that carbon. This is inevitable due to the entropy cost of de-mixing CO2 from the air, and from the limited efficiencies of thermal power generation (~33-40% for a coal power plant, perhaps 20% in an internal combustion engine), and limited efficiency of t…

Cheaper if you are planting trees/plants or algea for say diesel production

Re: The impact of direct air carbon capture on climate change

#13

Post by basicplus2 »

Would love to know how many Trees/Algea farms/plants generally would need to do the job

Also growing plants and converting to fuel is exceedingly cheap for diesel

And before anyone gets worried about food prices going up.. it takes a surprisingly small amount of land mass to cover currect sneeds in energy, sorry no references no time..

Re: The impact of direct air carbon capture on climate change

#14

Post by mirimir »

jarvist wrote: post #6

I'm not sure if this article hammers home the key point: extracting carbon from the air always takes more energy that was gained by burning the fossil fuel to make that carbon. This is inevitable due to the entropy cost of de-mixing CO2 from the air, and from the limited efficiencies of thermal power generation (~33-40% for a coal power plant, perhaps 20% in an internal combustion engine), and limited efficiency of t…

Exactly!

But even so, meaningful collective global action is seeming less and less likely. So I can imagine that some with surplus greenhouse-neutral energy could capture CO2 to offset emissions by others.

Re: The impact of direct air carbon capture on climate change

#15

Post by colechristensen »

jarvist wrote: post #6

I'm not sure if this article hammers home the key point: extracting carbon from the air always takes more energy that was gained by burning the fossil fuel to make that carbon. This is inevitable due to the entropy cost of de-mixing CO2 from the air, and from the limited efficiencies of thermal power generation (~33-40% for a coal power plant, perhaps 20% in an internal combustion engine), and limited efficiency of t…

You're assuming perfect elasticity of energy supply which there absolutely is not.

There is quite a mismatch between solar and wind production and electricity usage patters which is why storage is such a hot issue. Already there have been brief periods where 100% of energy production in a few regions was renewable. Those will certainly only grow in frequency and duration.

You don't start working on this technology when everything else is ready for it, you start as quickly as possible so the tech is ready when the rest of the world is ready for it.

Re: The impact of direct air carbon capture on climate change

#16

Post by aidenn0 »

ForHackernews wrote: post #7
jarvist wrote: post #6

I'm not sure if this article hammers home the key point: extracting carbon from the air always takes more energy that was gained by burning the fossil fuel to make that carbon. This is inevitable due to the entropy cost of de-mixing CO2 from the air, and from the limited efficiencies of thermal power generation (~33-40% for a coal power plant, perhaps 20% in an internal combustion engine), and limited efficiency of t…

> Maybe it has a future role (>2050? >2100?) It absolutely must, or else it's basically already too late: https://www.vox.com/2016/10/4/13118594/2-degrees-no-more-fos... > This image should terrify you. It should be on billboards. > As you can see, in either scenario, global emissions must peak and begin declining immediately. For a medium chance to avoid 1.5 degrees, the world has to zero out net carbon emissions by…

My dad sees articles like this and he'll just say that maybe the damage needed to prevent warming is worse than the damage that will be done by the warming.

Re: The impact of direct air carbon capture on climate change

#17

Post by gibybo »

jarvist wrote: post #6

I'm not sure if this article hammers home the key point: extracting carbon from the air always takes more energy that was gained by burning the fossil fuel to make that carbon. This is inevitable due to the entropy cost of de-mixing CO2 from the air, and from the limited efficiencies of thermal power generation (~33-40% for a coal power plant, perhaps 20% in an internal combustion engine), and limited efficiency of t…

> extracting carbon from the air always takes more energy that was gained by burning the fossil fuel to make that carbon.

This sounds true at first glance, but is it always? It seems like it's obviously true for simple reactions like burning methane and converting it back to methane since the energy you get from it is equal to or less than the energy required to turn it back into methane, but might there be some other chemical reactions where you can turn it into something less energetic than the molecule it came from?

Re: The impact of direct air carbon capture on climate change

#18

Post by strainer »

_rpd wrote: post #11
jarvist wrote: post #6

I'm not sure if this article hammers home the key point: extracting carbon from the air always takes more energy that was gained by burning the fossil fuel to make that carbon. This is inevitable due to the entropy cost of de-mixing CO2 from the air, and from the limited efficiencies of thermal power generation (~33-40% for a coal power plant, perhaps 20% in an internal combustion engine), and limited efficiency of t…

> it only makes sense to spend energy on sucking CO2 out of the atmosphere, once you've already de-carbonised everything which you possibly can. Except possibly when energy prices are negative due to wind and solar intermittency - although that is also a signal that you need more storage in the grid, additional storage may not be economic for some reason.

Some captured CO2 might be used with cheap electricity to make carbon neutral fuel - which is of course a form of stored energy itself. A pilot project in Germany is doing this[1]:

> The green hydrogen will be combined with carbon dioxide captured from the cement plant to produce synthetic methanol, which would then be refined into carbon-neutral synthetic kerosene (ie, aviation fuel), for use at the nearby Hamburg airport. The airport is hoping that 5% of all fuel used there will be carbon-neutral by 2025.

[1] https://www.rechargenews.com/transition/offshore-wind-to-pow...

Re: The impact of direct air carbon capture on climate change

#19

Post by zozbot234 »

gibybo wrote: post #17
jarvist wrote: post #6

I'm not sure if this article hammers home the key point: extracting carbon from the air always takes more energy that was gained by burning the fossil fuel to make that carbon. This is inevitable due to the entropy cost of de-mixing CO2 from the air, and from the limited efficiencies of thermal power generation (~33-40% for a coal power plant, perhaps 20% in an internal combustion engine), and limited efficiency of t…

> extracting carbon from the air always takes more energy that was gained by burning the fossil fuel to make that carbon. This sounds true at first glance, but is it always? It seems like it's obviously true for simple reactions like burning methane and converting it back to methane since the energy you get from it is equal to or less than the energy required to turn it back into methane, but might there be some othe…

Yes, there are rocks that will "extract" carbon from the air on their own if crushed into sand. They are even reasonably abundant, so it seems like they would be a feasible tool for carbon capture. It would basically amount to speeding up the natural carbon cycle, which normally keeps carbon dioxide concentrations relatively stable in the very long run.

Re: The impact of direct air carbon capture on climate change

#20

Post by btilly »

I would have liked to see https://projectvesta.org/ commented on in the article.

They claim to be able to sequester carbon by scattering olivine rock in an active and warm coast. The cost of the rock is $25/ton now, with the prospect of $10/ton in the future. Plus whatever it costs to break it up and scatter it.

That makes it at an interesting price point if it works as advertised.

Even more interesting to me is that the absorption happens in the water. Meaning that it can counteract ocean acidification near the coral reefs that are the most vulnerable.

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