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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

#51

Post by rb808 »

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…

> So 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.

Not necessarily. I'm thinking of cold polar winters with no wind and no sun, people burning fossil fuels to stay warm. Meanwhile in deserts solar panels powering carbon capture machines to reverse the greenhouse gases back again. Maybe even the carbon capture creates synthetic coal which can be shipped to the cold regions.

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

#52

Post by tedk-42 »

SystemOut wrote: post #47
relieferator wrote: post #43

Earlier quoted context omitted.

From what I can recall, landfills produce more methane than any other process. How about we build a carbon capture next to every landfill, divert the methane and burn it to run the DAC?

Landfills do collect and burn methane. Those pipe like structures you see sticking out of a completed landfill are part of the process. https://archive.epa.gov/climatechange/kids/solutions/technol...

TIL. Now we just need to execute the second part of his plan to capture the carbon from the energy produced

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

#53

Post by shartshooter »

spodek wrote: post #42

Not a word about the most effective, cheapest strategy: reduce emissions? Most Americans could reduce their emissions by 75% while improving their standard of living by buying less junk, wearing a sweater in the winter, eating more healthy, and other low hanging fruit that will make them more active, healthy, connected to their communities, etc. Reduce consumption by half. There, I just saved us $300 million. How is…

Because it’s also the least effective strategy. The reality is getting nearly everyone to change their behavior just isn’t gonna happen.

Even if everyone in America went vegan, showered once a day and biked everywhere wouldn’t change much with impoverished countries coming out of the third world. If you can’t get them to change then it doesn’t really matter.

Big problems require big, comprehensive solutions. For that you need government to function effectively regulate, make climate bills countries can stick to.

We already have the tools we need to get climate change turned around but we don’t have the political will.

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

#54

Post by pfdietz »

iso1337 wrote: post #22
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…

There is a well known relationship summarized in the Sherwood plot. https://www.pnas.org/content/pnas/108/51/20428/F1.large.jpg related paper: https://www.pnas.org/content/108/51/20428 Your basic intuition is correct in that the more dilute something is, the more costly it is to extract/purify it.

A properly engineered DAC system will be much less expensive than the number they found.

https://www.cell.com/joule/fulltext/S2542-4351(18)30225-3

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

#55

Post by pfdietz »

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…

It's not true at all. Turning the CO2 back into fuel would take as much energy as burning it released, but simply capturing the CO2 from the air need not.

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

#56

Post by pfdietz »

dv_dt wrote: post #30

If you're going to continue to burn fossil fuels, it seems better to burn it in a plant that inherently captures the carbon then trying to wrangle it back after it's release. The interesting part of the Allam cycle for power generation is that supercritical co2 is the working fluid for the turbine, and when you burn the fuel it increases the mass in the closed circuit. Both the size and the efficiency of the plant al…

That would be true, if the power plant has high capacity factor, and if it stationary, and if it is located near a place where the CO2 can be sequestered.

But if you (say) have peaking turbines that are intended to take over when renewables or short term storage are not available, they may have very low capacity factor. It could be economical to have them release the CO2 into the atmosphere, then steadily scrub that CO2 back out again, especially if that scrubbing could be done in a location with extremely cheap solar energy (like, say, Chile).

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

#57

Post by pfdietz »

btilly wrote: post #20

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…

I would worry about nickel and chromium pollution.

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

#59

Post by bamboozled »

It's really nice to even see this discussed, I've been really interested in this topic.

It's true, at some stage we're going to have to reduce the carbon we've already injected into the atmosphere, so why not get started now. It's amazing how little funding this has received.

I'd actually be interested in paying for this like any other utility, as electricity prices get cheaper from renewable energy, I'd be happy to pay a carbon capture bill to survive and breathe cleaner air. I'd also hope this would be a temporary thing as we completely transfer away from fossil fuels.

Pay to clean up some of my own mess,makes sense.

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

#60

Post by leh_chmp »

This argument is so naïve that I had to create an HN account (downvote ready comment for dissing HN commenters). Do note that I am not dissing the author. He did claim a lack of expertise, but I am sad to see the comments trying to analyze the directly presented facts than being detail driven. E.g. I saw some reference to Allum's process of reusing CO2. What it skips is the fact that it barely effects efficiency, but certainly sees that is better than excusing. I still don't understand how $ among is used to measure environmental impact is a relationship people can think is easy measure. Maybe because short term thinking is rewarded better, hence the success of capitalism (I'm not pro/anti, but that's the root of the philosophy). I am assuming that people understand that Carbon capture doesn't resolve environmental changes. It simply offsets a part of it - the global warming aspect. A LOT of impact is straight up coming from pollution/contamination of water and soil, recurring costs of restructuring landscapes, causing earthquakes to floods and terraforming from receding coastlines, destruction of habitats, leading from contaminated species to complete destruction is food sources. The cascading effect of environmental damages is like paying a loan. As humans we are known to be overconfident of "I can fix it". But remind me historically when THAT had worked? Almost in all cases, it had been "I can forget this". Except in this case, I think if we had to expend that sort of money to "solve the problem", then we might as well just find a new planet to squander. In 50 years, we would have spent trillions of dollars unanimously and probably got to Mars

[Edit] typos

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