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Comment by funklute | Hacker News Reader

Any time someone actually does the math on sucking carbon out of the atmosphere, it seemingly becomes clear that it is simply not scalable to suck the carbon out of the atmosphere. Have you done the math, and if so, why is everyone who comes to the aforementioned conclusion wrong?

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I have repeatedly heard scientists say that planting 1 trillion trees will singlehandedly set climate change back 10 years. I've done the math on that myself and found that such a plan is about 5000 times more cost-effective than driving Tesla vehicles: https://news.ycombinator.com/item?id=19714034

Anytime anybody says anything about the social cost of carbon being greater than $0.50 per ton, I just tune them out.

On what timescale? I.e. trees take time to grow and accumulate carbon. As I understand it, the climate clock is ticking - there's a threshold beyond which some runaway effects kick in.

Growing is the only time they collect carbon. We could plant enough trees to zero out carbon usage (for now).

> trees take time to grow and accumulate carbon

They also burn down or are harvested quite regularly.

Harvesting can be good because it provides space for more trees to grow and store yet more carbon. As long the timber is used for long-term purposes such as housing, then the carbon in the timber kept stored. It's not 100% efficient because when felled the roots and leaves rot and return carbon back to the atmosphere, but AFAIK it's better than not harvesting.

There is an argument that it will become cheaper if more investment flows into the technology. For example, when solar power was originally conceived it wasn't cost-effective, but over the years it has seen tremendous gains in efficiency.

That said, I'm not educated on the topic well enough to say whether this argument applies to carbon sequestration.

Same, I also don't think I'm educated enough... but many people who are educated in this area do conclude that carbon removal is a non-starter, so I feel there is a certain burden of proof to claim that it will work. Solar power is a good example of a technology that did better than I would have thought, but there are many others that have silently fallen by the wayside.

These guys seem to have a viable approach to accelerated weathering, a form of carbon removal: https://projectvesta.org/

There's not enough limestone deposits for this to work - that aren't actually being currently mined.

You cannot use a an active mine for this technique, you have to let the stone lie and weather.

Read their FAQ [1]. They're using olivine, not limestone, and there's a ton of olivine in the crust.

[1] https://projectvesta.org/frequently-asked-questions/

Yes, I really want to see that project grow. There was a HN post recently where they gave a lot of fantastic answers to questions about the project: https://news.ycombinator.com/item?id=20403570

Of course, the more we can scale back greenhouse gas emission the less we'll need to extract, so IMO it only makes sense to come at the problem from both sides.

I skimmed their site and I'm yet to read the whitepaper, but I have one question that wasn't so far answered: what about transportation costs? Is this still net carbon negative when you account for the costs of moving all this rock and spreading it on the beaches?

They discuss that in their detailed proposals. There's a lot of discussion on siting and various transportation options. The math ends up working out.

Ok, thanks! I'll head on to reading the white paper then.

that's actually pretty cool

I like the idea of getting to net neutral with carbon capture. I even did some napkin math about a month ago. I tried calculating the energy requirements to break the CO2 bond as to determine the number of solar panels you would need. To get net neutral with CO2 emissions you would need to spend something around $8.5 trillion and obtain around 84,584,490,753.28 of 300 watt, $100 panels! Note I did not calculate the cost of the actual carbon capture machines, just energy requirements. I think my number is perhaps still a bit low but I also think this is reasonably doable with global support.

If you have enough green energy to unburn CO2, why not just... use that energy directly? Digging up carbon, burning it, and polluting it, only to spend the effort to capture it, unburn it, and rebury it would be absurd and inefficient.

That being said, I believe carbon capture proposals don't typically involve unburning the carbon - just capturing it and storing it. So the energy situation isn't as bad as your calculations.

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