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Comment by yodon | Hacker News Reader

The existence of oil shows CO2 can be stored in solid or liquid form, but doesn't show we know how to convert CO2 into that stored form at scale or keep our hands off it once it's stored that way. It's easy to burn oil, it's hard to make it, and it's harder still to not burn it when you know it's readily available.

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CO2 is in the dense supercritical state at the temperature and pressure conditions in storage reservoirs. It's density is between 750 and 850 kg/m3 then (water is 1000). You just have to compress it and pump it down there, and it will stay like that.

Honestly, the storage part is a solved problem from the feasibility side. The remaining challenges are mainly cost optimization, across all of capture, transport and storage.

And the biggest hurdle is forcing businesses to actually pay for the currently externalized cost of CO2 emissions.

I agree with your thermodynamics, I'm just concerned about finding a volume big enough to store climatically meaningful amounts of CO2 in that form. 40 billion metric tons per year of CO2 in the form you describe is around 30 billion cubic meters, and you need to find that much storage volume every year just to keep things from getting worse. If you want to actually make a dent, like rolling things back to the year 2000 (which likely isn't enough, but is a real impact), that's more like 600 billion metric tons or 450 billion cubic meters. That's roughly equivalent to 400 mountains 5000 feet tall. It's a huge volume of material we're talking about finding a place to store if we're actually trying to make a real dent in climate change.

For context, Global Natural Gas production is approximately 4,000 billion cubic meters per year.

To sequester the world's carbon emissions, we would need to move and store <1% the volume per year.

That's apples to oranges: we don't store anything like a year's worth of gas.

And anyone in Europe can tell you that natural gas transfer and storage is far from a solved problem.

The idea is not to actively store it, but dump it somewhere where it will store itself.

Europe is a great example of how we have the technology to transfer huge amounts of gas, and the challenges are largely politics and capital.

Nordstream #1 moves 60 billion m3 of gas 1,200 km and cost ~$10 billion

We also got calculations that yielded literal mountains ranges of carbonate... That's not to say carbonate cannot be part of the solution, but maybe it is unlikely to be the only solution.

If you asked a pre-industrial person how in the world it would be possible to source, refine, and distribute enough crude oil to power the modern world they would quote some similarly breathless numbers. It's possible because there's a motivation to do it. Simple as that. If we had a similar level of motivation to sequester our excess carbon we could start planning to do that tomorrow and have it done within a decade or three. You can't sequester all the worlds carbon in one place, just like you don't pull it all out of the ground in one place. Big problems seem less so when you realize that solutions are usually distributed.

I don't have the sources or exact numbers on hand, but I remember reading that the world's extractive & production processes create something like ~4 billion tons of oil, ~4 billion tons of iron, ~x billion tons of cement, and ~50 billion tons of sand, per year. These industries developed over many years and as you note are distributed globally. With market demand and regulatory pressure, we believe achieving CO2 removal across different modalities at the giga-ton scale is possible in our lifetimes.

That being said, we try to bring a conservative approach to our scaleup plan. The most immediate challenge is demonstrating CO2 removal at the megaton scale (1 million tons per year) to validate the process and meet short-term demand for voluntary offsets.

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