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Comment by semi-extrinsic | Hacker News Reader

Steam methane reforming is a process that produces hydrogen and CO2, as you say. But we can just pump that CO2 back where the methane came from (or older depleted gas fields).

Since that storage was secure enough to contain the methane for a hundred million years, it can hold the CO2 just fine as well.

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Are we sure about that ? I must admit I'm not a geologist, but CO2 has a different chemistry as methane, it becomes acid when dissolved in water, how would rocks behave when exposed to acid for thousands of years ? Are the rocks still gas-tight when they have been emptied, which causes movement and potential fractures, or when fracking was used for extraction ? How does it work to pump back CO2 in the same field you extract methane from ? Do we even have enough room to store the massive volumes of CO2 were generating ? An accidental release of such a store of CO2 would be a disaster of enormous proportions.

> how would rocks behave when exposed to acid for thousands of years

Rocks react quite well. Most are stable, some others absorb the gas and become stable.

It's water that doesn't deal well with it. It carries the CO2 into any place that it goes. What concerns me is that it's common to extract methane from places where it's trapped between a solid rock and a porous one full of water. That does not look like a proper place to inject CO2, but it's the place that every article about CO2 entrapment talks about.

There has been so much research into caprock permeability/stability, we know that shit. People have produced several atlases full of possible CO2 sequestration reservoirs with different geological properties, injectivity and maturity based on 3D seismics and core sample drillings etc.

CO2 sequestration is ready to go. Just like CO2 capture is ready to go. You have several actors commissioning projects now in Europe with 20-40 megatonnes stored per year.

That's good to know.

AFAIK, that research did not make into the mainstream news. But then, geological research never does.

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