[t0mpr1c3]

Carbon capture is already done at scale because CO2 is commercially valuable.

The proposed carbon storage is permanent in the form of carbonates. This is a variant of the Solvay process used to make washing powder.

Chalk cliffs were once the shells of sea creatures. That's a whole load of sequestered carbon right there.

[wizzwizz4]

I was under the impression that commercial CO₂ was produced by mining chalk.

[t0mpr1c3]

Yes, lime kilns use the reverse process -- heating chalk to drive off the CO2.