It'll depend on the specific project in question (there are quite a few methods under investigation), but for enhanced weathering (the type under discussion), I found some articles in a quick search that suggest the energy cost of grinding and transporting the rocks is significantly smaller than the carbon removed by the programme, e.g. https://www.researchgate.net/publication/322664372_Potential...

Arbitrage it from places where green energy is cheap or free. For example, iceland has pretty much 100% renewable energy sources. Already it has an extensive aluminum industry because energy there is cheap, and aluminum is energy-intensive to use it.

So, in theory, if you use green energy to produce a carbon-offset product, it's still a useful product.

Surplus energy from wind farms over land with the right kind of rock.

Anything you can’t shove into the grid grinds rock.

It's about scalability of any particular process minimizing net $/t (which includes kWh/t).

energy is not important. reducing carbon in atmosphere is more important then energy consumption. a lot of energy just escape to space every day.