> $100 a ton is a round number close to estimates of what it costs to capture > carbon from an oil refinery or coal burning power plant

That's a wildly optimistic number, and almost certainly too low for the carbon sources yoU're naming. Equinor estimated over 600USD for gas burners at an LNG plant, under almost ideal conditions (existing nearby storage site, company with lots of experience): https://industrydecarbonization.com/news/is-carbon-capture-a...