To put that in perspective, pure graphite or carbon (basically equivalent to anthracite) releases about 2.5 MWh of heat per ton of CO2 produced.

Pure methane (if fully combusted) releases about 5.6 MWh of heat her ton of CO2 emitted.

Oil is somewhere in between.

In terms of electrical or mechanical (ie useful, low-entropy) energy produced per tonne of CO2 emitted, HHV efficiency typically 25-50%, so between 0.625 and 1.25 MWh/tonne of CO2 per tonne of coal and 1.4-2.8MWh/tonneCO2 for methane.

That's >18 GJ/tonne, with a goal of 3.6 to 7.2 GJ/tonne, making it much less efficient than post-combustion capture (which I think tends to aim for <2 GJ/tonne now).

Why not just do post-combustion capture if it's cheaper and more effective?

It should be done more but stronger tax & regulatory incentives are needed to encourage point-source polluters to adopt CO2 capture for emissions from industrial processes & energy production. It is very difficult to convince, say, a software company to pay for/subsidize the cleanup of another company's/utility's dirty process, because of the complex incentives & liabilities involved.

(Would love for an entrepreneur to come up with a way to find a market solution to this matching problem -- AirMyne might want to bid to be the technology platform on which such a CO2 capture system is built!)

Does that exclude the energy cost involved in injecting CO2 into a reservoir? Also, what would be the energy cost of converting captured CO2 to a more stable form (CaCO3, aka limestone), or a commodity such as methanol?

The energy estimate includes the costs of compression & injection using some figures in publicly available resources that look at CO2 removal end-to-end. Co-locating the capture as close as possible to removal/injection site (e.g. minimizing transit logistics) helps to keep the energy & financial costs low.

However at this stage, we are more focused on scaling our capture process so it can be integrated to injection/sequestration later on at a pilot plant scale.

Where do you envision this energy to come from and in which timescale? would that be electricity only or a mix? Thank you.

so ~40 PWh just to keep up with the carbon emitted each year. a mere 1000x more than the global electrical output.

and we're still arguing about whether fission is good in the year of our lord 2022