Graphite from CO2 should cost more energy

Coal can be turned into graphite by burning it in a boiler, capturing the exhaust, filtering it to CO2, and converting the CO2 into graphite. This indirect pathway is quite energy positive: 30/m coal -> 6/m graphite produces 15 MW power, with only 92 kW of that power consumed[1].

In real life, coal to graphite is theoretically energetically favorable. However, at least 75% of the energy produced by burning the coal is required to turn the CO2 into graphite: for anthracite, more like 90%[2]. I doubt that it's possible to convert coal to graphite without a net energy loss, given how close net negative you are on purely thermodynamic grounds.

I recommend increasing the power consumption of CO2->graphite about 30x (and possibly increasing graphite yields 15x to match direct coal to graphite). Disposing of CO2 should require gas injection or huge amounts of energy.

[1] https://doubleaxe.github.io/daxfb-calculator/?link=1aby1wz
[2] Data from CRC Handbook of Chemistry and Physics 97