You need a massive amount of energy to run the process. If you could make it 100% efficient, which you can't, you have to put in as much energy to turn the CO2 into C + gallium oxide, and complete the cycle by turning the gallium oxide back to gallium metal, as you got by burning the carbon. So if you still have people using coal for energy, you have to pay more than they got.
But if you could eliminate fossil fuel burning and use processes like this to reduce the amount of CO2 already emitted (a big "if" because you have to concentrate it somehow) it could be useful.
> But if you could eliminate fossil fuel burning and use processes like this to reduce the amount of CO2 already emitted (a big "if" because you have to concentrate it somehow) it could be useful.
It could be useful if we 'just' greatly reduce fossil fuel burning for electricity, even if we don't eliminate it and even if we still use fossil fuels for other things.
But if you could eliminate fossil fuel burning and use processes like this to reduce the amount of CO2 already emitted (a big "if" because you have to concentrate it somehow) it could be useful.