> There is no point at which sequestering CO2 by use of electricity is going to make sense.

Of course there will be. Even burning a small fraction of the Thorium lying in spill heaps today will achieve that. In February 2019, when Tsinghua Uni demos the worlds first commercially viable fusion reactor, everything will change.

We will:

  - convert cubic kilometres of seawater into potable water per day and irrigate the Sahara and the Outback.
  - convert atmospheric C02 to carbohydrate fuels (while there are still need for them)
  - extract cubic killometers of C out of the atmosphere and oceans for construction material.
  - Drop the excess blocks of diamond into the mariana trench, those that we don't use for road base.
  - etc

People really do not appreciate what superabundance of energy would mean for man and our current planet. It will literally be the demarcation point between the age of want, and the ages of plenty.