Is CCS (Carbon Capture & Sequestion) viable?

No.

And, no.  It's very clear: CCS plants are inferior to a combination of windpower and natural gas.  They cost much more, and don't emit any less CO2.

See the following article in MIT Technology review: http://www.technologyreview.com/demo/533351/a-coal-plant-that-buries-its-greenhouse-gases/

The plant only captures 90% of the CO2, and produces only 80% of the output of a conventional coal plant for the same coal input. Coal plants produce twice as much CO2 as natural gas.  The output reduction further decreases the CO2 emissions difference.  A combination of 50% wind and 50% natural gas would produce the same amount of CO2.

We find out that a plant with a capacity of 160MW cost $1B to equip with CCS.  That's $6 per watt.  If we estimate a basic cost of $3 per watt for the coal plant, this plant will cost $12 per watt (adjusted for an average coal capacity factor of 75%).  Windpower costs lesss than $6 per watt (adjusted for wind's average capacity factor of 33%).  So, CCS coal costs twice as much as a windfarm with comparable kWh output.  We could add 100% backup with natural gas generation to a windfarm, and have a far cheaper solution.

And, of course, there's far more potential for further reductions in CO2 emissions by reducing NG's share below 50%: levels of  20% are currently the optimal cost point, according to German research.

Finally, most of the CO2 isn't sequestered: it's sold for oil secondary recovery, which means that it 1) doesn't reduce emissions, and 2) generates revenue, rather than creating a cost for storage.  Oil well EOR can only use a relatively small amount of CO2 - this is not scalable.

CCS is clearly a bad solution.